]> git.saurik.com Git - apple/xnu.git/blobdiff - bsd/vfs/vfs_cluster.c
xnu-7195.101.1.tar.gz
[apple/xnu.git] / bsd / vfs / vfs_cluster.c
index 616f09e1ca6222a66fb8ff45738367bcaaae56c4..5de58feb966e3e887b83e425af9674d8b5d54383 100644 (file)
@@ -1,23 +1,29 @@
 /*
- * Copyright (c) 2000-2002 Apple Computer, Inc. All rights reserved.
+ * Copyright (c) 2000-2020 Apple Inc. All rights reserved.
  *
- * @APPLE_LICENSE_HEADER_START@
- * 
- * The contents of this file constitute Original Code as defined in and
- * are subject to the Apple Public Source License Version 1.1 (the
- * "License").  You may not use this file except in compliance with the
- * License.  Please obtain a copy of the License at
- * http://www.apple.com/publicsource and read it before using this file.
- * 
- * This Original Code and all software distributed under the License are
- * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
+ * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
+ *
+ * This file contains Original Code and/or Modifications of Original Code
+ * as defined in and that are subject to the Apple Public Source License
+ * Version 2.0 (the 'License'). You may not use this file except in
+ * compliance with the License. The rights granted to you under the License
+ * may not be used to create, or enable the creation or redistribution of,
+ * unlawful or unlicensed copies of an Apple operating system, or to
+ * circumvent, violate, or enable the circumvention or violation of, any
+ * terms of an Apple operating system software license agreement.
+ *
+ * Please obtain a copy of the License at
+ * http://www.opensource.apple.com/apsl/ and read it before using this file.
+ *
+ * The Original Code and all software distributed under the License are
+ * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
- * License for the specific language governing rights and limitations
- * under the License.
- * 
- * @APPLE_LICENSE_HEADER_END@
+ * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
+ * Please see the License for the specific language governing rights and
+ * limitations under the License.
+ *
+ * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  */
 /* Copyright (c) 1995 NeXT Computer, Inc. All Rights Reserved */
 /*
  */
 
 #include <sys/param.h>
-#include <sys/proc.h>
-#include <sys/buf.h>
-#include <sys/vnode.h>
-#include <sys/mount.h>
+#include <sys/proc_internal.h>
+#include <sys/buf_internal.h>
+#include <sys/mount_internal.h>
+#include <sys/vnode_internal.h>
 #include <sys/trace.h>
-#include <sys/malloc.h>
+#include <kern/kalloc.h>
 #include <sys/time.h>
 #include <sys/kernel.h>
 #include <sys/resourcevar.h>
+#include <miscfs/specfs/specdev.h>
+#include <sys/uio_internal.h>
 #include <libkern/libkern.h>
 #include <machine/machine_routines.h>
 
-#include <sys/ubc.h>
-#include <vm/vm_pageout.h>
+#include <sys/ubc_internal.h>
+#include <vm/vnode_pager.h>
 
 #include <mach/mach_types.h>
 #include <mach/memory_object_types.h>
+#include <mach/vm_map.h>
+#include <mach/upl.h>
+#include <kern/task.h>
+#include <kern/policy_internal.h>
 
-#include <sys/kdebug.h>
-
-#define CL_READ      0x01
-#define CL_ASYNC     0x02
-#define CL_COMMIT    0x04
-#define CL_PAGEOUT   0x10
-#define CL_AGE       0x20
-#define CL_DUMP      0x40
-#define CL_NOZERO    0x80
-#define CL_PAGEIN    0x100
-#define CL_DEV_MEMORY 0x200
-#define CL_PRESERVE   0x400
-#define CL_THROTTLE   0x800
+#include <vm/vm_kern.h>
+#include <vm/vm_map.h>
+#include <vm/vm_pageout.h>
+#include <vm/vm_fault.h>
 
+#include <sys/kdebug.h>
+#include <libkern/OSAtomic.h>
+
+#include <sys/sdt.h>
+
+#include <stdbool.h>
+
+#include <vfs/vfs_disk_conditioner.h>
+
+#if 0
+#undef KERNEL_DEBUG
+#define KERNEL_DEBUG KERNEL_DEBUG_CONSTANT
+#endif
+
+
+#define CL_READ         0x01
+#define CL_WRITE        0x02
+#define CL_ASYNC        0x04
+#define CL_COMMIT       0x08
+#define CL_PAGEOUT      0x10
+#define CL_AGE          0x20
+#define CL_NOZERO       0x40
+#define CL_PAGEIN       0x80
+#define CL_DEV_MEMORY   0x100
+#define CL_PRESERVE     0x200
+#define CL_THROTTLE     0x400
+#define CL_KEEPCACHED   0x800
+#define CL_DIRECT_IO    0x1000
+#define CL_PASSIVE      0x2000
+#define CL_IOSTREAMING  0x4000
+#define CL_CLOSE        0x8000
+#define CL_ENCRYPTED    0x10000
+#define CL_RAW_ENCRYPTED        0x20000
+#define CL_NOCACHE      0x40000
+
+#define MAX_VECTOR_UPL_ELEMENTS 8
+#define MAX_VECTOR_UPL_SIZE     (2 * MAX_UPL_SIZE_BYTES)
+
+#define CLUSTER_IO_WAITING              ((buf_t)1)
+
+extern upl_t vector_upl_create(vm_offset_t);
+extern boolean_t vector_upl_is_valid(upl_t);
+extern boolean_t vector_upl_set_subupl(upl_t, upl_t, u_int32_t);
+extern void vector_upl_set_pagelist(upl_t);
+extern void vector_upl_set_iostate(upl_t, upl_t, vm_offset_t, u_int32_t);
 
 struct clios {
-        u_int  io_completed;       /* amount of io that has currently completed */
-        u_int  io_issued;          /* amount of io that was successfully issued */
-        int    io_error;           /* error code of first error encountered */
-        int    io_wanted;          /* someone is sleeping waiting for a change in state */
+       lck_mtx_t io_mtxp;
+       u_int  io_completed;       /* amount of io that has currently completed */
+       u_int  io_issued;          /* amount of io that was successfully issued */
+       int    io_error;           /* error code of first error encountered */
+       int    io_wanted;          /* someone is sleeping waiting for a change in state */
+};
+
+struct cl_direct_read_lock {
+       LIST_ENTRY(cl_direct_read_lock)         chain;
+       int32_t                                                         ref_count;
+       vnode_t                                                         vp;
+       lck_rw_t                                                        rw_lock;
 };
 
+#define CL_DIRECT_READ_LOCK_BUCKETS 61
+
+static LIST_HEAD(cl_direct_read_locks, cl_direct_read_lock)
+cl_direct_read_locks[CL_DIRECT_READ_LOCK_BUCKETS];
+
+static LCK_GRP_DECLARE(cl_mtx_grp, "cluster I/O");
+static LCK_MTX_DECLARE(cl_transaction_mtxp, &cl_mtx_grp);
+static LCK_SPIN_DECLARE(cl_direct_read_spin_lock, &cl_mtx_grp);
+
+static ZONE_DECLARE(cl_rd_zone, "cluster_read",
+    sizeof(struct cl_readahead), ZC_ZFREE_CLEARMEM | ZC_NOENCRYPT);
+
+static ZONE_DECLARE(cl_wr_zone, "cluster_write",
+    sizeof(struct cl_writebehind), ZC_ZFREE_CLEARMEM | ZC_NOENCRYPT);
+
+#define IO_UNKNOWN      0
+#define IO_DIRECT       1
+#define IO_CONTIG       2
+#define IO_COPY         3
+
+#define PUSH_DELAY      0x01
+#define PUSH_ALL        0x02
+#define PUSH_SYNC       0x04
+
+
+static void cluster_EOT(buf_t cbp_head, buf_t cbp_tail, int zero_offset);
+static void cluster_wait_IO(buf_t cbp_head, int async);
+static void cluster_complete_transaction(buf_t *cbp_head, void *callback_arg, int *retval, int flags, int needwait);
+
+static int cluster_io_type(struct uio *uio, int *io_type, u_int32_t *io_length, u_int32_t min_length);
+
+static int cluster_io(vnode_t vp, upl_t upl, vm_offset_t upl_offset, off_t f_offset, int non_rounded_size,
+    int flags, buf_t real_bp, struct clios *iostate, int (*)(buf_t, void *), void *callback_arg);
+static int cluster_iodone(buf_t bp, void *callback_arg);
+static int cluster_ioerror(upl_t upl, int upl_offset, int abort_size, int error, int io_flags, vnode_t vp);
+static int cluster_is_throttled(vnode_t vp);
+
+static void cluster_iostate_wait(struct clios *iostate, u_int target, const char *wait_name);
+
+static void cluster_syncup(vnode_t vp, off_t newEOF, int (*)(buf_t, void *), void *callback_arg, int flags);
+
+static void cluster_read_upl_release(upl_t upl, int start_pg, int last_pg, int take_reference);
+static int cluster_copy_ubc_data_internal(vnode_t vp, struct uio *uio, int *io_resid, int mark_dirty, int take_reference);
+
+static int cluster_read_copy(vnode_t vp, struct uio *uio, u_int32_t io_req_size, off_t filesize, int flags,
+    int (*)(buf_t, void *), void *callback_arg) __attribute__((noinline));
+static int cluster_read_direct(vnode_t vp, struct uio *uio, off_t filesize, int *read_type, u_int32_t *read_length,
+    int flags, int (*)(buf_t, void *), void *callback_arg) __attribute__((noinline));
+static int cluster_read_contig(vnode_t vp, struct uio *uio, off_t filesize, int *read_type, u_int32_t *read_length,
+    int (*)(buf_t, void *), void *callback_arg, int flags) __attribute__((noinline));
+
+static int cluster_write_copy(vnode_t vp, struct uio *uio, u_int32_t io_req_size, off_t oldEOF, off_t newEOF,
+    off_t headOff, off_t tailOff, int flags, int (*)(buf_t, void *), void *callback_arg) __attribute__((noinline));
+static int cluster_write_direct(vnode_t vp, struct uio *uio, off_t oldEOF, off_t newEOF,
+    int *write_type, u_int32_t *write_length, int flags, int (*)(buf_t, void *), void *callback_arg) __attribute__((noinline));
+static int cluster_write_contig(vnode_t vp, struct uio *uio, off_t newEOF,
+    int *write_type, u_int32_t *write_length, int (*)(buf_t, void *), void *callback_arg, int bflag) __attribute__((noinline));
+
+static void cluster_update_state_internal(vnode_t vp, struct cl_extent *cl, int flags, boolean_t defer_writes, boolean_t *first_pass,
+    off_t write_off, int write_cnt, off_t newEOF, int (*callback)(buf_t, void *), void *callback_arg, boolean_t vm_initiated);
+
+static int cluster_align_phys_io(vnode_t vp, struct uio *uio, addr64_t usr_paddr, u_int32_t xsize, int flags, int (*)(buf_t, void *), void *callback_arg);
+
+static int      cluster_read_prefetch(vnode_t vp, off_t f_offset, u_int size, off_t filesize, int (*callback)(buf_t, void *), void *callback_arg, int bflag);
+static void     cluster_read_ahead(vnode_t vp, struct cl_extent *extent, off_t filesize, struct cl_readahead *ra,
+    int (*callback)(buf_t, void *), void *callback_arg, int bflag);
+
+static int      cluster_push_now(vnode_t vp, struct cl_extent *, off_t EOF, int flags, int (*)(buf_t, void *), void *callback_arg, boolean_t vm_ioitiated);
+
+static int      cluster_try_push(struct cl_writebehind *, vnode_t vp, off_t EOF, int push_flag, int flags, int (*)(buf_t, void *),
+    void *callback_arg, int *err, boolean_t vm_initiated);
+
+static int      sparse_cluster_switch(struct cl_writebehind *, vnode_t vp, off_t EOF, int (*)(buf_t, void *), void *callback_arg, boolean_t vm_initiated);
+static int      sparse_cluster_push(struct cl_writebehind *, void **cmapp, vnode_t vp, off_t EOF, int push_flag,
+    int io_flags, int (*)(buf_t, void *), void *callback_arg, boolean_t vm_initiated);
+static int      sparse_cluster_add(struct cl_writebehind *, void **cmapp, vnode_t vp, struct cl_extent *, off_t EOF,
+    int (*)(buf_t, void *), void *callback_arg, boolean_t vm_initiated);
 
-static void cluster_zero(upl_t upl, vm_offset_t   upl_offset,
-               int size, struct buf *bp);
-static int cluster_read_x(struct vnode *vp, struct uio *uio,
-               off_t filesize, int devblocksize, int flags);
-static int cluster_write_x(struct vnode *vp, struct uio *uio,
-               off_t oldEOF, off_t newEOF, off_t headOff,
-               off_t tailOff, int devblocksize, int flags);
-static int cluster_nocopy_read(struct vnode *vp, struct uio *uio,
-               off_t filesize, int devblocksize, int flags);
-static int cluster_nocopy_write(struct vnode *vp, struct uio *uio,
-               off_t newEOF, int devblocksize, int flags);
-static int cluster_phys_read(struct vnode *vp, struct uio *uio,
-               off_t filesize, int devblocksize, int flags);
-static int cluster_phys_write(struct vnode *vp, struct uio *uio,
-               off_t newEOF, int devblocksize, int flags);
-static int cluster_align_phys_io(struct vnode *vp, struct uio *uio,
-                addr64_t usr_paddr, int xsize, int devblocksize, int flags);
-static int cluster_push_x(struct vnode *vp, off_t EOF, unsigned int first, unsigned int last, int can_delay);
-static int cluster_try_push(struct vnode *vp, off_t EOF, int can_delay, int push_all);
-
-static int sparse_cluster_switch(struct vnode *vp, off_t EOF);
-static int sparse_cluster_push(struct vnode *vp, off_t EOF, int push_all);
-static int sparse_cluster_add(struct vnode *vp, off_t EOF, daddr_t first, daddr_t last);
-
-static kern_return_t vfs_drt_mark_pages(void **cmapp, off_t offset, u_int length, int *setcountp);
-static kern_return_t vfs_drt_unmark_pages(void **cmapp, off_t offset, u_int length);
+static kern_return_t vfs_drt_mark_pages(void **cmapp, off_t offset, u_int length, u_int *setcountp);
 static kern_return_t vfs_drt_get_cluster(void **cmapp, off_t *offsetp, u_int *lengthp);
 static kern_return_t vfs_drt_control(void **cmapp, int op_type);
+static kern_return_t vfs_get_scmap_push_behavior_internal(void **cmapp, int *push_flag);
 
-int     ubc_page_op_with_control __P((memory_object_control_t, off_t, int, ppnum_t *, int *));
 
+/*
+ * For throttled IO to check whether
+ * a block is cached by the boot cache
+ * and thus it can avoid delaying the IO.
+ *
+ * bootcache_contains_block is initially
+ * NULL. The BootCache will set it while
+ * the cache is active and clear it when
+ * the cache is jettisoned.
+ *
+ * Returns 0 if the block is not
+ * contained in the cache, 1 if it is
+ * contained.
+ *
+ * The function pointer remains valid
+ * after the cache has been evicted even
+ * if bootcache_contains_block has been
+ * cleared.
+ *
+ * See rdar://9974130 The new throttling mechanism breaks the boot cache for throttled IOs
+ */
+int (*bootcache_contains_block)(dev_t device, u_int64_t blkno) = NULL;
+
+
+/*
+ * limit the internal I/O size so that we
+ * can represent it in a 32 bit int
+ */
+#define MAX_IO_REQUEST_SIZE     (1024 * 1024 * 512)
+#define MAX_IO_CONTIG_SIZE      MAX_UPL_SIZE_BYTES
+#define MAX_VECTS               16
+/*
+ * The MIN_DIRECT_WRITE_SIZE governs how much I/O should be issued before we consider
+ * allowing the caller to bypass the buffer cache.  For small I/Os (less than 16k),
+ * we have not historically allowed the write to bypass the UBC.
+ */
+#define MIN_DIRECT_WRITE_SIZE   (16384)
+
+#define WRITE_THROTTLE          6
+#define WRITE_THROTTLE_SSD      2
+#define WRITE_BEHIND            1
+#define WRITE_BEHIND_SSD        1
+
+#if !defined(XNU_TARGET_OS_OSX)
+#define PREFETCH                1
+#define PREFETCH_SSD            1
+uint32_t speculative_prefetch_max = (2048 * 1024);              /* maximum bytes in a specluative read-ahead */
+uint32_t speculative_prefetch_max_iosize = (512 * 1024);        /* maximum I/O size to use in a specluative read-ahead */
+#else /* XNU_TARGET_OS_OSX */
+#define PREFETCH                3
+#define PREFETCH_SSD            2
+uint32_t speculative_prefetch_max = (MAX_UPL_SIZE_BYTES * 3);   /* maximum bytes in a specluative read-ahead */
+uint32_t speculative_prefetch_max_iosize = (512 * 1024);        /* maximum I/O size to use in a specluative read-ahead on SSDs*/
+#endif /* ! XNU_TARGET_OS_OSX */
+
+
+#define IO_SCALE(vp, base)              (vp->v_mount->mnt_ioscale * (base))
+#define MAX_CLUSTER_SIZE(vp)            (cluster_max_io_size(vp->v_mount, CL_WRITE))
+#define MAX_PREFETCH(vp, size, is_ssd)  (size * IO_SCALE(vp, ((is_ssd) ? PREFETCH_SSD : PREFETCH)))
+
+int     speculative_reads_disabled = 0;
 
 /*
  * throttle the number of async writes that
  * can be outstanding on a single vnode
- * before we issue a synchronous write 
+ * before we issue a synchronous write
  */
-#define ASYNC_THROTTLE  18
-#define HARD_THROTTLE_MAXCNT 1
-#define HARD_THROTTLE_MAXSIZE (64 * 1024)
+#define THROTTLE_MAXCNT 0
 
-int hard_throttle_on_root = 0;
-struct timeval priority_IO_timestamp_for_root;
+uint32_t throttle_max_iosize = (128 * 1024);
 
+#define THROTTLE_MAX_IOSIZE (throttle_max_iosize)
 
-static int 
-cluster_hard_throttle_on(vp)
-        struct vnode *vp;
-{
-        static struct timeval hard_throttle_maxelapsed = { 0, 300000 };
+SYSCTL_INT(_debug, OID_AUTO, lowpri_throttle_max_iosize, CTLFLAG_RW | CTLFLAG_LOCKED, &throttle_max_iosize, 0, "");
 
-       if (vp->v_mount->mnt_kern_flag & MNTK_ROOTDEV) {
-               struct timeval elapsed;
 
-               if (hard_throttle_on_root)
-                       return(1);
+void
+cluster_init(void)
+{
+       for (int i = 0; i < CL_DIRECT_READ_LOCK_BUCKETS; ++i) {
+               LIST_INIT(&cl_direct_read_locks[i]);
+       }
+}
+
 
-               elapsed = time;
-               timevalsub(&elapsed, &priority_IO_timestamp_for_root);
+uint32_t
+cluster_max_io_size(mount_t mp, int type)
+{
+       uint32_t        max_io_size;
+       uint32_t        segcnt;
+       uint32_t        maxcnt;
+
+       switch (type) {
+       case CL_READ:
+               segcnt = mp->mnt_segreadcnt;
+               maxcnt = mp->mnt_maxreadcnt;
+               break;
+       case CL_WRITE:
+               segcnt = mp->mnt_segwritecnt;
+               maxcnt = mp->mnt_maxwritecnt;
+               break;
+       default:
+               segcnt = min(mp->mnt_segreadcnt, mp->mnt_segwritecnt);
+               maxcnt = min(mp->mnt_maxreadcnt, mp->mnt_maxwritecnt);
+               break;
+       }
+       if (segcnt > (MAX_UPL_SIZE_BYTES >> PAGE_SHIFT)) {
+               /*
+                * don't allow a size beyond the max UPL size we can create
+                */
+               segcnt = MAX_UPL_SIZE_BYTES >> PAGE_SHIFT;
+       }
+       max_io_size = min((segcnt * PAGE_SIZE), maxcnt);
 
-               if (timevalcmp(&elapsed, &hard_throttle_maxelapsed, <))
-                       return(1);
+       if (max_io_size < MAX_UPL_TRANSFER_BYTES) {
+               /*
+                * don't allow a size smaller than the old fixed limit
+                */
+               max_io_size = MAX_UPL_TRANSFER_BYTES;
+       } else {
+               /*
+                * make sure the size specified is a multiple of PAGE_SIZE
+                */
+               max_io_size &= ~PAGE_MASK;
        }
-       return(0);
+       return max_io_size;
 }
 
 
-static int
-cluster_iodone(bp)
-       struct buf *bp;
+
+
+#define CLW_ALLOCATE            0x01
+#define CLW_RETURNLOCKED        0x02
+#define CLW_IONOCACHE           0x04
+#define CLW_IOPASSIVE   0x08
+
+/*
+ * if the read ahead context doesn't yet exist,
+ * allocate and initialize it...
+ * the vnode lock serializes multiple callers
+ * during the actual assignment... first one
+ * to grab the lock wins... the other callers
+ * will release the now unnecessary storage
+ *
+ * once the context is present, try to grab (but don't block on)
+ * the lock associated with it... if someone
+ * else currently owns it, than the read
+ * will run without read-ahead.  this allows
+ * multiple readers to run in parallel and
+ * since there's only 1 read ahead context,
+ * there's no real loss in only allowing 1
+ * reader to have read-ahead enabled.
+ */
+static struct cl_readahead *
+cluster_get_rap(vnode_t vp)
 {
-        int         b_flags;
-        int         error;
-       int         total_size;
-       int         total_resid;
-       int         upl_offset;
-       int         zero_offset;
-       upl_t       upl;
-       struct buf *cbp;
-       struct buf *cbp_head;
-       struct buf *cbp_next;
-       struct buf *real_bp;
-       struct vnode *vp;
-       struct clios *iostate;
-       int         commit_size;
-       int         pg_offset;
-
-
-       cbp_head = (struct buf *)(bp->b_trans_head);
+       struct ubc_info         *ubc;
+       struct cl_readahead     *rap;
 
-       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 20)) | DBG_FUNC_START,
-                    (int)cbp_head, bp->b_lblkno, bp->b_bcount, bp->b_flags, 0);
+       ubc = vp->v_ubcinfo;
 
-       for (cbp = cbp_head; cbp; cbp = cbp->b_trans_next) {
-               /*
-                * all I/O requests that are part of this transaction
-                * have to complete before we can process it
-                */
-               if ( !(cbp->b_flags & B_DONE)) {
+       if ((rap = ubc->cl_rahead) == NULL) {
+               rap = zalloc_flags(cl_rd_zone, Z_WAITOK | Z_ZERO);
+               rap->cl_lastr = -1;
+               lck_mtx_init(&rap->cl_lockr, &cl_mtx_grp, LCK_ATTR_NULL);
 
-                       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 20)) | DBG_FUNC_END,
-                                    (int)cbp_head, (int)cbp, cbp->b_bcount, cbp->b_flags, 0);
+               vnode_lock(vp);
 
-                       return 0;
+               if (ubc->cl_rahead == NULL) {
+                       ubc->cl_rahead = rap;
+               } else {
+                       lck_mtx_destroy(&rap->cl_lockr, &cl_mtx_grp);
+                       zfree(cl_rd_zone, rap);
+                       rap = ubc->cl_rahead;
                }
+               vnode_unlock(vp);
+       }
+       if (lck_mtx_try_lock(&rap->cl_lockr) == TRUE) {
+               return rap;
        }
-       error       = 0;
-       total_size  = 0;
-       total_resid = 0;
 
-       cbp        = cbp_head;
-       upl_offset = cbp->b_uploffset;
-       upl        = cbp->b_pagelist;
-       b_flags    = cbp->b_flags;
-       real_bp    = cbp->b_real_bp;
-       vp         = cbp->b_vp;
-       zero_offset= cbp->b_validend;
-       iostate    = (struct clios *)cbp->b_iostate;
+       return (struct cl_readahead *)NULL;
+}
 
-       while (cbp) {
-               if ((cbp->b_flags & B_ERROR) && error == 0)
-                       error = cbp->b_error;
 
-               total_resid += cbp->b_resid;
-               total_size  += cbp->b_bcount;
+/*
+ * if the write behind context doesn't yet exist,
+ * and CLW_ALLOCATE is specified, allocate and initialize it...
+ * the vnode lock serializes multiple callers
+ * during the actual assignment... first one
+ * to grab the lock wins... the other callers
+ * will release the now unnecessary storage
+ *
+ * if CLW_RETURNLOCKED is set, grab (blocking if necessary)
+ * the lock associated with the write behind context before
+ * returning
+ */
 
-               cbp_next = cbp->b_trans_next;
+static struct cl_writebehind *
+cluster_get_wbp(vnode_t vp, int flags)
+{
+       struct ubc_info *ubc;
+       struct cl_writebehind *wbp;
 
-               free_io_buf(cbp);
+       ubc = vp->v_ubcinfo;
 
-               cbp = cbp_next;
-       }
-       if (zero_offset)
-               cluster_zero(upl, zero_offset, PAGE_SIZE - (zero_offset & PAGE_MASK), real_bp);
+       if ((wbp = ubc->cl_wbehind) == NULL) {
+               if (!(flags & CLW_ALLOCATE)) {
+                       return (struct cl_writebehind *)NULL;
+               }
 
-       if ((vp->v_flag & VTHROTTLED) && (vp->v_numoutput <= (ASYNC_THROTTLE / 3))) {
-               vp->v_flag &= ~VTHROTTLED;
-               wakeup((caddr_t)&vp->v_numoutput);
-       }
-       if (iostate) {
-               /*
-                * someone has issued multiple I/Os asynchrounsly
-                * and is waiting for them to complete (streaming)
-                */
-               if (error && iostate->io_error == 0)
-                       iostate->io_error = error;
+               wbp = zalloc_flags(cl_wr_zone, Z_WAITOK | Z_ZERO);
 
-               iostate->io_completed += total_size;
+               lck_mtx_init(&wbp->cl_lockw, &cl_mtx_grp, LCK_ATTR_NULL);
 
-               if (iostate->io_wanted) {
-                       /*
-                        * someone is waiting for the state of
-                        * this io stream to change
-                        */
-                       iostate->io_wanted = 0;
-                       wakeup((caddr_t)&iostate->io_wanted);
+               vnode_lock(vp);
+
+               if (ubc->cl_wbehind == NULL) {
+                       ubc->cl_wbehind = wbp;
+               } else {
+                       lck_mtx_destroy(&wbp->cl_lockw, &cl_mtx_grp);
+                       zfree(cl_wr_zone, wbp);
+                       wbp = ubc->cl_wbehind;
                }
+               vnode_unlock(vp);
        }
-       if ((b_flags & B_NEED_IODONE) && real_bp) {
-               if (error) {
-                       real_bp->b_flags |= B_ERROR;
-                       real_bp->b_error = error;
-               }
-               real_bp->b_resid = total_resid;
-
-               biodone(real_bp);
+       if (flags & CLW_RETURNLOCKED) {
+               lck_mtx_lock(&wbp->cl_lockw);
        }
-       if (error == 0 && total_resid)
-               error = EIO;
 
-       if (b_flags & B_COMMIT_UPL) {
-               pg_offset   = upl_offset & PAGE_MASK;
-               commit_size = (pg_offset + total_size + (PAGE_SIZE - 1)) & ~PAGE_MASK;
-
-               if (error || (b_flags & B_NOCACHE)) {
-                       int upl_abort_code;
-
-                       if ((b_flags & B_PAGEOUT) && (error != ENXIO)) /* transient error */
-                               upl_abort_code = UPL_ABORT_FREE_ON_EMPTY;
-                       else if (b_flags & B_PGIN)
-                               upl_abort_code = UPL_ABORT_FREE_ON_EMPTY | UPL_ABORT_ERROR;
-                       else
-                               upl_abort_code = UPL_ABORT_FREE_ON_EMPTY | UPL_ABORT_DUMP_PAGES;
-
-                       ubc_upl_abort_range(upl, upl_offset - pg_offset, commit_size,
-                                       upl_abort_code);
-                       
-                       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 20)) | DBG_FUNC_END,
-                                    (int)upl, upl_offset - pg_offset, commit_size,
-                                    0x80000000|upl_abort_code, 0);
+       return wbp;
+}
 
-               } else {
-                       int upl_commit_flags = UPL_COMMIT_FREE_ON_EMPTY;
 
-                       if (b_flags & B_PHYS) {
-                               if (b_flags & B_READ)
-                                       upl_commit_flags |= UPL_COMMIT_SET_DIRTY;
-                       } else if ( !(b_flags & B_PAGEOUT))
-                               upl_commit_flags |= UPL_COMMIT_CLEAR_DIRTY;
+static void
+cluster_syncup(vnode_t vp, off_t newEOF, int (*callback)(buf_t, void *), void *callback_arg, int flags)
+{
+       struct cl_writebehind *wbp;
 
-                       if (b_flags & B_AGE)
-                               upl_commit_flags |= UPL_COMMIT_INACTIVATE;
+       if ((wbp = cluster_get_wbp(vp, 0)) != NULL) {
+               if (wbp->cl_number) {
+                       lck_mtx_lock(&wbp->cl_lockw);
 
-                       ubc_upl_commit_range(upl, upl_offset - pg_offset, commit_size,
-                                       upl_commit_flags);
+                       cluster_try_push(wbp, vp, newEOF, PUSH_ALL | flags, 0, callback, callback_arg, NULL, FALSE);
 
-                       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 20)) | DBG_FUNC_END,
-                                    (int)upl, upl_offset - pg_offset, commit_size,
-                                    upl_commit_flags, 0);
+                       lck_mtx_unlock(&wbp->cl_lockw);
                }
-       } else 
-               KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 20)) | DBG_FUNC_END,
-                            (int)upl, upl_offset, 0, error, 0);
-
-       return (error);
+       }
 }
 
 
-static void
-cluster_zero(upl, upl_offset, size, bp)
-       upl_t         upl;
-       vm_offset_t   upl_offset;
-       int           size;
-       struct buf   *bp;
+static int
+cluster_io_present_in_BC(vnode_t vp, off_t f_offset)
 {
-       upl_page_info_t *pl;
+       daddr64_t blkno;
+       size_t    io_size;
+       int (*bootcache_check_fn)(dev_t device, u_int64_t blkno) = bootcache_contains_block;
 
-       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 23)) | DBG_FUNC_START,
-                    upl_offset, size, (int)bp, 0, 0);
+       if (bootcache_check_fn && vp->v_mount && vp->v_mount->mnt_devvp) {
+               if (VNOP_BLOCKMAP(vp, f_offset, PAGE_SIZE, &blkno, &io_size, NULL, VNODE_READ | VNODE_BLOCKMAP_NO_TRACK, NULL)) {
+                       return 0;
+               }
+
+               if (io_size == 0) {
+                       return 0;
+               }
 
-       if (bp == NULL || bp->b_data == NULL) {
+               if (bootcache_check_fn(vp->v_mount->mnt_devvp->v_rdev, blkno)) {
+                       return 1;
+               }
+       }
+       return 0;
+}
 
-               pl = ubc_upl_pageinfo(upl);
 
-               while (size) {
-                       int           page_offset;
-                       int           page_index;
-                       addr64_t      zero_addr;
-                       int           zero_cnt;
+static int
+cluster_is_throttled(vnode_t vp)
+{
+       return throttle_io_will_be_throttled(-1, vp->v_mount);
+}
 
-                       page_index  = upl_offset / PAGE_SIZE;
-                       page_offset = upl_offset & PAGE_MASK;
 
-                       zero_addr = ((addr64_t)upl_phys_page(pl, page_index) << 12) + page_offset;
-                       zero_cnt  = min(PAGE_SIZE - page_offset, size);
+static void
+cluster_iostate_wait(struct clios *iostate, u_int target, const char *wait_name)
+{
+       lck_mtx_lock(&iostate->io_mtxp);
 
-                       bzero_phys(zero_addr, zero_cnt);
+       while ((iostate->io_issued - iostate->io_completed) > target) {
+               KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 95)) | DBG_FUNC_START,
+                   iostate->io_issued, iostate->io_completed, target, 0, 0);
 
-                       size       -= zero_cnt;
-                       upl_offset += zero_cnt;
-               }
-       } else
-               bzero((caddr_t)((vm_offset_t)bp->b_data + upl_offset), size);
+               iostate->io_wanted = 1;
+               msleep((caddr_t)&iostate->io_wanted, &iostate->io_mtxp, PRIBIO + 1, wait_name, NULL);
 
-       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 23)) | DBG_FUNC_END,
-                    upl_offset, size, 0, 0, 0);
+               KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 95)) | DBG_FUNC_END,
+                   iostate->io_issued, iostate->io_completed, target, 0, 0);
+       }
+       lck_mtx_unlock(&iostate->io_mtxp);
 }
 
-static int
-cluster_io(vp, upl, upl_offset, f_offset, non_rounded_size, devblocksize, flags, real_bp, iostate)
-       struct vnode *vp;
-       upl_t         upl;
-       vm_offset_t   upl_offset;
-       off_t         f_offset;
-       int           non_rounded_size;
-       int           devblocksize;
-       int           flags;
-       struct buf   *real_bp;
-       struct clios *iostate;
+static void
+cluster_handle_associated_upl(struct clios *iostate, upl_t upl,
+    upl_offset_t upl_offset, upl_size_t size)
 {
-       struct buf   *cbp;
-       u_int         size;
-       u_int         io_size;
-       int           io_flags;
-       int           error = 0;
-       int           retval = 0;
-       struct buf   *cbp_head = 0;
-       struct buf   *cbp_tail = 0;
-       int buf_count = 0;
-       int pg_count;
-       int pg_offset;
-       u_int max_iosize;
-       u_int max_vectors;
-       int priv;
-       int zero_offset = 0;
-       int async_throttle;
-
-       if (devblocksize)
-               size = (non_rounded_size + (devblocksize - 1)) & ~(devblocksize - 1);
-       else
-               size = non_rounded_size;
-
-       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 22)) | DBG_FUNC_START,
-                    (int)f_offset, size, upl_offset, flags, 0);
+       if (!size) {
+               return;
+       }
 
+       upl_t associated_upl = upl_associated_upl(upl);
 
-       if (flags & CL_READ) {
-               io_flags = (B_VECTORLIST | B_READ);
+       if (!associated_upl) {
+               return;
+       }
 
-               vfs_io_attributes(vp, B_READ, &max_iosize, &max_vectors);
-       } else {
-               io_flags = (B_VECTORLIST | B_WRITEINPROG);
+#if 0
+       printf("1: %d %d\n", upl_offset, upl_offset + size);
+#endif
 
-               vfs_io_attributes(vp, B_WRITE, &max_iosize, &max_vectors);
-       }
        /*
-        * make sure the maximum iosize are at least the size of a page
-        * and that they are multiples of the page size
+        * The associated UPL is page aligned to file offsets whereas the
+        * UPL it's attached to has different alignment requirements.  The
+        * upl_offset that we have refers to @upl.  The code that follows
+        * has to deal with the first and last pages in this transaction
+        * which might straddle pages in the associated UPL.  To keep
+        * track of these pages, we use the mark bits: if the mark bit is
+        * set, we know another transaction has completed its part of that
+        * page and so we can unlock that page here.
+        *
+        * The following illustrates what we have to deal with:
+        *
+        *    MEM u <------------ 1 PAGE ------------> e
+        *        +-------------+----------------------+-----------------
+        *        |             |######################|#################
+        *        +-------------+----------------------+-----------------
+        *   FILE | <--- a ---> o <------------ 1 PAGE ------------>
+        *
+        * So here we show a write to offset @o.  The data that is to be
+        * written is in a buffer that is not page aligned; it has offset
+        * @a in the page.  The upl that carries the data starts in memory
+        * at @u.  The associated upl starts in the file at offset @o.  A
+        * transaction will always end on a page boundary (like @e above)
+        * except for the very last transaction in the group.  We cannot
+        * unlock the page at @o in the associated upl until both the
+        * transaction ending at @e and the following transaction (that
+        * starts at @e) has completed.
         */
-       max_iosize  &= ~PAGE_MASK;
 
-       if (flags & CL_THROTTLE) {
-               if ( !(flags & CL_PAGEOUT) && cluster_hard_throttle_on(vp)) {
-                       if (max_iosize > HARD_THROTTLE_MAXSIZE)
-                               max_iosize = HARD_THROTTLE_MAXSIZE;
-                       async_throttle = HARD_THROTTLE_MAXCNT;
-               } else
-                       async_throttle = ASYNC_THROTTLE;
-       }
-       if (flags & CL_AGE)
-               io_flags |= B_AGE;
-       if (flags & CL_DUMP)
-               io_flags |= B_NOCACHE;
-       if (flags & CL_PAGEIN)
-               io_flags |= B_PGIN;
-       if (flags & CL_PAGEOUT)
-               io_flags |= B_PAGEOUT;
-       if (flags & CL_COMMIT)
-               io_flags |= B_COMMIT_UPL;
-       if (flags & CL_PRESERVE)
-               io_flags |= B_PHYS;
+       /*
+        * We record whether or not the two UPLs are aligned as the mark
+        * bit in the first page of @upl.
+        */
+       upl_page_info_t *pl = UPL_GET_INTERNAL_PAGE_LIST(upl);
+       bool is_unaligned = upl_page_get_mark(pl, 0);
 
-       if ((flags & CL_READ) && ((upl_offset + non_rounded_size) & PAGE_MASK) && (!(flags & CL_NOZERO))) {
-               /*
-                * then we are going to end up
-                * with a page that we can't complete (the file size wasn't a multiple
-                * of PAGE_SIZE and we're trying to read to the end of the file
-                * so we'll go ahead and zero out the portion of the page we can't
-                * read in from the file
+       if (is_unaligned) {
+               upl_page_info_t *assoc_pl = UPL_GET_INTERNAL_PAGE_LIST(associated_upl);
+
+               upl_offset_t upl_end = upl_offset + size;
+               assert(upl_end >= PAGE_SIZE);
+
+               upl_size_t assoc_upl_size = upl_get_size(associated_upl);
+
+               /*
+                * In the very first transaction in the group, upl_offset will
+                * not be page aligned, but after that it will be and in that
+                * case we want the preceding page in the associated UPL hence
+                * the minus one.
                 */
-               zero_offset = upl_offset + non_rounded_size;
-       }
-       while (size) {
-               int vsize;
-               int i;
-               int pg_resid;
-               int num_contig;
-               daddr_t lblkno;
-               daddr_t blkno;
-
-               if (size > max_iosize)
-                       io_size = max_iosize;
-               else
-                       io_size = size;
-
-               if (error = VOP_CMAP(vp, f_offset, io_size, &blkno, (size_t *)&io_size, NULL)) {
-                       if (error == EOPNOTSUPP)
-                               panic("VOP_CMAP Unimplemented");
-                       break;
+               assert(upl_offset);
+               if (upl_offset) {
+                       upl_offset = trunc_page_32(upl_offset - 1);
                }
 
-               KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 24)) | DBG_FUNC_NONE,
-                            (int)f_offset, (int)blkno, io_size, zero_offset, 0);
+               lck_mtx_lock_spin(&iostate->io_mtxp);
 
-               if ( (!(flags & CL_READ) && (long)blkno == -1) || io_size == 0) {
-                       if (flags & CL_PAGEOUT) {
-                               error = EINVAL;
-                               break;
-                       };
-                       
-                       /* Try paging out the page individually before
-                          giving up entirely and dumping it (it could
-                          be mapped in a "hole" and require allocation
-                          before the I/O:
+               // Look at the first page...
+               if (upl_offset
+                   && !upl_page_get_mark(assoc_pl, upl_offset >> PAGE_SHIFT)) {
+                       /*
+                        * The first page isn't marked so let another transaction
+                        * completion handle it.
                         */
-                        ubc_upl_abort_range(upl, upl_offset, PAGE_SIZE, UPL_ABORT_FREE_ON_EMPTY);
-                        if (ubc_pushdirty_range(vp, f_offset, PAGE_SIZE_64) == 0) {
-                               error = EINVAL;
-                               break;
-                        };
-                        
-                       f_offset   += PAGE_SIZE_64;
+                       upl_page_set_mark(assoc_pl, upl_offset >> PAGE_SHIFT, true);
                        upl_offset += PAGE_SIZE;
-                       size       -= PAGE_SIZE;
-                       continue;
                }
-               lblkno = (daddr_t)(f_offset / PAGE_SIZE_64);
+
+               // And now the last page...
+
                /*
-                * we have now figured out how much I/O we can do - this is in 'io_size'
-                * pg_offset is the starting point in the first page for the I/O
-                * pg_count is the number of full and partial pages that 'io_size' encompasses
+                * This needs to be > rather than >= because if it's equal, it
+                * means there's another transaction that is sharing the last
+                * page.
                 */
-               pg_offset = upl_offset & PAGE_MASK;
+               if (upl_end > assoc_upl_size) {
+                       upl_end = assoc_upl_size;
+               } else {
+                       upl_end = trunc_page_32(upl_end);
+                       const int last_pg = (upl_end >> PAGE_SHIFT) - 1;
 
-               if (flags & CL_DEV_MEMORY) {
-                       /*
-                        * currently, can't deal with reading 'holes' in file
-                        */
-                       if ((long)blkno == -1) {
-                               error = EINVAL;
-                               break;
+                       if (!upl_page_get_mark(assoc_pl, last_pg)) {
+                               /*
+                                * The last page isn't marked so mark the page and let another
+                                * transaction completion handle it.
+                                */
+                               upl_page_set_mark(assoc_pl, last_pg, true);
+                               upl_end -= PAGE_SIZE;
                        }
-                       /*
-                        * treat physical requests as one 'giant' page
-                        */
-                       pg_count = 1;
-               } else
-                       pg_count  = (io_size + pg_offset + (PAGE_SIZE - 1)) / PAGE_SIZE;
+               }
 
-               if ((flags & CL_READ) && (long)blkno == -1) {
-                       int bytes_to_zero;
+               lck_mtx_unlock(&iostate->io_mtxp);
 
-                       /*
-                        * if we're reading and blkno == -1, then we've got a
-                        * 'hole' in the file that we need to deal with by zeroing
-                        * out the affected area in the upl
-                        */
-                       if (zero_offset && io_size == size) {
-                               /*
-                                * if this upl contains the EOF and it is not a multiple of PAGE_SIZE
-                                * than 'zero_offset' will be non-zero
-                                * if the 'hole' returned by VOP_CMAP extends all the way to the eof
-                                * (indicated by the io_size finishing off the I/O request for this UPL)
-                                * than we're not going to issue an I/O for the
-                                * last page in this upl... we need to zero both the hole and the tail
-                                * of the page beyond the EOF, since the delayed zero-fill won't kick in 
-                                */
-                               bytes_to_zero = (((upl_offset + io_size) + (PAGE_SIZE - 1)) & ~PAGE_MASK) - upl_offset;
+#if 0
+               printf("2: %d %d\n", upl_offset, upl_end);
+#endif
 
-                               zero_offset = 0;
-                       } else
-                               bytes_to_zero = io_size;
+               if (upl_end <= upl_offset) {
+                       return;
+               }
 
-                       cluster_zero(upl, upl_offset, bytes_to_zero, real_bp);
-                         
-                       if (cbp_head)
-                               /*
-                                * if there is a current I/O chain pending
-                                * then the first page of the group we just zero'd
-                                * will be handled by the I/O completion if the zero
-                                * fill started in the middle of the page
-                                */
-                               pg_count = (io_size - pg_offset) / PAGE_SIZE;
-                       else {
-                               /*
-                                * no pending I/O to pick up that first page
-                                * so, we have to make sure it gets committed
-                                * here.
-                                * set the pg_offset to 0 so that the upl_commit_range
-                                * starts with this page
-                                */
-                               pg_count = (io_size + pg_offset) / PAGE_SIZE;
-                               pg_offset = 0;
-                       }
-                       if (io_size == size && ((upl_offset + io_size) & PAGE_MASK))
-                               /*
-                                * if we're done with the request for this UPL
-                                * then we have to make sure to commit the last page
-                                * even if we only partially zero-filled it
-                                */
-                               pg_count++;
+               size = upl_end - upl_offset;
+       } else {
+               assert(!(upl_offset & PAGE_MASK));
+               assert(!(size & PAGE_MASK));
+       }
 
-                       if (pg_count) {
-                               if (pg_offset)
-                                       pg_resid = PAGE_SIZE - pg_offset;
-                               else
-                                       pg_resid = 0;
+       boolean_t empty;
 
-                               if (flags & CL_COMMIT)
-                                       ubc_upl_commit_range(upl,
-                                                       (upl_offset + pg_resid) & ~PAGE_MASK, 
-                                                       pg_count * PAGE_SIZE,
-                                                       UPL_COMMIT_CLEAR_DIRTY | UPL_COMMIT_FREE_ON_EMPTY);
-                       }
-                       upl_offset += io_size;
-                       f_offset   += io_size;
-                       size       -= io_size;
+       /*
+        * We can unlock these pages now and as this is for a
+        * direct/uncached write, we want to dump the pages too.
+        */
+       kern_return_t kr = upl_abort_range(associated_upl, upl_offset, size,
+           UPL_ABORT_DUMP_PAGES, &empty);
 
-                       if (cbp_head && pg_count) 
-                               goto start_io;
-                       continue;
+       assert(!kr);
 
-               } else if (real_bp && (real_bp->b_blkno == real_bp->b_lblkno)) {
-                       real_bp->b_blkno = blkno;
-               }
+       if (!kr && empty) {
+               upl_set_associated_upl(upl, NULL);
+               upl_deallocate(associated_upl);
+       }
+}
 
-               if (pg_count > max_vectors) {
-                       io_size -= (pg_count - max_vectors) * PAGE_SIZE;
+static int
+cluster_ioerror(upl_t upl, int upl_offset, int abort_size, int error, int io_flags, vnode_t vp)
+{
+       int upl_abort_code = 0;
+       int page_in  = 0;
+       int page_out = 0;
 
-                       if (io_size < 0) {
-                               io_size = PAGE_SIZE - pg_offset;
-                               pg_count = 1;
-                       } else
-                               pg_count = max_vectors;
+       if ((io_flags & (B_PHYS | B_CACHE)) == (B_PHYS | B_CACHE)) {
+               /*
+                * direct write of any flavor, or a direct read that wasn't aligned
+                */
+               ubc_upl_commit_range(upl, upl_offset, abort_size, UPL_COMMIT_FREE_ON_EMPTY);
+       } else {
+               if (io_flags & B_PAGEIO) {
+                       if (io_flags & B_READ) {
+                               page_in  = 1;
+                       } else {
+                               page_out = 1;
+                       }
                }
-
-               if ( !(vp->v_mount->mnt_kern_flag & MNTK_VIRTUALDEV))
-                       /*
-                        * if we're not targeting a virtual device i.e. a disk image
-                        * it's safe to dip into the reserve pool since real devices
-                        * can complete this I/O request without requiring additional
-                        * bufs from the alloc_io_buf pool
+               if (io_flags & B_CACHE) {
+                       /*
+                        * leave pages in the cache unchanged on error
                         */
-                       priv = 1;
-               else if ((flags & CL_ASYNC) && !(flags & CL_PAGEOUT))
-                       /*
-                        * Throttle the speculative IO
+                       upl_abort_code = UPL_ABORT_FREE_ON_EMPTY;
+               } else if (((io_flags & B_READ) == 0) && ((error != ENXIO) || vnode_isswap(vp))) {
+                       /*
+                        * transient error on pageout/write path... leave pages unchanged
                         */
-                       priv = 0;
-               else
-                       priv = 1;
+                       upl_abort_code = UPL_ABORT_FREE_ON_EMPTY;
+               } else if (page_in) {
+                       upl_abort_code = UPL_ABORT_FREE_ON_EMPTY | UPL_ABORT_ERROR;
+               } else {
+                       upl_abort_code = UPL_ABORT_FREE_ON_EMPTY | UPL_ABORT_DUMP_PAGES;
+               }
 
-               cbp = alloc_io_buf(vp, priv);
+               ubc_upl_abort_range(upl, upl_offset, abort_size, upl_abort_code);
+       }
+       return upl_abort_code;
+}
 
 
-               if (flags & CL_PAGEOUT) {
-                       for (i = 0; i < pg_count; i++) {
-                               int         s;
-                               struct buf *bp;
-
-                               s = splbio();
-                               if (bp = incore(vp, lblkno + i)) {
-                                       if (!ISSET(bp->b_flags, B_BUSY)) {
-                                               bremfree(bp);
-                                               SET(bp->b_flags, (B_BUSY | B_INVAL));
-                                               splx(s);
-                                               brelse(bp);
-                                       } else
-                                               panic("BUSY bp found in cluster_io");
-                               }
-                               splx(s);
-                       }
-               }
-               if (flags & CL_ASYNC) {
-                       cbp->b_flags |= (B_CALL | B_ASYNC);
-                       cbp->b_iodone = (void *)cluster_iodone;
-               }
-               cbp->b_flags |= io_flags;
+static int
+cluster_iodone(buf_t bp, void *callback_arg)
+{
+       int     b_flags;
+       int     error;
+       int     total_size;
+       int     total_resid;
+       int     upl_offset;
+       int     zero_offset;
+       int     pg_offset = 0;
+       int     commit_size = 0;
+       int     upl_flags = 0;
+       int     transaction_size = 0;
+       upl_t   upl;
+       buf_t   cbp;
+       buf_t   cbp_head;
+       buf_t   cbp_next;
+       buf_t   real_bp;
+       vnode_t vp;
+       struct  clios *iostate;
+       boolean_t       transaction_complete = FALSE;
+
+       __IGNORE_WCASTALIGN(cbp_head = (buf_t)(bp->b_trans_head));
 
-               cbp->b_lblkno = lblkno;
-               cbp->b_blkno  = blkno;
-               cbp->b_bcount = io_size;
-               cbp->b_pagelist  = upl;
-               cbp->b_uploffset = upl_offset;
-               cbp->b_trans_next = (struct buf *)0;
+       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 20)) | DBG_FUNC_START,
+           cbp_head, bp->b_lblkno, bp->b_bcount, bp->b_flags, 0);
 
-               if (cbp->b_iostate = (void *)iostate)
-                       /*
-                        * caller wants to track the state of this
-                        * io... bump the amount issued against this stream
-                        */
-                       iostate->io_issued += io_size;
+       if (cbp_head->b_trans_next || !(cbp_head->b_flags & B_EOT)) {
+               lck_mtx_lock_spin(&cl_transaction_mtxp);
 
-               if (flags & CL_READ)
-                       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 26)) | DBG_FUNC_NONE,
-                                    cbp->b_lblkno, cbp->b_blkno, upl_offset, io_size, 0);
-               else
-                       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 27)) | DBG_FUNC_NONE,
-                                    cbp->b_lblkno, cbp->b_blkno, upl_offset, io_size, 0);
+               bp->b_flags |= B_TDONE;
 
-               if (cbp_head) {
-                       cbp_tail->b_trans_next = cbp;
-                       cbp_tail = cbp;
-               } else {
-                       cbp_head = cbp;
-                       cbp_tail = cbp;
-               }
-               (struct buf *)(cbp->b_trans_head) = cbp_head;
-               buf_count++;
+               for (cbp = cbp_head; cbp; cbp = cbp->b_trans_next) {
+                       /*
+                        * all I/O requests that are part of this transaction
+                        * have to complete before we can process it
+                        */
+                       if (!(cbp->b_flags & B_TDONE)) {
+                               KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 20)) | DBG_FUNC_END,
+                                   cbp_head, cbp, cbp->b_bcount, cbp->b_flags, 0);
 
-               upl_offset += io_size;
-               f_offset   += io_size;
-               size       -= io_size;
+                               lck_mtx_unlock(&cl_transaction_mtxp);
 
-               if ( (!(upl_offset & PAGE_MASK) && !(flags & CL_DEV_MEMORY) && ((flags & CL_ASYNC) || buf_count > 8)) || size == 0) {
-                       /*
-                        * if we have no more I/O to issue or
-                        * the current I/O we've prepared fully
-                        * completes the last page in this request
-                        * and it's either an ASYNC request or 
-                        * we've already accumulated more than 8 I/O's into
-                        * this transaction and it's not an I/O directed to 
-                        * special DEVICE memory
-                        * then go ahead and issue the I/O
-                        */
-start_io:              
-                       if (real_bp) {
-                               cbp_head->b_flags |= B_NEED_IODONE;
-                               cbp_head->b_real_bp = real_bp;
-                       } else
-                               cbp_head->b_real_bp = (struct buf *)NULL;
-
-                       if (size == 0) {
-                               /*
-                                * we're about to issue the last I/O for this upl
-                                * if this was a read to the eof and the eof doesn't
-                                * finish on a page boundary, than we need to zero-fill
-                                * the rest of the page....
-                                */
-                               cbp_head->b_validend = zero_offset;
-                       } else
-                               cbp_head->b_validend = 0;
-                         
-                       if (flags & CL_THROTTLE) {
-                               while (vp->v_numoutput >= async_throttle) {
-                                       vp->v_flag |= VTHROTTLED;
-                                       tsleep((caddr_t)&vp->v_numoutput, PRIBIO + 1, "cluster_io", 0);
-                               }
+                               return 0;
                        }
-                       for (cbp = cbp_head; cbp;) {
-                               struct buf * cbp_next;
 
-                               if (io_flags & B_WRITEINPROG)
-                                       cbp->b_vp->v_numoutput++;
+                       if (cbp->b_trans_next == CLUSTER_IO_WAITING) {
+                               KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 20)) | DBG_FUNC_END,
+                                   cbp_head, cbp, cbp->b_bcount, cbp->b_flags, 0);
+
+                               lck_mtx_unlock(&cl_transaction_mtxp);
+                               wakeup(cbp);
 
-                               cbp_next = cbp->b_trans_next;
-                               
-                               (void) VOP_STRATEGY(cbp);
-                               cbp = cbp_next;
+                               return 0;
                        }
-                       if ( !(flags & CL_ASYNC)) {
-                               for (cbp = cbp_head; cbp; cbp = cbp->b_trans_next)
-                                       biowait(cbp);
 
-                               if (error = cluster_iodone(cbp_head)) {
-                                       if ((flags & CL_PAGEOUT) && (error == ENXIO))
-                                               retval = 0;     /* drop the error */
-                                       else
-                                               retval = error;
-                                       error  = 0;
-                               }
+                       if (cbp->b_flags & B_EOT) {
+                               transaction_complete = TRUE;
                        }
-                       cbp_head = (struct buf *)0;
-                       cbp_tail = (struct buf *)0;
+               }
+               lck_mtx_unlock(&cl_transaction_mtxp);
 
-                       buf_count = 0;
+               if (transaction_complete == FALSE) {
+                       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 20)) | DBG_FUNC_END,
+                           cbp_head, 0, 0, 0, 0);
+                       return 0;
                }
        }
-       if (error) {
-               int abort_size;
+       error       = 0;
+       total_size  = 0;
+       total_resid = 0;
 
-               io_size = 0;
-               
-               for (cbp = cbp_head; cbp;) {
-                       struct buf * cbp_next;
-                       upl_offset -= cbp->b_bcount;
-                       size       += cbp->b_bcount;
-                       io_size    += cbp->b_bcount;
+       cbp        = cbp_head;
+       vp         = cbp->b_vp;
+       upl_offset = cbp->b_uploffset;
+       upl        = cbp->b_upl;
+       b_flags    = cbp->b_flags;
+       real_bp    = cbp->b_real_bp;
+       zero_offset = cbp->b_validend;
+       iostate    = (struct clios *)cbp->b_iostate;
 
-                       cbp_next = cbp->b_trans_next;
-                       free_io_buf(cbp);
-                       cbp = cbp_next;
-               }
-               if (iostate) {
-                       /*
-                        * update the error condition for this stream
-                        * since we never really issued the io
-                        * just go ahead and adjust it back
-                        */
-                       if (iostate->io_error == 0)
-                               iostate->io_error = error;
-                       iostate->io_issued -= io_size;
+       if (real_bp) {
+               real_bp->b_dev = cbp->b_dev;
+       }
 
-                       if (iostate->io_wanted) {
-                               /*
-                                * someone is waiting for the state of
-                                * this io stream to change
-                                */
-                               iostate->io_wanted = 0;
-                               wakeup((caddr_t)&iostate->io_wanted);
-                       }
+       while (cbp) {
+               if ((cbp->b_flags & B_ERROR) && error == 0) {
+                       error = cbp->b_error;
                }
-               pg_offset  = upl_offset & PAGE_MASK;
-               abort_size = (size + pg_offset + (PAGE_SIZE - 1)) & ~PAGE_MASK;
 
-               if (flags & CL_COMMIT) {
-                       int upl_abort_code;
+               total_resid += cbp->b_resid;
+               total_size  += cbp->b_bcount;
 
-                       if (flags & CL_PRESERVE) {
-                               ubc_upl_commit_range(upl, upl_offset - pg_offset, abort_size,
-                                                    UPL_COMMIT_FREE_ON_EMPTY);
-                       } else {
-                               if ((flags & CL_PAGEOUT) && (error != ENXIO)) /* transient error */
-                                       upl_abort_code = UPL_ABORT_FREE_ON_EMPTY;
-                               else if (flags & CL_PAGEIN)
-                                       upl_abort_code = UPL_ABORT_FREE_ON_EMPTY | UPL_ABORT_ERROR;
-                               else
-                                       upl_abort_code = UPL_ABORT_FREE_ON_EMPTY | UPL_ABORT_DUMP_PAGES;
+               cbp_next = cbp->b_trans_next;
 
-                               ubc_upl_abort_range(upl, upl_offset - pg_offset, abort_size,
-                                               upl_abort_code);
-                       }
-                       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 28)) | DBG_FUNC_NONE,
-                                    (int)upl, upl_offset - pg_offset, abort_size, error, 0);
+               if (cbp_next == NULL) {
+                       /*
+                        * compute the overall size of the transaction
+                        * in case we created one that has 'holes' in it
+                        * 'total_size' represents the amount of I/O we
+                        * did, not the span of the transaction w/r to the UPL
+                        */
+                       transaction_size = cbp->b_uploffset + cbp->b_bcount - upl_offset;
                }
-               if (real_bp) {
-                       real_bp->b_flags |= B_ERROR;
-                       real_bp->b_error  = error;
 
-                       biodone(real_bp);
+               if (cbp != cbp_head) {
+                       free_io_buf(cbp);
                }
-               if (retval == 0)
-                       retval = error;
+
+               cbp = cbp_next;
        }
-       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 22)) | DBG_FUNC_END,
-                    (int)f_offset, size, upl_offset, retval, 0);
 
-       return (retval);
-}
+       if (ISSET(b_flags, B_COMMIT_UPL)) {
+               cluster_handle_associated_upl(iostate,
+                   cbp_head->b_upl,
+                   upl_offset,
+                   transaction_size);
+       }
 
+       if (error == 0 && total_resid) {
+               error = EIO;
+       }
 
-static int
-cluster_rd_prefetch(vp, f_offset, size, filesize, devblocksize)
-       struct vnode *vp;
-       off_t         f_offset;
-       u_int         size;
-       off_t         filesize;
-       int           devblocksize;
-{
-       int           pages_in_prefetch;
+       if (error == 0) {
+               int     (*cliodone_func)(buf_t, void *) = (int (*)(buf_t, void *))(cbp_head->b_cliodone);
 
-       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 49)) | DBG_FUNC_START,
-                    (int)f_offset, size, (int)filesize, 0, 0);
+               if (cliodone_func != NULL) {
+                       cbp_head->b_bcount = transaction_size;
 
-       if (f_offset >= filesize) {
-               KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 49)) | DBG_FUNC_END,
-                            (int)f_offset, 0, 0, 0, 0);
-               return(0);
+                       error = (*cliodone_func)(cbp_head, callback_arg);
+               }
+       }
+       if (zero_offset) {
+               cluster_zero(upl, zero_offset, PAGE_SIZE - (zero_offset & PAGE_MASK), real_bp);
        }
-       if (size > (MAX_UPL_TRANSFER * PAGE_SIZE))
-               size = (MAX_UPL_TRANSFER * PAGE_SIZE);
-       else
-               size = (size + (PAGE_SIZE - 1)) & ~PAGE_MASK;
 
-        if ((off_t)size > (filesize - f_offset))
-                size = filesize - f_offset;
-       pages_in_prefetch = (size + (PAGE_SIZE - 1)) / PAGE_SIZE;
+       free_io_buf(cbp_head);
 
-       advisory_read(vp, filesize, f_offset, size, devblocksize);
+       if (iostate) {
+               int need_wakeup = 0;
 
-       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 49)) | DBG_FUNC_END,
-                    (int)f_offset + size, pages_in_prefetch, 0, 1, 0);
+               /*
+                * someone has issued multiple I/Os asynchrounsly
+                * and is waiting for them to complete (streaming)
+                */
+               lck_mtx_lock_spin(&iostate->io_mtxp);
 
-       return (pages_in_prefetch);
-}
+               if (error && iostate->io_error == 0) {
+                       iostate->io_error = error;
+               }
+
+               iostate->io_completed += total_size;
 
+               if (iostate->io_wanted) {
+                       /*
+                        * someone is waiting for the state of
+                        * this io stream to change
+                        */
+                       iostate->io_wanted = 0;
+                       need_wakeup = 1;
+               }
+               lck_mtx_unlock(&iostate->io_mtxp);
 
+               if (need_wakeup) {
+                       wakeup((caddr_t)&iostate->io_wanted);
+               }
+       }
 
-static void
-cluster_rd_ahead(vp, b_lblkno, e_lblkno, filesize, devblocksize)
-       struct vnode *vp;
-       daddr_t       b_lblkno;
-       daddr_t       e_lblkno;
-       off_t         filesize;
-       int           devblocksize;
-{
-       daddr_t       r_lblkno;
-       off_t         f_offset;
-       int           size_of_prefetch;
+       if (b_flags & B_COMMIT_UPL) {
+               pg_offset   = upl_offset & PAGE_MASK;
+               commit_size = (pg_offset + transaction_size + (PAGE_SIZE - 1)) & ~PAGE_MASK;
 
-       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 48)) | DBG_FUNC_START,
-                    b_lblkno, e_lblkno, vp->v_lastr, 0, 0);
+               if (error) {
+                       upl_set_iodone_error(upl, error);
 
-       if (b_lblkno == vp->v_lastr && b_lblkno == e_lblkno) {
-               KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 48)) | DBG_FUNC_END,
-                            vp->v_ralen, vp->v_maxra, vp->v_lastr, 0, 0);
-               return;
-       }
-       if (vp->v_lastr == -1 || (b_lblkno != vp->v_lastr && b_lblkno != (vp->v_lastr + 1) &&
-                                (b_lblkno != (vp->v_maxra + 1) || vp->v_ralen == 0))) {
-               vp->v_ralen = 0;
-               vp->v_maxra = 0;
+                       upl_flags = cluster_ioerror(upl, upl_offset - pg_offset, commit_size, error, b_flags, vp);
+               } else {
+                       upl_flags = UPL_COMMIT_FREE_ON_EMPTY;
 
-               KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 48)) | DBG_FUNC_END,
-                            vp->v_ralen, vp->v_maxra, vp->v_lastr, 1, 0);
+                       if ((b_flags & B_PHYS) && (b_flags & B_READ)) {
+                               upl_flags |= UPL_COMMIT_SET_DIRTY;
+                       }
 
-               return;
-       }
-       if (e_lblkno < vp->v_maxra) {
-               if ((vp->v_maxra - e_lblkno) > (MAX_UPL_TRANSFER / 4)) {
+                       if (b_flags & B_AGE) {
+                               upl_flags |= UPL_COMMIT_INACTIVATE;
+                       }
 
-                       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 48)) | DBG_FUNC_END,
-                                    vp->v_ralen, vp->v_maxra, vp->v_lastr, 2, 0);
-                       return;
+                       ubc_upl_commit_range(upl, upl_offset - pg_offset, commit_size, upl_flags);
                }
        }
-       r_lblkno = max(e_lblkno, vp->v_maxra) + 1;
-       f_offset = (off_t)r_lblkno * PAGE_SIZE_64;
+       if (real_bp) {
+               if (error) {
+                       real_bp->b_flags |= B_ERROR;
+                       real_bp->b_error = error;
+               }
+               real_bp->b_resid = total_resid;
 
-        size_of_prefetch = 0;
+               buf_biodone(real_bp);
+       }
+       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 20)) | DBG_FUNC_END,
+           upl, upl_offset - pg_offset, commit_size, (error << 24) | upl_flags, 0);
 
-       ubc_range_op(vp, f_offset, f_offset + PAGE_SIZE_64, UPL_ROP_PRESENT, &size_of_prefetch);
+       return error;
+}
 
-       if (size_of_prefetch) {
-               KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 48)) | DBG_FUNC_END,
-                            vp->v_ralen, vp->v_maxra, vp->v_lastr, 3, 0);
-               return;
+
+uint32_t
+cluster_throttle_io_limit(vnode_t vp, uint32_t *limit)
+{
+       if (cluster_is_throttled(vp)) {
+               *limit = THROTTLE_MAX_IOSIZE;
+               return 1;
        }
-       if (f_offset < filesize) {
-               vp->v_ralen = vp->v_ralen ? min(MAX_UPL_TRANSFER, vp->v_ralen << 1) : 1;
+       return 0;
+}
+
+
+void
+cluster_zero(upl_t upl, upl_offset_t upl_offset, int size, buf_t bp)
+{
+       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 23)) | DBG_FUNC_START,
+           upl_offset, size, bp, 0, 0);
 
-               if (((e_lblkno + 1) - b_lblkno) > vp->v_ralen)
-                       vp->v_ralen = min(MAX_UPL_TRANSFER, (e_lblkno + 1) - b_lblkno);
+       if (bp == NULL || bp->b_datap == 0) {
+               upl_page_info_t *pl;
+               addr64_t        zero_addr;
 
-               size_of_prefetch = cluster_rd_prefetch(vp, f_offset, vp->v_ralen * PAGE_SIZE, filesize, devblocksize);
+               pl = ubc_upl_pageinfo(upl);
 
-               if (size_of_prefetch)
-                       vp->v_maxra = (r_lblkno + size_of_prefetch) - 1;
+               if (upl_device_page(pl) == TRUE) {
+                       zero_addr = ((addr64_t)upl_phys_page(pl, 0) << PAGE_SHIFT) + upl_offset;
+
+                       bzero_phys_nc(zero_addr, size);
+               } else {
+                       while (size) {
+                               int     page_offset;
+                               int     page_index;
+                               int     zero_cnt;
+
+                               page_index  = upl_offset / PAGE_SIZE;
+                               page_offset = upl_offset & PAGE_MASK;
+
+                               zero_addr = ((addr64_t)upl_phys_page(pl, page_index) << PAGE_SHIFT) + page_offset;
+                               zero_cnt  = min(PAGE_SIZE - page_offset, size);
+
+                               bzero_phys(zero_addr, zero_cnt);
+
+                               size       -= zero_cnt;
+                               upl_offset += zero_cnt;
+                       }
+               }
+       } else {
+               bzero((caddr_t)((vm_offset_t)bp->b_datap + upl_offset), size);
        }
-       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 48)) | DBG_FUNC_END,
-                    vp->v_ralen, vp->v_maxra, vp->v_lastr, 4, 0);
+
+       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 23)) | DBG_FUNC_END,
+           upl_offset, size, 0, 0, 0);
 }
 
-int
-cluster_pageout(vp, upl, upl_offset, f_offset, size, filesize, devblocksize, flags)
-       struct vnode *vp;
-       upl_t         upl;
-       vm_offset_t   upl_offset;
-       off_t         f_offset;
-       int           size;
-       off_t         filesize;
-       int           devblocksize;
-       int           flags;
+
+static void
+cluster_EOT(buf_t cbp_head, buf_t cbp_tail, int zero_offset)
 {
-       int           io_size;
-       int           rounded_size;
-        off_t         max_size;
-       int           local_flags;
+       cbp_head->b_validend = zero_offset;
+       cbp_tail->b_flags |= B_EOT;
+}
+
+static void
+cluster_wait_IO(buf_t cbp_head, int async)
+{
+       buf_t   cbp;
 
-       if (vp->v_mount->mnt_kern_flag & MNTK_VIRTUALDEV)
-               /*
-                * if we know we're issuing this I/O to a virtual device (i.e. disk image)
-                * then we don't want to enforce this throttle... if we do, we can 
-                * potentially deadlock since we're stalling the pageout thread at a time
-                * when the disk image might need additional memory (which won't be available
-                * if the pageout thread can't run)... instead we'll just depend on the throttle
-                * that the pageout thread now has in place to deal with external files
+       if (async) {
+               /*
+                * Async callback completion will not normally generate a
+                * wakeup upon I/O completion.  To get woken up, we set
+                * b_trans_next (which is safe for us to modify) on the last
+                * buffer to CLUSTER_IO_WAITING so that cluster_iodone knows
+                * to wake us up when all buffers as part of this transaction
+                * are completed.  This is done under the umbrella of
+                * cl_transaction_mtxp which is also taken in cluster_iodone.
                 */
-               local_flags = CL_PAGEOUT;
-       else
-               local_flags = CL_PAGEOUT | CL_THROTTLE;
+               bool done = true;
+               buf_t last = NULL;
 
-       if ((flags & UPL_IOSYNC) == 0) 
-               local_flags |= CL_ASYNC;
-       if ((flags & UPL_NOCOMMIT) == 0) 
-               local_flags |= CL_COMMIT;
+               lck_mtx_lock_spin(&cl_transaction_mtxp);
 
+               for (cbp = cbp_head; cbp; last = cbp, cbp = cbp->b_trans_next) {
+                       if (!ISSET(cbp->b_flags, B_TDONE)) {
+                               done = false;
+                       }
+               }
 
-       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 52)) | DBG_FUNC_NONE,
-                    (int)f_offset, size, (int)filesize, local_flags, 0);
+               if (!done) {
+                       last->b_trans_next = CLUSTER_IO_WAITING;
+
+                       DTRACE_IO1(wait__start, buf_t, last);
+                       do {
+                               msleep(last, &cl_transaction_mtxp, PSPIN | (PRIBIO + 1), "cluster_wait_IO", NULL);
+
+                               /*
+                                * We should only have been woken up if all the
+                                * buffers are completed, but just in case...
+                                */
+                               done = true;
+                               for (cbp = cbp_head; cbp != CLUSTER_IO_WAITING; cbp = cbp->b_trans_next) {
+                                       if (!ISSET(cbp->b_flags, B_TDONE)) {
+                                               done = false;
+                                               break;
+                                       }
+                               }
+                       } while (!done);
+                       DTRACE_IO1(wait__done, buf_t, last);
+
+                       last->b_trans_next = NULL;
+               }
+
+               lck_mtx_unlock(&cl_transaction_mtxp);
+       } else { // !async
+               for (cbp = cbp_head; cbp; cbp = cbp->b_trans_next) {
+                       buf_biowait(cbp);
+               }
+       }
+}
+
+static void
+cluster_complete_transaction(buf_t *cbp_head, void *callback_arg, int *retval, int flags, int needwait)
+{
+       buf_t   cbp;
+       int     error;
+       boolean_t isswapout = FALSE;
 
        /*
-        * If they didn't specify any I/O, then we are done...
-        * we can't issue an abort because we don't know how
-        * big the upl really is
+        * cluster_complete_transaction will
+        * only be called if we've issued a complete chain in synchronous mode
+        * or, we've already done a cluster_wait_IO on an incomplete chain
         */
-       if (size <= 0)
-               return (EINVAL);
-
-        if (vp->v_mount->mnt_flag & MNT_RDONLY) {
-               if (local_flags & CL_COMMIT)
-                       ubc_upl_abort_range(upl, upl_offset, size, UPL_ABORT_FREE_ON_EMPTY);
-               return (EROFS);
+       if (needwait) {
+               for (cbp = *cbp_head; cbp; cbp = cbp->b_trans_next) {
+                       buf_biowait(cbp);
+               }
        }
        /*
-        * can't page-in from a negative offset
-        * or if we're starting beyond the EOF
-        * or if the file offset isn't page aligned
-        * or the size requested isn't a multiple of PAGE_SIZE
+        * we've already waited on all of the I/Os in this transaction,
+        * so mark all of the buf_t's in this transaction as B_TDONE
+        * so that cluster_iodone sees the transaction as completed
         */
-       if (f_offset < 0 || f_offset >= filesize ||
-          (f_offset & PAGE_MASK_64) || (size & PAGE_MASK)) {
-               if (local_flags & CL_COMMIT)
-                       ubc_upl_abort_range(upl, upl_offset, size, UPL_ABORT_FREE_ON_EMPTY);
-               return (EINVAL);
+       for (cbp = *cbp_head; cbp; cbp = cbp->b_trans_next) {
+               cbp->b_flags |= B_TDONE;
        }
-       max_size = filesize - f_offset;
+       cbp = *cbp_head;
 
-       if (size < max_size)
-               io_size = size;
-       else
-               io_size = max_size;
+       if ((flags & (CL_ASYNC | CL_PAGEOUT)) == CL_PAGEOUT && vnode_isswap(cbp->b_vp)) {
+               isswapout = TRUE;
+       }
 
-       rounded_size = (io_size + (PAGE_SIZE - 1)) & ~PAGE_MASK;
+       error = cluster_iodone(cbp, callback_arg);
 
-       if (size > rounded_size) {
-               if (local_flags & CL_COMMIT)
-                       ubc_upl_abort_range(upl, upl_offset + rounded_size, size - rounded_size,
-                                       UPL_ABORT_FREE_ON_EMPTY);
+       if (!(flags & CL_ASYNC) && error && *retval == 0) {
+               if (((flags & (CL_PAGEOUT | CL_KEEPCACHED)) != CL_PAGEOUT) || (error != ENXIO)) {
+                       *retval = error;
+               } else if (isswapout == TRUE) {
+                       *retval = error;
+               }
        }
-       vp->v_flag |= VHASBEENPAGED;
-
-       return (cluster_io(vp, upl, upl_offset, f_offset, io_size, devblocksize,
-                          local_flags, (struct buf *)0, (struct clios *)0));
+       *cbp_head = (buf_t)NULL;
 }
 
-int
-cluster_pagein(vp, upl, upl_offset, f_offset, size, filesize, devblocksize, flags)
-       struct vnode *vp;
-       upl_t         upl;
-       vm_offset_t   upl_offset;
-       off_t         f_offset;
-       int           size;
-       off_t         filesize;
-       int           devblocksize;
-       int           flags;
+
+static int
+cluster_io(vnode_t vp, upl_t upl, vm_offset_t upl_offset, off_t f_offset, int non_rounded_size,
+    int flags, buf_t real_bp, struct clios *iostate, int (*callback)(buf_t, void *), void *callback_arg)
 {
-       u_int         io_size;
-       int           rounded_size;
-        off_t         max_size;
-       int           retval;
-       int           local_flags = 0;
+       buf_t   cbp;
+       u_int   size;
+       u_int   io_size;
+       int     io_flags;
+       int     bmap_flags;
+       int     error = 0;
+       int     retval = 0;
+       buf_t   cbp_head = NULL;
+       buf_t   cbp_tail = NULL;
+       int     trans_count = 0;
+       int     max_trans_count;
+       u_int   pg_count;
+       int     pg_offset;
+       u_int   max_iosize;
+       u_int   max_vectors;
+       int     priv;
+       int     zero_offset = 0;
+       int     async_throttle = 0;
+       mount_t mp;
+       vm_offset_t upl_end_offset;
+       boolean_t   need_EOT = FALSE;
+
+       /*
+        * we currently don't support buffers larger than a page
+        */
+       if (real_bp && non_rounded_size > PAGE_SIZE) {
+               panic("%s(): Called with real buffer of size %d bytes which "
+                   "is greater than the maximum allowed size of "
+                   "%d bytes (the system PAGE_SIZE).\n",
+                   __FUNCTION__, non_rounded_size, PAGE_SIZE);
+       }
 
-       if (upl == NULL || size < 0)
-               panic("cluster_pagein: NULL upl passed in");
+       mp = vp->v_mount;
 
-       if ((flags & UPL_IOSYNC) == 0)
-               local_flags |= CL_ASYNC;
-       if ((flags & UPL_NOCOMMIT) == 0) 
-               local_flags |= CL_COMMIT;
+       /*
+        * we don't want to do any funny rounding of the size for IO requests
+        * coming through the DIRECT or CONTIGUOUS paths...  those pages don't
+        * belong to us... we can't extend (nor do we need to) the I/O to fill
+        * out a page
+        */
+       if (mp->mnt_devblocksize > 1 && !(flags & (CL_DEV_MEMORY | CL_DIRECT_IO))) {
+               /*
+                * round the requested size up so that this I/O ends on a
+                * page boundary in case this is a 'write'... if the filesystem
+                * has blocks allocated to back the page beyond the EOF, we want to
+                * make sure to write out the zero's that are sitting beyond the EOF
+                * so that in case the filesystem doesn't explicitly zero this area
+                * if a hole is created via a lseek/write beyond the current EOF,
+                * it will return zeros when it's read back from the disk.  If the
+                * physical allocation doesn't extend for the whole page, we'll
+                * only write/read from the disk up to the end of this allocation
+                * via the extent info returned from the VNOP_BLOCKMAP call.
+                */
+               pg_offset = upl_offset & PAGE_MASK;
 
+               size = (((non_rounded_size + pg_offset) + (PAGE_SIZE - 1)) & ~PAGE_MASK) - pg_offset;
+       } else {
+               /*
+                * anyone advertising a blocksize of 1 byte probably
+                * can't deal with us rounding up the request size
+                * AFP is one such filesystem/device
+                */
+               size = non_rounded_size;
+       }
+       upl_end_offset = upl_offset + size;
 
-       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 56)) | DBG_FUNC_NONE,
-                    (int)f_offset, size, (int)filesize, local_flags, 0);
+       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 22)) | DBG_FUNC_START, (int)f_offset, size, upl_offset, flags, 0);
 
        /*
-        * can't page-in from a negative offset
-        * or if we're starting beyond the EOF
-        * or if the file offset isn't page aligned
-        * or the size requested isn't a multiple of PAGE_SIZE
+        * Set the maximum transaction size to the maximum desired number of
+        * buffers.
         */
-       if (f_offset < 0 || f_offset >= filesize ||
-          (f_offset & PAGE_MASK_64) || (size & PAGE_MASK) || (upl_offset & PAGE_MASK)) {
-               if (local_flags & CL_COMMIT)
-                       ubc_upl_abort_range(upl, upl_offset, size, UPL_ABORT_FREE_ON_EMPTY | UPL_ABORT_ERROR);
-               return (EINVAL);
+       max_trans_count = 8;
+       if (flags & CL_DEV_MEMORY) {
+               max_trans_count = 16;
        }
-       max_size = filesize - f_offset;
 
-       if (size < max_size)
-               io_size = size;
-       else
-               io_size = max_size;
+       if (flags & CL_READ) {
+               io_flags = B_READ;
+               bmap_flags = VNODE_READ;
 
-       rounded_size = (io_size + (PAGE_SIZE - 1)) & ~PAGE_MASK;
+               max_iosize  = mp->mnt_maxreadcnt;
+               max_vectors = mp->mnt_segreadcnt;
+       } else {
+               io_flags = B_WRITE;
+               bmap_flags = VNODE_WRITE;
+
+               max_iosize  = mp->mnt_maxwritecnt;
+               max_vectors = mp->mnt_segwritecnt;
+       }
+       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 22)) | DBG_FUNC_NONE, max_iosize, max_vectors, mp->mnt_devblocksize, 0, 0);
+
+       /*
+        * make sure the maximum iosize is a
+        * multiple of the page size
+        */
+       max_iosize  &= ~PAGE_MASK;
+
+       /*
+        * Ensure the maximum iosize is sensible.
+        */
+       if (!max_iosize) {
+               max_iosize = PAGE_SIZE;
+       }
+
+       if (flags & CL_THROTTLE) {
+               if (!(flags & CL_PAGEOUT) && cluster_is_throttled(vp)) {
+                       if (max_iosize > THROTTLE_MAX_IOSIZE) {
+                               max_iosize = THROTTLE_MAX_IOSIZE;
+                       }
+                       async_throttle = THROTTLE_MAXCNT;
+               } else {
+                       if ((flags & CL_DEV_MEMORY)) {
+                               async_throttle = IO_SCALE(vp, VNODE_ASYNC_THROTTLE);
+                       } else {
+                               u_int max_cluster;
+                               u_int max_cluster_size;
+                               u_int scale;
+
+                               if (vp->v_mount->mnt_minsaturationbytecount) {
+                                       max_cluster_size = vp->v_mount->mnt_minsaturationbytecount;
+
+                                       scale = 1;
+                               } else {
+                                       max_cluster_size = MAX_CLUSTER_SIZE(vp);
+
+                                       if (disk_conditioner_mount_is_ssd(vp->v_mount)) {
+                                               scale = WRITE_THROTTLE_SSD;
+                                       } else {
+                                               scale = WRITE_THROTTLE;
+                                       }
+                               }
+                               if (max_iosize > max_cluster_size) {
+                                       max_cluster = max_cluster_size;
+                               } else {
+                                       max_cluster = max_iosize;
+                               }
+
+                               if (size < max_cluster) {
+                                       max_cluster = size;
+                               }
+
+                               if (flags & CL_CLOSE) {
+                                       scale += MAX_CLUSTERS;
+                               }
+
+                               async_throttle = min(IO_SCALE(vp, VNODE_ASYNC_THROTTLE), ((scale * max_cluster_size) / max_cluster) - 1);
+                       }
+               }
+       }
+       if (flags & CL_AGE) {
+               io_flags |= B_AGE;
+       }
+       if (flags & (CL_PAGEIN | CL_PAGEOUT)) {
+               io_flags |= B_PAGEIO;
+       }
+       if (flags & (CL_IOSTREAMING)) {
+               io_flags |= B_IOSTREAMING;
+       }
+       if (flags & CL_COMMIT) {
+               io_flags |= B_COMMIT_UPL;
+       }
+       if (flags & CL_DIRECT_IO) {
+               io_flags |= B_PHYS;
+       }
+       if (flags & (CL_PRESERVE | CL_KEEPCACHED)) {
+               io_flags |= B_CACHE;
+       }
+       if (flags & CL_PASSIVE) {
+               io_flags |= B_PASSIVE;
+       }
+       if (flags & CL_ENCRYPTED) {
+               io_flags |= B_ENCRYPTED_IO;
+       }
+
+       if (vp->v_flag & VSYSTEM) {
+               io_flags |= B_META;
+       }
+
+       if ((flags & CL_READ) && ((upl_offset + non_rounded_size) & PAGE_MASK) && (!(flags & CL_NOZERO))) {
+               /*
+                * then we are going to end up
+                * with a page that we can't complete (the file size wasn't a multiple
+                * of PAGE_SIZE and we're trying to read to the end of the file
+                * so we'll go ahead and zero out the portion of the page we can't
+                * read in from the file
+                */
+               zero_offset = (int)(upl_offset + non_rounded_size);
+       } else if (!ISSET(flags, CL_READ) && ISSET(flags, CL_DIRECT_IO)) {
+               assert(ISSET(flags, CL_COMMIT));
+
+               // For a direct/uncached write, we need to lock pages...
+
+               upl_t cached_upl;
+
+               /*
+                * Create a UPL to lock the pages in the cache whilst the
+                * write is in progress.
+                */
+               ubc_create_upl_kernel(vp, f_offset, non_rounded_size, &cached_upl,
+                   NULL, UPL_SET_LITE, VM_KERN_MEMORY_FILE);
+
+               /*
+                * Attach this UPL to the other UPL so that we can find it
+                * later.
+                */
+               upl_set_associated_upl(upl, cached_upl);
+
+               if (upl_offset & PAGE_MASK) {
+                       /*
+                        * The two UPLs are not aligned, so mark the first page in
+                        * @upl so that cluster_handle_associated_upl can handle
+                        * it accordingly.
+                        */
+                       upl_page_info_t *pl = UPL_GET_INTERNAL_PAGE_LIST(upl);
+                       upl_page_set_mark(pl, 0, true);
+               }
+       }
+
+       while (size) {
+               daddr64_t blkno;
+               daddr64_t lblkno;
+               u_int   io_size_wanted;
+               size_t  io_size_tmp;
+
+               if (size > max_iosize) {
+                       io_size = max_iosize;
+               } else {
+                       io_size = size;
+               }
+
+               io_size_wanted = io_size;
+               io_size_tmp = (size_t)io_size;
+
+               if ((error = VNOP_BLOCKMAP(vp, f_offset, io_size, &blkno, &io_size_tmp, NULL, bmap_flags, NULL))) {
+                       break;
+               }
+
+               if (io_size_tmp > io_size_wanted) {
+                       io_size = io_size_wanted;
+               } else {
+                       io_size = (u_int)io_size_tmp;
+               }
+
+               if (real_bp && (real_bp->b_blkno == real_bp->b_lblkno)) {
+                       real_bp->b_blkno = blkno;
+               }
+
+               KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 24)) | DBG_FUNC_NONE,
+                   (int)f_offset, (int)(blkno >> 32), (int)blkno, io_size, 0);
+
+               if (io_size == 0) {
+                       /*
+                        * vnop_blockmap didn't return an error... however, it did
+                        * return an extent size of 0 which means we can't
+                        * make forward progress on this I/O... a hole in the
+                        * file would be returned as a blkno of -1 with a non-zero io_size
+                        * a real extent is returned with a blkno != -1 and a non-zero io_size
+                        */
+                       error = EINVAL;
+                       break;
+               }
+               if (!(flags & CL_READ) && blkno == -1) {
+                       off_t   e_offset;
+                       int     pageout_flags;
+
+                       if (upl_get_internal_vectorupl(upl)) {
+                               panic("Vector UPLs should not take this code-path\n");
+                       }
+                       /*
+                        * we're writing into a 'hole'
+                        */
+                       if (flags & CL_PAGEOUT) {
+                               /*
+                                * if we got here via cluster_pageout
+                                * then just error the request and return
+                                * the 'hole' should already have been covered
+                                */
+                               error = EINVAL;
+                               break;
+                       }
+                       /*
+                        * we can get here if the cluster code happens to
+                        * pick up a page that was dirtied via mmap vs
+                        * a 'write' and the page targets a 'hole'...
+                        * i.e. the writes to the cluster were sparse
+                        * and the file was being written for the first time
+                        *
+                        * we can also get here if the filesystem supports
+                        * 'holes' that are less than PAGE_SIZE.... because
+                        * we can't know if the range in the page that covers
+                        * the 'hole' has been dirtied via an mmap or not,
+                        * we have to assume the worst and try to push the
+                        * entire page to storage.
+                        *
+                        * Try paging out the page individually before
+                        * giving up entirely and dumping it (the pageout
+                        * path will insure that the zero extent accounting
+                        * has been taken care of before we get back into cluster_io)
+                        *
+                        * go direct to vnode_pageout so that we don't have to
+                        * unbusy the page from the UPL... we used to do this
+                        * so that we could call ubc_msync, but that results
+                        * in a potential deadlock if someone else races us to acquire
+                        * that page and wins and in addition needs one of the pages
+                        * we're continuing to hold in the UPL
+                        */
+                       pageout_flags = UPL_MSYNC | UPL_VNODE_PAGER | UPL_NESTED_PAGEOUT;
+
+                       if (!(flags & CL_ASYNC)) {
+                               pageout_flags |= UPL_IOSYNC;
+                       }
+                       if (!(flags & CL_COMMIT)) {
+                               pageout_flags |= UPL_NOCOMMIT;
+                       }
+
+                       if (cbp_head) {
+                               buf_t prev_cbp;
+                               uint32_t   bytes_in_last_page;
+
+                               /*
+                                * first we have to wait for the the current outstanding I/Os
+                                * to complete... EOT hasn't been set yet on this transaction
+                                * so the pages won't be released
+                                */
+                               cluster_wait_IO(cbp_head, (flags & CL_ASYNC));
+
+                               bytes_in_last_page = cbp_head->b_uploffset & PAGE_MASK;
+                               for (cbp = cbp_head; cbp; cbp = cbp->b_trans_next) {
+                                       bytes_in_last_page += cbp->b_bcount;
+                               }
+                               bytes_in_last_page &= PAGE_MASK;
+
+                               while (bytes_in_last_page) {
+                                       /*
+                                        * we've got a transcation that
+                                        * includes the page we're about to push out through vnode_pageout...
+                                        * find the bp's in the list which intersect this page and either
+                                        * remove them entirely from the transaction (there could be multiple bp's), or
+                                        * round it's iosize down to the page boundary (there can only be one)...
+                                        *
+                                        * find the last bp in the list and act on it
+                                        */
+                                       for (prev_cbp = cbp = cbp_head; cbp->b_trans_next; cbp = cbp->b_trans_next) {
+                                               prev_cbp = cbp;
+                                       }
+
+                                       if (bytes_in_last_page >= cbp->b_bcount) {
+                                               /*
+                                                * this buf no longer has any I/O associated with it
+                                                */
+                                               bytes_in_last_page -= cbp->b_bcount;
+                                               cbp->b_bcount = 0;
+
+                                               free_io_buf(cbp);
+
+                                               if (cbp == cbp_head) {
+                                                       assert(bytes_in_last_page == 0);
+                                                       /*
+                                                        * the buf we just freed was the only buf in
+                                                        * this transaction... so there's no I/O to do
+                                                        */
+                                                       cbp_head = NULL;
+                                                       cbp_tail = NULL;
+                                               } else {
+                                                       /*
+                                                        * remove the buf we just freed from
+                                                        * the transaction list
+                                                        */
+                                                       prev_cbp->b_trans_next = NULL;
+                                                       cbp_tail = prev_cbp;
+                                               }
+                                       } else {
+                                               /*
+                                                * this is the last bp that has I/O
+                                                * intersecting the page of interest
+                                                * only some of the I/O is in the intersection
+                                                * so clip the size but keep it in the transaction list
+                                                */
+                                               cbp->b_bcount -= bytes_in_last_page;
+                                               cbp_tail = cbp;
+                                               bytes_in_last_page = 0;
+                                       }
+                               }
+                               if (cbp_head) {
+                                       /*
+                                        * there was more to the current transaction
+                                        * than just the page we are pushing out via vnode_pageout...
+                                        * mark it as finished and complete it... we've already
+                                        * waited for the I/Os to complete above in the call to cluster_wait_IO
+                                        */
+                                       cluster_EOT(cbp_head, cbp_tail, 0);
+
+                                       cluster_complete_transaction(&cbp_head, callback_arg, &retval, flags, 0);
+
+                                       trans_count = 0;
+                               }
+                       }
+                       if (vnode_pageout(vp, upl, (upl_offset_t)trunc_page(upl_offset), trunc_page_64(f_offset), PAGE_SIZE, pageout_flags, NULL) != PAGER_SUCCESS) {
+                               error = EINVAL;
+                       }
+                       e_offset = round_page_64(f_offset + 1);
+                       io_size = (u_int)(e_offset - f_offset);
+
+                       f_offset   += io_size;
+                       upl_offset += io_size;
+
+                       if (size >= io_size) {
+                               size -= io_size;
+                       } else {
+                               size = 0;
+                       }
+                       /*
+                        * keep track of how much of the original request
+                        * that we've actually completed... non_rounded_size
+                        * may go negative due to us rounding the request
+                        * to a page size multiple (i.e.  size > non_rounded_size)
+                        */
+                       non_rounded_size -= io_size;
+
+                       if (non_rounded_size <= 0) {
+                               /*
+                                * we've transferred all of the data in the original
+                                * request, but we were unable to complete the tail
+                                * of the last page because the file didn't have
+                                * an allocation to back that portion... this is ok.
+                                */
+                               size = 0;
+                       }
+                       if (error) {
+                               if (size == 0) {
+                                       flags &= ~CL_COMMIT;
+                               }
+                               break;
+                       }
+                       continue;
+               }
+               lblkno = (daddr64_t)(f_offset / 0x1000);
+               /*
+                * we have now figured out how much I/O we can do - this is in 'io_size'
+                * pg_offset is the starting point in the first page for the I/O
+                * pg_count is the number of full and partial pages that 'io_size' encompasses
+                */
+               pg_offset = upl_offset & PAGE_MASK;
+
+               if (flags & CL_DEV_MEMORY) {
+                       /*
+                        * treat physical requests as one 'giant' page
+                        */
+                       pg_count = 1;
+               } else {
+                       pg_count  = (io_size + pg_offset + (PAGE_SIZE - 1)) / PAGE_SIZE;
+               }
+
+               if ((flags & CL_READ) && blkno == -1) {
+                       vm_offset_t  commit_offset;
+                       int bytes_to_zero;
+                       int complete_transaction_now = 0;
+
+                       /*
+                        * if we're reading and blkno == -1, then we've got a
+                        * 'hole' in the file that we need to deal with by zeroing
+                        * out the affected area in the upl
+                        */
+                       if (io_size >= (u_int)non_rounded_size) {
+                               /*
+                                * if this upl contains the EOF and it is not a multiple of PAGE_SIZE
+                                * than 'zero_offset' will be non-zero
+                                * if the 'hole' returned by vnop_blockmap extends all the way to the eof
+                                * (indicated by the io_size finishing off the I/O request for this UPL)
+                                * than we're not going to issue an I/O for the
+                                * last page in this upl... we need to zero both the hole and the tail
+                                * of the page beyond the EOF, since the delayed zero-fill won't kick in
+                                */
+                               bytes_to_zero = non_rounded_size;
+                               if (!(flags & CL_NOZERO)) {
+                                       bytes_to_zero = (int)((((upl_offset + io_size) + (PAGE_SIZE - 1)) & ~PAGE_MASK) - upl_offset);
+                               }
+
+                               zero_offset = 0;
+                       } else {
+                               bytes_to_zero = io_size;
+                       }
+
+                       pg_count = 0;
+
+                       cluster_zero(upl, (upl_offset_t)upl_offset, bytes_to_zero, real_bp);
+
+                       if (cbp_head) {
+                               int     pg_resid;
+
+                               /*
+                                * if there is a current I/O chain pending
+                                * then the first page of the group we just zero'd
+                                * will be handled by the I/O completion if the zero
+                                * fill started in the middle of the page
+                                */
+                               commit_offset = (upl_offset + (PAGE_SIZE - 1)) & ~PAGE_MASK;
+
+                               pg_resid = (int)(commit_offset - upl_offset);
+
+                               if (bytes_to_zero >= pg_resid) {
+                                       /*
+                                        * the last page of the current I/O
+                                        * has been completed...
+                                        * compute the number of fully zero'd
+                                        * pages that are beyond it
+                                        * plus the last page if its partial
+                                        * and we have no more I/O to issue...
+                                        * otherwise a partial page is left
+                                        * to begin the next I/O
+                                        */
+                                       if ((int)io_size >= non_rounded_size) {
+                                               pg_count = (bytes_to_zero - pg_resid + (PAGE_SIZE - 1)) / PAGE_SIZE;
+                                       } else {
+                                               pg_count = (bytes_to_zero - pg_resid) / PAGE_SIZE;
+                                       }
+
+                                       complete_transaction_now = 1;
+                               }
+                       } else {
+                               /*
+                                * no pending I/O to deal with
+                                * so, commit all of the fully zero'd pages
+                                * plus the last page if its partial
+                                * and we have no more I/O to issue...
+                                * otherwise a partial page is left
+                                * to begin the next I/O
+                                */
+                               if ((int)io_size >= non_rounded_size) {
+                                       pg_count = (pg_offset + bytes_to_zero + (PAGE_SIZE - 1)) / PAGE_SIZE;
+                               } else {
+                                       pg_count = (pg_offset + bytes_to_zero) / PAGE_SIZE;
+                               }
+
+                               commit_offset = upl_offset & ~PAGE_MASK;
+                       }
+
+                       // Associated UPL is currently only used in the direct write path
+                       assert(!upl_associated_upl(upl));
+
+                       if ((flags & CL_COMMIT) && pg_count) {
+                               ubc_upl_commit_range(upl, (upl_offset_t)commit_offset,
+                                   pg_count * PAGE_SIZE,
+                                   UPL_COMMIT_CLEAR_DIRTY | UPL_COMMIT_FREE_ON_EMPTY);
+                       }
+                       upl_offset += io_size;
+                       f_offset   += io_size;
+                       size       -= io_size;
+
+                       /*
+                        * keep track of how much of the original request
+                        * that we've actually completed... non_rounded_size
+                        * may go negative due to us rounding the request
+                        * to a page size multiple (i.e.  size > non_rounded_size)
+                        */
+                       non_rounded_size -= io_size;
+
+                       if (non_rounded_size <= 0) {
+                               /*
+                                * we've transferred all of the data in the original
+                                * request, but we were unable to complete the tail
+                                * of the last page because the file didn't have
+                                * an allocation to back that portion... this is ok.
+                                */
+                               size = 0;
+                       }
+                       if (cbp_head && (complete_transaction_now || size == 0)) {
+                               cluster_wait_IO(cbp_head, (flags & CL_ASYNC));
+
+                               cluster_EOT(cbp_head, cbp_tail, size == 0 ? zero_offset : 0);
+
+                               cluster_complete_transaction(&cbp_head, callback_arg, &retval, flags, 0);
+
+                               trans_count = 0;
+                       }
+                       continue;
+               }
+               if (pg_count > max_vectors) {
+                       if (((pg_count - max_vectors) * PAGE_SIZE) > io_size) {
+                               io_size = PAGE_SIZE - pg_offset;
+                               pg_count = 1;
+                       } else {
+                               io_size -= (pg_count - max_vectors) * PAGE_SIZE;
+                               pg_count = max_vectors;
+                       }
+               }
+               /*
+                * If the transaction is going to reach the maximum number of
+                * desired elements, truncate the i/o to the nearest page so
+                * that the actual i/o is initiated after this buffer is
+                * created and added to the i/o chain.
+                *
+                * I/O directed to physically contiguous memory
+                * doesn't have a requirement to make sure we 'fill' a page
+                */
+               if (!(flags & CL_DEV_MEMORY) && trans_count >= max_trans_count &&
+                   ((upl_offset + io_size) & PAGE_MASK)) {
+                       vm_offset_t aligned_ofs;
+
+                       aligned_ofs = (upl_offset + io_size) & ~PAGE_MASK;
+                       /*
+                        * If the io_size does not actually finish off even a
+                        * single page we have to keep adding buffers to the
+                        * transaction despite having reached the desired limit.
+                        *
+                        * Eventually we get here with the page being finished
+                        * off (and exceeded) and then we truncate the size of
+                        * this i/o request so that it is page aligned so that
+                        * we can finally issue the i/o on the transaction.
+                        */
+                       if (aligned_ofs > upl_offset) {
+                               io_size = (u_int)(aligned_ofs - upl_offset);
+                               pg_count--;
+                       }
+               }
+
+               if (!(mp->mnt_kern_flag & MNTK_VIRTUALDEV)) {
+                       /*
+                        * if we're not targeting a virtual device i.e. a disk image
+                        * it's safe to dip into the reserve pool since real devices
+                        * can complete this I/O request without requiring additional
+                        * bufs from the alloc_io_buf pool
+                        */
+                       priv = 1;
+               } else if ((flags & CL_ASYNC) && !(flags & CL_PAGEOUT) && !cbp_head) {
+                       /*
+                        * Throttle the speculative IO
+                        *
+                        * We can only throttle this if it is the first iobuf
+                        * for the transaction. alloc_io_buf implements
+                        * additional restrictions for diskimages anyway.
+                        */
+                       priv = 0;
+               } else {
+                       priv = 1;
+               }
+
+               cbp = alloc_io_buf(vp, priv);
+
+               if (flags & CL_PAGEOUT) {
+                       u_int i;
+
+                       /*
+                        * since blocks are in offsets of 0x1000, scale
+                        * iteration to (PAGE_SIZE * pg_count) of blks.
+                        */
+                       for (i = 0; i < (PAGE_SIZE * pg_count) / 0x1000; i++) {
+                               if (buf_invalblkno(vp, lblkno + i, 0) == EBUSY) {
+                                       panic("BUSY bp found in cluster_io");
+                               }
+                       }
+               }
+               if (flags & CL_ASYNC) {
+                       if (buf_setcallback(cbp, (void *)cluster_iodone, callback_arg)) {
+                               panic("buf_setcallback failed\n");
+                       }
+               }
+               cbp->b_cliodone = (void *)callback;
+               cbp->b_flags |= io_flags;
+               if (flags & CL_NOCACHE) {
+                       cbp->b_attr.ba_flags |= BA_NOCACHE;
+               }
+
+               cbp->b_lblkno = lblkno;
+               cbp->b_blkno  = blkno;
+               cbp->b_bcount = io_size;
+
+               if (buf_setupl(cbp, upl, (uint32_t)upl_offset)) {
+                       panic("buf_setupl failed\n");
+               }
+#if CONFIG_IOSCHED
+               upl_set_blkno(upl, upl_offset, io_size, blkno);
+#endif
+               cbp->b_trans_next = (buf_t)NULL;
+
+               if ((cbp->b_iostate = (void *)iostate)) {
+                       /*
+                        * caller wants to track the state of this
+                        * io... bump the amount issued against this stream
+                        */
+                       iostate->io_issued += io_size;
+               }
+
+               if (flags & CL_READ) {
+                       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 26)) | DBG_FUNC_NONE,
+                           (int)cbp->b_lblkno, (int)cbp->b_blkno, upl_offset, io_size, 0);
+               } else {
+                       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 27)) | DBG_FUNC_NONE,
+                           (int)cbp->b_lblkno, (int)cbp->b_blkno, upl_offset, io_size, 0);
+               }
+
+               if (cbp_head) {
+                       cbp_tail->b_trans_next = cbp;
+                       cbp_tail = cbp;
+               } else {
+                       cbp_head = cbp;
+                       cbp_tail = cbp;
+
+                       if ((cbp_head->b_real_bp = real_bp)) {
+                               real_bp = (buf_t)NULL;
+                       }
+               }
+               *(buf_t *)(&cbp->b_trans_head) = cbp_head;
+
+               trans_count++;
+
+               upl_offset += io_size;
+               f_offset   += io_size;
+               size       -= io_size;
+               /*
+                * keep track of how much of the original request
+                * that we've actually completed... non_rounded_size
+                * may go negative due to us rounding the request
+                * to a page size multiple (i.e.  size > non_rounded_size)
+                */
+               non_rounded_size -= io_size;
+
+               if (non_rounded_size <= 0) {
+                       /*
+                        * we've transferred all of the data in the original
+                        * request, but we were unable to complete the tail
+                        * of the last page because the file didn't have
+                        * an allocation to back that portion... this is ok.
+                        */
+                       size = 0;
+               }
+               if (size == 0) {
+                       /*
+                        * we have no more I/O to issue, so go
+                        * finish the final transaction
+                        */
+                       need_EOT = TRUE;
+               } else if (((flags & CL_DEV_MEMORY) || (upl_offset & PAGE_MASK) == 0) &&
+                   ((flags & CL_ASYNC) || trans_count > max_trans_count)) {
+                       /*
+                        * I/O directed to physically contiguous memory...
+                        * which doesn't have a requirement to make sure we 'fill' a page
+                        * or...
+                        * the current I/O we've prepared fully
+                        * completes the last page in this request
+                        * and ...
+                        * it's either an ASYNC request or
+                        * we've already accumulated more than 8 I/O's into
+                        * this transaction so mark it as complete so that
+                        * it can finish asynchronously or via the cluster_complete_transaction
+                        * below if the request is synchronous
+                        */
+                       need_EOT = TRUE;
+               }
+               if (need_EOT == TRUE) {
+                       cluster_EOT(cbp_head, cbp_tail, size == 0 ? zero_offset : 0);
+               }
+
+               if (flags & CL_THROTTLE) {
+                       (void)vnode_waitforwrites(vp, async_throttle, 0, 0, "cluster_io");
+               }
+
+               if (!(io_flags & B_READ)) {
+                       vnode_startwrite(vp);
+               }
+
+               if (flags & CL_RAW_ENCRYPTED) {
+                       /*
+                        * User requested raw encrypted bytes.
+                        * Twiddle the bit in the ba_flags for the buffer
+                        */
+                       cbp->b_attr.ba_flags |= BA_RAW_ENCRYPTED_IO;
+               }
+
+               (void) VNOP_STRATEGY(cbp);
+
+               if (need_EOT == TRUE) {
+                       if (!(flags & CL_ASYNC)) {
+                               cluster_complete_transaction(&cbp_head, callback_arg, &retval, flags, 1);
+                       }
+
+                       need_EOT = FALSE;
+                       trans_count = 0;
+                       cbp_head = NULL;
+               }
+       }
+       if (error) {
+               int abort_size;
+
+               io_size = 0;
+
+               if (cbp_head) {
+                       /*
+                        * Wait until all of the outstanding I/O
+                        * for this partial transaction has completed
+                        */
+                       cluster_wait_IO(cbp_head, (flags & CL_ASYNC));
+
+                       /*
+                        * Rewind the upl offset to the beginning of the
+                        * transaction.
+                        */
+                       upl_offset = cbp_head->b_uploffset;
+               }
+
+               if (ISSET(flags, CL_COMMIT)) {
+                       cluster_handle_associated_upl(iostate, upl,
+                           (upl_offset_t)upl_offset,
+                           (upl_size_t)(upl_end_offset - upl_offset));
+               }
+
+               // Free all the IO buffers in this transaction
+               for (cbp = cbp_head; cbp;) {
+                       buf_t   cbp_next;
+
+                       size       += cbp->b_bcount;
+                       io_size    += cbp->b_bcount;
+
+                       cbp_next = cbp->b_trans_next;
+                       free_io_buf(cbp);
+                       cbp = cbp_next;
+               }
+
+               if (iostate) {
+                       int need_wakeup = 0;
+
+                       /*
+                        * update the error condition for this stream
+                        * since we never really issued the io
+                        * just go ahead and adjust it back
+                        */
+                       lck_mtx_lock_spin(&iostate->io_mtxp);
+
+                       if (iostate->io_error == 0) {
+                               iostate->io_error = error;
+                       }
+                       iostate->io_issued -= io_size;
+
+                       if (iostate->io_wanted) {
+                               /*
+                                * someone is waiting for the state of
+                                * this io stream to change
+                                */
+                               iostate->io_wanted = 0;
+                               need_wakeup = 1;
+                       }
+                       lck_mtx_unlock(&iostate->io_mtxp);
+
+                       if (need_wakeup) {
+                               wakeup((caddr_t)&iostate->io_wanted);
+                       }
+               }
+
+               if (flags & CL_COMMIT) {
+                       int     upl_flags;
+
+                       pg_offset  = upl_offset & PAGE_MASK;
+                       abort_size = (int)((upl_end_offset - upl_offset + PAGE_MASK) & ~PAGE_MASK);
+
+                       upl_flags = cluster_ioerror(upl, (int)(upl_offset - pg_offset),
+                           abort_size, error, io_flags, vp);
+
+                       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 28)) | DBG_FUNC_NONE,
+                           upl, upl_offset - pg_offset, abort_size, (error << 24) | upl_flags, 0);
+               }
+               if (retval == 0) {
+                       retval = error;
+               }
+       } else if (cbp_head) {
+               panic("%s(): cbp_head is not NULL.\n", __FUNCTION__);
+       }
+
+       if (real_bp) {
+               /*
+                * can get here if we either encountered an error
+                * or we completely zero-filled the request and
+                * no I/O was issued
+                */
+               if (error) {
+                       real_bp->b_flags |= B_ERROR;
+                       real_bp->b_error = error;
+               }
+               buf_biodone(real_bp);
+       }
+       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 22)) | DBG_FUNC_END, (int)f_offset, size, upl_offset, retval, 0);
+
+       return retval;
+}
+
+#define reset_vector_run_state()                                                                                \
+       issueVectorUPL = vector_upl_offset = vector_upl_index = vector_upl_iosize = vector_upl_size = 0;
+
+static int
+vector_cluster_io(vnode_t vp, upl_t vector_upl, vm_offset_t vector_upl_offset, off_t v_upl_uio_offset, int vector_upl_iosize,
+    int io_flag, buf_t real_bp, struct clios *iostate, int (*callback)(buf_t, void *), void *callback_arg)
+{
+       vector_upl_set_pagelist(vector_upl);
+
+       if (io_flag & CL_READ) {
+               if (vector_upl_offset == 0 && ((vector_upl_iosize & PAGE_MASK) == 0)) {
+                       io_flag &= ~CL_PRESERVE; /*don't zero fill*/
+               } else {
+                       io_flag |= CL_PRESERVE; /*zero fill*/
+               }
+       }
+       return cluster_io(vp, vector_upl, vector_upl_offset, v_upl_uio_offset, vector_upl_iosize, io_flag, real_bp, iostate, callback, callback_arg);
+}
+
+static int
+cluster_read_prefetch(vnode_t vp, off_t f_offset, u_int size, off_t filesize, int (*callback)(buf_t, void *), void *callback_arg, int bflag)
+{
+       int           pages_in_prefetch;
+
+       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 49)) | DBG_FUNC_START,
+           (int)f_offset, size, (int)filesize, 0, 0);
+
+       if (f_offset >= filesize) {
+               KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 49)) | DBG_FUNC_END,
+                   (int)f_offset, 0, 0, 0, 0);
+               return 0;
+       }
+       if ((off_t)size > (filesize - f_offset)) {
+               size = (u_int)(filesize - f_offset);
+       }
+       pages_in_prefetch = (size + (PAGE_SIZE - 1)) / PAGE_SIZE;
+
+       advisory_read_ext(vp, filesize, f_offset, size, callback, callback_arg, bflag);
+
+       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 49)) | DBG_FUNC_END,
+           (int)f_offset + size, pages_in_prefetch, 0, 1, 0);
+
+       return pages_in_prefetch;
+}
+
+
+
+static void
+cluster_read_ahead(vnode_t vp, struct cl_extent *extent, off_t filesize, struct cl_readahead *rap, int (*callback)(buf_t, void *), void *callback_arg,
+    int bflag)
+{
+       daddr64_t       r_addr;
+       off_t           f_offset;
+       int             size_of_prefetch;
+       u_int           max_prefetch;
+
+
+       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 48)) | DBG_FUNC_START,
+           (int)extent->b_addr, (int)extent->e_addr, (int)rap->cl_lastr, 0, 0);
+
+       if (extent->b_addr == rap->cl_lastr && extent->b_addr == extent->e_addr) {
+               KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 48)) | DBG_FUNC_END,
+                   rap->cl_ralen, (int)rap->cl_maxra, (int)rap->cl_lastr, 0, 0);
+               return;
+       }
+       if (rap->cl_lastr == -1 || (extent->b_addr != rap->cl_lastr && extent->b_addr != (rap->cl_lastr + 1))) {
+               rap->cl_ralen = 0;
+               rap->cl_maxra = 0;
+
+               KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 48)) | DBG_FUNC_END,
+                   rap->cl_ralen, (int)rap->cl_maxra, (int)rap->cl_lastr, 1, 0);
+
+               return;
+       }
+       max_prefetch = MAX_PREFETCH(vp, cluster_max_io_size(vp->v_mount, CL_READ), disk_conditioner_mount_is_ssd(vp->v_mount));
+
+       if (max_prefetch > speculative_prefetch_max) {
+               max_prefetch = speculative_prefetch_max;
+       }
+
+       if (max_prefetch <= PAGE_SIZE) {
+               KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 48)) | DBG_FUNC_END,
+                   rap->cl_ralen, (int)rap->cl_maxra, (int)rap->cl_lastr, 6, 0);
+               return;
+       }
+       if (extent->e_addr < rap->cl_maxra && rap->cl_ralen >= 4) {
+               if ((rap->cl_maxra - extent->e_addr) > (rap->cl_ralen / 4)) {
+                       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 48)) | DBG_FUNC_END,
+                           rap->cl_ralen, (int)rap->cl_maxra, (int)rap->cl_lastr, 2, 0);
+                       return;
+               }
+       }
+       r_addr = MAX(extent->e_addr, rap->cl_maxra) + 1;
+       f_offset = (off_t)(r_addr * PAGE_SIZE_64);
+
+       size_of_prefetch = 0;
+
+       ubc_range_op(vp, f_offset, f_offset + PAGE_SIZE_64, UPL_ROP_PRESENT, &size_of_prefetch);
+
+       if (size_of_prefetch) {
+               KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 48)) | DBG_FUNC_END,
+                   rap->cl_ralen, (int)rap->cl_maxra, (int)rap->cl_lastr, 3, 0);
+               return;
+       }
+       if (f_offset < filesize) {
+               daddr64_t read_size;
+
+               rap->cl_ralen = rap->cl_ralen ? min(max_prefetch / PAGE_SIZE, rap->cl_ralen << 1) : 1;
+
+               read_size = (extent->e_addr + 1) - extent->b_addr;
+
+               if (read_size > rap->cl_ralen) {
+                       if (read_size > max_prefetch / PAGE_SIZE) {
+                               rap->cl_ralen = max_prefetch / PAGE_SIZE;
+                       } else {
+                               rap->cl_ralen = (int)read_size;
+                       }
+               }
+               size_of_prefetch = cluster_read_prefetch(vp, f_offset, rap->cl_ralen * PAGE_SIZE, filesize, callback, callback_arg, bflag);
+
+               if (size_of_prefetch) {
+                       rap->cl_maxra = (r_addr + size_of_prefetch) - 1;
+               }
+       }
+       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 48)) | DBG_FUNC_END,
+           rap->cl_ralen, (int)rap->cl_maxra, (int)rap->cl_lastr, 4, 0);
+}
+
+
+int
+cluster_pageout(vnode_t vp, upl_t upl, upl_offset_t upl_offset, off_t f_offset,
+    int size, off_t filesize, int flags)
+{
+       return cluster_pageout_ext(vp, upl, upl_offset, f_offset, size, filesize, flags, NULL, NULL);
+}
+
+
+int
+cluster_pageout_ext(vnode_t vp, upl_t upl, upl_offset_t upl_offset, off_t f_offset,
+    int size, off_t filesize, int flags, int (*callback)(buf_t, void *), void *callback_arg)
+{
+       int           io_size;
+       int           rounded_size;
+       off_t         max_size;
+       int           local_flags;
+
+       local_flags = CL_PAGEOUT | CL_THROTTLE;
+
+       if ((flags & UPL_IOSYNC) == 0) {
+               local_flags |= CL_ASYNC;
+       }
+       if ((flags & UPL_NOCOMMIT) == 0) {
+               local_flags |= CL_COMMIT;
+       }
+       if ((flags & UPL_KEEPCACHED)) {
+               local_flags |= CL_KEEPCACHED;
+       }
+       if (flags & UPL_PAGING_ENCRYPTED) {
+               local_flags |= CL_ENCRYPTED;
+       }
+
+
+       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 52)) | DBG_FUNC_NONE,
+           (int)f_offset, size, (int)filesize, local_flags, 0);
+
+       /*
+        * If they didn't specify any I/O, then we are done...
+        * we can't issue an abort because we don't know how
+        * big the upl really is
+        */
+       if (size <= 0) {
+               return EINVAL;
+       }
+
+       if (vp->v_mount->mnt_flag & MNT_RDONLY) {
+               if (local_flags & CL_COMMIT) {
+                       ubc_upl_abort_range(upl, upl_offset, size, UPL_ABORT_FREE_ON_EMPTY);
+               }
+               return EROFS;
+       }
+       /*
+        * can't page-in from a negative offset
+        * or if we're starting beyond the EOF
+        * or if the file offset isn't page aligned
+        * or the size requested isn't a multiple of PAGE_SIZE
+        */
+       if (f_offset < 0 || f_offset >= filesize ||
+           (f_offset & PAGE_MASK_64) || (size & PAGE_MASK)) {
+               if (local_flags & CL_COMMIT) {
+                       ubc_upl_abort_range(upl, upl_offset, size, UPL_ABORT_FREE_ON_EMPTY);
+               }
+               return EINVAL;
+       }
+       max_size = filesize - f_offset;
+
+       if (size < max_size) {
+               io_size = size;
+       } else {
+               io_size = (int)max_size;
+       }
+
+       rounded_size = (io_size + (PAGE_SIZE - 1)) & ~PAGE_MASK;
+
+       if (size > rounded_size) {
+               if (local_flags & CL_COMMIT) {
+                       ubc_upl_abort_range(upl, upl_offset + rounded_size, size - rounded_size,
+                           UPL_ABORT_FREE_ON_EMPTY);
+               }
+       }
+       return cluster_io(vp, upl, upl_offset, f_offset, io_size,
+                  local_flags, (buf_t)NULL, (struct clios *)NULL, callback, callback_arg);
+}
+
+
+int
+cluster_pagein(vnode_t vp, upl_t upl, upl_offset_t upl_offset, off_t f_offset,
+    int size, off_t filesize, int flags)
+{
+       return cluster_pagein_ext(vp, upl, upl_offset, f_offset, size, filesize, flags, NULL, NULL);
+}
+
+
+int
+cluster_pagein_ext(vnode_t vp, upl_t upl, upl_offset_t upl_offset, off_t f_offset,
+    int size, off_t filesize, int flags, int (*callback)(buf_t, void *), void *callback_arg)
+{
+       u_int         io_size;
+       int           rounded_size;
+       off_t         max_size;
+       int           retval;
+       int           local_flags = 0;
+
+       if (upl == NULL || size < 0) {
+               panic("cluster_pagein: NULL upl passed in");
+       }
+
+       if ((flags & UPL_IOSYNC) == 0) {
+               local_flags |= CL_ASYNC;
+       }
+       if ((flags & UPL_NOCOMMIT) == 0) {
+               local_flags |= CL_COMMIT;
+       }
+       if (flags & UPL_IOSTREAMING) {
+               local_flags |= CL_IOSTREAMING;
+       }
+       if (flags & UPL_PAGING_ENCRYPTED) {
+               local_flags |= CL_ENCRYPTED;
+       }
+
+
+       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 56)) | DBG_FUNC_NONE,
+           (int)f_offset, size, (int)filesize, local_flags, 0);
+
+       /*
+        * can't page-in from a negative offset
+        * or if we're starting beyond the EOF
+        * or if the file offset isn't page aligned
+        * or the size requested isn't a multiple of PAGE_SIZE
+        */
+       if (f_offset < 0 || f_offset >= filesize ||
+           (f_offset & PAGE_MASK_64) || (size & PAGE_MASK) || (upl_offset & PAGE_MASK)) {
+               if (local_flags & CL_COMMIT) {
+                       ubc_upl_abort_range(upl, upl_offset, size, UPL_ABORT_FREE_ON_EMPTY | UPL_ABORT_ERROR);
+               }
+               return EINVAL;
+       }
+       max_size = filesize - f_offset;
+
+       if (size < max_size) {
+               io_size = size;
+       } else {
+               io_size = (int)max_size;
+       }
+
+       rounded_size = (io_size + (PAGE_SIZE - 1)) & ~PAGE_MASK;
+
+       if (size > rounded_size && (local_flags & CL_COMMIT)) {
+               ubc_upl_abort_range(upl, upl_offset + rounded_size,
+                   size - rounded_size, UPL_ABORT_FREE_ON_EMPTY | UPL_ABORT_ERROR);
+       }
+
+       retval = cluster_io(vp, upl, upl_offset, f_offset, io_size,
+           local_flags | CL_READ | CL_PAGEIN, (buf_t)NULL, (struct clios *)NULL, callback, callback_arg);
+
+       return retval;
+}
+
+
+int
+cluster_bp(buf_t bp)
+{
+       return cluster_bp_ext(bp, NULL, NULL);
+}
+
+
+int
+cluster_bp_ext(buf_t bp, int (*callback)(buf_t, void *), void *callback_arg)
+{
+       off_t  f_offset;
+       int    flags;
+
+       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 19)) | DBG_FUNC_START,
+           bp, (int)bp->b_lblkno, bp->b_bcount, bp->b_flags, 0);
+
+       if (bp->b_flags & B_READ) {
+               flags = CL_ASYNC | CL_READ;
+       } else {
+               flags = CL_ASYNC;
+       }
+       if (bp->b_flags & B_PASSIVE) {
+               flags |= CL_PASSIVE;
+       }
+
+       f_offset = ubc_blktooff(bp->b_vp, bp->b_lblkno);
+
+       return cluster_io(bp->b_vp, bp->b_upl, 0, f_offset, bp->b_bcount, flags, bp, (struct clios *)NULL, callback, callback_arg);
+}
+
+
+
+int
+cluster_write(vnode_t vp, struct uio *uio, off_t oldEOF, off_t newEOF, off_t headOff, off_t tailOff, int xflags)
+{
+       return cluster_write_ext(vp, uio, oldEOF, newEOF, headOff, tailOff, xflags, NULL, NULL);
+}
+
+
+int
+cluster_write_ext(vnode_t vp, struct uio *uio, off_t oldEOF, off_t newEOF, off_t headOff, off_t tailOff,
+    int xflags, int (*callback)(buf_t, void *), void *callback_arg)
+{
+       user_ssize_t    cur_resid;
+       int             retval = 0;
+       int             flags;
+       int             zflags;
+       int             bflag;
+       int             write_type = IO_COPY;
+       u_int32_t       write_length;
+
+       flags = xflags;
+
+       if (flags & IO_PASSIVE) {
+               bflag = CL_PASSIVE;
+       } else {
+               bflag = 0;
+       }
+
+       if (vp->v_flag & VNOCACHE_DATA) {
+               flags |= IO_NOCACHE;
+               bflag |= CL_NOCACHE;
+       }
+       if (uio == NULL) {
+               /*
+                * no user data...
+                * this call is being made to zero-fill some range in the file
+                */
+               retval = cluster_write_copy(vp, NULL, (u_int32_t)0, oldEOF, newEOF, headOff, tailOff, flags, callback, callback_arg);
+
+               return retval;
+       }
+       /*
+        * do a write through the cache if one of the following is true....
+        *   NOCACHE is not true or NODIRECT is true
+        *   the uio request doesn't target USERSPACE
+        * otherwise, find out if we want the direct or contig variant for
+        * the first vector in the uio request
+        */
+       if (((flags & (IO_NOCACHE | IO_NODIRECT)) == IO_NOCACHE) && UIO_SEG_IS_USER_SPACE(uio->uio_segflg)) {
+               retval = cluster_io_type(uio, &write_type, &write_length, MIN_DIRECT_WRITE_SIZE);
+       }
+
+       if ((flags & (IO_TAILZEROFILL | IO_HEADZEROFILL)) && write_type == IO_DIRECT) {
+               /*
+                * must go through the cached variant in this case
+                */
+               write_type = IO_COPY;
+       }
+
+       while ((cur_resid = uio_resid(uio)) && uio->uio_offset < newEOF && retval == 0) {
+               switch (write_type) {
+               case IO_COPY:
+                       /*
+                        * make sure the uio_resid isn't too big...
+                        * internally, we want to handle all of the I/O in
+                        * chunk sizes that fit in a 32 bit int
+                        */
+                       if (cur_resid > (user_ssize_t)(MAX_IO_REQUEST_SIZE)) {
+                               /*
+                                * we're going to have to call cluster_write_copy
+                                * more than once...
+                                *
+                                * only want the last call to cluster_write_copy to
+                                * have the IO_TAILZEROFILL flag set and only the
+                                * first call should have IO_HEADZEROFILL
+                                */
+                               zflags = flags & ~IO_TAILZEROFILL;
+                               flags &= ~IO_HEADZEROFILL;
+
+                               write_length = MAX_IO_REQUEST_SIZE;
+                       } else {
+                               /*
+                                * last call to cluster_write_copy
+                                */
+                               zflags = flags;
+
+                               write_length = (u_int32_t)cur_resid;
+                       }
+                       retval = cluster_write_copy(vp, uio, write_length, oldEOF, newEOF, headOff, tailOff, zflags, callback, callback_arg);
+                       break;
+
+               case IO_CONTIG:
+                       zflags = flags & ~(IO_TAILZEROFILL | IO_HEADZEROFILL);
+
+                       if (flags & IO_HEADZEROFILL) {
+                               /*
+                                * only do this once per request
+                                */
+                               flags &= ~IO_HEADZEROFILL;
+
+                               retval = cluster_write_copy(vp, (struct uio *)0, (u_int32_t)0, (off_t)0, uio->uio_offset,
+                                   headOff, (off_t)0, zflags | IO_HEADZEROFILL | IO_SYNC, callback, callback_arg);
+                               if (retval) {
+                                       break;
+                               }
+                       }
+                       retval = cluster_write_contig(vp, uio, newEOF, &write_type, &write_length, callback, callback_arg, bflag);
+
+                       if (retval == 0 && (flags & IO_TAILZEROFILL) && uio_resid(uio) == 0) {
+                               /*
+                                * we're done with the data from the user specified buffer(s)
+                                * and we've been requested to zero fill at the tail
+                                * treat this as an IO_HEADZEROFILL which doesn't require a uio
+                                * by rearranging the args and passing in IO_HEADZEROFILL
+                                */
+                               retval = cluster_write_copy(vp, (struct uio *)0, (u_int32_t)0, (off_t)0, tailOff, uio->uio_offset,
+                                   (off_t)0, zflags | IO_HEADZEROFILL | IO_SYNC, callback, callback_arg);
+                       }
+                       break;
+
+               case IO_DIRECT:
+                       /*
+                        * cluster_write_direct is never called with IO_TAILZEROFILL || IO_HEADZEROFILL
+                        */
+                       retval = cluster_write_direct(vp, uio, oldEOF, newEOF, &write_type, &write_length, flags, callback, callback_arg);
+                       break;
+
+               case IO_UNKNOWN:
+                       retval = cluster_io_type(uio, &write_type, &write_length, MIN_DIRECT_WRITE_SIZE);
+                       break;
+               }
+               /*
+                * in case we end up calling cluster_write_copy (from cluster_write_direct)
+                * multiple times to service a multi-vector request that is not aligned properly
+                * we need to update the oldEOF so that we
+                * don't zero-fill the head of a page if we've successfully written
+                * data to that area... 'cluster_write_copy' will zero-fill the head of a
+                * page that is beyond the oldEOF if the write is unaligned... we only
+                * want that to happen for the very first page of the cluster_write,
+                * NOT the first page of each vector making up a multi-vector write.
+                */
+               if (uio->uio_offset > oldEOF) {
+                       oldEOF = uio->uio_offset;
+               }
+       }
+       return retval;
+}
+
+
+static int
+cluster_write_direct(vnode_t vp, struct uio *uio, off_t oldEOF, off_t newEOF, int *write_type, u_int32_t *write_length,
+    int flags, int (*callback)(buf_t, void *), void *callback_arg)
+{
+       upl_t            upl;
+       upl_page_info_t  *pl;
+       vm_offset_t      upl_offset;
+       vm_offset_t      vector_upl_offset = 0;
+       u_int32_t        io_req_size;
+       u_int32_t        offset_in_file;
+       u_int32_t        offset_in_iovbase;
+       u_int32_t        io_size;
+       int              io_flag = 0;
+       upl_size_t       upl_size, vector_upl_size = 0;
+       vm_size_t        upl_needed_size;
+       mach_msg_type_number_t  pages_in_pl;
+       upl_control_flags_t upl_flags;
+       kern_return_t    kret;
+       mach_msg_type_number_t  i;
+       int              force_data_sync;
+       int              retval = 0;
+       int              first_IO = 1;
+       struct clios     iostate;
+       user_addr_t      iov_base;
+       u_int32_t        mem_alignment_mask;
+       u_int32_t        devblocksize;
+       u_int32_t        max_io_size;
+       u_int32_t        max_upl_size;
+       u_int32_t        max_vector_size;
+       u_int32_t        bytes_outstanding_limit;
+       boolean_t        io_throttled = FALSE;
+
+       u_int32_t        vector_upl_iosize = 0;
+       int              issueVectorUPL = 0, useVectorUPL = (uio->uio_iovcnt > 1);
+       off_t            v_upl_uio_offset = 0;
+       int              vector_upl_index = 0;
+       upl_t            vector_upl = NULL;
+
+
+       /*
+        * When we enter this routine, we know
+        *  -- the resid will not exceed iov_len
+        */
+       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 75)) | DBG_FUNC_START,
+           (int)uio->uio_offset, *write_length, (int)newEOF, 0, 0);
+
+       assert(vm_map_page_shift(current_map()) >= PAGE_SHIFT);
+
+       max_upl_size = cluster_max_io_size(vp->v_mount, CL_WRITE);
+
+       io_flag = CL_ASYNC | CL_PRESERVE | CL_COMMIT | CL_THROTTLE | CL_DIRECT_IO;
+
+       if (flags & IO_PASSIVE) {
+               io_flag |= CL_PASSIVE;
+       }
+
+       if (flags & IO_NOCACHE) {
+               io_flag |= CL_NOCACHE;
+       }
+
+       if (flags & IO_SKIP_ENCRYPTION) {
+               io_flag |= CL_ENCRYPTED;
+       }
+
+       iostate.io_completed = 0;
+       iostate.io_issued = 0;
+       iostate.io_error = 0;
+       iostate.io_wanted = 0;
+
+       lck_mtx_init(&iostate.io_mtxp, &cl_mtx_grp, LCK_ATTR_NULL);
+
+       mem_alignment_mask = (u_int32_t)vp->v_mount->mnt_alignmentmask;
+       devblocksize = (u_int32_t)vp->v_mount->mnt_devblocksize;
+
+       if (devblocksize == 1) {
+               /*
+                * the AFP client advertises a devblocksize of 1
+                * however, its BLOCKMAP routine maps to physical
+                * blocks that are PAGE_SIZE in size...
+                * therefore we can't ask for I/Os that aren't page aligned
+                * or aren't multiples of PAGE_SIZE in size
+                * by setting devblocksize to PAGE_SIZE, we re-instate
+                * the old behavior we had before the mem_alignment_mask
+                * changes went in...
+                */
+               devblocksize = PAGE_SIZE;
+       }
+
+next_dwrite:
+       io_req_size = *write_length;
+       iov_base = uio_curriovbase(uio);
+
+       offset_in_file = (u_int32_t)uio->uio_offset & PAGE_MASK;
+       offset_in_iovbase = (u_int32_t)iov_base & mem_alignment_mask;
+
+       if (offset_in_file || offset_in_iovbase) {
+               /*
+                * one of the 2 important offsets is misaligned
+                * so fire an I/O through the cache for this entire vector
+                */
+               goto wait_for_dwrites;
+       }
+       if (iov_base & (devblocksize - 1)) {
+               /*
+                * the offset in memory must be on a device block boundary
+                * so that we can guarantee that we can generate an
+                * I/O that ends on a page boundary in cluster_io
+                */
+               goto wait_for_dwrites;
+       }
+
+       task_update_logical_writes(current_task(), (io_req_size & ~PAGE_MASK), TASK_WRITE_IMMEDIATE, vp);
+       while (io_req_size >= PAGE_SIZE && uio->uio_offset < newEOF && retval == 0) {
+               int     throttle_type;
+
+               if ((throttle_type = cluster_is_throttled(vp))) {
+                       /*
+                        * we're in the throttle window, at the very least
+                        * we want to limit the size of the I/O we're about
+                        * to issue
+                        */
+                       if ((flags & IO_RETURN_ON_THROTTLE) && throttle_type == THROTTLE_NOW) {
+                               /*
+                                * we're in the throttle window and at least 1 I/O
+                                * has already been issued by a throttleable thread
+                                * in this window, so return with EAGAIN to indicate
+                                * to the FS issuing the cluster_write call that it
+                                * should now throttle after dropping any locks
+                                */
+                               throttle_info_update_by_mount(vp->v_mount);
+
+                               io_throttled = TRUE;
+                               goto wait_for_dwrites;
+                       }
+                       max_vector_size = THROTTLE_MAX_IOSIZE;
+                       max_io_size = THROTTLE_MAX_IOSIZE;
+               } else {
+                       max_vector_size = MAX_VECTOR_UPL_SIZE;
+                       max_io_size = max_upl_size;
+               }
+
+               if (first_IO) {
+                       cluster_syncup(vp, newEOF, callback, callback_arg, callback ? PUSH_SYNC : 0);
+                       first_IO = 0;
+               }
+               io_size  = io_req_size & ~PAGE_MASK;
+               iov_base = uio_curriovbase(uio);
+
+               if (io_size > max_io_size) {
+                       io_size = max_io_size;
+               }
+
+               if (useVectorUPL && (iov_base & PAGE_MASK)) {
+                       /*
+                        * We have an iov_base that's not page-aligned.
+                        * Issue all I/O's that have been collected within
+                        * this Vectored UPL.
+                        */
+                       if (vector_upl_index) {
+                               retval = vector_cluster_io(vp, vector_upl, vector_upl_offset, v_upl_uio_offset, vector_upl_iosize, io_flag, (buf_t)NULL, &iostate, callback, callback_arg);
+                               reset_vector_run_state();
+                       }
+
+                       /*
+                        * After this point, if we are using the Vector UPL path and the base is
+                        * not page-aligned then the UPL with that base will be the first in the vector UPL.
+                        */
+               }
+
+               upl_offset = (vm_offset_t)((u_int32_t)iov_base & PAGE_MASK);
+               upl_needed_size = (upl_offset + io_size + (PAGE_SIZE - 1)) & ~PAGE_MASK;
+
+               KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 76)) | DBG_FUNC_START,
+                   (int)upl_offset, upl_needed_size, (int)iov_base, io_size, 0);
+
+               vm_map_t map = UIO_SEG_IS_USER_SPACE(uio->uio_segflg) ? current_map() : kernel_map;
+               for (force_data_sync = 0; force_data_sync < 3; force_data_sync++) {
+                       pages_in_pl = 0;
+                       upl_size = (upl_size_t)upl_needed_size;
+                       upl_flags = UPL_FILE_IO | UPL_COPYOUT_FROM | UPL_NO_SYNC |
+                           UPL_CLEAN_IN_PLACE | UPL_SET_INTERNAL | UPL_SET_LITE | UPL_SET_IO_WIRE;
+
+                       kret = vm_map_get_upl(map,
+                           vm_map_trunc_page(iov_base, vm_map_page_mask(map)),
+                           &upl_size,
+                           &upl,
+                           NULL,
+                           &pages_in_pl,
+                           &upl_flags,
+                           VM_KERN_MEMORY_FILE,
+                           force_data_sync);
+
+                       if (kret != KERN_SUCCESS) {
+                               KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 76)) | DBG_FUNC_END,
+                                   0, 0, 0, kret, 0);
+                               /*
+                                * failed to get pagelist
+                                *
+                                * we may have already spun some portion of this request
+                                * off as async requests... we need to wait for the I/O
+                                * to complete before returning
+                                */
+                               goto wait_for_dwrites;
+                       }
+                       pl = UPL_GET_INTERNAL_PAGE_LIST(upl);
+                       pages_in_pl = upl_size / PAGE_SIZE;
+
+                       for (i = 0; i < pages_in_pl; i++) {
+                               if (!upl_valid_page(pl, i)) {
+                                       break;
+                               }
+                       }
+                       if (i == pages_in_pl) {
+                               break;
+                       }
+
+                       /*
+                        * didn't get all the pages back that we
+                        * needed... release this upl and try again
+                        */
+                       ubc_upl_abort(upl, 0);
+               }
+               if (force_data_sync >= 3) {
+                       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 76)) | DBG_FUNC_END,
+                           i, pages_in_pl, upl_size, kret, 0);
+                       /*
+                        * for some reason, we couldn't acquire a hold on all
+                        * the pages needed in the user's address space
+                        *
+                        * we may have already spun some portion of this request
+                        * off as async requests... we need to wait for the I/O
+                        * to complete before returning
+                        */
+                       goto wait_for_dwrites;
+               }
+
+               /*
+                * Consider the possibility that upl_size wasn't satisfied.
+                */
+               if (upl_size < upl_needed_size) {
+                       if (upl_size && upl_offset == 0) {
+                               io_size = upl_size;
+                       } else {
+                               io_size = 0;
+                       }
+               }
+               KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 76)) | DBG_FUNC_END,
+                   (int)upl_offset, upl_size, (int)iov_base, io_size, 0);
+
+               if (io_size == 0) {
+                       ubc_upl_abort(upl, 0);
+                       /*
+                        * we may have already spun some portion of this request
+                        * off as async requests... we need to wait for the I/O
+                        * to complete before returning
+                        */
+                       goto wait_for_dwrites;
+               }
+
+               if (useVectorUPL) {
+                       vm_offset_t end_off = ((iov_base + io_size) & PAGE_MASK);
+                       if (end_off) {
+                               issueVectorUPL = 1;
+                       }
+                       /*
+                        * After this point, if we are using a vector UPL, then
+                        * either all the UPL elements end on a page boundary OR
+                        * this UPL is the last element because it does not end
+                        * on a page boundary.
+                        */
+               }
+
+               /*
+                * we want push out these writes asynchronously so that we can overlap
+                * the preparation of the next I/O
+                * if there are already too many outstanding writes
+                * wait until some complete before issuing the next
+                */
+               if (vp->v_mount->mnt_minsaturationbytecount) {
+                       bytes_outstanding_limit = vp->v_mount->mnt_minsaturationbytecount;
+               } else {
+                       bytes_outstanding_limit = max_upl_size * IO_SCALE(vp, 2);
+               }
+
+               cluster_iostate_wait(&iostate, bytes_outstanding_limit, "cluster_write_direct");
+
+               if (iostate.io_error) {
+                       /*
+                        * one of the earlier writes we issued ran into a hard error
+                        * don't issue any more writes, cleanup the UPL
+                        * that was just created but not used, then
+                        * go wait for all writes that are part of this stream
+                        * to complete before returning the error to the caller
+                        */
+                       ubc_upl_abort(upl, 0);
+
+                       goto wait_for_dwrites;
+               }
+
+               KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 77)) | DBG_FUNC_START,
+                   (int)upl_offset, (int)uio->uio_offset, io_size, io_flag, 0);
+
+               if (!useVectorUPL) {
+                       retval = cluster_io(vp, upl, upl_offset, uio->uio_offset,
+                           io_size, io_flag, (buf_t)NULL, &iostate, callback, callback_arg);
+               } else {
+                       if (!vector_upl_index) {
+                               vector_upl = vector_upl_create(upl_offset);
+                               v_upl_uio_offset = uio->uio_offset;
+                               vector_upl_offset = upl_offset;
+                       }
+
+                       vector_upl_set_subupl(vector_upl, upl, upl_size);
+                       vector_upl_set_iostate(vector_upl, upl, vector_upl_size, upl_size);
+                       vector_upl_index++;
+                       vector_upl_iosize += io_size;
+                       vector_upl_size += upl_size;
+
+                       if (issueVectorUPL || vector_upl_index == MAX_VECTOR_UPL_ELEMENTS || vector_upl_size >= max_vector_size) {
+                               retval = vector_cluster_io(vp, vector_upl, vector_upl_offset, v_upl_uio_offset, vector_upl_iosize, io_flag, (buf_t)NULL, &iostate, callback, callback_arg);
+                               reset_vector_run_state();
+                       }
+               }
+
+               /*
+                * update the uio structure to
+                * reflect the I/O that we just issued
+                */
+               uio_update(uio, (user_size_t)io_size);
+
+               /*
+                * in case we end up calling through to cluster_write_copy to finish
+                * the tail of this request, we need to update the oldEOF so that we
+                * don't zero-fill the head of a page if we've successfully written
+                * data to that area... 'cluster_write_copy' will zero-fill the head of a
+                * page that is beyond the oldEOF if the write is unaligned... we only
+                * want that to happen for the very first page of the cluster_write,
+                * NOT the first page of each vector making up a multi-vector write.
+                */
+               if (uio->uio_offset > oldEOF) {
+                       oldEOF = uio->uio_offset;
+               }
+
+               io_req_size -= io_size;
+
+               KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 77)) | DBG_FUNC_END,
+                   (int)upl_offset, (int)uio->uio_offset, io_req_size, retval, 0);
+       } /* end while */
+
+       if (retval == 0 && iostate.io_error == 0 && io_req_size == 0) {
+               retval = cluster_io_type(uio, write_type, write_length, MIN_DIRECT_WRITE_SIZE);
+
+               if (retval == 0 && *write_type == IO_DIRECT) {
+                       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 75)) | DBG_FUNC_NONE,
+                           (int)uio->uio_offset, *write_length, (int)newEOF, 0, 0);
+
+                       goto next_dwrite;
+               }
+       }
+
+wait_for_dwrites:
+
+       if (retval == 0 && iostate.io_error == 0 && useVectorUPL && vector_upl_index) {
+               retval = vector_cluster_io(vp, vector_upl, vector_upl_offset, v_upl_uio_offset, vector_upl_iosize, io_flag, (buf_t)NULL, &iostate, callback, callback_arg);
+               reset_vector_run_state();
+       }
+       /*
+        * make sure all async writes issued as part of this stream
+        * have completed before we return
+        */
+       cluster_iostate_wait(&iostate, 0, "cluster_write_direct");
+
+       if (iostate.io_error) {
+               retval = iostate.io_error;
+       }
+
+       lck_mtx_destroy(&iostate.io_mtxp, &cl_mtx_grp);
+
+       if (io_throttled == TRUE && retval == 0) {
+               retval = EAGAIN;
+       }
+
+       if (io_req_size && retval == 0) {
+               /*
+                * we couldn't handle the tail of this request in DIRECT mode
+                * so fire it through the copy path
+                *
+                * note that flags will never have IO_HEADZEROFILL or IO_TAILZEROFILL set
+                * so we can just pass 0 in for the headOff and tailOff
+                */
+               if (uio->uio_offset > oldEOF) {
+                       oldEOF = uio->uio_offset;
+               }
+
+               retval = cluster_write_copy(vp, uio, io_req_size, oldEOF, newEOF, (off_t)0, (off_t)0, flags, callback, callback_arg);
+
+               *write_type = IO_UNKNOWN;
+       }
+       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 75)) | DBG_FUNC_END,
+           (int)uio->uio_offset, io_req_size, retval, 4, 0);
+
+       return retval;
+}
+
+
+static int
+cluster_write_contig(vnode_t vp, struct uio *uio, off_t newEOF, int *write_type, u_int32_t *write_length,
+    int (*callback)(buf_t, void *), void *callback_arg, int bflag)
+{
+       upl_page_info_t *pl;
+       addr64_t         src_paddr = 0;
+       upl_t            upl[MAX_VECTS];
+       vm_offset_t      upl_offset;
+       u_int32_t        tail_size = 0;
+       u_int32_t        io_size;
+       u_int32_t        xsize;
+       upl_size_t       upl_size;
+       vm_size_t        upl_needed_size;
+       mach_msg_type_number_t  pages_in_pl;
+       upl_control_flags_t upl_flags;
+       kern_return_t    kret;
+       struct clios     iostate;
+       int              error  = 0;
+       int              cur_upl = 0;
+       int              num_upl = 0;
+       int              n;
+       user_addr_t      iov_base;
+       u_int32_t        devblocksize;
+       u_int32_t        mem_alignment_mask;
+
+       /*
+        * When we enter this routine, we know
+        *  -- the io_req_size will not exceed iov_len
+        *  -- the target address is physically contiguous
+        */
+       cluster_syncup(vp, newEOF, callback, callback_arg, callback ? PUSH_SYNC : 0);
+
+       devblocksize = (u_int32_t)vp->v_mount->mnt_devblocksize;
+       mem_alignment_mask = (u_int32_t)vp->v_mount->mnt_alignmentmask;
+
+       iostate.io_completed = 0;
+       iostate.io_issued = 0;
+       iostate.io_error = 0;
+       iostate.io_wanted = 0;
+
+       lck_mtx_init(&iostate.io_mtxp, &cl_mtx_grp, LCK_ATTR_NULL);
+
+next_cwrite:
+       io_size = *write_length;
+
+       iov_base = uio_curriovbase(uio);
+
+       upl_offset = (vm_offset_t)((u_int32_t)iov_base & PAGE_MASK);
+       upl_needed_size = upl_offset + io_size;
+
+       pages_in_pl = 0;
+       upl_size = (upl_size_t)upl_needed_size;
+       upl_flags = UPL_FILE_IO | UPL_COPYOUT_FROM | UPL_NO_SYNC |
+           UPL_CLEAN_IN_PLACE | UPL_SET_INTERNAL | UPL_SET_LITE | UPL_SET_IO_WIRE;
+
+       vm_map_t map = UIO_SEG_IS_USER_SPACE(uio->uio_segflg) ? current_map() : kernel_map;
+       kret = vm_map_get_upl(map,
+           vm_map_trunc_page(iov_base, vm_map_page_mask(map)),
+           &upl_size, &upl[cur_upl], NULL, &pages_in_pl, &upl_flags, VM_KERN_MEMORY_FILE, 0);
+
+       if (kret != KERN_SUCCESS) {
+               /*
+                * failed to get pagelist
+                */
+               error = EINVAL;
+               goto wait_for_cwrites;
+       }
+       num_upl++;
+
+       /*
+        * Consider the possibility that upl_size wasn't satisfied.
+        */
+       if (upl_size < upl_needed_size) {
+               /*
+                * This is a failure in the physical memory case.
+                */
+               error = EINVAL;
+               goto wait_for_cwrites;
+       }
+       pl = ubc_upl_pageinfo(upl[cur_upl]);
+
+       src_paddr = ((addr64_t)upl_phys_page(pl, 0) << PAGE_SHIFT) + (addr64_t)upl_offset;
+
+       while (((uio->uio_offset & (devblocksize - 1)) || io_size < devblocksize) && io_size) {
+               u_int32_t   head_size;
+
+               head_size = devblocksize - (u_int32_t)(uio->uio_offset & (devblocksize - 1));
+
+               if (head_size > io_size) {
+                       head_size = io_size;
+               }
+
+               error = cluster_align_phys_io(vp, uio, src_paddr, head_size, 0, callback, callback_arg);
+
+               if (error) {
+                       goto wait_for_cwrites;
+               }
+
+               upl_offset += head_size;
+               src_paddr  += head_size;
+               io_size    -= head_size;
+
+               iov_base   += head_size;
+       }
+       if ((u_int32_t)iov_base & mem_alignment_mask) {
+               /*
+                * request doesn't set up on a memory boundary
+                * the underlying DMA engine can handle...
+                * return an error instead of going through
+                * the slow copy path since the intent of this
+                * path is direct I/O from device memory
+                */
+               error = EINVAL;
+               goto wait_for_cwrites;
+       }
+
+       tail_size = io_size & (devblocksize - 1);
+       io_size  -= tail_size;
+
+       while (io_size && error == 0) {
+               if (io_size > MAX_IO_CONTIG_SIZE) {
+                       xsize = MAX_IO_CONTIG_SIZE;
+               } else {
+                       xsize = io_size;
+               }
+               /*
+                * request asynchronously so that we can overlap
+                * the preparation of the next I/O... we'll do
+                * the commit after all the I/O has completed
+                * since its all issued against the same UPL
+                * if there are already too many outstanding writes
+                * wait until some have completed before issuing the next
+                */
+               cluster_iostate_wait(&iostate, MAX_IO_CONTIG_SIZE * IO_SCALE(vp, 2), "cluster_write_contig");
+
+               if (iostate.io_error) {
+                       /*
+                        * one of the earlier writes we issued ran into a hard error
+                        * don't issue any more writes...
+                        * go wait for all writes that are part of this stream
+                        * to complete before returning the error to the caller
+                        */
+                       goto wait_for_cwrites;
+               }
+               /*
+                * issue an asynchronous write to cluster_io
+                */
+               error = cluster_io(vp, upl[cur_upl], upl_offset, uio->uio_offset,
+                   xsize, CL_DEV_MEMORY | CL_ASYNC | bflag, (buf_t)NULL, (struct clios *)&iostate, callback, callback_arg);
+
+               if (error == 0) {
+                       /*
+                        * The cluster_io write completed successfully,
+                        * update the uio structure
+                        */
+                       uio_update(uio, (user_size_t)xsize);
+
+                       upl_offset += xsize;
+                       src_paddr  += xsize;
+                       io_size    -= xsize;
+               }
+       }
+       if (error == 0 && iostate.io_error == 0 && tail_size == 0 && num_upl < MAX_VECTS) {
+               error = cluster_io_type(uio, write_type, write_length, 0);
+
+               if (error == 0 && *write_type == IO_CONTIG) {
+                       cur_upl++;
+                       goto next_cwrite;
+               }
+       } else {
+               *write_type = IO_UNKNOWN;
+       }
+
+wait_for_cwrites:
+       /*
+        * make sure all async writes that are part of this stream
+        * have completed before we proceed
+        */
+       cluster_iostate_wait(&iostate, 0, "cluster_write_contig");
+
+       if (iostate.io_error) {
+               error = iostate.io_error;
+       }
+
+       lck_mtx_destroy(&iostate.io_mtxp, &cl_mtx_grp);
+
+       if (error == 0 && tail_size) {
+               error = cluster_align_phys_io(vp, uio, src_paddr, tail_size, 0, callback, callback_arg);
+       }
+
+       for (n = 0; n < num_upl; n++) {
+               /*
+                * just release our hold on each physically contiguous
+                * region without changing any state
+                */
+               ubc_upl_abort(upl[n], 0);
+       }
+
+       return error;
+}
+
+
+/*
+ * need to avoid a race between an msync of a range of pages dirtied via mmap
+ * vs a filesystem such as HFS deciding to write a 'hole' to disk via cluster_write's
+ * zerofill mechanism before it has seen the VNOP_PAGEOUTs for the pages being msync'd
+ *
+ * we should never force-zero-fill pages that are already valid in the cache...
+ * the entire page contains valid data (either from disk, zero-filled or dirtied
+ * via an mmap) so we can only do damage by trying to zero-fill
+ *
+ */
+static int
+cluster_zero_range(upl_t upl, upl_page_info_t *pl, int flags, int io_offset, off_t zero_off, off_t upl_f_offset, int bytes_to_zero)
+{
+       int zero_pg_index;
+       boolean_t need_cluster_zero = TRUE;
+
+       if ((flags & (IO_NOZEROVALID | IO_NOZERODIRTY))) {
+               bytes_to_zero = min(bytes_to_zero, PAGE_SIZE - (int)(zero_off & PAGE_MASK_64));
+               zero_pg_index = (int)((zero_off - upl_f_offset) / PAGE_SIZE_64);
 
-       if (size > rounded_size && (local_flags & CL_COMMIT))
-               ubc_upl_abort_range(upl, upl_offset + rounded_size,
-                                   size - rounded_size, UPL_ABORT_FREE_ON_EMPTY | UPL_ABORT_ERROR);
-       
-       retval = cluster_io(vp, upl, upl_offset, f_offset, io_size, devblocksize,
-                          local_flags | CL_READ | CL_PAGEIN, (struct buf *)0, (struct clios *)0);
-
-       if (retval == 0) {
-               int b_lblkno;
-               int e_lblkno;
-
-               b_lblkno = (int)(f_offset / PAGE_SIZE_64);
-               e_lblkno = (int)
-                       ((f_offset + ((off_t)io_size - 1)) / PAGE_SIZE_64);
-
-               if (!(flags & UPL_NORDAHEAD) && !(vp->v_flag & VRAOFF) && rounded_size == PAGE_SIZE) {
-                       /*
-                        * we haven't read the last page in of the file yet
-                        * so let's try to read ahead if we're in 
-                        * a sequential access pattern
+               if (upl_valid_page(pl, zero_pg_index)) {
+                       /*
+                        * never force zero valid pages - dirty or clean
+                        * we'll leave these in the UPL for cluster_write_copy to deal with
                         */
-                       cluster_rd_ahead(vp, b_lblkno, e_lblkno, filesize, devblocksize);
+                       need_cluster_zero = FALSE;
                }
-               vp->v_lastr = e_lblkno;
        }
-       return (retval);
-}
+       if (need_cluster_zero == TRUE) {
+               cluster_zero(upl, io_offset, bytes_to_zero, NULL);
+       }
 
-int
-cluster_bp(bp)
-       struct buf *bp;
-{
-        off_t  f_offset;
-       int    flags;
+       return bytes_to_zero;
+}
 
-       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 19)) | DBG_FUNC_START,
-                    (int)bp, bp->b_lblkno, bp->b_bcount, bp->b_flags, 0);
 
-       if (bp->b_pagelist == (upl_t) 0)
-               panic("cluster_bp: can't handle NULL upl yet\n");
-       if (bp->b_flags & B_READ)
-               flags = CL_ASYNC | CL_READ;
-       else
-               flags = CL_ASYNC;
+void
+cluster_update_state(vnode_t vp, vm_object_offset_t s_offset, vm_object_offset_t e_offset, boolean_t vm_initiated)
+{
+       struct cl_extent cl;
+       boolean_t first_pass = TRUE;
 
-       f_offset = ubc_blktooff(bp->b_vp, bp->b_lblkno);
+       assert(s_offset < e_offset);
+       assert((s_offset & PAGE_MASK_64) == 0);
+       assert((e_offset & PAGE_MASK_64) == 0);
 
-        return (cluster_io(bp->b_vp, bp->b_pagelist, 0, f_offset, bp->b_bcount, 0, flags, bp, (struct clios *)0));
-}
+       cl.b_addr = (daddr64_t)(s_offset / PAGE_SIZE_64);
+       cl.e_addr = (daddr64_t)(e_offset / PAGE_SIZE_64);
 
-int
-cluster_write(vp, uio, oldEOF, newEOF, headOff, tailOff, devblocksize, flags)
-       struct vnode *vp;
-       struct uio   *uio;
-       off_t         oldEOF;
-       off_t         newEOF;
-       off_t         headOff;
-       off_t         tailOff;
-       int           devblocksize;
-       int           flags;
-{
-       int           prev_resid;
-       int           clip_size;
-       off_t         max_io_size;
-       struct iovec  *iov;
-       int           upl_size;
-       int           upl_flags;
-       upl_t         upl;
-       int           retval = 0;
-
-       
-       if (vp->v_flag & VHASBEENPAGED)
-         {
-           /*
-            * this vnode had pages cleaned to it by
-            * the pager which indicates that either
-            * it's not very 'hot', or the system is
-            * being overwhelmed by a lot of dirty 
-            * data being delayed in the VM cache...
-            * in either event, we'll push our remaining
-            * delayed data at this point...  this will
-            * be more efficient than paging out 1 page at 
-            * a time, and will also act as a throttle
-            * by delaying this client from writing any
-            * more data until all his delayed data has
-            * at least been queued to the uderlying driver.
-            */
-           cluster_push(vp);
-         
-           vp->v_flag &= ~VHASBEENPAGED;
-         }
-
-       if ( (!(vp->v_flag & VNOCACHE_DATA)) || (!uio) || (uio->uio_segflg != UIO_USERSPACE))
-         {
-           /*
-            * go do a write through the cache if one of the following is true....
-            *   NOCACHE is not true
-            *   there is no uio structure or it doesn't target USERSPACE
-            */
-           return (cluster_write_x(vp, uio, oldEOF, newEOF, headOff, tailOff, devblocksize, flags));
-         }
-       
-       while (uio->uio_resid && uio->uio_offset < newEOF && retval == 0)
-         {
-           /*
-            * we know we have a resid, so this is safe
-            * skip over any emtpy vectors
-            */
-           iov = uio->uio_iov;
-
-           while (iov->iov_len == 0) {
-             uio->uio_iov++;
-             uio->uio_iovcnt--;
-             iov = uio->uio_iov;
-           }
-            upl_size  = PAGE_SIZE;
-            upl_flags = UPL_QUERY_OBJECT_TYPE;
-
-            if ((vm_map_get_upl(current_map(),
-                               (vm_offset_t)iov->iov_base & ~PAGE_MASK,
-                               &upl_size, &upl, NULL, NULL, &upl_flags, 0)) != KERN_SUCCESS)
-              {
-               /*
-                * the user app must have passed in an invalid address
-                */
-               return (EFAULT);
-              }              
-
-            /*
-             * We check every vector target but if it is physically
-             * contiguous space, we skip the sanity checks.
-             */
-            if (upl_flags & UPL_PHYS_CONTIG)
-             {
-               if (flags & IO_HEADZEROFILL)
-                 {
-                   flags &= ~IO_HEADZEROFILL;
-
-                   if (retval = cluster_write_x(vp, (struct uio *)0, 0, uio->uio_offset, headOff, 0, devblocksize, IO_HEADZEROFILL))
-                       return(retval);
-                 }
-
-               retval = cluster_phys_write(vp, uio, newEOF, devblocksize, flags);
-
-               if (uio->uio_resid == 0 && (flags & IO_TAILZEROFILL))
-                 {
-                   return (cluster_write_x(vp, (struct uio *)0, 0, tailOff, uio->uio_offset, 0, devblocksize, IO_HEADZEROFILL));
-                 }
-             }
-           else if ((uio->uio_resid < PAGE_SIZE) || (flags & (IO_TAILZEROFILL | IO_HEADZEROFILL)))
-             {
-               /*
-                * we're here because we're don't have a physically contiguous target buffer
-                * go do a write through the cache if one of the following is true....
-                *   the total xfer size is less than a page...
-                *   we're being asked to ZEROFILL either the head or the tail of the I/O...
-                */
-               return (cluster_write_x(vp, uio, oldEOF, newEOF, headOff, tailOff, devblocksize, flags));
-             }
-           else if (((int)uio->uio_offset & PAGE_MASK) || ((int)iov->iov_base & PAGE_MASK))
-             {
-               if (((int)uio->uio_offset & PAGE_MASK) == ((int)iov->iov_base & PAGE_MASK))
-                 {
-                   /*
-                    * Bring the file offset write up to a pagesize boundary
-                    * this will also bring the base address to a page boundary
-                    * since they both are currently on the same offset within a page
-                    * note: if we get here, uio->uio_resid is greater than PAGE_SIZE
-                    * so the computed clip_size must always be less than the current uio_resid
-                    */
-                   clip_size = (PAGE_SIZE - (uio->uio_offset & PAGE_MASK_64));
-
-                   /* 
-                    * Fake the resid going into the cluster_write_x call
-                    * and restore it on the way out.
-                    */
-                   prev_resid = uio->uio_resid;
-                   uio->uio_resid = clip_size;
-                   retval = cluster_write_x(vp, uio, oldEOF, newEOF, headOff, tailOff, devblocksize, flags);
-                   uio->uio_resid = prev_resid - (clip_size - uio->uio_resid);
-                 }
-               else 
-                 {
-                   /*
-                    * can't get both the file offset and the buffer offset aligned to a page boundary
-                    * so fire an I/O through the cache for this entire vector
-                    */
-                   clip_size = iov->iov_len;
-                   prev_resid = uio->uio_resid;
-                   uio->uio_resid = clip_size;
-                   retval = cluster_write_x(vp, uio, oldEOF, newEOF, headOff, tailOff, devblocksize, flags);
-                   uio->uio_resid = prev_resid - (clip_size - uio->uio_resid);
-                 }
-             }
-           else
-             {
-               /* 
-                * If we come in here, we know the offset into
-                * the file is on a pagesize boundary and the
-                * target buffer address is also on a page boundary
-                */
-               max_io_size = newEOF - uio->uio_offset;
-               clip_size = uio->uio_resid;
-               if (iov->iov_len < clip_size)
-                 clip_size = iov->iov_len;
-               if (max_io_size < clip_size)
-                 clip_size = max_io_size;
-
-               if (clip_size < PAGE_SIZE)
-                 {
-                   /*
-                    * Take care of tail end of write in this vector
-                    */
-                   prev_resid = uio->uio_resid;
-                   uio->uio_resid = clip_size;
-                   retval = cluster_write_x(vp, uio, oldEOF, newEOF, headOff, tailOff, devblocksize, flags);
-                   uio->uio_resid = prev_resid - (clip_size - uio->uio_resid);
-                 }
-               else
-                 {
-                   /* round clip_size down to a multiple of pagesize */
-                   clip_size = clip_size & ~(PAGE_MASK);
-                   prev_resid = uio->uio_resid;
-                   uio->uio_resid = clip_size;
-                   retval = cluster_nocopy_write(vp, uio, newEOF, devblocksize, flags);
-                   if ((retval == 0) && uio->uio_resid)
-                     retval = cluster_write_x(vp, uio, oldEOF, newEOF, headOff, tailOff, devblocksize, flags);
-                   uio->uio_resid = prev_resid - (clip_size - uio->uio_resid);
-                 }
-             } /* end else */
-         } /* end while */
-       return(retval);
+       cluster_update_state_internal(vp, &cl, 0, TRUE, &first_pass, s_offset, (int)(e_offset - s_offset),
+           vp->v_un.vu_ubcinfo->ui_size, NULL, NULL, vm_initiated);
 }
 
 
-static int
-cluster_nocopy_write(vp, uio, newEOF, devblocksize, flags)
-       struct vnode *vp;
-       struct uio   *uio;
-       off_t         newEOF;
-       int           devblocksize;
-       int           flags;
+static void
+cluster_update_state_internal(vnode_t vp, struct cl_extent *cl, int flags, boolean_t defer_writes,
+    boolean_t *first_pass, off_t write_off, int write_cnt, off_t newEOF,
+    int (*callback)(buf_t, void *), void *callback_arg, boolean_t vm_initiated)
 {
-       upl_t            upl;
-       upl_page_info_t  *pl;
-       off_t            upl_f_offset;
-       vm_offset_t      upl_offset;
-       off_t            max_io_size;
-       int              io_size;
-       int              io_flag;
-       int              upl_size;
-       int              upl_needed_size;
-       int              pages_in_pl;
-       int              upl_flags;
-       kern_return_t    kret;
-       struct iovec     *iov;
-       int              i;
-       int              force_data_sync;
-       int              error  = 0;
-       struct clios     iostate;
+       struct cl_writebehind *wbp;
+       int     cl_index;
+       int     ret_cluster_try_push;
+       u_int   max_cluster_pgcount;
 
-       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 75)) | DBG_FUNC_START,
-                    (int)uio->uio_offset, (int)uio->uio_resid, 
-                    (int)newEOF, devblocksize, 0);
+
+       max_cluster_pgcount = MAX_CLUSTER_SIZE(vp) / PAGE_SIZE;
 
        /*
-        * When we enter this routine, we know
-        *  -- the offset into the file is on a pagesize boundary
-        *  -- the resid is a page multiple
-        *  -- the resid will not exceed iov_len
+        * take the lock to protect our accesses
+        * of the writebehind and sparse cluster state
         */
-       cluster_try_push(vp, newEOF, 0, 1);
-
-       iostate.io_completed = 0;
-       iostate.io_issued = 0;
-       iostate.io_error = 0;
-       iostate.io_wanted = 0;
-
-       iov = uio->uio_iov;
+       wbp = cluster_get_wbp(vp, CLW_ALLOCATE | CLW_RETURNLOCKED);
 
-       while (uio->uio_resid && uio->uio_offset < newEOF && error == 0) {
-               io_size = uio->uio_resid;
-
-               if (io_size > (MAX_UPL_TRANSFER * PAGE_SIZE))
-                       io_size = MAX_UPL_TRANSFER * PAGE_SIZE;
+       if (wbp->cl_scmap) {
+               if (!(flags & IO_NOCACHE)) {
+                       /*
+                        * we've fallen into the sparse
+                        * cluster method of delaying dirty pages
+                        */
+                       sparse_cluster_add(wbp, &(wbp->cl_scmap), vp, cl, newEOF, callback, callback_arg, vm_initiated);
 
-               upl_offset = (vm_offset_t)iov->iov_base & PAGE_MASK;
-               upl_needed_size = (upl_offset + io_size + (PAGE_SIZE -1)) & ~PAGE_MASK;
+                       lck_mtx_unlock(&wbp->cl_lockw);
+                       return;
+               }
+               /*
+                * must have done cached writes that fell into
+                * the sparse cluster mechanism... we've switched
+                * to uncached writes on the file, so go ahead
+                * and push whatever's in the sparse map
+                * and switch back to normal clustering
+                */
+               wbp->cl_number = 0;
 
-               KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 76)) | DBG_FUNC_START,
-                            (int)upl_offset, upl_needed_size, (int)iov->iov_base, io_size, 0);
+               sparse_cluster_push(wbp, &(wbp->cl_scmap), vp, newEOF, PUSH_ALL, 0, callback, callback_arg, vm_initiated);
+               /*
+                * no clusters of either type present at this point
+                * so just go directly to start_new_cluster since
+                * we know we need to delay this I/O since we've
+                * already released the pages back into the cache
+                * to avoid the deadlock with sparse_cluster_push
+                */
+               goto start_new_cluster;
+       }
+       if (*first_pass == TRUE) {
+               if (write_off == wbp->cl_last_write) {
+                       wbp->cl_seq_written += write_cnt;
+               } else {
+                       wbp->cl_seq_written = write_cnt;
+               }
 
-               for (force_data_sync = 0; force_data_sync < 3; force_data_sync++) {
-                       pages_in_pl = 0;
-                       upl_size = upl_needed_size;
-                       upl_flags = UPL_FILE_IO | UPL_COPYOUT_FROM | UPL_NO_SYNC |
-                                   UPL_CLEAN_IN_PLACE | UPL_SET_INTERNAL | UPL_SET_LITE | UPL_SET_IO_WIRE;
+               wbp->cl_last_write = write_off + write_cnt;
 
-                       kret = vm_map_get_upl(current_map(),
-                                             (vm_offset_t)iov->iov_base & ~PAGE_MASK,
-                                             &upl_size,
-                                             &upl, 
-                                             NULL, 
-                                             &pages_in_pl,
-                                             &upl_flags,
-                                             force_data_sync);
+               *first_pass = FALSE;
+       }
+       if (wbp->cl_number == 0) {
+               /*
+                * no clusters currently present
+                */
+               goto start_new_cluster;
+       }
 
-                       if (kret != KERN_SUCCESS) {
-                               KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 76)) | DBG_FUNC_END,
-                                            0, 0, 0, kret, 0);
+       for (cl_index = 0; cl_index < wbp->cl_number; cl_index++) {
+               /*
+                * check each cluster that we currently hold
+                * try to merge some or all of this write into
+                * one or more of the existing clusters... if
+                * any portion of the write remains, start a
+                * new cluster
+                */
+               if (cl->b_addr >= wbp->cl_clusters[cl_index].b_addr) {
+                       /*
+                        * the current write starts at or after the current cluster
+                        */
+                       if (cl->e_addr <= (wbp->cl_clusters[cl_index].b_addr + max_cluster_pgcount)) {
                                /*
-                                * cluster_nocopy_write: failed to get pagelist
-                                *
-                                * we may have already spun some portion of this request
-                                * off as async requests... we need to wait for the I/O
-                                * to complete before returning
+                                * we have a write that fits entirely
+                                * within the existing cluster limits
                                 */
-                               goto wait_for_writes;
+                               if (cl->e_addr > wbp->cl_clusters[cl_index].e_addr) {
+                                       /*
+                                        * update our idea of where the cluster ends
+                                        */
+                                       wbp->cl_clusters[cl_index].e_addr = cl->e_addr;
+                               }
+                               break;
                        }
-                       pl = UPL_GET_INTERNAL_PAGE_LIST(upl);
-                       pages_in_pl = upl_size / PAGE_SIZE;
+                       if (cl->b_addr < (wbp->cl_clusters[cl_index].b_addr + max_cluster_pgcount)) {
+                               /*
+                                * we have a write that starts in the middle of the current cluster
+                                * but extends beyond the cluster's limit... we know this because
+                                * of the previous checks
+                                * we'll extend the current cluster to the max
+                                * and update the b_addr for the current write to reflect that
+                                * the head of it was absorbed into this cluster...
+                                * note that we'll always have a leftover tail in this case since
+                                * full absorbtion would have occurred in the clause above
+                                */
+                               wbp->cl_clusters[cl_index].e_addr = wbp->cl_clusters[cl_index].b_addr + max_cluster_pgcount;
 
-                       for (i = 0; i < pages_in_pl; i++) {
-                               if (!upl_valid_page(pl, i))
-                                       break;            
+                               cl->b_addr = wbp->cl_clusters[cl_index].e_addr;
                        }
-                       if (i == pages_in_pl)
-                               break;
-
                        /*
-                        * didn't get all the pages back that we
-                        * needed... release this upl and try again
+                        * we come here for the case where the current write starts
+                        * beyond the limit of the existing cluster or we have a leftover
+                        * tail after a partial absorbtion
+                        *
+                        * in either case, we'll check the remaining clusters before
+                        * starting a new one
                         */
-                       ubc_upl_abort_range(upl, (upl_offset & ~PAGE_MASK), upl_size, 
-                                           UPL_ABORT_FREE_ON_EMPTY);
-               }
-               if (force_data_sync >= 3) {
-                       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 76)) | DBG_FUNC_END,
-                                    i, pages_in_pl, upl_size, kret, 0);
+               } else {
                        /*
-                        * for some reason, we couldn't acquire a hold on all
-                        * the pages needed in the user's address space
-                        *
-                        * we may have already spun some portion of this request
-                        * off as async requests... we need to wait for the I/O
-                        * to complete before returning
+                        * the current write starts in front of the cluster we're currently considering
                         */
-                       goto wait_for_writes;
-               }
-
-               /*
-                * Consider the possibility that upl_size wasn't satisfied.
-                */
-               if (upl_size != upl_needed_size)
-                       io_size = (upl_size - (int)upl_offset) & ~PAGE_MASK;
+                       if ((wbp->cl_clusters[cl_index].e_addr - cl->b_addr) <= max_cluster_pgcount) {
+                               /*
+                                * we can just merge the new request into
+                                * this cluster and leave it in the cache
+                                * since the resulting cluster is still
+                                * less than the maximum allowable size
+                                */
+                               wbp->cl_clusters[cl_index].b_addr = cl->b_addr;
 
-               KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 76)) | DBG_FUNC_END,
-                            (int)upl_offset, upl_size, (int)iov->iov_base, io_size, 0);                       
+                               if (cl->e_addr > wbp->cl_clusters[cl_index].e_addr) {
+                                       /*
+                                        * the current write completely
+                                        * envelops the existing cluster and since
+                                        * each write is limited to at most max_cluster_pgcount pages
+                                        * we can just use the start and last blocknos of the write
+                                        * to generate the cluster limits
+                                        */
+                                       wbp->cl_clusters[cl_index].e_addr = cl->e_addr;
+                               }
+                               break;
+                       }
+                       /*
+                        * if we were to combine this write with the current cluster
+                        * we would exceed the cluster size limit.... so,
+                        * let's see if there's any overlap of the new I/O with
+                        * the cluster we're currently considering... in fact, we'll
+                        * stretch the cluster out to it's full limit and see if we
+                        * get an intersection with the current write
+                        *
+                        */
+                       if (cl->e_addr > wbp->cl_clusters[cl_index].e_addr - max_cluster_pgcount) {
+                               /*
+                                * the current write extends into the proposed cluster
+                                * clip the length of the current write after first combining it's
+                                * tail with the newly shaped cluster
+                                */
+                               wbp->cl_clusters[cl_index].b_addr = wbp->cl_clusters[cl_index].e_addr - max_cluster_pgcount;
 
-               if (io_size == 0) {
-                       ubc_upl_abort_range(upl, (upl_offset & ~PAGE_MASK), upl_size, 
-                                           UPL_ABORT_FREE_ON_EMPTY);
+                               cl->e_addr = wbp->cl_clusters[cl_index].b_addr;
+                       }
                        /*
-                        * we may have already spun some portion of this request
-                        * off as async requests... we need to wait for the I/O
-                        * to complete before returning
+                        * if we get here, there was no way to merge
+                        * any portion of this write with this cluster
+                        * or we could only merge part of it which
+                        * will leave a tail...
+                        * we'll check the remaining clusters before starting a new one
                         */
-                       goto wait_for_writes;
                }
+       }
+       if (cl_index < wbp->cl_number) {
                /*
-                * Now look for pages already in the cache
-                * and throw them away.
-                * uio->uio_offset is page aligned within the file
-                * io_size is a multiple of PAGE_SIZE
-                */
-               ubc_range_op(vp, uio->uio_offset, uio->uio_offset + io_size, UPL_ROP_DUMP, NULL);
-
-               /*
-                * we want push out these writes asynchronously so that we can overlap
-                * the preparation of the next I/O
-                * if there are already too many outstanding writes
-                * wait until some complete before issuing the next
+                * we found an existing cluster(s) that we
+                * could entirely merge this I/O into
                 */
-               while ((iostate.io_issued - iostate.io_completed) > (2 * MAX_UPL_TRANSFER * PAGE_SIZE)) {
-                       iostate.io_wanted = 1;
-                       tsleep((caddr_t)&iostate.io_wanted, PRIBIO + 1, "cluster_nocopy_write", 0);
-               }       
-               if (iostate.io_error) {
-                       /*
-                        * one of the earlier writes we issued ran into a hard error
-                        * don't issue any more writes, cleanup the UPL
-                        * that was just created but not used, then
-                        * go wait for all writes that are part of this stream
-                        * to complete before returning the error to the caller
-                        */
-                       ubc_upl_abort_range(upl, (upl_offset & ~PAGE_MASK), upl_size, 
-                                           UPL_ABORT_FREE_ON_EMPTY);
-
-                       goto wait_for_writes;
-               }
-               io_flag = CL_ASYNC | CL_PRESERVE | CL_COMMIT | CL_THROTTLE;
-
-               KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 77)) | DBG_FUNC_START,
-                            (int)upl_offset, (int)uio->uio_offset, io_size, io_flag, 0);
-
-               error = cluster_io(vp, upl, upl_offset, uio->uio_offset,
-                                  io_size, devblocksize, io_flag, (struct buf *)0, &iostate);
+               goto delay_io;
+       }
 
-               iov->iov_len    -= io_size;
-               iov->iov_base   += io_size;
-               uio->uio_resid  -= io_size;
-               uio->uio_offset += io_size;
+       if (defer_writes == FALSE &&
+           wbp->cl_number == MAX_CLUSTERS &&
+           wbp->cl_seq_written >= (MAX_CLUSTERS * (max_cluster_pgcount * PAGE_SIZE))) {
+               uint32_t        n;
 
-               KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 77)) | DBG_FUNC_END,
-                            (int)upl_offset, (int)uio->uio_offset, (int)uio->uio_resid, error, 0);
+               if (vp->v_mount->mnt_minsaturationbytecount) {
+                       n = vp->v_mount->mnt_minsaturationbytecount / MAX_CLUSTER_SIZE(vp);
 
-       } /* end while */
+                       if (n > MAX_CLUSTERS) {
+                               n = MAX_CLUSTERS;
+                       }
+               } else {
+                       n = 0;
+               }
 
-wait_for_writes:
+               if (n == 0) {
+                       if (disk_conditioner_mount_is_ssd(vp->v_mount)) {
+                               n = WRITE_BEHIND_SSD;
+                       } else {
+                               n = WRITE_BEHIND;
+                       }
+               }
+               while (n--) {
+                       cluster_try_push(wbp, vp, newEOF, 0, 0, callback, callback_arg, NULL, vm_initiated);
+               }
+       }
+       if (wbp->cl_number < MAX_CLUSTERS) {
+               /*
+                * we didn't find an existing cluster to
+                * merge into, but there's room to start
+                * a new one
+                */
+               goto start_new_cluster;
+       }
        /*
-        * make sure all async writes issued as part of this stream
-        * have completed before we return
+        * no exisitng cluster to merge with and no
+        * room to start a new one... we'll try
+        * pushing one of the existing ones... if none of
+        * them are able to be pushed, we'll switch
+        * to the sparse cluster mechanism
+        * cluster_try_push updates cl_number to the
+        * number of remaining clusters... and
+        * returns the number of currently unused clusters
         */
-       while (iostate.io_issued != iostate.io_completed) {
-               iostate.io_wanted = 1;
-               tsleep((caddr_t)&iostate.io_wanted, PRIBIO + 1, "cluster_nocopy_write", 0);
-       }       
-       if (iostate.io_error)
-               error = iostate.io_error;
-
-       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 75)) | DBG_FUNC_END,
-                    (int)uio->uio_offset, (int)uio->uio_resid, error, 4, 0);
-
-       return (error);
-}
-
-
-static int
-cluster_phys_write(vp, uio, newEOF, devblocksize, flags)
-       struct vnode *vp;
-       struct uio   *uio;
-       off_t        newEOF;
-       int          devblocksize;
-       int          flags;
-{
-       upl_page_info_t *pl;
-       addr64_t         src_paddr;
-       upl_t            upl;
-       vm_offset_t      upl_offset;
-       int              tail_size;
-       int              io_size;
-       int              upl_size;
-       int              upl_needed_size;
-       int              pages_in_pl;
-       int              upl_flags;
-       kern_return_t    kret;
-       struct iovec     *iov;
-       int              error  = 0;
+       ret_cluster_try_push = 0;
 
        /*
-        * When we enter this routine, we know
-        *  -- the resid will not exceed iov_len
-        *  -- the vector target address is physcially contiguous
+        * if writes are not deferred, call cluster push immediately
         */
-       cluster_try_push(vp, newEOF, 0, 1);
-
-       iov = uio->uio_iov;
-       io_size = iov->iov_len;
-       upl_offset = (vm_offset_t)iov->iov_base & PAGE_MASK;
-       upl_needed_size = upl_offset + io_size;
-
-       pages_in_pl = 0;
-       upl_size = upl_needed_size;
-       upl_flags = UPL_FILE_IO | UPL_COPYOUT_FROM | UPL_NO_SYNC | 
-                   UPL_CLEAN_IN_PLACE | UPL_SET_INTERNAL | UPL_SET_LITE | UPL_SET_IO_WIRE;
-
-       kret = vm_map_get_upl(current_map(),
-                             (vm_offset_t)iov->iov_base & ~PAGE_MASK,
-                             &upl_size, &upl, NULL, &pages_in_pl, &upl_flags, 0);
-
-       if (kret != KERN_SUCCESS) {
-               /*
-                * cluster_phys_write: failed to get pagelist
-                * note: return kret here
-                */
-             return(EINVAL);
+       if (defer_writes == FALSE) {
+               ret_cluster_try_push = cluster_try_push(wbp, vp, newEOF, (flags & IO_NOCACHE) ? 0 : PUSH_DELAY, 0, callback, callback_arg, NULL, vm_initiated);
        }
        /*
-        * Consider the possibility that upl_size wasn't satisfied.
-        * This is a failure in the physical memory case.
+        * execute following regardless of writes being deferred or not
         */
-       if (upl_size < upl_needed_size) {
-               kernel_upl_abort_range(upl, 0, upl_size, UPL_ABORT_FREE_ON_EMPTY);
-               return(EINVAL);
-       }
-       pl = ubc_upl_pageinfo(upl);
-
-       src_paddr = ((addr64_t)upl_phys_page(pl, 0) << 12) + ((addr64_t)((u_int)iov->iov_base & PAGE_MASK));
-
-       while (((uio->uio_offset & (devblocksize - 1)) || io_size < devblocksize) && io_size) {
-               int   head_size;
-
-               head_size = devblocksize - (int)(uio->uio_offset & (devblocksize - 1));
-
-               if (head_size > io_size)
-                       head_size = io_size;
-
-               error = cluster_align_phys_io(vp, uio, src_paddr, head_size, devblocksize, 0);
-
-               if (error) {
-                       ubc_upl_abort_range(upl, 0, upl_size, UPL_ABORT_FREE_ON_EMPTY);
+       if (ret_cluster_try_push == 0) {
+               /*
+                * no more room in the normal cluster mechanism
+                * so let's switch to the more expansive but expensive
+                * sparse mechanism....
+                */
+               sparse_cluster_switch(wbp, vp, newEOF, callback, callback_arg, vm_initiated);
+               sparse_cluster_add(wbp, &(wbp->cl_scmap), vp, cl, newEOF, callback, callback_arg, vm_initiated);
 
-                       return(EINVAL);
-               }
-               upl_offset += head_size;
-               src_paddr  += head_size;
-               io_size    -= head_size;
+               lck_mtx_unlock(&wbp->cl_lockw);
+               return;
        }
-       tail_size = io_size & (devblocksize - 1);
-       io_size  -= tail_size;
+start_new_cluster:
+       wbp->cl_clusters[wbp->cl_number].b_addr = cl->b_addr;
+       wbp->cl_clusters[wbp->cl_number].e_addr = cl->e_addr;
 
-       if (io_size) {
-               /*
-                * issue a synchronous write to cluster_io
-                */
-               error = cluster_io(vp, upl, upl_offset, uio->uio_offset,
-                                  io_size, 0, CL_DEV_MEMORY, (struct buf *)0, (struct clios *)0);
+       wbp->cl_clusters[wbp->cl_number].io_flags = 0;
+
+       if (flags & IO_NOCACHE) {
+               wbp->cl_clusters[wbp->cl_number].io_flags |= CLW_IONOCACHE;
        }
-       if (error == 0) {
-               /*
-                * The cluster_io write completed successfully,
-                * update the uio structure
-                */
-               uio->uio_resid  -= io_size;
-               iov->iov_len    -= io_size;
-               iov->iov_base   += io_size;
-               uio->uio_offset += io_size;
-               src_paddr       += io_size;
 
-               if (tail_size)
-                       error = cluster_align_phys_io(vp, uio, src_paddr, tail_size, devblocksize, 0);
+       if (flags & IO_PASSIVE) {
+               wbp->cl_clusters[wbp->cl_number].io_flags |= CLW_IOPASSIVE;
        }
-       /*
-        * just release our hold on the physically contiguous
-        * region without changing any state
-        */
-       ubc_upl_abort_range(upl, 0, upl_size, UPL_ABORT_FREE_ON_EMPTY);
 
-       return (error);
+       wbp->cl_number++;
+delay_io:
+       lck_mtx_unlock(&wbp->cl_lockw);
+       return;
 }
 
 
 static int
-cluster_write_x(vp, uio, oldEOF, newEOF, headOff, tailOff, devblocksize, flags)
-       struct vnode *vp;
-       struct uio   *uio;
-       off_t         oldEOF;
-       off_t         newEOF;
-       off_t         headOff;
-       off_t         tailOff;
-       int           devblocksize;
-       int           flags;
+cluster_write_copy(vnode_t vp, struct uio *uio, u_int32_t io_req_size, off_t oldEOF, off_t newEOF, off_t headOff,
+    off_t tailOff, int flags, int (*callback)(buf_t, void *), void *callback_arg)
 {
        upl_page_info_t *pl;
        upl_t            upl;
-       vm_offset_t      upl_offset;
-       int              upl_size;
-       off_t            upl_f_offset;
+       vm_offset_t      upl_offset = 0;
+       vm_size_t        upl_size;
+       off_t            upl_f_offset;
        int              pages_in_upl;
-       int              start_offset;
+       int              start_offset;
        int              xfer_resid;
        int              io_size;
-       int              io_flags;
        int              io_offset;
        int              bytes_to_zero;
        int              bytes_to_move;
        kern_return_t    kret;
        int              retval = 0;
-       int              uio_resid;
+       int              io_resid;
        long long        total_size;
        long long        zero_cnt;
        off_t            zero_off;
        long long        zero_cnt1;
        off_t            zero_off1;
-       daddr_t          start_blkno;
-       daddr_t          last_blkno;
-        int              intersection;
-
+       off_t            write_off = 0;
+       int              write_cnt = 0;
+       boolean_t        first_pass = FALSE;
+       struct cl_extent cl;
+       int              bflag;
+       u_int            max_io_size;
 
        if (uio) {
-               KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 40)) | DBG_FUNC_START,
-                            (int)uio->uio_offset, uio->uio_resid, (int)oldEOF, (int)newEOF, 0);
+               KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 40)) | DBG_FUNC_START,
+                   (int)uio->uio_offset, io_req_size, (int)oldEOF, (int)newEOF, 0);
+
+               io_resid = io_req_size;
+       } else {
+               KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 40)) | DBG_FUNC_START,
+                   0, 0, (int)oldEOF, (int)newEOF, 0);
 
-               uio_resid = uio->uio_resid;
+               io_resid = 0;
+       }
+       if (flags & IO_PASSIVE) {
+               bflag = CL_PASSIVE;
        } else {
-               KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 40)) | DBG_FUNC_START,
-                            0, 0, (int)oldEOF, (int)newEOF, 0);
+               bflag = 0;
+       }
+       if (flags & IO_NOCACHE) {
+               bflag |= CL_NOCACHE;
+       }
 
-               uio_resid = 0;
+       if (flags & IO_SKIP_ENCRYPTION) {
+               bflag |= CL_ENCRYPTED;
        }
+
        zero_cnt  = 0;
        zero_cnt1 = 0;
+       zero_off  = 0;
+       zero_off1 = 0;
+
+       max_io_size = cluster_max_io_size(vp->v_mount, CL_WRITE);
 
        if (flags & IO_HEADZEROFILL) {
-               /*
+               /*
                 * some filesystems (HFS is one) don't support unallocated holes within a file...
                 * so we zero fill the intervening space between the old EOF and the offset
                 * where the next chunk of real data begins.... ftruncate will also use this
                 * routine to zero fill to the new EOF when growing a file... in this case, the
                 * uio structure will not be provided
                 */
-               if (uio) {
-                       if (headOff < uio->uio_offset) {
-                               zero_cnt = uio->uio_offset - headOff;
+               if (uio) {
+                       if (headOff < uio->uio_offset) {
+                               zero_cnt = uio->uio_offset - headOff;
                                zero_off = headOff;
                        }
-               } else if (headOff < newEOF) {  
-                       zero_cnt = newEOF - headOff;
+               } else if (headOff < newEOF) {
+                       zero_cnt = newEOF - headOff;
                        zero_off = headOff;
                }
+       } else {
+               if (uio && uio->uio_offset > oldEOF) {
+                       zero_off = uio->uio_offset & ~PAGE_MASK_64;
+
+                       if (zero_off >= oldEOF) {
+                               zero_cnt = uio->uio_offset - zero_off;
+
+                               flags |= IO_HEADZEROFILL;
+                       }
+               }
        }
        if (flags & IO_TAILZEROFILL) {
-               if (uio) {
-                       zero_off1 = uio->uio_offset + uio->uio_resid;
+               if (uio) {
+                       zero_off1 = uio->uio_offset + io_req_size;
+
+                       if (zero_off1 < tailOff) {
+                               zero_cnt1 = tailOff - zero_off1;
+                       }
+               }
+       } else {
+               if (uio && newEOF > oldEOF) {
+                       zero_off1 = uio->uio_offset + io_req_size;
+
+                       if (zero_off1 == newEOF && (zero_off1 & PAGE_MASK_64)) {
+                               zero_cnt1 = PAGE_SIZE_64 - (zero_off1 & PAGE_MASK_64);
 
-                       if (zero_off1 < tailOff)
-                               zero_cnt1 = tailOff - zero_off1;
-               }       
+                               flags |= IO_TAILZEROFILL;
+                       }
+               }
        }
        if (zero_cnt == 0 && uio == (struct uio *) 0) {
-           KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 40)) | DBG_FUNC_END,
-                        retval, 0, 0, 0, 0);
-           return (0);
+               KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 40)) | DBG_FUNC_END,
+                   retval, 0, 0, 0, 0);
+               return 0;
        }
-
-       while ((total_size = (uio_resid + zero_cnt + zero_cnt1)) && retval == 0) {
-               /*
+       if (uio) {
+               write_off = uio->uio_offset;
+               write_cnt = (int)uio_resid(uio);
+               /*
+                * delay updating the sequential write info
+                * in the control block until we've obtained
+                * the lock for it
+                */
+               first_pass = TRUE;
+       }
+       while ((total_size = (io_resid + zero_cnt + zero_cnt1)) && retval == 0) {
+               /*
                 * for this iteration of the loop, figure out where our starting point is
                 */
-               if (zero_cnt) {
-                       start_offset = (int)(zero_off & PAGE_MASK_64);
+               if (zero_cnt) {
+                       start_offset = (int)(zero_off & PAGE_MASK_64);
                        upl_f_offset = zero_off - start_offset;
-               } else if (uio_resid) {
-                       start_offset = (int)(uio->uio_offset & PAGE_MASK_64);
+               } else if (io_resid) {
+                       start_offset = (int)(uio->uio_offset & PAGE_MASK_64);
                        upl_f_offset = uio->uio_offset - start_offset;
                } else {
-                       start_offset = (int)(zero_off1 & PAGE_MASK_64);
+                       start_offset = (int)(zero_off1 & PAGE_MASK_64);
                        upl_f_offset = zero_off1 - start_offset;
                }
-               KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 46)) | DBG_FUNC_NONE,
-                            (int)zero_off, (int)zero_cnt, (int)zero_off1, (int)zero_cnt1, 0);
+               KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 46)) | DBG_FUNC_NONE,
+                   (int)zero_off, (int)zero_cnt, (int)zero_off1, (int)zero_cnt1, 0);
+
+               if (total_size > max_io_size) {
+                       total_size = max_io_size;
+               }
 
-               if (total_size > (MAX_UPL_TRANSFER * PAGE_SIZE))
-                       total_size = MAX_UPL_TRANSFER * PAGE_SIZE;
+               cl.b_addr = (daddr64_t)(upl_f_offset / PAGE_SIZE_64);
 
-               start_blkno = (daddr_t)(upl_f_offset / PAGE_SIZE_64);
-               
-               if (uio && !(vp->v_flag & VNOCACHE_DATA) &&
-                  (flags & (IO_SYNC | IO_HEADZEROFILL | IO_TAILZEROFILL)) == 0) {
-                       /*
-                        * assumption... total_size <= uio_resid
+               if (uio && ((flags & (IO_SYNC | IO_HEADZEROFILL | IO_TAILZEROFILL)) == 0)) {
+                       /*
+                        * assumption... total_size <= io_resid
                         * because IO_HEADZEROFILL and IO_TAILZEROFILL not set
                         */
-                       if ((start_offset + total_size) > (MAX_UPL_TRANSFER * PAGE_SIZE))
-                               total_size -= start_offset;
-                       xfer_resid = total_size;
+                       if ((start_offset + total_size) > max_io_size) {
+                               total_size = max_io_size - start_offset;
+                       }
+                       xfer_resid = (int)total_size;
+
+                       retval = cluster_copy_ubc_data_internal(vp, uio, &xfer_resid, 1, 1);
 
-                       retval = cluster_copy_ubc_data(vp, uio, &xfer_resid, 1);
-                       
-                       if (retval)
-                               break;
+                       if (retval) {
+                               break;
+                       }
 
-                       uio_resid   -= (total_size - xfer_resid);
+                       io_resid    -= (total_size - xfer_resid);
                        total_size   = xfer_resid;
                        start_offset = (int)(uio->uio_offset & PAGE_MASK_64);
                        upl_f_offset = uio->uio_offset - start_offset;
 
                        if (total_size == 0) {
-                               if (start_offset) {
-                                       /*
+                               if (start_offset) {
+                                       /*
                                         * the write did not finish on a page boundary
                                         * which will leave upl_f_offset pointing to the
                                         * beginning of the last page written instead of
@@ -1731,11 +3549,11 @@ cluster_write_x(vp, uio, oldEOF, newEOF, headOff, tailOff, devblocksize, flags)
                                         * so that the cluster code records the last page
                                         * written as dirty
                                         */
-                                       upl_f_offset += PAGE_SIZE_64;
+                                       upl_f_offset += PAGE_SIZE_64;
                                }
-                               upl_size = 0;
-                               
-                               goto check_cluster;
+                               upl_size = 0;
+
+                               goto check_cluster;
                        }
                }
                /*
@@ -1743,36 +3561,45 @@ cluster_write_x(vp, uio, oldEOF, newEOF, headOff, tailOff, devblocksize, flags)
                 * the requested write... limit each call to cluster_io
                 * to the maximum UPL size... cluster_io will clip if
                 * this exceeds the maximum io_size for the device,
-                * make sure to account for 
+                * make sure to account for
                 * a starting offset that's not page aligned
                 */
                upl_size = (start_offset + total_size + (PAGE_SIZE - 1)) & ~PAGE_MASK;
 
-               if (upl_size > (MAX_UPL_TRANSFER * PAGE_SIZE))
-                       upl_size = MAX_UPL_TRANSFER * PAGE_SIZE;
+               if (upl_size > max_io_size) {
+                       upl_size = max_io_size;
+               }
+
+               pages_in_upl = (int)(upl_size / PAGE_SIZE);
+               io_size      = (int)(upl_size - start_offset);
 
-               pages_in_upl = upl_size / PAGE_SIZE;
-               io_size      = upl_size - start_offset;
-               
-               if ((long long)io_size > total_size)
-                       io_size = total_size;
+               if ((long long)io_size > total_size) {
+                       io_size = (int)total_size;
+               }
 
                KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 41)) | DBG_FUNC_START, upl_size, io_size, total_size, 0, 0);
-                       
 
-               kret = ubc_create_upl(vp, 
-                                                       upl_f_offset,
-                                                       upl_size,
-                                                       &upl,
-                                                       &pl,
-                                                       UPL_SET_LITE);
-               if (kret != KERN_SUCCESS)
-                       panic("cluster_write: failed to get pagelist");
+
+               /*
+                * Gather the pages from the buffer cache.
+                * The UPL_WILL_MODIFY flag lets the UPL subsystem know
+                * that we intend to modify these pages.
+                */
+               kret = ubc_create_upl_kernel(vp,
+                   upl_f_offset,
+                   (int)upl_size,
+                   &upl,
+                   &pl,
+                   UPL_SET_LITE | ((uio != NULL && (uio->uio_flags & UIO_FLAGS_IS_COMPRESSED_FILE)) ? 0 : UPL_WILL_MODIFY),
+                   VM_KERN_MEMORY_FILE);
+               if (kret != KERN_SUCCESS) {
+                       panic("cluster_write_copy: failed to get pagelist");
+               }
 
                KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 41)) | DBG_FUNC_END,
-                       (int)upl, (int)upl_f_offset, start_offset, 0, 0);
+                   upl, (int)upl_f_offset, start_offset, 0, 0);
 
-               if (start_offset && !upl_valid_page(pl, 0)) {
+               if (start_offset && upl_f_offset < oldEOF && !upl_valid_page(pl, 0)) {
                        int   read_size;
 
                        /*
@@ -1782,11 +3609,12 @@ cluster_write_x(vp, uio, oldEOF, newEOF, headOff, tailOff, devblocksize, flags)
                         */
                        read_size = PAGE_SIZE;
 
-                       if ((upl_f_offset + read_size) > newEOF)
-                               read_size = newEOF - upl_f_offset;
+                       if ((upl_f_offset + read_size) > oldEOF) {
+                               read_size = (int)(oldEOF - upl_f_offset);
+                       }
 
-                       retval = cluster_io(vp, upl, 0, upl_f_offset, read_size, devblocksize,
-                                           CL_READ, (struct buf *)0, (struct clios *)0);
+                       retval = cluster_io(vp, upl, 0, upl_f_offset, read_size,
+                           CL_READ | bflag, (buf_t)NULL, (struct clios *)NULL, callback, callback_arg);
                        if (retval) {
                                /*
                                 * we had an error during the read which causes us to abort
@@ -1794,33 +3622,38 @@ cluster_write_x(vp, uio, oldEOF, newEOF, headOff, tailOff, devblocksize, flags)
                                 * to release the rest of the pages in the upl without modifying
                                 * there state and mark the failed page in error
                                 */
-                               ubc_upl_abort_range(upl, 0, PAGE_SIZE, UPL_ABORT_DUMP_PAGES);
-                               ubc_upl_abort_range(upl, 0, upl_size,  UPL_ABORT_FREE_ON_EMPTY);
+                               ubc_upl_abort_range(upl, 0, PAGE_SIZE, UPL_ABORT_DUMP_PAGES | UPL_ABORT_FREE_ON_EMPTY);
+
+                               if (upl_size > PAGE_SIZE) {
+                                       ubc_upl_abort_range(upl, 0, (upl_size_t)upl_size,
+                                           UPL_ABORT_FREE_ON_EMPTY);
+                               }
 
                                KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 45)) | DBG_FUNC_NONE,
-                                            (int)upl, 0, 0, retval, 0);
+                                   upl, 0, 0, retval, 0);
                                break;
                        }
                }
                if ((start_offset == 0 || upl_size > PAGE_SIZE) && ((start_offset + io_size) & PAGE_MASK)) {
-                       /* 
+                       /*
                         * the last offset we're writing to in this upl does not end on a page
                         * boundary... if it's not beyond the old EOF, then we'll also need to
                         * pre-read this page in if it isn't already valid
                         */
-                       upl_offset = upl_size - PAGE_SIZE;
+                       upl_offset = upl_size - PAGE_SIZE;
 
-                       if ((upl_f_offset + start_offset + io_size) < oldEOF &&
-                           !upl_valid_page(pl, upl_offset / PAGE_SIZE)) {
-                               int   read_size;
+                       if ((upl_f_offset + start_offset + io_size) < oldEOF &&
+                           !upl_valid_page(pl, (int)(upl_offset / PAGE_SIZE))) {
+                               int   read_size;
 
                                read_size = PAGE_SIZE;
 
-                               if ((upl_f_offset + upl_offset + read_size) > newEOF)
-                                       read_size = newEOF - (upl_f_offset + upl_offset);
+                               if ((off_t)(upl_f_offset + upl_offset + read_size) > oldEOF) {
+                                       read_size = (int)(oldEOF - (upl_f_offset + upl_offset));
+                               }
 
-                               retval = cluster_io(vp, upl, upl_offset, upl_f_offset + upl_offset, read_size, devblocksize,
-                                                   CL_READ, (struct buf *)0, (struct clios *)0);
+                               retval = cluster_io(vp, upl, upl_offset, upl_f_offset + upl_offset, read_size,
+                                   CL_READ | bflag, (buf_t)NULL, (struct clios *)NULL, callback, callback_arg);
                                if (retval) {
                                        /*
                                         * we had an error during the read which causes us to abort
@@ -1828,11 +3661,14 @@ cluster_write_x(vp, uio, oldEOF, newEOF, headOff, tailOff, devblocksize, flags)
                                         * need to release the rest of the pages in the upl without
                                         * modifying there state and mark the failed page in error
                                         */
-                                       ubc_upl_abort_range(upl, upl_offset, PAGE_SIZE, UPL_ABORT_DUMP_PAGES);
-                                       ubc_upl_abort_range(upl, 0,          upl_size,  UPL_ABORT_FREE_ON_EMPTY);
+                                       ubc_upl_abort_range(upl, (upl_offset_t)upl_offset, PAGE_SIZE, UPL_ABORT_DUMP_PAGES | UPL_ABORT_FREE_ON_EMPTY);
+
+                                       if (upl_size > PAGE_SIZE) {
+                                               ubc_upl_abort_range(upl, 0, (upl_size_t)upl_size, UPL_ABORT_FREE_ON_EMPTY);
+                                       }
 
                                        KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 45)) | DBG_FUNC_NONE,
-                                                    (int)upl, 0, 0, retval, 0);
+                                           upl, 0, 0, retval, 0);
                                        break;
                                }
                        }
@@ -1841,738 +3677,512 @@ cluster_write_x(vp, uio, oldEOF, newEOF, headOff, tailOff, devblocksize, flags)
                io_offset = start_offset;
 
                while (zero_cnt && xfer_resid) {
-
-                       if (zero_cnt < (long long)xfer_resid)
-                               bytes_to_zero = zero_cnt;
-                       else
-                               bytes_to_zero = xfer_resid;
-
-                       if ( !(flags & (IO_NOZEROVALID | IO_NOZERODIRTY))) {
-                               cluster_zero(upl, io_offset, bytes_to_zero, NULL);
+                       if (zero_cnt < (long long)xfer_resid) {
+                               bytes_to_zero = (int)zero_cnt;
                        } else {
-                               int zero_pg_index;
-
-                               bytes_to_zero = min(bytes_to_zero, PAGE_SIZE - (int)(zero_off & PAGE_MASK_64));
-                               zero_pg_index = (int)((zero_off - upl_f_offset) / PAGE_SIZE_64);
+                               bytes_to_zero = xfer_resid;
+                       }
 
-                               if ( !upl_valid_page(pl, zero_pg_index)) {
-                                       cluster_zero(upl, io_offset, bytes_to_zero, NULL); 
+                       bytes_to_zero = cluster_zero_range(upl, pl, flags, io_offset, zero_off, upl_f_offset, bytes_to_zero);
 
-                               } else if ((flags & (IO_NOZERODIRTY | IO_NOZEROVALID)) == IO_NOZERODIRTY &&
-                                          !upl_dirty_page(pl, zero_pg_index)) {
-                                       cluster_zero(upl, io_offset, bytes_to_zero, NULL); 
-                               }
-                       }
                        xfer_resid -= bytes_to_zero;
                        zero_cnt   -= bytes_to_zero;
                        zero_off   += bytes_to_zero;
                        io_offset  += bytes_to_zero;
                }
-               if (xfer_resid && uio_resid) {
-                       bytes_to_move = min(uio_resid, xfer_resid);
+               if (xfer_resid && io_resid) {
+                       u_int32_t  io_requested;
 
-                       retval = cluster_copy_upl_data(uio, upl, io_offset, bytes_to_move);
+                       bytes_to_move = min(io_resid, xfer_resid);
+                       io_requested = bytes_to_move;
 
-                       if (retval) {
+                       retval = cluster_copy_upl_data(uio, upl, io_offset, (int *)&io_requested);
 
-                               ubc_upl_abort_range(upl, 0, upl_size, UPL_ABORT_DUMP_PAGES | UPL_ABORT_FREE_ON_EMPTY);
+                       if (retval) {
+                               ubc_upl_abort_range(upl, 0, (upl_size_t)upl_size, UPL_ABORT_FREE_ON_EMPTY);
 
                                KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 45)) | DBG_FUNC_NONE,
-                                            (int)upl, 0, 0, retval, 0);
+                                   upl, 0, 0, retval, 0);
                        } else {
-                               uio_resid  -= bytes_to_move;
+                               io_resid   -= bytes_to_move;
                                xfer_resid -= bytes_to_move;
                                io_offset  += bytes_to_move;
                        }
                }
                while (xfer_resid && zero_cnt1 && retval == 0) {
-
-                       if (zero_cnt1 < (long long)xfer_resid)
-                               bytes_to_zero = zero_cnt1;
-                       else
-                               bytes_to_zero = xfer_resid;
-
-                       if ( !(flags & (IO_NOZEROVALID | IO_NOZERODIRTY))) {
-                               cluster_zero(upl, io_offset, bytes_to_zero, NULL); 
+                       if (zero_cnt1 < (long long)xfer_resid) {
+                               bytes_to_zero = (int)zero_cnt1;
                        } else {
-                               int zero_pg_index;
-                       
-                               bytes_to_zero = min(bytes_to_zero, PAGE_SIZE - (int)(zero_off1 & PAGE_MASK_64));
-                               zero_pg_index = (int)((zero_off1 - upl_f_offset) / PAGE_SIZE_64);
-
-                               if ( !upl_valid_page(pl, zero_pg_index)) {
-                                       cluster_zero(upl, io_offset, bytes_to_zero, NULL); 
-                               } else if ((flags & (IO_NOZERODIRTY | IO_NOZEROVALID)) == IO_NOZERODIRTY &&
-                                          !upl_dirty_page(pl, zero_pg_index)) {
-                                       cluster_zero(upl, io_offset, bytes_to_zero, NULL); 
-                               }
+                               bytes_to_zero = xfer_resid;
                        }
+
+                       bytes_to_zero = cluster_zero_range(upl, pl, flags, io_offset, zero_off1, upl_f_offset, bytes_to_zero);
+
                        xfer_resid -= bytes_to_zero;
                        zero_cnt1  -= bytes_to_zero;
                        zero_off1  += bytes_to_zero;
                        io_offset  += bytes_to_zero;
                }
-
                if (retval == 0) {
-                       int cl_index;
-                       int can_delay;
+                       int do_zeroing = 1;
 
-                       io_size += start_offset;
+                       io_size += start_offset;
+
+                       /* Force more restrictive zeroing behavior only on APFS */
+                       if ((vnode_tag(vp) == VT_APFS) && (newEOF < oldEOF)) {
+                               do_zeroing = 0;
+                       }
 
-                       if ((upl_f_offset + io_size) >= newEOF && io_size < upl_size) {
-                               /*
+                       if (do_zeroing && (upl_f_offset + io_size) >= newEOF && (u_int)io_size < upl_size) {
+                               /*
                                 * if we're extending the file with this write
                                 * we'll zero fill the rest of the page so that
                                 * if the file gets extended again in such a way as to leave a
                                 * hole starting at this EOF, we'll have zero's in the correct spot
                                 */
-                               cluster_zero(upl, io_size, upl_size - io_size, NULL); 
+                               cluster_zero(upl, io_size, (int)(upl_size - io_size), NULL);
                        }
-                       if (flags & IO_SYNC)
-                               /*
-                                * if the IO_SYNC flag is set than we need to 
-                                * bypass any clusters and immediately issue
-                                * the I/O
-                                */
-                               goto issue_io;
+                       /*
+                        * release the upl now if we hold one since...
+                        * 1) pages in it may be present in the sparse cluster map
+                        *    and may span 2 separate buckets there... if they do and
+                        *    we happen to have to flush a bucket to make room and it intersects
+                        *    this upl, a deadlock may result on page BUSY
+                        * 2) we're delaying the I/O... from this point forward we're just updating
+                        *    the cluster state... no need to hold the pages, so commit them
+                        * 3) IO_SYNC is set...
+                        *    because we had to ask for a UPL that provides currenty non-present pages, the
+                        *    UPL has been automatically set to clear the dirty flags (both software and hardware)
+                        *    upon committing it... this is not the behavior we want since it's possible for
+                        *    pages currently present as part of a mapped file to be dirtied while the I/O is in flight.
+                        *    we'll pick these pages back up later with the correct behavior specified.
+                        * 4) we don't want to hold pages busy in a UPL and then block on the cluster lock... if a flush
+                        *    of this vnode is in progress, we will deadlock if the pages being flushed intersect the pages
+                        *    we hold since the flushing context is holding the cluster lock.
+                        */
+                       ubc_upl_commit_range(upl, 0, (upl_size_t)upl_size,
+                           UPL_COMMIT_SET_DIRTY | UPL_COMMIT_INACTIVATE | UPL_COMMIT_FREE_ON_EMPTY);
 check_cluster:
                        /*
-                        * calculate the last logical block number 
+                        * calculate the last logical block number
                         * that this delayed I/O encompassed
                         */
-                       last_blkno = (upl_f_offset + (off_t)upl_size) / PAGE_SIZE_64;
-
-                       if (vp->v_flag & VHASDIRTY) {
-
-                               if ( !(vp->v_flag & VNOCACHE_DATA)) {
-                                       /*
-                                        * we've fallen into the sparse
-                                        * cluster method of delaying dirty pages
-                                        * first, we need to release the upl if we hold one
-                                        * since pages in it may be present in the sparse cluster map
-                                        * and may span 2 separate buckets there... if they do and 
-                                        * we happen to have to flush a bucket to make room and it intersects
-                                        * this upl, a deadlock may result on page BUSY
-                                        */
-                                       if (upl_size)
-                                               ubc_upl_commit_range(upl, 0, upl_size,
-                                                                    UPL_COMMIT_SET_DIRTY | UPL_COMMIT_INACTIVATE | UPL_COMMIT_FREE_ON_EMPTY);
-
-                                       sparse_cluster_add(vp, newEOF, start_blkno, last_blkno);
+                       cl.e_addr = (daddr64_t)((upl_f_offset + (off_t)upl_size) / PAGE_SIZE_64);
 
-                                       continue;
-                               }
+                       if (flags & IO_SYNC) {
                                /*
-                                * must have done cached writes that fell into
-                                * the sparse cluster mechanism... we've switched
-                                * to uncached writes on the file, so go ahead
-                                * and push whatever's in the sparse map
-                                * and switch back to normal clustering
+                                * if the IO_SYNC flag is set than we need to bypass
+                                * any clustering and immediately issue the I/O
                                 *
-                                * see the comment above concerning a possible deadlock...
+                                * we don't hold the lock at this point
+                                *
+                                * we've already dropped the current upl, so pick it back up with COPYOUT_FROM set
+                                * so that we correctly deal with a change in state of the hardware modify bit...
+                                * we do this via cluster_push_now... by passing along the IO_SYNC flag, we force
+                                * cluster_push_now to wait until all the I/Os have completed... cluster_push_now is also
+                                * responsible for generating the correct sized I/O(s)
                                 */
-                               if (upl_size) {
-                                       ubc_upl_commit_range(upl, 0, upl_size,
-                                                            UPL_COMMIT_SET_DIRTY | UPL_COMMIT_INACTIVATE | UPL_COMMIT_FREE_ON_EMPTY);
-                                       /*
-                                        * setting upl_size to 0 keeps us from committing a
-                                        * second time in the start_new_cluster path
-                                        */
-                                       upl_size = 0;
+                               retval = cluster_push_now(vp, &cl, newEOF, flags, callback, callback_arg, FALSE);
+                       } else {
+                               boolean_t defer_writes = FALSE;
+
+                               if (vfs_flags(vp->v_mount) & MNT_DEFWRITE) {
+                                       defer_writes = TRUE;
                                }
-                               sparse_cluster_push(vp, ubc_getsize(vp), 1);
 
-                               /*
-                                * no clusters of either type present at this point
-                                * so just go directly to start_new_cluster since
-                                * we know we need to delay this I/O since we've
-                                * already released the pages back into the cache
-                                * to avoid the deadlock with sparse_cluster_push
-                                */
-                               goto start_new_cluster;
-                       }                   
-                       upl_offset = 0;
+                               cluster_update_state_internal(vp, &cl, flags, defer_writes, &first_pass,
+                                   write_off, write_cnt, newEOF, callback, callback_arg, FALSE);
+                       }
+               }
+       }
+       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 40)) | DBG_FUNC_END, retval, 0, io_resid, 0, 0);
 
-                       if (vp->v_clen == 0)
-                               /*
-                                * no clusters currently present
-                                */
-                               goto start_new_cluster;
-
-                       for (cl_index = 0; cl_index < vp->v_clen; cl_index++) {
-                               /*
-                                * check each cluster that we currently hold
-                                * try to merge some or all of this write into
-                                * one or more of the existing clusters... if
-                                * any portion of the write remains, start a
-                                * new cluster
-                                */
-                               if (start_blkno >= vp->v_clusters[cl_index].start_pg) {
-                                       /*
-                                        * the current write starts at or after the current cluster
-                                        */
-                                       if (last_blkno <= (vp->v_clusters[cl_index].start_pg + MAX_UPL_TRANSFER)) {
-                                               /*
-                                                * we have a write that fits entirely
-                                                * within the existing cluster limits
-                                                */
-                                               if (last_blkno > vp->v_clusters[cl_index].last_pg)
-                                                       /*
-                                                        * update our idea of where the cluster ends
-                                                        */
-                                                       vp->v_clusters[cl_index].last_pg = last_blkno;
-                                               break;
-                                       }
-                                       if (start_blkno < (vp->v_clusters[cl_index].start_pg + MAX_UPL_TRANSFER)) {
-                                               /*
-                                                * we have a write that starts in the middle of the current cluster
-                                                * but extends beyond the cluster's limit... we know this because
-                                                * of the previous checks
-                                                * we'll extend the current cluster to the max
-                                                * and update the start_blkno for the current write to reflect that
-                                                * the head of it was absorbed into this cluster...
-                                                * note that we'll always have a leftover tail in this case since
-                                                * full absorbtion would have occurred in the clause above
-                                                */
-                                               vp->v_clusters[cl_index].last_pg = vp->v_clusters[cl_index].start_pg + MAX_UPL_TRANSFER;
-
-                                               if (upl_size) {
-                                                       int  start_pg_in_upl;
-
-                                                       start_pg_in_upl = upl_f_offset / PAGE_SIZE_64;
-                                                       
-                                                       if (start_pg_in_upl < vp->v_clusters[cl_index].last_pg) {
-                                                               intersection = (vp->v_clusters[cl_index].last_pg - start_pg_in_upl) * PAGE_SIZE;
-
-                                                               ubc_upl_commit_range(upl, upl_offset, intersection,
-                                                                                    UPL_COMMIT_SET_DIRTY | UPL_COMMIT_INACTIVATE | UPL_COMMIT_FREE_ON_EMPTY);
-                                                               upl_f_offset += intersection;
-                                                               upl_offset   += intersection;
-                                                               upl_size     -= intersection;
-                                                       }
-                                               }
-                                               start_blkno = vp->v_clusters[cl_index].last_pg;
-                                       }
-                                       /*
-                                        * we come here for the case where the current write starts
-                                        * beyond the limit of the existing cluster or we have a leftover
-                                        * tail after a partial absorbtion
-                                        *
-                                        * in either case, we'll check the remaining clusters before 
-                                        * starting a new one
-                                        */
-                               } else {
-                                       /*
-                                        * the current write starts in front of the cluster we're currently considering
-                                        */
-                                       if ((vp->v_clusters[cl_index].last_pg - start_blkno) <= MAX_UPL_TRANSFER) {
-                                               /*
-                                                * we can just merge the new request into
-                                                * this cluster and leave it in the cache
-                                                * since the resulting cluster is still 
-                                                * less than the maximum allowable size
-                                                */
-                                               vp->v_clusters[cl_index].start_pg = start_blkno;
-
-                                               if (last_blkno > vp->v_clusters[cl_index].last_pg) {
-                                                       /*
-                                                        * the current write completely
-                                                        * envelops the existing cluster and since
-                                                        * each write is limited to at most MAX_UPL_TRANSFER bytes
-                                                        * we can just use the start and last blocknos of the write
-                                                        * to generate the cluster limits
-                                                        */
-                                                       vp->v_clusters[cl_index].last_pg = last_blkno;
-                                               }
-                                               break;
-                                       }
+       return retval;
+}
 
-                                       /*
-                                        * if we were to combine this write with the current cluster
-                                        * we would exceed the cluster size limit.... so,
-                                        * let's see if there's any overlap of the new I/O with
-                                        * the cluster we're currently considering... in fact, we'll
-                                        * stretch the cluster out to it's full limit and see if we
-                                        * get an intersection with the current write
-                                        * 
-                                        */
-                                       if (last_blkno > vp->v_clusters[cl_index].last_pg - MAX_UPL_TRANSFER) {
-                                               /*
-                                                * the current write extends into the proposed cluster
-                                                * clip the length of the current write after first combining it's
-                                                * tail with the newly shaped cluster
-                                                */
-                                               vp->v_clusters[cl_index].start_pg = vp->v_clusters[cl_index].last_pg - MAX_UPL_TRANSFER;
-
-                                               if (upl_size) {
-                                                       intersection = (last_blkno - vp->v_clusters[cl_index].start_pg) * PAGE_SIZE;
-
-                                                       if (intersection > upl_size)
-                                                               /*
-                                                                * because the current write may consist of a number of pages found in the cache
-                                                                * which are not part of the UPL, we may have an intersection that exceeds
-                                                                * the size of the UPL that is also part of this write
-                                                                */
-                                                               intersection = upl_size;
-
-                                                       ubc_upl_commit_range(upl, upl_offset + (upl_size - intersection), intersection,
-                                                                            UPL_COMMIT_SET_DIRTY | UPL_COMMIT_INACTIVATE | UPL_COMMIT_FREE_ON_EMPTY);
-                                                       upl_size -= intersection;
-                                               }
-                                               last_blkno = vp->v_clusters[cl_index].start_pg;
-                                       }
-                                       /*
-                                        * if we get here, there was no way to merge
-                                        * any portion of this write with this cluster 
-                                        * or we could only merge part of it which 
-                                        * will leave a tail...
-                                        * we'll check the remaining clusters before starting a new one
-                                        */
-                               }
-                       }
-                       if (cl_index < vp->v_clen)
-                               /*
-                                * we found an existing cluster(s) that we
-                                * could entirely merge this I/O into
-                                */
-                               goto delay_io;
 
-                       if (vp->v_clen < MAX_CLUSTERS && !(vp->v_flag & VNOCACHE_DATA))
-                               /*
-                                * we didn't find an existing cluster to
-                                * merge into, but there's room to start
-                                * a new one
-                                */
-                               goto start_new_cluster;
 
-                       /*
-                        * no exisitng cluster to merge with and no
-                        * room to start a new one... we'll try 
-                        * pushing one of the existing ones... if none of
-                        * them are able to be pushed, we'll switch
-                        * to the sparse cluster mechanism
-                        * cluster_try_push updates v_clen to the
-                        * number of remaining clusters... and
-                        * returns the number of currently unused clusters
-                        */
-                       if (vp->v_flag & VNOCACHE_DATA)
-                               can_delay = 0;
-                       else
-                               can_delay = 1;
-
-                       if (cluster_try_push(vp, newEOF, can_delay, 0) == 0) {
-                               /*
-                                * no more room in the normal cluster mechanism
-                                * so let's switch to the more expansive but expensive
-                                * sparse mechanism....
-                                * first, we need to release the upl if we hold one
-                                * since pages in it may be present in the sparse cluster map (after the cluster_switch)
-                                * and may span 2 separate buckets there... if they do and 
-                                * we happen to have to flush a bucket to make room and it intersects
-                                * this upl, a deadlock may result on page BUSY
-                                */
-                               if (upl_size)
-                                       ubc_upl_commit_range(upl, upl_offset, upl_size,
-                                                            UPL_COMMIT_SET_DIRTY | UPL_COMMIT_INACTIVATE | UPL_COMMIT_FREE_ON_EMPTY);
+int
+cluster_read(vnode_t vp, struct uio *uio, off_t filesize, int xflags)
+{
+       return cluster_read_ext(vp, uio, filesize, xflags, NULL, NULL);
+}
 
-                               sparse_cluster_switch(vp, newEOF);
-                               sparse_cluster_add(vp, newEOF, start_blkno, last_blkno);
 
-                               continue;
-                       }
-                       /*
-                        * we pushed one cluster successfully, so we must be sequentially writing this file
-                        * otherwise, we would have failed and fallen into the sparse cluster support
-                        * so let's take the opportunity to push out additional clusters as long as we
-                        * remain below the throttle... this will give us better I/O locality if we're
-                        * in a copy loop (i.e.  we won't jump back and forth between the read and write points
-                        * however, we don't want to push so much out that the write throttle kicks in and
-                        * hangs this thread up until some of the I/O completes...
-                        */
-                       while (vp->v_clen && (vp->v_numoutput <= (ASYNC_THROTTLE / 2)))
-                               cluster_try_push(vp, newEOF, 0, 0);
+int
+cluster_read_ext(vnode_t vp, struct uio *uio, off_t filesize, int xflags, int (*callback)(buf_t, void *), void *callback_arg)
+{
+       int             retval = 0;
+       int             flags;
+       user_ssize_t    cur_resid;
+       u_int32_t       io_size;
+       u_int32_t       read_length = 0;
+       int             read_type = IO_COPY;
 
-start_new_cluster:
-                       if (vp->v_clen == 0)
-                               vp->v_ciosiz = devblocksize;
+       flags = xflags;
 
-                       vp->v_clusters[vp->v_clen].start_pg = start_blkno;
-                       vp->v_clusters[vp->v_clen].last_pg  = last_blkno;
-                       vp->v_clen++;
+       if (vp->v_flag & VNOCACHE_DATA) {
+               flags |= IO_NOCACHE;
+       }
+       if ((vp->v_flag & VRAOFF) || speculative_reads_disabled) {
+               flags |= IO_RAOFF;
+       }
 
-delay_io:
-                       if (upl_size)
-                               ubc_upl_commit_range(upl, upl_offset, upl_size,
-                                                    UPL_COMMIT_SET_DIRTY | UPL_COMMIT_INACTIVATE | UPL_COMMIT_FREE_ON_EMPTY);
-                       continue;
-issue_io:
+       if (flags & IO_SKIP_ENCRYPTION) {
+               flags |= IO_ENCRYPTED;
+       }
+
+       /*
+        * do a read through the cache if one of the following is true....
+        *   NOCACHE is not true
+        *   the uio request doesn't target USERSPACE
+        * Alternatively, if IO_ENCRYPTED is set, then we want to bypass the cache as well.
+        * Reading encrypted data from a CP filesystem should never result in the data touching
+        * the UBC.
+        *
+        * otherwise, find out if we want the direct or contig variant for
+        * the first vector in the uio request
+        */
+       if (((flags & IO_NOCACHE) && UIO_SEG_IS_USER_SPACE(uio->uio_segflg)) || (flags & IO_ENCRYPTED)) {
+               retval = cluster_io_type(uio, &read_type, &read_length, 0);
+       }
+
+       while ((cur_resid = uio_resid(uio)) && uio->uio_offset < filesize && retval == 0) {
+               switch (read_type) {
+               case IO_COPY:
                        /*
-                        * in order to maintain some semblance of coherency with mapped writes
-                        * we need to write the cluster back out as a multiple of the PAGESIZE
-                        * unless the cluster encompasses the last page of the file... in this
-                        * case we'll round out to the nearest device block boundary
+                        * make sure the uio_resid isn't too big...
+                        * internally, we want to handle all of the I/O in
+                        * chunk sizes that fit in a 32 bit int
                         */
-                       io_size = upl_size;
-
-                       if ((upl_f_offset + io_size) > newEOF) {
-                               io_size = newEOF - upl_f_offset;
-                               io_size = (io_size + (devblocksize - 1)) & ~(devblocksize - 1);
+                       if (cur_resid > (user_ssize_t)(MAX_IO_REQUEST_SIZE)) {
+                               io_size = MAX_IO_REQUEST_SIZE;
+                       } else {
+                               io_size = (u_int32_t)cur_resid;
                        }
 
-                       if (flags & IO_SYNC)
-                               io_flags = CL_THROTTLE | CL_COMMIT | CL_AGE;
-                       else
-                               io_flags = CL_THROTTLE | CL_COMMIT | CL_AGE | CL_ASYNC;
+                       retval = cluster_read_copy(vp, uio, io_size, filesize, flags, callback, callback_arg);
+                       break;
+
+               case IO_DIRECT:
+                       retval = cluster_read_direct(vp, uio, filesize, &read_type, &read_length, flags, callback, callback_arg);
+                       break;
 
-                       if (vp->v_flag & VNOCACHE_DATA)
-                               io_flags |= CL_DUMP;
+               case IO_CONTIG:
+                       retval = cluster_read_contig(vp, uio, filesize, &read_type, &read_length, callback, callback_arg, flags);
+                       break;
 
-                       retval = cluster_io(vp, upl, 0, upl_f_offset, io_size, devblocksize,
-                                           io_flags, (struct buf *)0, (struct clios *)0);
+               case IO_UNKNOWN:
+                       retval = cluster_io_type(uio, &read_type, &read_length, 0);
+                       break;
                }
        }
-       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 40)) | DBG_FUNC_END,
-                    retval, 0, uio_resid, 0, 0);
-
-       return (retval);
+       return retval;
 }
 
-int
-cluster_read(vp, uio, filesize, devblocksize, flags)
-       struct vnode *vp;
-       struct uio   *uio;
-       off_t         filesize;
-       int           devblocksize;
-       int           flags;
+
+
+static void
+cluster_read_upl_release(upl_t upl, int start_pg, int last_pg, int take_reference)
 {
-       int           prev_resid;
-       int           clip_size;
-       off_t         max_io_size;
-       struct iovec  *iov;
-       int           upl_size;
-       int           upl_flags;
-       upl_t         upl;
-       int           retval = 0;
-
-
-       if (!((vp->v_flag & VNOCACHE_DATA) && (uio->uio_segflg == UIO_USERSPACE)))
-         {
-           /*
-            * go do a read through the cache if one of the following is true....
-            *   NOCACHE is not true
-            *   the uio request doesn't target USERSPACE
-            */
-           return (cluster_read_x(vp, uio, filesize, devblocksize, flags));
-         }
-
-       while (uio->uio_resid && uio->uio_offset < filesize && retval == 0)
-         {
-           /*
-            * we know we have a resid, so this is safe
-            * skip over any emtpy vectors
-            */
-           iov = uio->uio_iov;
-
-           while (iov->iov_len == 0) {
-             uio->uio_iov++;
-             uio->uio_iovcnt--;
-             iov = uio->uio_iov;
-           }
-            upl_size  = PAGE_SIZE;
-            upl_flags = UPL_QUERY_OBJECT_TYPE;
-  
-           if ((vm_map_get_upl(current_map(),
-                              (vm_offset_t)iov->iov_base & ~PAGE_MASK,
-                               &upl_size, &upl, NULL, NULL, &upl_flags, 0)) != KERN_SUCCESS)
-              {
-               /*
-                * the user app must have passed in an invalid address
-                */
-               return (EFAULT);
-              }
-
-           /*
-            * We check every vector target but if it is physically 
-            * contiguous space, we skip the sanity checks.
-            */
-           if (upl_flags & UPL_PHYS_CONTIG)
-             {
-               retval = cluster_phys_read(vp, uio, filesize, devblocksize, flags);
-             }
-           else if (uio->uio_resid < PAGE_SIZE)
-             {
-               /*
-                * we're here because we're don't have a physically contiguous target buffer
-                * go do a read through the cache if
-                *   the total xfer size is less than a page...
-                */
-               return (cluster_read_x(vp, uio, filesize, devblocksize, flags));
-             }
-           else if (((int)uio->uio_offset & PAGE_MASK) || ((int)iov->iov_base & PAGE_MASK))
-             {
-               if (((int)uio->uio_offset & PAGE_MASK) == ((int)iov->iov_base & PAGE_MASK))
-                 {
-                   /*
-                    * Bring the file offset read up to a pagesize boundary
-                    * this will also bring the base address to a page boundary
-                    * since they both are currently on the same offset within a page
-                    * note: if we get here, uio->uio_resid is greater than PAGE_SIZE
-                    * so the computed clip_size must always be less than the current uio_resid
-                    */
-                   clip_size = (PAGE_SIZE - (int)(uio->uio_offset & PAGE_MASK_64));
-
-                   /* 
-                    * Fake the resid going into the cluster_read_x call
-                    * and restore it on the way out.
-                    */
-                   prev_resid = uio->uio_resid;
-                   uio->uio_resid = clip_size;
-                   retval = cluster_read_x(vp, uio, filesize, devblocksize, flags);
-                   uio->uio_resid = prev_resid - (clip_size - uio->uio_resid);
-                 }
-               else
-                 {
-                   /*
-                    * can't get both the file offset and the buffer offset aligned to a page boundary
-                    * so fire an I/O through the cache for this entire vector
-                    */
-                   clip_size = iov->iov_len;
-                   prev_resid = uio->uio_resid;
-                   uio->uio_resid = clip_size;
-                   retval = cluster_read_x(vp, uio, filesize, devblocksize, flags);
-                   uio->uio_resid = prev_resid - (clip_size - uio->uio_resid);
-                 }
-             }
-           else
-             {
-               /* 
-                * If we come in here, we know the offset into
-                * the file is on a pagesize boundary
-                */
+       int range;
+       int abort_flags = UPL_ABORT_FREE_ON_EMPTY;
+
+       if ((range = last_pg - start_pg)) {
+               if (take_reference) {
+                       abort_flags |= UPL_ABORT_REFERENCE;
+               }
 
-               max_io_size = filesize - uio->uio_offset;
-               clip_size = uio->uio_resid;
-               if (iov->iov_len < clip_size)
-                 clip_size = iov->iov_len;
-               if (max_io_size < clip_size)
-                 clip_size = (int)max_io_size;
-
-               if (clip_size < PAGE_SIZE)
-                 {
-                   /*
-                    * Take care of the tail end of the read in this vector.
-                    */
-                   prev_resid = uio->uio_resid;
-                   uio->uio_resid = clip_size;
-                   retval = cluster_read_x(vp, uio, filesize, devblocksize, flags);
-                   uio->uio_resid = prev_resid - (clip_size - uio->uio_resid);
-                 }
-               else
-                 {
-                   /* round clip_size down to a multiple of pagesize */
-                   clip_size = clip_size & ~(PAGE_MASK);
-                   prev_resid = uio->uio_resid;
-                   uio->uio_resid = clip_size;
-                   retval = cluster_nocopy_read(vp, uio, filesize, devblocksize, flags);
-                   if ((retval==0) && uio->uio_resid)
-                     retval = cluster_read_x(vp, uio, filesize, devblocksize, flags);
-                   uio->uio_resid = prev_resid - (clip_size - uio->uio_resid);
-                 }
-             } /* end else */
-         } /* end while */
-
-       return(retval);
+               ubc_upl_abort_range(upl, start_pg * PAGE_SIZE, range * PAGE_SIZE, abort_flags);
+       }
 }
 
+
 static int
-cluster_read_x(vp, uio, filesize, devblocksize, flags)
-       struct vnode *vp;
-       struct uio   *uio;
-       off_t         filesize;
-       int           devblocksize;
-       int           flags;
+cluster_read_copy(vnode_t vp, struct uio *uio, u_int32_t io_req_size, off_t filesize, int flags, int (*callback)(buf_t, void *), void *callback_arg)
 {
        upl_page_info_t *pl;
        upl_t            upl;
        vm_offset_t      upl_offset;
-       int              upl_size;
-       off_t            upl_f_offset;
-       int              start_offset;
-       int              start_pg;
-       int              last_pg;
-       int              uio_last;
+       u_int32_t        upl_size;
+       off_t            upl_f_offset;
+       int              start_offset;
+       int              start_pg;
+       int              last_pg;
+       int              uio_last = 0;
        int              pages_in_upl;
        off_t            max_size;
        off_t            last_ioread_offset;
        off_t            last_request_offset;
-       u_int            size_of_prefetch;
-       int              io_size;
        kern_return_t    kret;
        int              error  = 0;
        int              retval = 0;
-       u_int            b_lblkno;
-       u_int            e_lblkno;
-       struct clios     iostate;
-       u_int            max_rd_size = MAX_UPL_TRANSFER * PAGE_SIZE;
+       u_int32_t        size_of_prefetch;
+       u_int32_t        xsize;
+       u_int32_t        io_size;
+       u_int32_t        max_rd_size;
+       u_int32_t        max_io_size;
+       u_int32_t        max_prefetch;
        u_int            rd_ahead_enabled = 1;
        u_int            prefetch_enabled = 1;
-
+       struct cl_readahead *   rap;
+       struct clios            iostate;
+       struct cl_extent        extent;
+       int              bflag;
+       int              take_reference = 1;
+       int              policy = IOPOL_DEFAULT;
+       boolean_t        iolock_inited = FALSE;
 
        KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 32)) | DBG_FUNC_START,
-                    (int)uio->uio_offset, uio->uio_resid, (int)filesize, devblocksize, 0);
+           (int)uio->uio_offset, io_req_size, (int)filesize, flags, 0);
 
-       if (cluster_hard_throttle_on(vp)) {
-               rd_ahead_enabled = 0;
-               prefetch_enabled = 0;
+       if (flags & IO_ENCRYPTED) {
+               panic("encrypted blocks will hit UBC!");
+       }
+
+       policy = throttle_get_io_policy(NULL);
+
+       if (policy == THROTTLE_LEVEL_TIER3 || policy == THROTTLE_LEVEL_TIER2 || (flags & IO_NOCACHE)) {
+               take_reference = 0;
+       }
+
+       if (flags & IO_PASSIVE) {
+               bflag = CL_PASSIVE;
+       } else {
+               bflag = 0;
+       }
+
+       if (flags & IO_NOCACHE) {
+               bflag |= CL_NOCACHE;
+       }
 
-               max_rd_size = HARD_THROTTLE_MAXSIZE;
+       if (flags & IO_SKIP_ENCRYPTION) {
+               bflag |= CL_ENCRYPTED;
        }
-       if (vp->v_flag & (VRAOFF|VNOCACHE_DATA))
-               rd_ahead_enabled = 0;
 
-       last_request_offset = uio->uio_offset + uio->uio_resid;
+       max_io_size = cluster_max_io_size(vp->v_mount, CL_READ);
+       max_prefetch = MAX_PREFETCH(vp, max_io_size, disk_conditioner_mount_is_ssd(vp->v_mount));
+       max_rd_size = max_prefetch;
+
+       last_request_offset = uio->uio_offset + io_req_size;
+
+       if (last_request_offset > filesize) {
+               last_request_offset = filesize;
+       }
 
-       if (last_request_offset > filesize)
-               last_request_offset = filesize;
-       b_lblkno = (u_int)(uio->uio_offset / PAGE_SIZE_64);
-        e_lblkno = (u_int)((last_request_offset - 1) / PAGE_SIZE_64);
+       if ((flags & (IO_RAOFF | IO_NOCACHE)) || ((last_request_offset & ~PAGE_MASK_64) == (uio->uio_offset & ~PAGE_MASK_64))) {
+               rd_ahead_enabled = 0;
+               rap = NULL;
+       } else {
+               if (cluster_is_throttled(vp)) {
+                       /*
+                        * we're in the throttle window, at the very least
+                        * we want to limit the size of the I/O we're about
+                        * to issue
+                        */
+                       rd_ahead_enabled = 0;
+                       prefetch_enabled = 0;
 
-       if (vp->v_ralen && (vp->v_lastr == b_lblkno || (vp->v_lastr + 1) == b_lblkno)) {
-               /*
+                       max_rd_size = THROTTLE_MAX_IOSIZE;
+               }
+               if ((rap = cluster_get_rap(vp)) == NULL) {
+                       rd_ahead_enabled = 0;
+               } else {
+                       extent.b_addr = uio->uio_offset / PAGE_SIZE_64;
+                       extent.e_addr = (last_request_offset - 1) / PAGE_SIZE_64;
+               }
+       }
+       if (rap != NULL && rap->cl_ralen && (rap->cl_lastr == extent.b_addr || (rap->cl_lastr + 1) == extent.b_addr)) {
+               /*
                 * determine if we already have a read-ahead in the pipe courtesy of the
                 * last read systemcall that was issued...
                 * if so, pick up it's extent to determine where we should start
-                * with respect to any read-ahead that might be necessary to 
+                * with respect to any read-ahead that might be necessary to
                 * garner all the data needed to complete this read systemcall
                 */
-               last_ioread_offset = (vp->v_maxra * PAGE_SIZE_64) + PAGE_SIZE_64;
+               last_ioread_offset = (rap->cl_maxra * PAGE_SIZE_64) + PAGE_SIZE_64;
 
-               if (last_ioread_offset < uio->uio_offset)
-                       last_ioread_offset = (off_t)0;
-               else if (last_ioread_offset > last_request_offset)
-                       last_ioread_offset = last_request_offset;
-       } else
-               last_ioread_offset = (off_t)0;
-
-       while (uio->uio_resid && uio->uio_offset < filesize && retval == 0) {
-               /*
-                * compute the size of the upl needed to encompass
-                * the requested read... limit each call to cluster_io
-                * to the maximum UPL size... cluster_io will clip if
-                * this exceeds the maximum io_size for the device,
-                * make sure to account for 
-                * a starting offset that's not page aligned
-                */
-               start_offset = (int)(uio->uio_offset & PAGE_MASK_64);
-               upl_f_offset = uio->uio_offset - (off_t)start_offset;
-               max_size     = filesize - uio->uio_offset;
+               if (last_ioread_offset < uio->uio_offset) {
+                       last_ioread_offset = (off_t)0;
+               } else if (last_ioread_offset > last_request_offset) {
+                       last_ioread_offset = last_request_offset;
+               }
+       } else {
+               last_ioread_offset = (off_t)0;
+       }
 
-               if ((off_t)((unsigned int)uio->uio_resid) < max_size)
-                       io_size = uio->uio_resid;
-               else
-                       io_size = max_size;
+       while (io_req_size && uio->uio_offset < filesize && retval == 0) {
+               max_size = filesize - uio->uio_offset;
+               bool leftover_upl_aborted = false;
 
-               if (!(vp->v_flag & VNOCACHE_DATA)) {
+               if ((off_t)(io_req_size) < max_size) {
+                       io_size = io_req_size;
+               } else {
+                       io_size = (u_int32_t)max_size;
+               }
 
-                       while (io_size) {
-                               u_int io_resid;
-                               u_int io_requested;
+               if (!(flags & IO_NOCACHE)) {
+                       while (io_size) {
+                               u_int32_t io_resid;
+                               u_int32_t io_requested;
 
                                /*
                                 * if we keep finding the pages we need already in the cache, then
-                                * don't bother to call cluster_rd_prefetch since it costs CPU cycles
+                                * don't bother to call cluster_read_prefetch since it costs CPU cycles
                                 * to determine that we have all the pages we need... once we miss in
                                 * the cache and have issued an I/O, than we'll assume that we're likely
                                 * to continue to miss in the cache and it's to our advantage to try and prefetch
                                 */
-                               if (last_request_offset && last_ioread_offset && (size_of_prefetch = (last_request_offset - last_ioread_offset))) {
-                                       if ((last_ioread_offset - uio->uio_offset) <= max_rd_size && prefetch_enabled) {
-                                               /*
+                               if (last_request_offset && last_ioread_offset && (size_of_prefetch = (u_int32_t)(last_request_offset - last_ioread_offset))) {
+                                       if ((last_ioread_offset - uio->uio_offset) <= max_rd_size && prefetch_enabled) {
+                                               /*
                                                 * we've already issued I/O for this request and
                                                 * there's still work to do and
                                                 * our prefetch stream is running dry, so issue a
                                                 * pre-fetch I/O... the I/O latency will overlap
                                                 * with the copying of the data
                                                 */
-                                               if (size_of_prefetch > max_rd_size)
-                                                       size_of_prefetch = max_rd_size;
+                                               if (size_of_prefetch > max_rd_size) {
+                                                       size_of_prefetch = max_rd_size;
+                                               }
 
-                                               size_of_prefetch = cluster_rd_prefetch(vp, last_ioread_offset, size_of_prefetch, filesize, devblocksize);
+                                               size_of_prefetch = cluster_read_prefetch(vp, last_ioread_offset, size_of_prefetch, filesize, callback, callback_arg, bflag);
 
                                                last_ioread_offset += (off_t)(size_of_prefetch * PAGE_SIZE);
-                               
-                                               if (last_ioread_offset > last_request_offset)
-                                                       last_ioread_offset = last_request_offset;
+
+                                               if (last_ioread_offset > last_request_offset) {
+                                                       last_ioread_offset = last_request_offset;
+                                               }
                                        }
                                }
                                /*
-                                * limit the size of the copy we're about to do so that 
-                                * we can notice that our I/O pipe is running dry and 
+                                * limit the size of the copy we're about to do so that
+                                * we can notice that our I/O pipe is running dry and
                                 * get the next I/O issued before it does go dry
                                 */
-                               if (last_ioread_offset && io_size > ((MAX_UPL_TRANSFER * PAGE_SIZE) / 4))
-                                       io_resid = ((MAX_UPL_TRANSFER * PAGE_SIZE) / 4);
-                               else
-                                       io_resid = io_size;
+                               if (last_ioread_offset && io_size > (max_io_size / 4)) {
+                                       io_resid = (max_io_size / 4);
+                               } else {
+                                       io_resid = io_size;
+                               }
 
                                io_requested = io_resid;
 
-                               retval = cluster_copy_ubc_data(vp, uio, &io_resid, 0);
+                               retval = cluster_copy_ubc_data_internal(vp, uio, (int *)&io_resid, 0, take_reference);
 
-                               io_size -= (io_requested - io_resid);
+                               xsize = io_requested - io_resid;
 
-                               if (retval || io_resid)
-                                       /*
+                               io_size -= xsize;
+                               io_req_size -= xsize;
+
+                               if (retval || io_resid) {
+                                       /*
                                         * if we run into a real error or
                                         * a page that is not in the cache
                                         * we need to leave streaming mode
                                         */
-                                       break;
-                               
-                               if ((io_size == 0 || last_ioread_offset == last_request_offset) && rd_ahead_enabled) {
-                                       /*
+                                       break;
+                               }
+
+                               if (rd_ahead_enabled && (io_size == 0 || last_ioread_offset == last_request_offset)) {
+                                       /*
                                         * we're already finished the I/O for this read request
                                         * let's see if we should do a read-ahead
                                         */
-                                       cluster_rd_ahead(vp, b_lblkno, e_lblkno, filesize, devblocksize);
+                                       cluster_read_ahead(vp, &extent, filesize, rap, callback, callback_arg, bflag);
                                }
                        }
-                       if (retval)
-                               break;
+                       if (retval) {
+                               break;
+                       }
                        if (io_size == 0) {
-                               if (e_lblkno < vp->v_lastr)
-                                       vp->v_maxra = 0;
-                               vp->v_lastr = e_lblkno;
+                               if (rap != NULL) {
+                                       if (extent.e_addr < rap->cl_lastr) {
+                                               rap->cl_maxra = 0;
+                                       }
+                                       rap->cl_lastr = extent.e_addr;
+                               }
+                               break;
+                       }
+                       /*
+                        * recompute max_size since cluster_copy_ubc_data_internal
+                        * may have advanced uio->uio_offset
+                        */
+                       max_size = filesize - uio->uio_offset;
+               }
+
+               iostate.io_completed = 0;
+               iostate.io_issued = 0;
+               iostate.io_error = 0;
+               iostate.io_wanted = 0;
+
+               if ((flags & IO_RETURN_ON_THROTTLE)) {
+                       if (cluster_is_throttled(vp) == THROTTLE_NOW) {
+                               if (!cluster_io_present_in_BC(vp, uio->uio_offset)) {
+                                       /*
+                                        * we're in the throttle window and at least 1 I/O
+                                        * has already been issued by a throttleable thread
+                                        * in this window, so return with EAGAIN to indicate
+                                        * to the FS issuing the cluster_read call that it
+                                        * should now throttle after dropping any locks
+                                        */
+                                       throttle_info_update_by_mount(vp->v_mount);
 
-                               break;
+                                       retval = EAGAIN;
+                                       break;
+                               }
                        }
-                       start_offset = (int)(uio->uio_offset & PAGE_MASK_64);
-                       upl_f_offset = uio->uio_offset - (off_t)start_offset;
-                       max_size     = filesize - uio->uio_offset;
                }
-               if (io_size > max_rd_size)
-                       io_size = max_rd_size;
+
+               /*
+                * compute the size of the upl needed to encompass
+                * the requested read... limit each call to cluster_io
+                * to the maximum UPL size... cluster_io will clip if
+                * this exceeds the maximum io_size for the device,
+                * make sure to account for
+                * a starting offset that's not page aligned
+                */
+               start_offset = (int)(uio->uio_offset & PAGE_MASK_64);
+               upl_f_offset = uio->uio_offset - (off_t)start_offset;
+
+               if (io_size > max_rd_size) {
+                       io_size = max_rd_size;
+               }
 
                upl_size = (start_offset + io_size + (PAGE_SIZE - 1)) & ~PAGE_MASK;
 
-               if (upl_size > (MAX_UPL_TRANSFER * PAGE_SIZE) / 4)
-                       upl_size = (MAX_UPL_TRANSFER * PAGE_SIZE) / 4;
+               if (flags & IO_NOCACHE) {
+                       if (upl_size > max_io_size) {
+                               upl_size = max_io_size;
+                       }
+               } else {
+                       if (upl_size > max_io_size / 4) {
+                               upl_size = max_io_size / 4;
+                               upl_size &= ~PAGE_MASK;
+
+                               if (upl_size == 0) {
+                                       upl_size = PAGE_SIZE;
+                               }
+                       }
+               }
                pages_in_upl = upl_size / PAGE_SIZE;
 
                KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 33)) | DBG_FUNC_START,
-                            (int)upl, (int)upl_f_offset, upl_size, start_offset, 0);
-
-               kret = ubc_create_upl(vp, 
-                                               upl_f_offset,
-                                               upl_size,
-                                               &upl,
-                                               &pl,
-                                               UPL_SET_LITE);
-               if (kret != KERN_SUCCESS)
-                       panic("cluster_read: failed to get pagelist");
+                   upl, (int)upl_f_offset, upl_size, start_offset, 0);
+
+               kret = ubc_create_upl_kernel(vp,
+                   upl_f_offset,
+                   upl_size,
+                   &upl,
+                   &pl,
+                   UPL_FILE_IO | UPL_SET_LITE,
+                   VM_KERN_MEMORY_FILE);
+               if (kret != KERN_SUCCESS) {
+                       panic("cluster_read_copy: failed to get pagelist");
+               }
 
                KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 33)) | DBG_FUNC_END,
-                            (int)upl, (int)upl_f_offset, upl_size, start_offset, 0);
+                   upl, (int)upl_f_offset, upl_size, start_offset, 0);
 
                /*
                 * scan from the beginning of the upl looking for the first
@@ -2581,47 +4191,89 @@ cluster_read_x(vp, uio, filesize, devblocksize, flags)
                 * of the pages are valid, we won't call through to 'cluster_io'
                 */
                for (start_pg = 0; start_pg < pages_in_upl; start_pg++) {
-                       if (!upl_valid_page(pl, start_pg))
+                       if (!upl_valid_page(pl, start_pg)) {
                                break;
+                       }
                }
 
                /*
                 * scan from the starting invalid page looking for a valid
-                * page before the end of the upl is reached, if we 
+                * page before the end of the upl is reached, if we
                 * find one, then it will be the last page of the request to
                 * 'cluster_io'
                 */
                for (last_pg = start_pg; last_pg < pages_in_upl; last_pg++) {
-                       if (upl_valid_page(pl, last_pg))
+                       if (upl_valid_page(pl, last_pg)) {
                                break;
+                       }
                }
-               iostate.io_completed = 0;
-               iostate.io_issued = 0;
-               iostate.io_error = 0;
-               iostate.io_wanted = 0;
 
-               if (start_pg < last_pg) {               
-                       /*
+               if (start_pg < last_pg) {
+                       /*
                         * we found a range of 'invalid' pages that must be filled
                         * if the last page in this range is the last page of the file
                         * we may have to clip the size of it to keep from reading past
                         * the end of the last physical block associated with the file
                         */
+                       if (iolock_inited == FALSE) {
+                               lck_mtx_init(&iostate.io_mtxp, &cl_mtx_grp, LCK_ATTR_NULL);
+
+                               iolock_inited = TRUE;
+                       }
                        upl_offset = start_pg * PAGE_SIZE;
                        io_size    = (last_pg - start_pg) * PAGE_SIZE;
 
-                       if ((upl_f_offset + upl_offset + io_size) > filesize)
-                               io_size = filesize - (upl_f_offset + upl_offset);
+                       if ((off_t)(upl_f_offset + upl_offset + io_size) > filesize) {
+                               io_size = (u_int32_t)(filesize - (upl_f_offset + upl_offset));
+                       }
+
+                       /*
+                        * Find out if this needs verification, we'll have to manage the UPL
+                        * diffrently if so. Note that this call only lets us know if
+                        * verification is enabled on this mount point, the actual verification
+                        * is performed in the File system.
+                        */
+                       size_t verify_block_size = 0;
+                       if ((VNOP_VERIFY(vp, start_offset, NULL, 0, &verify_block_size, VNODE_VERIFY_DEFAULT, NULL) == 0) /* && verify_block_size */) {
+                               for (uio_last = last_pg; uio_last < pages_in_upl; uio_last++) {
+                                       if (!upl_valid_page(pl, uio_last)) {
+                                               break;
+                                       }
+                               }
+                               if (uio_last < pages_in_upl) {
+                                       /*
+                                        * there were some invalid pages beyond the valid pages
+                                        * that we didn't issue an I/O for, just release them
+                                        * unchanged now, so that any prefetch/readahed can
+                                        * include them
+                                        */
+                                       ubc_upl_abort_range(upl, uio_last * PAGE_SIZE,
+                                           (pages_in_upl - uio_last) * PAGE_SIZE, UPL_ABORT_FREE_ON_EMPTY);
+                                       leftover_upl_aborted = true;
+                               }
+                       }
 
                        /*
                         * issue an asynchronous read to cluster_io
                         */
 
                        error = cluster_io(vp, upl, upl_offset, upl_f_offset + upl_offset,
-                                          io_size, devblocksize, CL_READ | CL_ASYNC, (struct buf *)0, &iostate);
+                           io_size, CL_READ | CL_ASYNC | bflag, (buf_t)NULL, &iostate, callback, callback_arg);
+
+                       if (rap) {
+                               if (extent.e_addr < rap->cl_maxra) {
+                                       /*
+                                        * we've just issued a read for a block that should have been
+                                        * in the cache courtesy of the read-ahead engine... something
+                                        * has gone wrong with the pipeline, so reset the read-ahead
+                                        * logic which will cause us to restart from scratch
+                                        */
+                                       rap->cl_maxra = 0;
+                               }
+                       }
                }
                if (error == 0) {
-                       /*
+                       /*
                         * if the read completed successfully, or there was no I/O request
                         * issued, than copy the data into user land via 'cluster_upl_copy_data'
                         * we'll first add on any 'valid'
@@ -2629,325 +4281,715 @@ cluster_read_x(vp, uio, filesize, devblocksize, flags)
                         */
                        u_int  val_size;
 
-                       for (uio_last = last_pg; uio_last < pages_in_upl; uio_last++) {
-                               if (!upl_valid_page(pl, uio_last))
-                                       break;
+                       if (!leftover_upl_aborted) {
+                               for (uio_last = last_pg; uio_last < pages_in_upl; uio_last++) {
+                                       if (!upl_valid_page(pl, uio_last)) {
+                                               break;
+                                       }
+                               }
+                               if (uio_last < pages_in_upl) {
+                                       /*
+                                        * there were some invalid pages beyond the valid pages
+                                        * that we didn't issue an I/O for, just release them
+                                        * unchanged now, so that any prefetch/readahed can
+                                        * include them
+                                        */
+                                       ubc_upl_abort_range(upl, uio_last * PAGE_SIZE,
+                                           (pages_in_upl - uio_last) * PAGE_SIZE, UPL_ABORT_FREE_ON_EMPTY);
+                               }
                        }
+
                        /*
-                        * compute size to transfer this round,  if uio->uio_resid is
+                        * compute size to transfer this round,  if io_req_size is
                         * still non-zero after this attempt, we'll loop around and
                         * set up for another I/O.
                         */
                        val_size = (uio_last * PAGE_SIZE) - start_offset;
-               
-                       if (val_size > max_size)
-                               val_size = max_size;
-
-                       if (val_size > uio->uio_resid)
-                               val_size = uio->uio_resid;
-
-                       if (last_ioread_offset == 0)
-                               last_ioread_offset = uio->uio_offset + val_size;
-
-                       if ((size_of_prefetch = (last_request_offset - last_ioread_offset)) && prefetch_enabled) {
-                               /*
-                                * if there's still I/O left to do for this request, and...
-                                * we're not in hard throttle mode, then issue a
-                                * pre-fetch I/O... the I/O latency will overlap
-                                * with the copying of the data
-                                */
-                               size_of_prefetch = cluster_rd_prefetch(vp, last_ioread_offset, size_of_prefetch, filesize, devblocksize);
 
-                               last_ioread_offset += (off_t)(size_of_prefetch * PAGE_SIZE);
-                               
-                               if (last_ioread_offset > last_request_offset)
-                                       last_ioread_offset = last_request_offset;
+                       if (val_size > max_size) {
+                               val_size = (u_int)max_size;
+                       }
+
+                       if (val_size > io_req_size) {
+                               val_size = io_req_size;
+                       }
+
+                       if ((uio->uio_offset + val_size) > last_ioread_offset) {
+                               last_ioread_offset = uio->uio_offset + val_size;
+                       }
+
+                       if ((size_of_prefetch = (u_int32_t)(last_request_offset - last_ioread_offset)) && prefetch_enabled) {
+                               if ((last_ioread_offset - (uio->uio_offset + val_size)) <= upl_size) {
+                                       /*
+                                        * if there's still I/O left to do for this request, and...
+                                        * we're not in hard throttle mode, and...
+                                        * we're close to using up the previous prefetch, then issue a
+                                        * new pre-fetch I/O... the I/O latency will overlap
+                                        * with the copying of the data
+                                        */
+                                       if (size_of_prefetch > max_rd_size) {
+                                               size_of_prefetch = max_rd_size;
+                                       }
+
+                                       size_of_prefetch = cluster_read_prefetch(vp, last_ioread_offset, size_of_prefetch, filesize, callback, callback_arg, bflag);
+
+                                       last_ioread_offset += (off_t)(size_of_prefetch * PAGE_SIZE);
 
+                                       if (last_ioread_offset > last_request_offset) {
+                                               last_ioread_offset = last_request_offset;
+                                       }
+                               }
                        } else if ((uio->uio_offset + val_size) == last_request_offset) {
-                               /*
+                               /*
                                 * this transfer will finish this request, so...
-                                * let's try to read ahead if we're in 
+                                * let's try to read ahead if we're in
                                 * a sequential access pattern and we haven't
                                 * explicitly disabled it
                                 */
-                               if (rd_ahead_enabled)
-                                       cluster_rd_ahead(vp, b_lblkno, e_lblkno, filesize, devblocksize);
-
-                               if (e_lblkno < vp->v_lastr)
-                                       vp->v_maxra = 0;
-                               vp->v_lastr = e_lblkno;
-                       }
-                       while (iostate.io_issued != iostate.io_completed) {
-                               iostate.io_wanted = 1;
-                               tsleep((caddr_t)&iostate.io_wanted, PRIBIO + 1, "cluster_read_x", 0);
-                       }       
-                       if (iostate.io_error)
-                               error = iostate.io_error;
-                       else
-                               retval = cluster_copy_upl_data(uio, upl, start_offset, val_size);
+                               if (rd_ahead_enabled) {
+                                       cluster_read_ahead(vp, &extent, filesize, rap, callback, callback_arg, bflag);
+                               }
+
+                               if (rap != NULL) {
+                                       if (extent.e_addr < rap->cl_lastr) {
+                                               rap->cl_maxra = 0;
+                                       }
+                                       rap->cl_lastr = extent.e_addr;
+                               }
+                       }
+                       if (iolock_inited == TRUE) {
+                               cluster_iostate_wait(&iostate, 0, "cluster_read_copy");
+                       }
+
+                       if (iostate.io_error) {
+                               error = iostate.io_error;
+                       } else {
+                               u_int32_t io_requested;
+
+                               io_requested = val_size;
+
+                               retval = cluster_copy_upl_data(uio, upl, start_offset, (int *)&io_requested);
+
+                               io_req_size -= (val_size - io_requested);
+                       }
+               } else {
+                       if (iolock_inited == TRUE) {
+                               cluster_iostate_wait(&iostate, 0, "cluster_read_copy");
+                       }
                }
                if (start_pg < last_pg) {
-                       /*
+                       /*
                         * compute the range of pages that we actually issued an I/O for
                         * and either commit them as valid if the I/O succeeded
-                        * or abort them if the I/O failed
+                        * or abort them if the I/O failed or we're not supposed to
+                        * keep them in the cache
                         */
-                       io_size = (last_pg - start_pg) * PAGE_SIZE;
+                       io_size = (last_pg - start_pg) * PAGE_SIZE;
 
-                       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 35)) | DBG_FUNC_START,
-                                    (int)upl, start_pg * PAGE_SIZE, io_size, error, 0);
+                       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 35)) | DBG_FUNC_START, upl, start_pg * PAGE_SIZE, io_size, error, 0);
+
+                       if (error || (flags & IO_NOCACHE)) {
+                               ubc_upl_abort_range(upl, start_pg * PAGE_SIZE, io_size,
+                                   UPL_ABORT_DUMP_PAGES | UPL_ABORT_FREE_ON_EMPTY);
+                       } else {
+                               int     commit_flags = UPL_COMMIT_CLEAR_DIRTY | UPL_COMMIT_FREE_ON_EMPTY;
 
-                       if (error || (vp->v_flag & VNOCACHE_DATA))
-                               ubc_upl_abort_range(upl, start_pg * PAGE_SIZE, io_size,
-                                               UPL_ABORT_DUMP_PAGES | UPL_ABORT_FREE_ON_EMPTY);
-                       else
-                               ubc_upl_commit_range(upl, start_pg * PAGE_SIZE, io_size, 
-                                                    UPL_COMMIT_CLEAR_DIRTY |
-                                                    UPL_COMMIT_FREE_ON_EMPTY | 
-                                                    UPL_COMMIT_INACTIVATE);
+                               if (take_reference) {
+                                       commit_flags |= UPL_COMMIT_INACTIVATE;
+                               } else {
+                                       commit_flags |= UPL_COMMIT_SPECULATE;
+                               }
 
-                       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 35)) | DBG_FUNC_END,
-                                    (int)upl, start_pg * PAGE_SIZE, io_size, error, 0);
+                               ubc_upl_commit_range(upl, start_pg * PAGE_SIZE, io_size, commit_flags);
+                       }
+                       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 35)) | DBG_FUNC_END, upl, start_pg * PAGE_SIZE, io_size, error, 0);
                }
                if ((last_pg - start_pg) < pages_in_upl) {
-                       int cur_pg;
-                       int commit_flags;
-
-                       /*
+                       /*
                         * the set of pages that we issued an I/O for did not encompass
                         * the entire upl... so just release these without modifying
                         * their state
                         */
-                       if (error)
-                               ubc_upl_abort_range(upl, 0, upl_size, UPL_ABORT_FREE_ON_EMPTY);
-                       else {
+                       if (error) {
+                               if (leftover_upl_aborted) {
+                                       ubc_upl_abort_range(upl, start_pg * PAGE_SIZE, (uio_last - start_pg) * PAGE_SIZE,
+                                           UPL_ABORT_FREE_ON_EMPTY);
+                               } else {
+                                       ubc_upl_abort_range(upl, 0, upl_size, UPL_ABORT_FREE_ON_EMPTY);
+                               }
+                       } else {
                                KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 35)) | DBG_FUNC_START,
-                                            (int)upl, -1, pages_in_upl - (last_pg - start_pg), 0, 0);
+                                   upl, -1, pages_in_upl - (last_pg - start_pg), 0, 0);
 
-                               if (start_pg) {
-                                       /*
-                                        * we found some already valid pages at the beginning of
-                                        * the upl commit these back to the inactive list with
-                                        * reference cleared
-                                        */
-                                       for (cur_pg = 0; cur_pg < start_pg; cur_pg++) {
-                                               commit_flags = UPL_COMMIT_FREE_ON_EMPTY 
-                                                                  | UPL_COMMIT_INACTIVATE;
-                                               
-                                               if (upl_dirty_page(pl, cur_pg))
-                                                       commit_flags |= UPL_COMMIT_SET_DIRTY;
-                                               
-                                               if ( !(commit_flags & UPL_COMMIT_SET_DIRTY) && (vp->v_flag & VNOCACHE_DATA))
-                                                       ubc_upl_abort_range(upl, cur_pg * PAGE_SIZE, PAGE_SIZE,
-                                                               UPL_ABORT_DUMP_PAGES | UPL_ABORT_FREE_ON_EMPTY);
-                                               else
-                                                       ubc_upl_commit_range(upl, cur_pg * PAGE_SIZE, 
-                                                               PAGE_SIZE, commit_flags);
-                                       }
-                               }
-                               if (last_pg < uio_last) {
+                               /*
+                                * handle any valid pages at the beginning of
+                                * the upl... release these appropriately
+                                */
+                               cluster_read_upl_release(upl, 0, start_pg, take_reference);
+
+                               /*
+                                * handle any valid pages immediately after the
+                                * pages we issued I/O for... ... release these appropriately
+                                */
+                               cluster_read_upl_release(upl, last_pg, uio_last, take_reference);
+
+                               KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 35)) | DBG_FUNC_END, upl, -1, -1, 0, 0);
+                       }
+               }
+               if (retval == 0) {
+                       retval = error;
+               }
+
+               if (io_req_size) {
+                       if (cluster_is_throttled(vp)) {
+                               /*
+                                * we're in the throttle window, at the very least
+                                * we want to limit the size of the I/O we're about
+                                * to issue
+                                */
+                               rd_ahead_enabled = 0;
+                               prefetch_enabled = 0;
+                               max_rd_size = THROTTLE_MAX_IOSIZE;
+                       } else {
+                               if (max_rd_size == THROTTLE_MAX_IOSIZE) {
                                        /*
-                                        * we found some already valid pages immediately after the
-                                        * pages we issued I/O for, commit these back to the
-                                        * inactive list with reference cleared
+                                        * coming out of throttled state
                                         */
-                                       for (cur_pg = last_pg; cur_pg < uio_last; cur_pg++) {
-                                               commit_flags =  UPL_COMMIT_FREE_ON_EMPTY 
-                                                                               | UPL_COMMIT_INACTIVATE;
-
-                                               if (upl_dirty_page(pl, cur_pg))
-                                                       commit_flags |= UPL_COMMIT_SET_DIRTY;
-                                               
-                                               if ( !(commit_flags & UPL_COMMIT_SET_DIRTY) && (vp->v_flag & VNOCACHE_DATA))
-                                                       ubc_upl_abort_range(upl, cur_pg * PAGE_SIZE, PAGE_SIZE,
-                                                               UPL_ABORT_DUMP_PAGES | UPL_ABORT_FREE_ON_EMPTY);
-                                               else
-                                                       ubc_upl_commit_range(upl, cur_pg * PAGE_SIZE, 
-                                                               PAGE_SIZE, commit_flags);
+                                       if (policy != THROTTLE_LEVEL_TIER3 && policy != THROTTLE_LEVEL_TIER2) {
+                                               if (rap != NULL) {
+                                                       rd_ahead_enabled = 1;
+                                               }
+                                               prefetch_enabled = 1;
                                        }
+                                       max_rd_size = max_prefetch;
+                                       last_ioread_offset = 0;
                                }
-                               if (uio_last < pages_in_upl) {
-                                       /*
-                                        * there were some invalid pages beyond the valid pages
-                                        * that we didn't issue an I/O for, just release them
-                                        * unchanged
-                                        */
-                                       ubc_upl_abort_range(upl, uio_last * PAGE_SIZE,
-                                                           (pages_in_upl - uio_last) * PAGE_SIZE, UPL_ABORT_FREE_ON_EMPTY);
-                               }
-
-                               KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 35)) | DBG_FUNC_END,
-                                       (int)upl, -1, -1, 0, 0);
                        }
                }
-               if (retval == 0)
-                       retval = error;
        }
-       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 32)) | DBG_FUNC_END,
-                    (int)uio->uio_offset, uio->uio_resid, vp->v_lastr, retval, 0);
+       if (iolock_inited == TRUE) {
+               /*
+                * cluster_io returned an error after it
+                * had already issued some I/O.  we need
+                * to wait for that I/O to complete before
+                * we can destroy the iostate mutex...
+                * 'retval' already contains the early error
+                * so no need to pick it up from iostate.io_error
+                */
+               cluster_iostate_wait(&iostate, 0, "cluster_read_copy");
+
+               lck_mtx_destroy(&iostate.io_mtxp, &cl_mtx_grp);
+       }
+       if (rap != NULL) {
+               KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 32)) | DBG_FUNC_END,
+                   (int)uio->uio_offset, io_req_size, rap->cl_lastr, retval, 0);
+
+               lck_mtx_unlock(&rap->cl_lockr);
+       } else {
+               KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 32)) | DBG_FUNC_END,
+                   (int)uio->uio_offset, io_req_size, 0, retval, 0);
+       }
+
+       return retval;
+}
+
+/*
+ * We don't want another read/write lock for every vnode in the system
+ * so we keep a hash of them here.  There should never be very many of
+ * these around at any point in time.
+ */
+cl_direct_read_lock_t *
+cluster_lock_direct_read(vnode_t vp, lck_rw_type_t type)
+{
+       struct cl_direct_read_locks *head
+               = &cl_direct_read_locks[(uintptr_t)vp / sizeof(*vp)
+           % CL_DIRECT_READ_LOCK_BUCKETS];
 
-       return (retval);
+       struct cl_direct_read_lock *lck, *new_lck = NULL;
+
+       for (;;) {
+               lck_spin_lock(&cl_direct_read_spin_lock);
+
+               LIST_FOREACH(lck, head, chain) {
+                       if (lck->vp == vp) {
+                               ++lck->ref_count;
+                               lck_spin_unlock(&cl_direct_read_spin_lock);
+                               if (new_lck) {
+                                       // Someone beat us to it, ditch the allocation
+                                       lck_rw_destroy(&new_lck->rw_lock, &cl_mtx_grp);
+                                       kheap_free(KHEAP_DEFAULT, new_lck, sizeof(cl_direct_read_lock_t));
+                               }
+                               lck_rw_lock(&lck->rw_lock, type);
+                               return lck;
+                       }
+               }
+
+               if (new_lck) {
+                       // Use the lock we allocated
+                       LIST_INSERT_HEAD(head, new_lck, chain);
+                       lck_spin_unlock(&cl_direct_read_spin_lock);
+                       lck_rw_lock(&new_lck->rw_lock, type);
+                       return new_lck;
+               }
+
+               lck_spin_unlock(&cl_direct_read_spin_lock);
+
+               // Allocate a new lock
+               new_lck = kheap_alloc(KHEAP_DEFAULT, sizeof(cl_direct_read_lock_t),
+                   Z_WAITOK);
+               lck_rw_init(&new_lck->rw_lock, &cl_mtx_grp, LCK_ATTR_NULL);
+               new_lck->vp = vp;
+               new_lck->ref_count = 1;
+
+               // Got to go round again
+       }
 }
 
+void
+cluster_unlock_direct_read(cl_direct_read_lock_t *lck)
+{
+       lck_rw_done(&lck->rw_lock);
+
+       lck_spin_lock(&cl_direct_read_spin_lock);
+       if (lck->ref_count == 1) {
+               LIST_REMOVE(lck, chain);
+               lck_spin_unlock(&cl_direct_read_spin_lock);
+               lck_rw_destroy(&lck->rw_lock, &cl_mtx_grp);
+               kheap_free(KHEAP_DEFAULT, lck, sizeof(cl_direct_read_lock_t));
+       } else {
+               --lck->ref_count;
+               lck_spin_unlock(&cl_direct_read_spin_lock);
+       }
+}
 
 static int
-cluster_nocopy_read(vp, uio, filesize, devblocksize, flags)
-       struct vnode *vp;
-       struct uio   *uio;
-       off_t         filesize;
-       int           devblocksize;
-       int           flags;
+cluster_read_direct(vnode_t vp, struct uio *uio, off_t filesize, int *read_type, u_int32_t *read_length,
+    int flags, int (*callback)(buf_t, void *), void *callback_arg)
 {
        upl_t            upl;
        upl_page_info_t  *pl;
-       vm_offset_t      upl_offset;
        off_t            max_io_size;
-       int              io_size;
-       int              upl_size;
-       int              upl_needed_size;
-       int              pages_in_pl;
-       int              upl_flags;
+       vm_offset_t      upl_offset, vector_upl_offset = 0;
+       upl_size_t       upl_size, vector_upl_size = 0;
+       vm_size_t        upl_needed_size;
+       unsigned int     pages_in_pl;
+       upl_control_flags_t upl_flags;
        kern_return_t    kret;
-       struct iovec     *iov;
-       int              i;
+       unsigned int     i;
        int              force_data_sync;
        int              retval = 0;
+       int              no_zero_fill = 0;
+       int              io_flag = 0;
+       int              misaligned = 0;
        struct clios     iostate;
-       u_int            max_rd_size  = MAX_UPL_TRANSFER * PAGE_SIZE;
-       u_int            max_rd_ahead = MAX_UPL_TRANSFER * PAGE_SIZE * 2;
-
+       user_addr_t      iov_base;
+       u_int32_t        io_req_size;
+       u_int32_t        offset_in_file;
+       u_int32_t        offset_in_iovbase;
+       u_int32_t        io_size;
+       u_int32_t        io_min;
+       u_int32_t        xsize;
+       u_int32_t        devblocksize;
+       u_int32_t        mem_alignment_mask;
+       u_int32_t        max_upl_size;
+       u_int32_t        max_rd_size;
+       u_int32_t        max_rd_ahead;
+       u_int32_t        max_vector_size;
+       boolean_t        io_throttled = FALSE;
+
+       u_int32_t        vector_upl_iosize = 0;
+       int              issueVectorUPL = 0, useVectorUPL = (uio->uio_iovcnt > 1);
+       off_t            v_upl_uio_offset = 0;
+       int              vector_upl_index = 0;
+       upl_t            vector_upl = NULL;
+       cl_direct_read_lock_t *lock = NULL;
+
+       user_addr_t      orig_iov_base = 0;
+       user_addr_t      last_iov_base = 0;
+       user_addr_t      next_iov_base = 0;
+
+       assert(vm_map_page_shift(current_map()) >= PAGE_SHIFT);
 
        KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 70)) | DBG_FUNC_START,
-                    (int)uio->uio_offset, uio->uio_resid, (int)filesize, devblocksize, 0);
+           (int)uio->uio_offset, (int)filesize, *read_type, *read_length, 0);
 
-       /*
-        * When we enter this routine, we know
-        *  -- the offset into the file is on a pagesize boundary
-        *  -- the resid is a page multiple
-        *  -- the resid will not exceed iov_len
-        */
+       max_upl_size = cluster_max_io_size(vp->v_mount, CL_READ);
+
+       max_rd_size = max_upl_size;
+       max_rd_ahead = max_rd_size * IO_SCALE(vp, 2);
+
+       io_flag = CL_COMMIT | CL_READ | CL_ASYNC | CL_NOZERO | CL_DIRECT_IO;
+
+       if (flags & IO_PASSIVE) {
+               io_flag |= CL_PASSIVE;
+       }
+
+       if (flags & IO_ENCRYPTED) {
+               io_flag |= CL_RAW_ENCRYPTED;
+       }
+
+       if (flags & IO_NOCACHE) {
+               io_flag |= CL_NOCACHE;
+       }
+
+       if (flags & IO_SKIP_ENCRYPTION) {
+               io_flag |= CL_ENCRYPTED;
+       }
 
        iostate.io_completed = 0;
        iostate.io_issued = 0;
        iostate.io_error = 0;
        iostate.io_wanted = 0;
 
-       iov = uio->uio_iov;
+       lck_mtx_init(&iostate.io_mtxp, &cl_mtx_grp, LCK_ATTR_NULL);
+
+       devblocksize = (u_int32_t)vp->v_mount->mnt_devblocksize;
+       mem_alignment_mask = (u_int32_t)vp->v_mount->mnt_alignmentmask;
+
+       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 70)) | DBG_FUNC_NONE,
+           (int)devblocksize, (int)mem_alignment_mask, 0, 0, 0);
 
-       if (cluster_hard_throttle_on(vp)) {
-               max_rd_size  = HARD_THROTTLE_MAXSIZE;
-               max_rd_ahead = HARD_THROTTLE_MAXSIZE - 1;
+       if (devblocksize == 1) {
+               /*
+                * the AFP client advertises a devblocksize of 1
+                * however, its BLOCKMAP routine maps to physical
+                * blocks that are PAGE_SIZE in size...
+                * therefore we can't ask for I/Os that aren't page aligned
+                * or aren't multiples of PAGE_SIZE in size
+                * by setting devblocksize to PAGE_SIZE, we re-instate
+                * the old behavior we had before the mem_alignment_mask
+                * changes went in...
+                */
+               devblocksize = PAGE_SIZE;
        }
-       while (uio->uio_resid && uio->uio_offset < filesize && retval == 0) {
 
-               max_io_size = filesize - uio->uio_offset;
+       orig_iov_base = uio_curriovbase(uio);
+       last_iov_base = orig_iov_base;
 
-               if (max_io_size < (off_t)((unsigned int)uio->uio_resid))
-                       io_size = max_io_size;
-               else
-                       io_size = uio->uio_resid;
+next_dread:
+       io_req_size = *read_length;
+       iov_base = uio_curriovbase(uio);
 
+       offset_in_file = (u_int32_t)uio->uio_offset & (devblocksize - 1);
+       offset_in_iovbase = (u_int32_t)iov_base & mem_alignment_mask;
+
+       if (vm_map_page_mask(current_map()) < PAGE_MASK) {
                /*
-                * First look for pages already in the cache
-                * and move them to user space.
+                * XXX TODO4K
+                * Direct I/O might not work as expected from a 16k kernel space
+                * to a 4k user space because each 4k chunk might point to
+                * a different 16k physical page...
+                * Let's go the "misaligned" way.
+                */
+               if (!misaligned) {
+                       DEBUG4K_VFS("forcing misaligned\n");
+               }
+               misaligned = 1;
+       }
+
+       if (offset_in_file || offset_in_iovbase) {
+               /*
+                * one of the 2 important offsets is misaligned
+                * so fire an I/O through the cache for this entire vector
+                */
+               misaligned = 1;
+       }
+       if (iov_base & (devblocksize - 1)) {
+               /*
+                * the offset in memory must be on a device block boundary
+                * so that we can guarantee that we can generate an
+                * I/O that ends on a page boundary in cluster_io
                 */
-               retval = cluster_copy_ubc_data(vp, uio, &io_size, 0);
-                       
-               if (retval) {
+               misaligned = 1;
+       }
+
+       max_io_size = filesize - uio->uio_offset;
+
+       /*
+        * The user must request IO in aligned chunks.  If the
+        * offset into the file is bad, or the userland pointer
+        * is non-aligned, then we cannot service the encrypted IO request.
+        */
+       if (flags & IO_ENCRYPTED) {
+               if (misaligned || (io_req_size & (devblocksize - 1))) {
+                       retval = EINVAL;
+               }
+
+               max_io_size = roundup(max_io_size, devblocksize);
+       }
+
+       if ((off_t)io_req_size > max_io_size) {
+               io_req_size = (u_int32_t)max_io_size;
+       }
+
+       /*
+        * When we get to this point, we know...
+        *  -- the offset into the file is on a devblocksize boundary
+        */
+
+       while (io_req_size && retval == 0) {
+               u_int32_t io_start;
+
+               if (cluster_is_throttled(vp)) {
                        /*
-                        * we may have already spun some portion of this request
-                        * off as async requests... we need to wait for the I/O
-                        * to complete before returning
+                        * we're in the throttle window, at the very least
+                        * we want to limit the size of the I/O we're about
+                        * to issue
                         */
-                       goto wait_for_reads;
+                       max_rd_size  = THROTTLE_MAX_IOSIZE;
+                       max_rd_ahead = THROTTLE_MAX_IOSIZE - 1;
+                       max_vector_size = THROTTLE_MAX_IOSIZE;
+               } else {
+                       max_rd_size  = max_upl_size;
+                       max_rd_ahead = max_rd_size * IO_SCALE(vp, 2);
+                       max_vector_size = MAX_VECTOR_UPL_SIZE;
                }
+               io_start = io_size = io_req_size;
+
                /*
-                * If we are already finished with this read, then return
+                * First look for pages already in the cache
+                * and move them to user space.  But only do this
+                * check if we are not retrieving encrypted data directly
+                * from the filesystem;  those blocks should never
+                * be in the UBC.
+                *
+                * cluster_copy_ubc_data returns the resid
+                * in io_size
                 */
-               if (io_size == 0) {
+               if ((flags & IO_ENCRYPTED) == 0) {
+                       retval = cluster_copy_ubc_data_internal(vp, uio, (int *)&io_size, 0, 0);
+               }
+               /*
+                * calculate the number of bytes actually copied
+                * starting size - residual
+                */
+               xsize = io_start - io_size;
+
+               io_req_size -= xsize;
+
+               if (useVectorUPL && (xsize || (iov_base & PAGE_MASK))) {
                        /*
-                        * we may have already spun some portion of this request
-                        * off as async requests... we need to wait for the I/O
-                        * to complete before returning
+                        * We found something in the cache or we have an iov_base that's not
+                        * page-aligned.
+                        *
+                        * Issue all I/O's that have been collected within this Vectored UPL.
                         */
-                       goto wait_for_reads;
-               }
-               max_io_size = io_size;
+                       if (vector_upl_index) {
+                               retval = vector_cluster_io(vp, vector_upl, vector_upl_offset, v_upl_uio_offset, vector_upl_iosize, io_flag, (buf_t)NULL, &iostate, callback, callback_arg);
+                               reset_vector_run_state();
+                       }
 
-               if (max_io_size > max_rd_size)
-                       max_io_size = max_rd_size;
+                       if (xsize) {
+                               useVectorUPL = 0;
+                       }
 
-               io_size = 0;
+                       /*
+                        * After this point, if we are using the Vector UPL path and the base is
+                        * not page-aligned then the UPL with that base will be the first in the vector UPL.
+                        */
+               }
 
-               ubc_range_op(vp, uio->uio_offset, uio->uio_offset + max_io_size, UPL_ROP_ABSENT, &io_size);
+               /*
+                * check to see if we are finished with this request.
+                *
+                * If we satisfied this IO already, then io_req_size will be 0.
+                * Otherwise, see if the IO was mis-aligned and needs to go through
+                * the UBC to deal with the 'tail'.
+                *
+                */
+               if (io_req_size == 0 || (misaligned)) {
+                       /*
+                        * see if there's another uio vector to
+                        * process that's of type IO_DIRECT
+                        *
+                        * break out of while loop to get there
+                        */
+                       break;
+               }
+               /*
+                * assume the request ends on a device block boundary
+                */
+               io_min = devblocksize;
 
-               if (io_size == 0)
+               /*
+                * we can handle I/O's in multiples of the device block size
+                * however, if io_size isn't a multiple of devblocksize we
+                * want to clip it back to the nearest page boundary since
+                * we are going to have to go through cluster_read_copy to
+                * deal with the 'overhang'... by clipping it to a PAGE_SIZE
+                * multiple, we avoid asking the drive for the same physical
+                * blocks twice.. once for the partial page at the end of the
+                * request and a 2nd time for the page we read into the cache
+                * (which overlaps the end of the direct read) in order to
+                * get at the overhang bytes
+                */
+               if (io_size & (devblocksize - 1)) {
+                       assert(!(flags & IO_ENCRYPTED));
                        /*
+                        * Clip the request to the previous page size boundary
+                        * since request does NOT end on a device block boundary
+                        */
+                       io_size &= ~PAGE_MASK;
+                       io_min = PAGE_SIZE;
+               }
+               if (retval || io_size < io_min) {
+                       /*
+                        * either an error or we only have the tail left to
+                        * complete via the copy path...
                         * we may have already spun some portion of this request
                         * off as async requests... we need to wait for the I/O
                         * to complete before returning
                         */
-                       goto wait_for_reads;
+                       goto wait_for_dreads;
+               }
+
+               /*
+                * Don't re-check the UBC data if we are looking for uncached IO
+                * or asking for encrypted blocks.
+                */
+               if ((flags & IO_ENCRYPTED) == 0) {
+                       if ((xsize = io_size) > max_rd_size) {
+                               xsize = max_rd_size;
+                       }
+
+                       io_size = 0;
+
+                       if (!lock) {
+                               /*
+                                * We hold a lock here between the time we check the
+                                * cache and the time we issue I/O.  This saves us
+                                * from having to lock the pages in the cache.  Not
+                                * all clients will care about this lock but some
+                                * clients may want to guarantee stability between
+                                * here and when the I/O is issued in which case they
+                                * will take the lock exclusively.
+                                */
+                               lock = cluster_lock_direct_read(vp, LCK_RW_TYPE_SHARED);
+                       }
+
+                       ubc_range_op(vp, uio->uio_offset, uio->uio_offset + xsize, UPL_ROP_ABSENT, (int *)&io_size);
+
+                       if (io_size == 0) {
+                               /*
+                                * a page must have just come into the cache
+                                * since the first page in this range is no
+                                * longer absent, go back and re-evaluate
+                                */
+                               continue;
+                       }
+               }
+               if ((flags & IO_RETURN_ON_THROTTLE)) {
+                       if (cluster_is_throttled(vp) == THROTTLE_NOW) {
+                               if (!cluster_io_present_in_BC(vp, uio->uio_offset)) {
+                                       /*
+                                        * we're in the throttle window and at least 1 I/O
+                                        * has already been issued by a throttleable thread
+                                        * in this window, so return with EAGAIN to indicate
+                                        * to the FS issuing the cluster_read call that it
+                                        * should now throttle after dropping any locks
+                                        */
+                                       throttle_info_update_by_mount(vp->v_mount);
+
+                                       io_throttled = TRUE;
+                                       goto wait_for_dreads;
+                               }
+                       }
+               }
+               if (io_size > max_rd_size) {
+                       io_size = max_rd_size;
+               }
 
-               upl_offset = (vm_offset_t)iov->iov_base & PAGE_MASK;
-               upl_needed_size = (upl_offset + io_size + (PAGE_SIZE -1)) & ~PAGE_MASK;
+               iov_base = uio_curriovbase(uio);
+
+               upl_offset = (vm_offset_t)((u_int32_t)iov_base & PAGE_MASK);
+               upl_needed_size = (upl_offset + io_size + (PAGE_SIZE - 1)) & ~PAGE_MASK;
 
                KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 72)) | DBG_FUNC_START,
-                            (int)upl_offset, upl_needed_size, (int)iov->iov_base, io_size, 0);
+                   (int)upl_offset, upl_needed_size, (int)iov_base, io_size, 0);
+
+               if (upl_offset == 0 && ((io_size & PAGE_MASK) == 0)) {
+                       no_zero_fill = 1;
+               } else {
+                       no_zero_fill = 0;
+               }
 
+               vm_map_t map = UIO_SEG_IS_USER_SPACE(uio->uio_segflg) ? current_map() : kernel_map;
                for (force_data_sync = 0; force_data_sync < 3; force_data_sync++) {
-                       pages_in_pl = 0;
-                       upl_size = upl_needed_size;
+                       pages_in_pl = 0;
+                       upl_size = (upl_size_t)upl_needed_size;
                        upl_flags = UPL_FILE_IO | UPL_NO_SYNC | UPL_SET_INTERNAL | UPL_SET_LITE | UPL_SET_IO_WIRE;
+                       if (no_zero_fill) {
+                               upl_flags |= UPL_NOZEROFILL;
+                       }
+                       if (force_data_sync) {
+                               upl_flags |= UPL_FORCE_DATA_SYNC;
+                       }
 
-                       kret = vm_map_get_upl(current_map(),
-                                             (vm_offset_t)iov->iov_base & ~PAGE_MASK,
-                                             &upl_size, &upl, NULL, &pages_in_pl, &upl_flags, force_data_sync);
+                       kret = vm_map_create_upl(map,
+                           (vm_map_offset_t)(iov_base & ~((user_addr_t)PAGE_MASK)),
+                           &upl_size, &upl, NULL, &pages_in_pl, &upl_flags, VM_KERN_MEMORY_FILE);
 
                        if (kret != KERN_SUCCESS) {
-                               KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 72)) | DBG_FUNC_END,
-                                            (int)upl_offset, upl_size, io_size, kret, 0);
+                               KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 72)) | DBG_FUNC_END,
+                                   (int)upl_offset, upl_size, io_size, kret, 0);
                                /*
-                                * cluster_nocopy_read: failed to get pagelist
+                                * failed to get pagelist
                                 *
                                 * we may have already spun some portion of this request
                                 * off as async requests... we need to wait for the I/O
                                 * to complete before returning
                                 */
-                               goto wait_for_reads;
+                               goto wait_for_dreads;
                        }
                        pages_in_pl = upl_size / PAGE_SIZE;
                        pl = UPL_GET_INTERNAL_PAGE_LIST(upl);
 
                        for (i = 0; i < pages_in_pl; i++) {
-                               if (!upl_valid_page(pl, i))
-                                       break;            
+                               if (!upl_page_present(pl, i)) {
+                                       break;
+                               }
+                       }
+                       if (i == pages_in_pl) {
+                               break;
                        }
-                       if (i == pages_in_pl)
-                               break;
 
-                       ubc_upl_abort_range(upl, (upl_offset & ~PAGE_MASK), upl_size, 
-                                           UPL_ABORT_FREE_ON_EMPTY);
+                       ubc_upl_abort(upl, 0);
                }
                if (force_data_sync >= 3) {
-                       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 72)) | DBG_FUNC_END,
-                                    (int)upl_offset, upl_size, io_size, kret, 0);
-                 
-                       goto wait_for_reads;
+                       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 72)) | DBG_FUNC_END,
+                           (int)upl_offset, upl_size, io_size, kret, 0);
+
+                       goto wait_for_dreads;
                }
                /*
                 * Consider the possibility that upl_size wasn't satisfied.
                 */
-               if (upl_size != upl_needed_size)
-                       io_size = (upl_size - (int)upl_offset) & ~PAGE_MASK;
-
+               if (upl_size < upl_needed_size) {
+                       if (upl_size && upl_offset == 0) {
+                               io_size = upl_size;
+                       } else {
+                               io_size = 0;
+                       }
+               }
                if (io_size == 0) {
-                       ubc_upl_abort_range(upl, (upl_offset & ~PAGE_MASK), upl_size, 
-                                           UPL_ABORT_FREE_ON_EMPTY);
-                       goto wait_for_reads;
+                       ubc_upl_abort(upl, 0);
+                       goto wait_for_dreads;
                }
                KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 72)) | DBG_FUNC_END,
-                            (int)upl_offset, upl_size, io_size, kret, 0);
+                   (int)upl_offset, upl_size, io_size, kret, 0);
+
+               if (useVectorUPL) {
+                       vm_offset_t end_off = ((iov_base + io_size) & PAGE_MASK);
+                       if (end_off) {
+                               issueVectorUPL = 1;
+                       }
+                       /*
+                        * After this point, if we are using a vector UPL, then
+                        * either all the UPL elements end on a page boundary OR
+                        * this UPL is the last element because it does not end
+                        * on a page boundary.
+                        */
+               }
 
                /*
                 * request asynchronously so that we can overlap
@@ -2955,166 +4997,297 @@ cluster_nocopy_read(vp, uio, filesize, devblocksize, flags)
                 * if there are already too many outstanding reads
                 * wait until some have completed before issuing the next read
                 */
-               while ((iostate.io_issued - iostate.io_completed) > max_rd_ahead) {
-                       iostate.io_wanted = 1;
-                       tsleep((caddr_t)&iostate.io_wanted, PRIBIO + 1, "cluster_nocopy_read", 0);
-               }       
+               cluster_iostate_wait(&iostate, max_rd_ahead, "cluster_read_direct");
+
                if (iostate.io_error) {
-                       /*
+                       /*
                         * one of the earlier reads we issued ran into a hard error
                         * don't issue any more reads, cleanup the UPL
                         * that was just created but not used, then
                         * go wait for any other reads to complete before
                         * returning the error to the caller
                         */
-                       ubc_upl_abort_range(upl, (upl_offset & ~PAGE_MASK), upl_size, 
-                                           UPL_ABORT_FREE_ON_EMPTY);
+                       ubc_upl_abort(upl, 0);
 
-                       goto wait_for_reads;
-               }
+                       goto wait_for_dreads;
+               }
                KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 73)) | DBG_FUNC_START,
-                            (int)upl, (int)upl_offset, (int)uio->uio_offset, io_size, 0);
+                   upl, (int)upl_offset, (int)uio->uio_offset, io_size, 0);
+
+               if (!useVectorUPL) {
+                       if (no_zero_fill) {
+                               io_flag &= ~CL_PRESERVE;
+                       } else {
+                               io_flag |= CL_PRESERVE;
+                       }
+
+                       retval = cluster_io(vp, upl, upl_offset, uio->uio_offset, io_size, io_flag, (buf_t)NULL, &iostate, callback, callback_arg);
+               } else {
+                       if (!vector_upl_index) {
+                               vector_upl = vector_upl_create(upl_offset);
+                               v_upl_uio_offset = uio->uio_offset;
+                               vector_upl_offset = upl_offset;
+                       }
 
-               retval = cluster_io(vp, upl, upl_offset, uio->uio_offset,
-                                  io_size, devblocksize,
-                                  CL_PRESERVE | CL_COMMIT | CL_READ | CL_ASYNC | CL_NOZERO,
-                                  (struct buf *)0, &iostate);
+                       vector_upl_set_subupl(vector_upl, upl, upl_size);
+                       vector_upl_set_iostate(vector_upl, upl, vector_upl_size, upl_size);
+                       vector_upl_index++;
+                       vector_upl_size += upl_size;
+                       vector_upl_iosize += io_size;
+
+                       if (issueVectorUPL || vector_upl_index == MAX_VECTOR_UPL_ELEMENTS || vector_upl_size >= max_vector_size) {
+                               retval = vector_cluster_io(vp, vector_upl, vector_upl_offset, v_upl_uio_offset, vector_upl_iosize, io_flag, (buf_t)NULL, &iostate, callback, callback_arg);
+                               reset_vector_run_state();
+                       }
+               }
+               last_iov_base = iov_base + io_size;
+
+               if (lock) {
+                       // We don't need to wait for the I/O to complete
+                       cluster_unlock_direct_read(lock);
+                       lock = NULL;
+               }
 
                /*
                 * update the uio structure
                 */
-               iov->iov_base   += io_size;
-               iov->iov_len    -= io_size;
-               uio->uio_resid  -= io_size;
-               uio->uio_offset += io_size;
+               if ((flags & IO_ENCRYPTED) && (max_io_size < io_size)) {
+                       uio_update(uio, (user_size_t)max_io_size);
+               } else {
+                       uio_update(uio, (user_size_t)io_size);
+               }
+
+               io_req_size -= io_size;
 
                KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 73)) | DBG_FUNC_END,
-                            (int)upl, (int)uio->uio_offset, (int)uio->uio_resid, retval, 0);
+                   upl, (int)uio->uio_offset, io_req_size, retval, 0);
+       } /* end while */
+
+       if (retval == 0 && iostate.io_error == 0 && io_req_size == 0 && uio->uio_offset < filesize) {
+               retval = cluster_io_type(uio, read_type, read_length, 0);
+
+               if (retval == 0 && *read_type == IO_DIRECT) {
+                       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 70)) | DBG_FUNC_NONE,
+                           (int)uio->uio_offset, (int)filesize, *read_type, *read_length, 0);
+
+                       goto next_dread;
+               }
+       }
+
+wait_for_dreads:
+
+       if (retval == 0 && iostate.io_error == 0 && useVectorUPL && vector_upl_index) {
+               retval = vector_cluster_io(vp, vector_upl, vector_upl_offset, v_upl_uio_offset, vector_upl_iosize, io_flag, (buf_t)NULL, &iostate, callback, callback_arg);
+               reset_vector_run_state();
+       }
 
-       } /* end while */
+       // We don't need to wait for the I/O to complete
+       if (lock) {
+               cluster_unlock_direct_read(lock);
+       }
 
-wait_for_reads:
        /*
         * make sure all async reads that are part of this stream
         * have completed before we return
         */
-       while (iostate.io_issued != iostate.io_completed) {
-               iostate.io_wanted = 1;
-               tsleep((caddr_t)&iostate.io_wanted, PRIBIO + 1, "cluster_nocopy_read", 0);
-       }       
-       if (iostate.io_error)
+       cluster_iostate_wait(&iostate, 0, "cluster_read_direct");
+
+       if (iostate.io_error) {
                retval = iostate.io_error;
+       }
+
+       lck_mtx_destroy(&iostate.io_mtxp, &cl_mtx_grp);
+
+       if (io_throttled == TRUE && retval == 0) {
+               retval = EAGAIN;
+       }
+
+       vm_map_offset_t current_page_size, current_page_mask;
+       current_page_size = vm_map_page_size(current_map());
+       current_page_mask = vm_map_page_mask(current_map());
+       for (next_iov_base = orig_iov_base;
+           next_iov_base < last_iov_base;
+           next_iov_base += current_page_size) {
+               /*
+                * This is specifically done for pmap accounting purposes.
+                * vm_pre_fault() will call vm_fault() to enter the page into
+                * the pmap if there isn't _a_ physical page for that VA already.
+                */
+               vm_pre_fault(vm_map_trunc_page(next_iov_base, current_page_mask), VM_PROT_READ);
+       }
+
+       if (io_req_size && retval == 0) {
+               /*
+                * we couldn't handle the tail of this request in DIRECT mode
+                * so fire it through the copy path
+                */
+               if (flags & IO_ENCRYPTED) {
+                       /*
+                        * We cannot fall back to the copy path for encrypted I/O. If this
+                        * happens, there is something wrong with the user buffer passed
+                        * down.
+                        */
+                       retval = EFAULT;
+               } else {
+                       retval = cluster_read_copy(vp, uio, io_req_size, filesize, flags, callback, callback_arg);
+               }
 
+               *read_type = IO_UNKNOWN;
+       }
        KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 70)) | DBG_FUNC_END,
-                    (int)uio->uio_offset, (int)uio->uio_resid, 6, retval, 0);
+           (int)uio->uio_offset, (int)uio_resid(uio), io_req_size, retval, 0);
 
-       return (retval);
+       return retval;
 }
 
 
 static int
-cluster_phys_read(vp, uio, filesize, devblocksize, flags)
-       struct vnode *vp;
-       struct uio   *uio;
-       off_t        filesize;
-       int          devblocksize;
-       int          flags;
+cluster_read_contig(vnode_t vp, struct uio *uio, off_t filesize, int *read_type, u_int32_t *read_length,
+    int (*callback)(buf_t, void *), void *callback_arg, int flags)
 {
        upl_page_info_t *pl;
-       upl_t            upl;
+       upl_t            upl[MAX_VECTS];
        vm_offset_t      upl_offset;
-       addr64_t         dst_paddr;
+       addr64_t         dst_paddr = 0;
+       user_addr_t      iov_base;
        off_t            max_size;
-       int              io_size;
-       int              tail_size;
-       int              upl_size;
-       int              upl_needed_size;
-       int              pages_in_pl;
-       int              upl_flags;
+       upl_size_t       upl_size;
+       vm_size_t        upl_needed_size;
+       mach_msg_type_number_t  pages_in_pl;
+       upl_control_flags_t upl_flags;
        kern_return_t    kret;
-       struct iovec     *iov;
        struct clios     iostate;
-       int              error;
+       int              error = 0;
+       int              cur_upl = 0;
+       int              num_upl = 0;
+       int              n;
+       u_int32_t        xsize;
+       u_int32_t        io_size;
+       u_int32_t        devblocksize;
+       u_int32_t        mem_alignment_mask;
+       u_int32_t        tail_size = 0;
+       int              bflag;
+
+       if (flags & IO_PASSIVE) {
+               bflag = CL_PASSIVE;
+       } else {
+               bflag = 0;
+       }
+
+       if (flags & IO_NOCACHE) {
+               bflag |= CL_NOCACHE;
+       }
 
        /*
         * When we enter this routine, we know
-        *  -- the resid will not exceed iov_len
-        *  -- the target address is physically contiguous
+        *  -- the read_length will not exceed the current iov_len
+        *  -- the target address is physically contiguous for read_length
         */
+       cluster_syncup(vp, filesize, callback, callback_arg, PUSH_SYNC);
+
+       devblocksize = (u_int32_t)vp->v_mount->mnt_devblocksize;
+       mem_alignment_mask = (u_int32_t)vp->v_mount->mnt_alignmentmask;
 
-       iov = uio->uio_iov;
+       iostate.io_completed = 0;
+       iostate.io_issued = 0;
+       iostate.io_error = 0;
+       iostate.io_wanted = 0;
+
+       lck_mtx_init(&iostate.io_mtxp, &cl_mtx_grp, LCK_ATTR_NULL);
+
+next_cread:
+       io_size = *read_length;
 
        max_size = filesize - uio->uio_offset;
 
-       if (max_size > (off_t)((unsigned int)iov->iov_len))
-               io_size = iov->iov_len;
-       else
-               io_size = max_size;
+       if (io_size > max_size) {
+               io_size = (u_int32_t)max_size;
+       }
+
+       iov_base = uio_curriovbase(uio);
 
-       upl_offset = (vm_offset_t)iov->iov_base & PAGE_MASK;
+       upl_offset = (vm_offset_t)((u_int32_t)iov_base & PAGE_MASK);
        upl_needed_size = upl_offset + io_size;
 
-       error       = 0;
        pages_in_pl = 0;
-       upl_size = upl_needed_size;
+       upl_size = (upl_size_t)upl_needed_size;
        upl_flags = UPL_FILE_IO | UPL_NO_SYNC | UPL_CLEAN_IN_PLACE | UPL_SET_INTERNAL | UPL_SET_LITE | UPL_SET_IO_WIRE;
 
-       kret = vm_map_get_upl(current_map(),
-                             (vm_offset_t)iov->iov_base & ~PAGE_MASK,
-                             &upl_size, &upl, NULL, &pages_in_pl, &upl_flags, 0);
+
+       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 92)) | DBG_FUNC_START,
+           (int)upl_offset, (int)upl_size, (int)iov_base, io_size, 0);
+
+       vm_map_t map = UIO_SEG_IS_USER_SPACE(uio->uio_segflg) ? current_map() : kernel_map;
+       kret = vm_map_get_upl(map,
+           vm_map_trunc_page(iov_base, vm_map_page_mask(map)),
+           &upl_size, &upl[cur_upl], NULL, &pages_in_pl, &upl_flags, VM_KERN_MEMORY_FILE, 0);
+
+       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 92)) | DBG_FUNC_END,
+           (int)upl_offset, upl_size, io_size, kret, 0);
 
        if (kret != KERN_SUCCESS) {
-               /*
-                * cluster_phys_read: failed to get pagelist
+               /*
+                * failed to get pagelist
                 */
-               return(EINVAL);
+               error = EINVAL;
+               goto wait_for_creads;
        }
+       num_upl++;
+
        if (upl_size < upl_needed_size) {
-               /*
+               /*
                 * The upl_size wasn't satisfied.
                 */
-               ubc_upl_abort_range(upl, 0, upl_size, UPL_ABORT_FREE_ON_EMPTY);
-
-               return(EINVAL);
+               error = EINVAL;
+               goto wait_for_creads;
        }
-       pl = ubc_upl_pageinfo(upl);
+       pl = ubc_upl_pageinfo(upl[cur_upl]);
 
-       dst_paddr = ((addr64_t)upl_phys_page(pl, 0) << 12) + ((addr64_t)((u_int)iov->iov_base & PAGE_MASK));
+       dst_paddr = ((addr64_t)upl_phys_page(pl, 0) << PAGE_SHIFT) + (addr64_t)upl_offset;
 
        while (((uio->uio_offset & (devblocksize - 1)) || io_size < devblocksize) && io_size) {
-               int   head_size;
+               u_int32_t   head_size;
 
-               head_size = devblocksize - (int)(uio->uio_offset & (devblocksize - 1));
+               head_size = devblocksize - (u_int32_t)(uio->uio_offset & (devblocksize - 1));
 
-               if (head_size > io_size)
-                       head_size = io_size;
+               if (head_size > io_size) {
+                       head_size = io_size;
+               }
 
-               error = cluster_align_phys_io(vp, uio, dst_paddr, head_size, devblocksize, CL_READ);
+               error = cluster_align_phys_io(vp, uio, dst_paddr, head_size, CL_READ, callback, callback_arg);
 
                if (error) {
-                       ubc_upl_abort_range(upl, 0, upl_size, UPL_ABORT_FREE_ON_EMPTY);
-
-                       return(EINVAL);
+                       goto wait_for_creads;
                }
+
                upl_offset += head_size;
                dst_paddr  += head_size;
                io_size    -= head_size;
+
+               iov_base   += head_size;
+       }
+       if ((u_int32_t)iov_base & mem_alignment_mask) {
+               /*
+                * request doesn't set up on a memory boundary
+                * the underlying DMA engine can handle...
+                * return an error instead of going through
+                * the slow copy path since the intent of this
+                * path is direct I/O to device memory
+                */
+               error = EINVAL;
+               goto wait_for_creads;
        }
+
        tail_size = io_size & (devblocksize - 1);
-       io_size  -= tail_size;
 
-       iostate.io_completed = 0;
-       iostate.io_issued = 0;
-       iostate.io_error = 0;
-       iostate.io_wanted = 0;
+       io_size  -= tail_size;
 
        while (io_size && error == 0) {
-               int  xsize;
-
-               if (io_size > (MAX_UPL_TRANSFER * PAGE_SIZE))
-                       xsize = MAX_UPL_TRANSFER * PAGE_SIZE;
-               else
-                       xsize = io_size;
+               if (io_size > MAX_IO_CONTIG_SIZE) {
+                       xsize = MAX_IO_CONTIG_SIZE;
+               } else {
+                       xsize = io_size;
+               }
                /*
                 * request asynchronously so that we can overlap
                 * the preparation of the next I/O... we'll do
@@ -3123,49 +5296,145 @@ cluster_phys_read(vp, uio, filesize, devblocksize, flags)
                 * if there are already too many outstanding reads
                 * wait until some have completed before issuing the next
                 */
-               while ((iostate.io_issued - iostate.io_completed) > (2 * MAX_UPL_TRANSFER * PAGE_SIZE)) {
-                       iostate.io_wanted = 1;
-                       tsleep((caddr_t)&iostate.io_wanted, PRIBIO + 1, "cluster_phys_read", 0);
-               }       
-
-               error = cluster_io(vp, upl, upl_offset, uio->uio_offset, xsize, 0, 
-                                  CL_READ | CL_NOZERO | CL_DEV_MEMORY | CL_ASYNC,
-                                  (struct buf *)0, &iostate);
-               /*
+               cluster_iostate_wait(&iostate, MAX_IO_CONTIG_SIZE * IO_SCALE(vp, 2), "cluster_read_contig");
+
+               if (iostate.io_error) {
+                       /*
+                        * one of the earlier reads we issued ran into a hard error
+                        * don't issue any more reads...
+                        * go wait for any other reads to complete before
+                        * returning the error to the caller
+                        */
+                       goto wait_for_creads;
+               }
+               error = cluster_io(vp, upl[cur_upl], upl_offset, uio->uio_offset, xsize,
+                   CL_READ | CL_NOZERO | CL_DEV_MEMORY | CL_ASYNC | bflag,
+                   (buf_t)NULL, &iostate, callback, callback_arg);
+               /*
                 * The cluster_io read was issued successfully,
                 * update the uio structure
                 */
                if (error == 0) {
-                       uio->uio_resid  -= xsize;
-                       iov->iov_len    -= xsize;
-                       iov->iov_base   += xsize;
-                       uio->uio_offset += xsize;
-                       dst_paddr       += xsize;
-                       upl_offset      += xsize;
-                       io_size         -= xsize;
+                       uio_update(uio, (user_size_t)xsize);
+
+                       dst_paddr  += xsize;
+                       upl_offset += xsize;
+                       io_size    -= xsize;
                }
        }
+       if (error == 0 && iostate.io_error == 0 && tail_size == 0 && num_upl < MAX_VECTS && uio->uio_offset < filesize) {
+               error = cluster_io_type(uio, read_type, read_length, 0);
+
+               if (error == 0 && *read_type == IO_CONTIG) {
+                       cur_upl++;
+                       goto next_cread;
+               }
+       } else {
+               *read_type = IO_UNKNOWN;
+       }
+
+wait_for_creads:
        /*
         * make sure all async reads that are part of this stream
         * have completed before we proceed
         */
-       while (iostate.io_issued != iostate.io_completed) {
-               iostate.io_wanted = 1;
-               tsleep((caddr_t)&iostate.io_wanted, PRIBIO + 1, "cluster_phys_read", 0);
-       }       
+       cluster_iostate_wait(&iostate, 0, "cluster_read_contig");
+
        if (iostate.io_error) {
-               error = iostate.io_error;
+               error = iostate.io_error;
+       }
+
+       lck_mtx_destroy(&iostate.io_mtxp, &cl_mtx_grp);
+
+       if (error == 0 && tail_size) {
+               error = cluster_align_phys_io(vp, uio, dst_paddr, tail_size, CL_READ, callback, callback_arg);
+       }
+
+       for (n = 0; n < num_upl; n++) {
+               /*
+                * just release our hold on each physically contiguous
+                * region without changing any state
+                */
+               ubc_upl_abort(upl[n], 0);
        }
-       if (error == 0 && tail_size)
-               error = cluster_align_phys_io(vp, uio, dst_paddr, tail_size, devblocksize, CL_READ);
+
+       return error;
+}
+
+
+static int
+cluster_io_type(struct uio *uio, int *io_type, u_int32_t *io_length, u_int32_t min_length)
+{
+       user_size_t      iov_len;
+       user_addr_t      iov_base = 0;
+       upl_t            upl;
+       upl_size_t       upl_size;
+       upl_control_flags_t upl_flags;
+       int              retval = 0;
 
        /*
-        * just release our hold on the physically contiguous
-        * region without changing any state
+        * skip over any emtpy vectors
         */
-       ubc_upl_abort_range(upl, 0, upl_size, UPL_ABORT_FREE_ON_EMPTY);
-       
-       return (error);
+       uio_update(uio, (user_size_t)0);
+
+       iov_len = uio_curriovlen(uio);
+
+       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 94)) | DBG_FUNC_START, uio, (int)iov_len, 0, 0, 0);
+
+       if (iov_len) {
+               iov_base = uio_curriovbase(uio);
+               /*
+                * make sure the size of the vector isn't too big...
+                * internally, we want to handle all of the I/O in
+                * chunk sizes that fit in a 32 bit int
+                */
+               if (iov_len > (user_size_t)MAX_IO_REQUEST_SIZE) {
+                       upl_size = MAX_IO_REQUEST_SIZE;
+               } else {
+                       upl_size = (u_int32_t)iov_len;
+               }
+
+               upl_flags = UPL_QUERY_OBJECT_TYPE;
+
+               vm_map_t map = UIO_SEG_IS_USER_SPACE(uio->uio_segflg) ? current_map() : kernel_map;
+               if ((vm_map_get_upl(map,
+                   vm_map_trunc_page(iov_base, vm_map_page_mask(map)),
+                   &upl_size, &upl, NULL, NULL, &upl_flags, VM_KERN_MEMORY_FILE, 0)) != KERN_SUCCESS) {
+                       /*
+                        * the user app must have passed in an invalid address
+                        */
+                       retval = EFAULT;
+               }
+               if (upl_size == 0) {
+                       retval = EFAULT;
+               }
+
+               *io_length = upl_size;
+
+               if (upl_flags & UPL_PHYS_CONTIG) {
+                       *io_type = IO_CONTIG;
+               } else if (iov_len >= min_length) {
+                       *io_type = IO_DIRECT;
+               } else {
+                       *io_type = IO_COPY;
+               }
+       } else {
+               /*
+                * nothing left to do for this uio
+                */
+               *io_length = 0;
+               *io_type   = IO_UNKNOWN;
+       }
+       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 94)) | DBG_FUNC_END, iov_base, *io_type, *io_length, retval, 0);
+
+       if (*io_type == IO_DIRECT &&
+           vm_map_page_shift(current_map()) < PAGE_SHIFT) {
+               /* no direct I/O for sub-page-size address spaces */
+               DEBUG4K_VFS("io_type IO_DIRECT -> IO_COPY\n");
+               *io_type = IO_COPY;
+       }
+
+       return retval;
 }
 
 
@@ -3174,21 +5443,22 @@ cluster_phys_read(vp, uio, filesize, devblocksize, flags)
  * the completed pages will be released into the VM cache
  */
 int
-advisory_read(vp, filesize, f_offset, resid, devblocksize)
-       struct vnode *vp;
-       off_t         filesize;
-       off_t         f_offset;
-       int           resid;
-       int           devblocksize;
+advisory_read(vnode_t vp, off_t filesize, off_t f_offset, int resid)
+{
+       return advisory_read_ext(vp, filesize, f_offset, resid, NULL, NULL, CL_PASSIVE);
+}
+
+int
+advisory_read_ext(vnode_t vp, off_t filesize, off_t f_offset, int resid, int (*callback)(buf_t, void *), void *callback_arg, int bflag)
 {
        upl_page_info_t *pl;
        upl_t            upl;
        vm_offset_t      upl_offset;
        int              upl_size;
-       off_t            upl_f_offset;
-       int              start_offset;
-       int              start_pg;
-       int              last_pg;
+       off_t            upl_f_offset;
+       int              start_offset;
+       int              start_pg;
+       int              last_pg;
        int              pages_in_upl;
        off_t            max_size;
        int              io_size;
@@ -3196,12 +5466,27 @@ advisory_read(vp, filesize, f_offset, resid, devblocksize)
        int              retval = 0;
        int              issued_io;
        int              skip_range;
+       uint32_t         max_io_size;
 
-       if (!UBCINFOEXISTS(vp))
-               return(EINVAL);
+
+       if (!UBCINFOEXISTS(vp)) {
+               return EINVAL;
+       }
+
+       if (f_offset < 0 || resid < 0) {
+               return EINVAL;
+       }
+
+       max_io_size = cluster_max_io_size(vp->v_mount, CL_READ);
+
+       if (disk_conditioner_mount_is_ssd(vp->v_mount)) {
+               if (max_io_size > speculative_prefetch_max_iosize) {
+                       max_io_size = speculative_prefetch_max_iosize;
+               }
+       }
 
        KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 60)) | DBG_FUNC_START,
-                    (int)f_offset, resid, (int)filesize, devblocksize, 0);
+           (int)f_offset, resid, (int)filesize, 0, 0);
 
        while (resid && f_offset < filesize && retval == 0) {
                /*
@@ -3209,21 +5494,23 @@ advisory_read(vp, filesize, f_offset, resid, devblocksize)
                 * the requested read... limit each call to cluster_io
                 * to the maximum UPL size... cluster_io will clip if
                 * this exceeds the maximum io_size for the device,
-                * make sure to account for 
+                * make sure to account for
                 * a starting offset that's not page aligned
                 */
                start_offset = (int)(f_offset & PAGE_MASK_64);
                upl_f_offset = f_offset - (off_t)start_offset;
                max_size     = filesize - f_offset;
 
-               if (resid < max_size)
-                       io_size = resid;
-               else
-                       io_size = max_size;
+               if (resid < max_size) {
+                       io_size = resid;
+               } else {
+                       io_size = (int)max_size;
+               }
 
                upl_size = (start_offset + io_size + (PAGE_SIZE - 1)) & ~PAGE_MASK;
-               if (upl_size > (MAX_UPL_TRANSFER * PAGE_SIZE))
-                       upl_size = MAX_UPL_TRANSFER * PAGE_SIZE;
+               if ((uint32_t)upl_size > max_io_size) {
+                       upl_size = max_io_size;
+               }
 
                skip_range = 0;
                /*
@@ -3233,16 +5520,17 @@ advisory_read(vp, filesize, f_offset, resid, devblocksize)
                ubc_range_op(vp, upl_f_offset, upl_f_offset + upl_size, UPL_ROP_PRESENT, &skip_range);
 
                if (skip_range) {
-                       /*
+                       /*
                         * skip over pages already present in the cache
                         */
-                       io_size = skip_range - start_offset;
+                       io_size = skip_range - start_offset;
 
-                       f_offset += io_size;
+                       f_offset += io_size;
                        resid    -= io_size;
 
-                       if (skip_range == upl_size)
-                               continue;
+                       if (skip_range == upl_size) {
+                               continue;
+                       }
                        /*
                         * have to issue some real I/O
                         * at this point, we know it's starting on a page boundary
@@ -3255,184 +5543,343 @@ advisory_read(vp, filesize, f_offset, resid, devblocksize)
                pages_in_upl = upl_size / PAGE_SIZE;
 
                KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 61)) | DBG_FUNC_START,
-                            (int)upl, (int)upl_f_offset, upl_size, start_offset, 0);
-
-               kret = ubc_create_upl(vp, 
-                                               upl_f_offset,
-                                               upl_size,
-                                               &upl,
-                                               &pl,
-                                               UPL_RET_ONLY_ABSENT | UPL_SET_LITE);
-               if (kret != KERN_SUCCESS)
-                       return(retval);
+                   upl, (int)upl_f_offset, upl_size, start_offset, 0);
+
+               kret = ubc_create_upl_kernel(vp,
+                   upl_f_offset,
+                   upl_size,
+                   &upl,
+                   &pl,
+                   UPL_RET_ONLY_ABSENT | UPL_SET_LITE,
+                   VM_KERN_MEMORY_FILE);
+               if (kret != KERN_SUCCESS) {
+                       return retval;
+               }
                issued_io = 0;
 
                /*
-                * before we start marching forward, we must make sure we end on 
+                * before we start marching forward, we must make sure we end on
                 * a present page, otherwise we will be working with a freed
                 * upl
                 */
                for (last_pg = pages_in_upl - 1; last_pg >= 0; last_pg--) {
-                       if (upl_page_present(pl, last_pg))
-                               break;
+                       if (upl_page_present(pl, last_pg)) {
+                               break;
+                       }
                }
                pages_in_upl = last_pg + 1;
 
 
                KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 61)) | DBG_FUNC_END,
-                            (int)upl, (int)upl_f_offset, upl_size, start_offset, 0);
+                   upl, (int)upl_f_offset, upl_size, start_offset, 0);
 
 
-               for (last_pg = 0; last_pg < pages_in_upl; ) {
-                       /*
+               for (last_pg = 0; last_pg < pages_in_upl;) {
+                       /*
                         * scan from the beginning of the upl looking for the first
                         * page that is present.... this will become the first page in
                         * the request we're going to make to 'cluster_io'... if all
                         * of the pages are absent, we won't call through to 'cluster_io'
                         */
-                       for (start_pg = last_pg; start_pg < pages_in_upl; start_pg++) {
-                               if (upl_page_present(pl, start_pg))
-                                       break;
+                       for (start_pg = last_pg; start_pg < pages_in_upl; start_pg++) {
+                               if (upl_page_present(pl, start_pg)) {
+                                       break;
+                               }
                        }
 
                        /*
                         * scan from the starting present page looking for an absent
-                        * page before the end of the upl is reached, if we 
+                        * page before the end of the upl is reached, if we
                         * find one, then it will terminate the range of pages being
                         * presented to 'cluster_io'
                         */
                        for (last_pg = start_pg; last_pg < pages_in_upl; last_pg++) {
-                               if (!upl_page_present(pl, last_pg))
-                                       break;
+                               if (!upl_page_present(pl, last_pg)) {
+                                       break;
+                               }
                        }
 
-                       if (last_pg > start_pg) {               
-                               /*
+                       if (last_pg > start_pg) {
+                               /*
                                 * we found a range of pages that must be filled
                                 * if the last page in this range is the last page of the file
                                 * we may have to clip the size of it to keep from reading past
                                 * the end of the last physical block associated with the file
                                 */
-                               upl_offset = start_pg * PAGE_SIZE;
+                               upl_offset = start_pg * PAGE_SIZE;
                                io_size    = (last_pg - start_pg) * PAGE_SIZE;
 
-                               if ((upl_f_offset + upl_offset + io_size) > filesize)
-                                       io_size = filesize - (upl_f_offset + upl_offset);
+                               if ((off_t)(upl_f_offset + upl_offset + io_size) > filesize) {
+                                       io_size = (int)(filesize - (upl_f_offset + upl_offset));
+                               }
 
                                /*
                                 * issue an asynchronous read to cluster_io
                                 */
-                               retval = cluster_io(vp, upl, upl_offset, upl_f_offset + upl_offset, io_size, devblocksize,
-                                                   CL_ASYNC | CL_READ | CL_COMMIT | CL_AGE, (struct buf *)0, (struct clios *)0);
+                               retval = cluster_io(vp, upl, upl_offset, upl_f_offset + upl_offset, io_size,
+                                   CL_ASYNC | CL_READ | CL_COMMIT | CL_AGE | bflag, (buf_t)NULL, (struct clios *)NULL, callback, callback_arg);
 
                                issued_io = 1;
                        }
                }
-               if (issued_io == 0)
-                       ubc_upl_abort(upl, 0);
+               if (issued_io == 0) {
+                       ubc_upl_abort(upl, 0);
+               }
 
                io_size = upl_size - start_offset;
-               
-               if (io_size > resid)
-                       io_size = resid;
+
+               if (io_size > resid) {
+                       io_size = resid;
+               }
                f_offset += io_size;
                resid    -= io_size;
        }
 
        KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 60)) | DBG_FUNC_END,
-                    (int)f_offset, resid, retval, 0, 0);
+           (int)f_offset, resid, retval, 0, 0);
 
-       return(retval);
+       return retval;
+}
+
+
+int
+cluster_push(vnode_t vp, int flags)
+{
+       return cluster_push_ext(vp, flags, NULL, NULL);
 }
 
 
 int
-cluster_push(vp)
-        struct vnode *vp;
+cluster_push_ext(vnode_t vp, int flags, int (*callback)(buf_t, void *), void *callback_arg)
+{
+       return cluster_push_err(vp, flags, callback, callback_arg, NULL);
+}
+
+/* write errors via err, but return the number of clusters written */
+int
+cluster_push_err(vnode_t vp, int flags, int (*callback)(buf_t, void *), void *callback_arg, int *err)
 {
-        int  retval;
+       int     retval;
+       int     my_sparse_wait = 0;
+       struct  cl_writebehind *wbp;
+       int     local_err = 0;
+
+       if (err) {
+               *err = 0;
+       }
 
-       if (!UBCINFOEXISTS(vp) || (vp->v_clen == 0 && !(vp->v_flag & VHASDIRTY)))
-               return(0);
+       if (!UBCINFOEXISTS(vp)) {
+               KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 53)) | DBG_FUNC_NONE, kdebug_vnode(vp), flags, 0, -1, 0);
+               return 0;
+       }
+       /* return if deferred write is set */
+       if (((unsigned int)vfs_flags(vp->v_mount) & MNT_DEFWRITE) && (flags & IO_DEFWRITE)) {
+               return 0;
+       }
+       if ((wbp = cluster_get_wbp(vp, CLW_RETURNLOCKED)) == NULL) {
+               KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 53)) | DBG_FUNC_NONE, kdebug_vnode(vp), flags, 0, -2, 0);
+               return 0;
+       }
+       if (!ISSET(flags, IO_SYNC) && wbp->cl_number == 0 && wbp->cl_scmap == NULL) {
+               lck_mtx_unlock(&wbp->cl_lockw);
 
+               KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 53)) | DBG_FUNC_NONE, kdebug_vnode(vp), flags, 0, -3, 0);
+               return 0;
+       }
        KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 53)) | DBG_FUNC_START,
-                    vp->v_flag & VHASDIRTY, vp->v_clen, 0, 0, 0);
+           wbp->cl_scmap, wbp->cl_number, flags, 0, 0);
+
+       /*
+        * if we have an fsync in progress, we don't want to allow any additional
+        * sync/fsync/close(s) to occur until it finishes.
+        * note that its possible for writes to continue to occur to this file
+        * while we're waiting and also once the fsync starts to clean if we're
+        * in the sparse map case
+        */
+       while (wbp->cl_sparse_wait) {
+               KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 97)) | DBG_FUNC_START, kdebug_vnode(vp), 0, 0, 0, 0);
+
+               msleep((caddr_t)&wbp->cl_sparse_wait, &wbp->cl_lockw, PRIBIO + 1, "cluster_push_ext", NULL);
+
+               KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 97)) | DBG_FUNC_END, kdebug_vnode(vp), 0, 0, 0, 0);
+       }
+       if (flags & IO_SYNC) {
+               my_sparse_wait = 1;
+               wbp->cl_sparse_wait = 1;
+
+               /*
+                * this is an fsync (or equivalent)... we must wait for any existing async
+                * cleaning operations to complete before we evaulate the current state
+                * and finish cleaning... this insures that all writes issued before this
+                * fsync actually get cleaned to the disk before this fsync returns
+                */
+               while (wbp->cl_sparse_pushes) {
+                       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 98)) | DBG_FUNC_START, kdebug_vnode(vp), 0, 0, 0, 0);
+
+                       msleep((caddr_t)&wbp->cl_sparse_pushes, &wbp->cl_lockw, PRIBIO + 1, "cluster_push_ext", NULL);
+
+                       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 98)) | DBG_FUNC_END, kdebug_vnode(vp), 0, 0, 0, 0);
+               }
+       }
+       if (wbp->cl_scmap) {
+               void    *scmap;
+
+               if (wbp->cl_sparse_pushes < SPARSE_PUSH_LIMIT) {
+                       scmap = wbp->cl_scmap;
+                       wbp->cl_scmap = NULL;
+
+                       wbp->cl_sparse_pushes++;
+
+                       lck_mtx_unlock(&wbp->cl_lockw);
+
+                       retval = sparse_cluster_push(wbp, &scmap, vp, ubc_getsize(vp), PUSH_ALL, flags, callback, callback_arg, FALSE);
+
+                       lck_mtx_lock(&wbp->cl_lockw);
+
+                       wbp->cl_sparse_pushes--;
+
+                       if (retval) {
+                               if (wbp->cl_scmap != NULL) {
+                                       panic("cluster_push_err: Expected NULL cl_scmap\n");
+                               }
+
+                               wbp->cl_scmap = scmap;
+                       }
+
+                       if (wbp->cl_sparse_wait && wbp->cl_sparse_pushes == 0) {
+                               wakeup((caddr_t)&wbp->cl_sparse_pushes);
+                       }
+               } else {
+                       retval = sparse_cluster_push(wbp, &(wbp->cl_scmap), vp, ubc_getsize(vp), PUSH_ALL, flags, callback, callback_arg, FALSE);
+               }
 
-       if (vp->v_flag & VHASDIRTY) {
-               sparse_cluster_push(vp, ubc_getsize(vp), 1);
+               local_err = retval;
 
-               vp->v_clen = 0;
+               if (err) {
+                       *err = retval;
+               }
                retval = 1;
-       } else 
-               retval = cluster_try_push(vp, ubc_getsize(vp), 0, 1);
+       } else {
+               retval = cluster_try_push(wbp, vp, ubc_getsize(vp), PUSH_ALL, flags, callback, callback_arg, &local_err, FALSE);
+               if (err) {
+                       *err = local_err;
+               }
+       }
+       lck_mtx_unlock(&wbp->cl_lockw);
+
+       if (flags & IO_SYNC) {
+               (void)vnode_waitforwrites(vp, 0, 0, 0, "cluster_push");
+       }
+
+       if (my_sparse_wait) {
+               /*
+                * I'm the owner of the serialization token
+                * clear it and wakeup anyone that is waiting
+                * for me to finish
+                */
+               lck_mtx_lock(&wbp->cl_lockw);
 
+               wbp->cl_sparse_wait = 0;
+               wakeup((caddr_t)&wbp->cl_sparse_wait);
+
+               lck_mtx_unlock(&wbp->cl_lockw);
+       }
        KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 53)) | DBG_FUNC_END,
-                    vp->v_flag & VHASDIRTY, vp->v_clen, retval, 0, 0);
+           wbp->cl_scmap, wbp->cl_number, retval, local_err, 0);
 
-       return (retval);
+       return retval;
 }
 
 
-int
-cluster_release(vp)
-        struct vnode *vp;
+__private_extern__ void
+cluster_release(struct ubc_info *ubc)
 {
-        off_t offset;
-       u_int length;
+       struct cl_writebehind *wbp;
+       struct cl_readahead   *rap;
 
-       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 81)) | DBG_FUNC_START, (int)vp, (int)vp->v_scmap, vp->v_scdirty, 0, 0);
+       if ((wbp = ubc->cl_wbehind)) {
+               KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 81)) | DBG_FUNC_START, ubc, wbp->cl_scmap, 0, 0, 0);
 
-        if (vp->v_flag & VHASDIRTY) {
-               vfs_drt_control(&(vp->v_scmap), 0);
+               if (wbp->cl_scmap) {
+                       vfs_drt_control(&(wbp->cl_scmap), 0);
+               }
+               lck_mtx_destroy(&wbp->cl_lockw, &cl_mtx_grp);
+               zfree(cl_wr_zone, wbp);
+               ubc->cl_wbehind = NULL;
+       } else {
+               KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 81)) | DBG_FUNC_START, ubc, 0, 0, 0, 0);
+       }
 
-               vp->v_flag &= ~VHASDIRTY;
+       if ((rap = ubc->cl_rahead)) {
+               lck_mtx_destroy(&rap->cl_lockr, &cl_mtx_grp);
+               zfree(cl_rd_zone, rap);
+               ubc->cl_rahead  = NULL;
        }
-       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 81)) | DBG_FUNC_END, (int)vp, (int)vp->v_scmap, vp->v_scdirty, 0, 0);
+
+       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 81)) | DBG_FUNC_END, ubc, rap, wbp, 0, 0);
 }
 
 
 static int
-cluster_try_push(vp, EOF, can_delay, push_all)
-        struct vnode *vp;
-       off_t  EOF;
-       int    can_delay;
-       int    push_all;
+cluster_try_push(struct cl_writebehind *wbp, vnode_t vp, off_t EOF, int push_flag, int io_flags, int (*callback)(buf_t, void *), void *callback_arg, int *err, boolean_t vm_initiated)
 {
-        int cl_index;
+       int cl_index;
        int cl_index1;
        int min_index;
-        int cl_len;
-       int cl_total;
+       int cl_len;
        int cl_pushed = 0;
-       struct v_cluster l_clusters[MAX_CLUSTERS];
+       struct cl_wextent l_clusters[MAX_CLUSTERS];
+       u_int  max_cluster_pgcount;
+       int error = 0;
+
+       max_cluster_pgcount = MAX_CLUSTER_SIZE(vp) / PAGE_SIZE;
+       /*
+        * the write behind context exists and has
+        * already been locked...
+        */
+       if (wbp->cl_number == 0) {
+               /*
+                * no clusters to push
+                * return number of empty slots
+                */
+               return MAX_CLUSTERS;
+       }
 
        /*
         * make a local 'sorted' copy of the clusters
-        * and clear vp->v_clen so that new clusters can
+        * and clear wbp->cl_number so that new clusters can
         * be developed
         */
-       for (cl_index = 0; cl_index < vp->v_clen; cl_index++) {
-               for (min_index = -1, cl_index1 = 0; cl_index1 < vp->v_clen; cl_index1++) {
-                       if (vp->v_clusters[cl_index1].start_pg == vp->v_clusters[cl_index1].last_pg)
-                               continue;
-                       if (min_index == -1)
-                               min_index = cl_index1;
-                       else if (vp->v_clusters[cl_index1].start_pg < vp->v_clusters[min_index].start_pg)
-                               min_index = cl_index1;
-               }
-               if (min_index == -1)
-                       break;
-               l_clusters[cl_index].start_pg = vp->v_clusters[min_index].start_pg;
-               l_clusters[cl_index].last_pg  = vp->v_clusters[min_index].last_pg;
-
-               vp->v_clusters[min_index].start_pg = vp->v_clusters[min_index].last_pg;
-       }
-       cl_len     = cl_index;
-       vp->v_clen = 0;
-
-       if (can_delay && cl_len == MAX_CLUSTERS) {
+       for (cl_index = 0; cl_index < wbp->cl_number; cl_index++) {
+               for (min_index = -1, cl_index1 = 0; cl_index1 < wbp->cl_number; cl_index1++) {
+                       if (wbp->cl_clusters[cl_index1].b_addr == wbp->cl_clusters[cl_index1].e_addr) {
+                               continue;
+                       }
+                       if (min_index == -1) {
+                               min_index = cl_index1;
+                       } else if (wbp->cl_clusters[cl_index1].b_addr < wbp->cl_clusters[min_index].b_addr) {
+                               min_index = cl_index1;
+                       }
+               }
+               if (min_index == -1) {
+                       break;
+               }
+
+               l_clusters[cl_index].b_addr = wbp->cl_clusters[min_index].b_addr;
+               l_clusters[cl_index].e_addr = wbp->cl_clusters[min_index].e_addr;
+               l_clusters[cl_index].io_flags = wbp->cl_clusters[min_index].io_flags;
+
+               wbp->cl_clusters[min_index].b_addr = wbp->cl_clusters[min_index].e_addr;
+       }
+       wbp->cl_number = 0;
+
+       cl_len = cl_index;
+
+       /* skip switching to the sparse cluster mechanism if on diskimage */
+       if (((push_flag & PUSH_DELAY) && cl_len == MAX_CLUSTERS) &&
+           !(vp->v_mount->mnt_kern_flag & MNTK_VIRTUALDEV)) {
                int   i;
-               
+
                /*
                 * determine if we appear to be writing the file sequentially
                 * if not, by returning without having pushed any clusters
@@ -3440,176 +5887,245 @@ cluster_try_push(vp, EOF, can_delay, push_all)
                 * used for managing more random I/O patterns
                 *
                 * we know that we've got all clusters currently in use and the next write doesn't fit into one of them...
-                * that's why we're in try_push with can_delay true...
+                * that's why we're in try_push with PUSH_DELAY...
                 *
                 * check to make sure that all the clusters except the last one are 'full'... and that each cluster
                 * is adjacent to the next (i.e. we're looking for sequential writes) they were sorted above
-                * so we can just make a simple pass through up, to but not including the last one...
-                * note that last_pg is not inclusive, so it will be equal to the start_pg of the next cluster if they
+                * so we can just make a simple pass through, up to, but not including the last one...
+                * note that e_addr is not inclusive, so it will be equal to the b_addr of the next cluster if they
                 * are sequential
-                * 
+                *
                 * we let the last one be partial as long as it was adjacent to the previous one...
                 * we need to do this to deal with multi-threaded servers that might write an I/O or 2 out
                 * of order... if this occurs at the tail of the last cluster, we don't want to fall into the sparse cluster world...
                 */
                for (i = 0; i < MAX_CLUSTERS - 1; i++) {
-                       if ((l_clusters[i].last_pg - l_clusters[i].start_pg) != MAX_UPL_TRANSFER)
-                               goto dont_try;
-                       if (l_clusters[i].last_pg != l_clusters[i+1].start_pg)
-                               goto dont_try;
+                       if ((l_clusters[i].e_addr - l_clusters[i].b_addr) != max_cluster_pgcount) {
+                               goto dont_try;
+                       }
+                       if (l_clusters[i].e_addr != l_clusters[i + 1].b_addr) {
+                               goto dont_try;
+                       }
                }
        }
+       if (vm_initiated == TRUE) {
+               lck_mtx_unlock(&wbp->cl_lockw);
+       }
+
        for (cl_index = 0; cl_index < cl_len; cl_index++) {
-               /*
-                * try to push each cluster in turn...  cluster_push_x may not
-                * push the cluster if can_delay is TRUE and the cluster doesn't
-                * meet the critera for an immediate push
+               int     flags;
+               struct  cl_extent cl;
+               int retval;
+
+               flags = io_flags & (IO_PASSIVE | IO_CLOSE);
+
+               /*
+                * try to push each cluster in turn...
                 */
-               if (cluster_push_x(vp, EOF, l_clusters[cl_index].start_pg, l_clusters[cl_index].last_pg, can_delay)) {
-                       l_clusters[cl_index].start_pg = 0;
-                       l_clusters[cl_index].last_pg  = 0;
+               if (l_clusters[cl_index].io_flags & CLW_IONOCACHE) {
+                       flags |= IO_NOCACHE;
+               }
+
+               if (l_clusters[cl_index].io_flags & CLW_IOPASSIVE) {
+                       flags |= IO_PASSIVE;
+               }
+
+               if (push_flag & PUSH_SYNC) {
+                       flags |= IO_SYNC;
+               }
+
+               cl.b_addr = l_clusters[cl_index].b_addr;
+               cl.e_addr = l_clusters[cl_index].e_addr;
+
+               retval = cluster_push_now(vp, &cl, EOF, flags, callback, callback_arg, vm_initiated);
 
-                       cl_pushed++;
+               if (retval == 0) {
+                       cl_pushed++;
+
+                       l_clusters[cl_index].b_addr = 0;
+                       l_clusters[cl_index].e_addr = 0;
+               } else if (error == 0) {
+                       error = retval;
+               }
 
-                       if (push_all == 0)
-                               break;
+               if (!(push_flag & PUSH_ALL)) {
+                       break;
                }
        }
+       if (vm_initiated == TRUE) {
+               lck_mtx_lock(&wbp->cl_lockw);
+       }
+
+       if (err) {
+               *err = error;
+       }
+
 dont_try:
        if (cl_len > cl_pushed) {
-              /*
-               * we didn't push all of the clusters, so
-               * lets try to merge them back in to the vnode
-               */
-               if ((MAX_CLUSTERS - vp->v_clen) < (cl_len - cl_pushed)) {
-                       /*
+               /*
+                * we didn't push all of the clusters, so
+                * lets try to merge them back in to the vnode
+                */
+               if ((MAX_CLUSTERS - wbp->cl_number) < (cl_len - cl_pushed)) {
+                       /*
                         * we picked up some new clusters while we were trying to
-                        * push the old ones (I don't think this can happen because
-                        * I'm holding the lock, but just in case)... the sum of the
+                        * push the old ones... this can happen because I've dropped
+                        * the vnode lock... the sum of the
                         * leftovers plus the new cluster count exceeds our ability
                         * to represent them, so switch to the sparse cluster mechanism
+                        *
+                        * collect the active public clusters...
                         */
+                       sparse_cluster_switch(wbp, vp, EOF, callback, callback_arg, vm_initiated);
 
-                       /*
-                        * first collect the new clusters sitting in the vp
-                        */
-                       sparse_cluster_switch(vp, EOF);
-
-                       for (cl_index = 0, cl_index1 = 0; cl_index < cl_len; cl_index++) {
-                               if (l_clusters[cl_index].start_pg == l_clusters[cl_index].last_pg)
-                                       continue;
-                               vp->v_clusters[cl_index1].start_pg = l_clusters[cl_index].start_pg;
-                               vp->v_clusters[cl_index1].last_pg  = l_clusters[cl_index].last_pg;
+                       for (cl_index = 0, cl_index1 = 0; cl_index < cl_len; cl_index++) {
+                               if (l_clusters[cl_index].b_addr == l_clusters[cl_index].e_addr) {
+                                       continue;
+                               }
+                               wbp->cl_clusters[cl_index1].b_addr = l_clusters[cl_index].b_addr;
+                               wbp->cl_clusters[cl_index1].e_addr = l_clusters[cl_index].e_addr;
+                               wbp->cl_clusters[cl_index1].io_flags = l_clusters[cl_index].io_flags;
 
                                cl_index1++;
                        }
                        /*
                         * update the cluster count
                         */
-                       vp->v_clen = cl_index1;
+                       wbp->cl_number = cl_index1;
 
-                       /*
-                        * and collect the original clusters that were moved into the 
+                       /*
+                        * and collect the original clusters that were moved into the
                         * local storage for sorting purposes
                         */
-                       sparse_cluster_switch(vp, EOF);
-
+                       sparse_cluster_switch(wbp, vp, EOF, callback, callback_arg, vm_initiated);
                } else {
-                       /*
+                       /*
                         * we've got room to merge the leftovers back in
                         * just append them starting at the next 'hole'
-                        * represented by vp->v_clen
+                        * represented by wbp->cl_number
                         */
-                       for (cl_index = 0, cl_index1 = vp->v_clen; cl_index < cl_len; cl_index++) {
-                               if (l_clusters[cl_index].start_pg == l_clusters[cl_index].last_pg)
-                                       continue;
+                       for (cl_index = 0, cl_index1 = wbp->cl_number; cl_index < cl_len; cl_index++) {
+                               if (l_clusters[cl_index].b_addr == l_clusters[cl_index].e_addr) {
+                                       continue;
+                               }
 
-                               vp->v_clusters[cl_index1].start_pg = l_clusters[cl_index].start_pg;
-                               vp->v_clusters[cl_index1].last_pg  = l_clusters[cl_index].last_pg;
+                               wbp->cl_clusters[cl_index1].b_addr = l_clusters[cl_index].b_addr;
+                               wbp->cl_clusters[cl_index1].e_addr = l_clusters[cl_index].e_addr;
+                               wbp->cl_clusters[cl_index1].io_flags = l_clusters[cl_index].io_flags;
 
                                cl_index1++;
                        }
                        /*
                         * update the cluster count
                         */
-                       vp->v_clen = cl_index1;
+                       wbp->cl_number = cl_index1;
                }
        }
-       return(MAX_CLUSTERS - vp->v_clen);
+       return MAX_CLUSTERS - wbp->cl_number;
 }
 
 
 
 static int
-cluster_push_x(vp, EOF, first, last, can_delay)
-        struct vnode *vp;
-       off_t  EOF;
-       unsigned int first;
-       unsigned int last;
-       int    can_delay;
+cluster_push_now(vnode_t vp, struct cl_extent *cl, off_t EOF, int flags,
+    int (*callback)(buf_t, void *), void *callback_arg, boolean_t vm_initiated)
 {
        upl_page_info_t *pl;
        upl_t            upl;
        vm_offset_t      upl_offset;
        int              upl_size;
-       off_t            upl_f_offset;
-        int              pages_in_upl;
+       off_t            upl_f_offset;
+       int              pages_in_upl;
        int              start_pg;
        int              last_pg;
        int              io_size;
        int              io_flags;
        int              upl_flags;
+       int              bflag;
        int              size;
+       int              error = 0;
+       int              retval;
        kern_return_t    kret;
 
+       if (flags & IO_PASSIVE) {
+               bflag = CL_PASSIVE;
+       } else {
+               bflag = 0;
+       }
+
+       if (flags & IO_SKIP_ENCRYPTION) {
+               bflag |= CL_ENCRYPTED;
+       }
 
        KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 51)) | DBG_FUNC_START,
-                    vp->v_clen, first, last, EOF, 0);
+           (int)cl->b_addr, (int)cl->e_addr, (int)EOF, flags, 0);
 
-       if ((pages_in_upl = last - first) == 0) {
-               KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 51)) | DBG_FUNC_END, 1, 0, 0, 0, 0);
+       if ((pages_in_upl = (int)(cl->e_addr - cl->b_addr)) == 0) {
+               KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 51)) | DBG_FUNC_END, 1, 0, 0, 0, 0);
 
-               return (1);
+               return 0;
        }
        upl_size = pages_in_upl * PAGE_SIZE;
-       upl_f_offset = (off_t)((unsigned long long)first * PAGE_SIZE_64);
+       upl_f_offset = (off_t)(cl->b_addr * PAGE_SIZE_64);
 
        if (upl_f_offset + upl_size >= EOF) {
-
-               if (upl_f_offset >= EOF) {
-                       /*
-                        * must have truncated the file and missed 
+               if (upl_f_offset >= EOF) {
+                       /*
+                        * must have truncated the file and missed
                         * clearing a dangling cluster (i.e. it's completely
                         * beyond the new EOF
                         */
-                       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 51)) | DBG_FUNC_END, 1, 1, 0, 0, 0);
+                       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 51)) | DBG_FUNC_END, 1, 1, 0, 0, 0);
 
-                       return(1);
+                       return 0;
                }
-               size = EOF - upl_f_offset;
+               size = (int)(EOF - upl_f_offset);
 
                upl_size = (size + (PAGE_SIZE - 1)) & ~PAGE_MASK;
                pages_in_upl = upl_size / PAGE_SIZE;
-       } else
-               size = upl_size;
+       } else {
+               size = upl_size;
+       }
+
+
+       if (vm_initiated) {
+               vnode_pageout(vp, NULL, (upl_offset_t)0, upl_f_offset, (upl_size_t)upl_size,
+                   UPL_MSYNC | UPL_VNODE_PAGER | UPL_KEEPCACHED, &error);
 
+               return error;
+       }
        KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 41)) | DBG_FUNC_START, upl_size, size, 0, 0, 0);
 
-       if (vp->v_flag & VNOCACHE_DATA)
-               upl_flags = UPL_COPYOUT_FROM | UPL_RET_ONLY_DIRTY | UPL_SET_LITE | UPL_WILL_BE_DUMPED;
-       else
-               upl_flags = UPL_COPYOUT_FROM | UPL_RET_ONLY_DIRTY | UPL_SET_LITE;
+       /*
+        * by asking for UPL_COPYOUT_FROM and UPL_RET_ONLY_DIRTY, we get the following desirable behavior
+        *
+        * - only pages that are currently dirty are returned... these are the ones we need to clean
+        * - the hardware dirty bit is cleared when the page is gathered into the UPL... the software dirty bit is set
+        * - if we have to abort the I/O for some reason, the software dirty bit is left set since we didn't clean the page
+        * - when we commit the page, the software dirty bit is cleared... the hardware dirty bit is untouched so that if
+        *   someone dirties this page while the I/O is in progress, we don't lose track of the new state
+        *
+        * when the I/O completes, we no longer ask for an explicit clear of the DIRTY state (either soft or hard)
+        */
+
+       if ((vp->v_flag & VNOCACHE_DATA) || (flags & IO_NOCACHE)) {
+               upl_flags = UPL_COPYOUT_FROM | UPL_RET_ONLY_DIRTY | UPL_SET_LITE | UPL_WILL_BE_DUMPED;
+       } else {
+               upl_flags = UPL_COPYOUT_FROM | UPL_RET_ONLY_DIRTY | UPL_SET_LITE;
+       }
 
-       kret = ubc_create_upl(vp, 
-                               upl_f_offset,
-                               upl_size,
-                               &upl,
-                               &pl,
-                               upl_flags);
-       if (kret != KERN_SUCCESS)
-               panic("cluster_push: failed to get pagelist");
+       kret = ubc_create_upl_kernel(vp,
+           upl_f_offset,
+           upl_size,
+           &upl,
+           &pl,
+           upl_flags,
+           VM_KERN_MEMORY_FILE);
+       if (kret != KERN_SUCCESS) {
+               panic("cluster_push: failed to get pagelist");
+       }
 
-       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 41)) | DBG_FUNC_END, (int)upl, upl_f_offset, 0, 0, 0);
+       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 41)) | DBG_FUNC_END, upl, upl_f_offset, 0, 0, 0);
 
        /*
         * since we only asked for the dirty pages back
@@ -3620,200 +6136,307 @@ cluster_push_x(vp, EOF, first, last, can_delay)
         * employed by commit_range and abort_range.
         */
        for (last_pg = pages_in_upl - 1; last_pg >= 0; last_pg--) {
-               if (upl_page_present(pl, last_pg))
-                       break;
+               if (upl_page_present(pl, last_pg)) {
+                       break;
+               }
        }
        pages_in_upl = last_pg + 1;
 
        if (pages_in_upl == 0) {
-               ubc_upl_abort(upl, 0);
+               ubc_upl_abort(upl, 0);
 
                KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 51)) | DBG_FUNC_END, 1, 2, 0, 0, 0);
-               return(1);
-       }         
+               return 0;
+       }
 
-       for (last_pg = 0; last_pg < pages_in_upl; ) {
-               /*
+       for (last_pg = 0; last_pg < pages_in_upl;) {
+               /*
                 * find the next dirty page in the UPL
-                * this will become the first page in the 
+                * this will become the first page in the
                 * next I/O to generate
                 */
                for (start_pg = last_pg; start_pg < pages_in_upl; start_pg++) {
-                       if (upl_dirty_page(pl, start_pg))
+                       if (upl_dirty_page(pl, start_pg)) {
                                break;
-                       if (upl_page_present(pl, start_pg))
-                               /*
+                       }
+                       if (upl_page_present(pl, start_pg)) {
+                               /*
                                 * RET_ONLY_DIRTY will return non-dirty 'precious' pages
                                 * just release these unchanged since we're not going
                                 * to steal them or change their state
                                 */
-                               ubc_upl_abort_range(upl, start_pg * PAGE_SIZE, PAGE_SIZE, UPL_ABORT_FREE_ON_EMPTY);
+                               ubc_upl_abort_range(upl, start_pg * PAGE_SIZE, PAGE_SIZE, UPL_ABORT_FREE_ON_EMPTY);
+                       }
                }
-               if (start_pg >= pages_in_upl)
-                       /*
+               if (start_pg >= pages_in_upl) {
+                       /*
                         * done... no more dirty pages to push
                         */
-                       break;
-               if (start_pg > last_pg)
-                       /*
+                       break;
+               }
+               if (start_pg > last_pg) {
+                       /*
                         * skipped over some non-dirty pages
                         */
                        size -= ((start_pg - last_pg) * PAGE_SIZE);
+               }
 
                /*
                 * find a range of dirty pages to write
                 */
                for (last_pg = start_pg; last_pg < pages_in_upl; last_pg++) {
-                       if (!upl_dirty_page(pl, last_pg))
+                       if (!upl_dirty_page(pl, last_pg)) {
                                break;
+                       }
                }
                upl_offset = start_pg * PAGE_SIZE;
 
                io_size = min(size, (last_pg - start_pg) * PAGE_SIZE);
 
-               if (vp->v_flag & VNOCACHE_DATA)
-                       io_flags = CL_THROTTLE | CL_COMMIT | CL_ASYNC | CL_DUMP;
-               else
-                       io_flags = CL_THROTTLE | CL_COMMIT | CL_ASYNC;
+               io_flags = CL_THROTTLE | CL_COMMIT | CL_AGE | bflag;
+
+               if (!(flags & IO_SYNC)) {
+                       io_flags |= CL_ASYNC;
+               }
+
+               if (flags & IO_CLOSE) {
+                       io_flags |= CL_CLOSE;
+               }
+
+               if (flags & IO_NOCACHE) {
+                       io_flags |= CL_NOCACHE;
+               }
+
+               retval = cluster_io(vp, upl, upl_offset, upl_f_offset + upl_offset, io_size,
+                   io_flags, (buf_t)NULL, (struct clios *)NULL, callback, callback_arg);
 
-               cluster_io(vp, upl, upl_offset, upl_f_offset + upl_offset, io_size, vp->v_ciosiz, io_flags, (struct buf *)0, (struct clios *)0);
+               if (error == 0 && retval) {
+                       error = retval;
+               }
 
                size -= io_size;
        }
-       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 51)) | DBG_FUNC_END, 1, 3, 0, 0, 0);
+       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 51)) | DBG_FUNC_END, 1, 3, error, 0, 0);
 
-       return(1);
+       return error;
 }
 
 
+/*
+ * sparse_cluster_switch is called with the write behind lock held
+ */
 static int
-sparse_cluster_switch(struct vnode *vp, off_t EOF)
+sparse_cluster_switch(struct cl_writebehind *wbp, vnode_t vp, off_t EOF, int (*callback)(buf_t, void *), void *callback_arg, boolean_t vm_initiated)
 {
-        int cl_index;
+       int     cl_index;
+       int     error;
 
-       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 78)) | DBG_FUNC_START, (int)vp, (int)vp->v_scmap, vp->v_scdirty, 0, 0);
+       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 78)) | DBG_FUNC_START, kdebug_vnode(vp), wbp->cl_scmap, wbp->cl_number, 0, 0);
 
-       if ( !(vp->v_flag & VHASDIRTY)) {
-               vp->v_flag |= VHASDIRTY;
-               vp->v_scdirty = 0;
-               vp->v_scmap   = 0;
-       }
-       for (cl_index = 0; cl_index < vp->v_clen; cl_index++) {
-               int    flags;
-               int    start_pg;
-               int    last_pg;
+       for (cl_index = 0; cl_index < wbp->cl_number; cl_index++) {
+               int       flags;
+               struct cl_extent cl;
 
-               for (start_pg = vp->v_clusters[cl_index].start_pg; start_pg < vp->v_clusters[cl_index].last_pg; start_pg++) {
+               for (cl.b_addr = wbp->cl_clusters[cl_index].b_addr; cl.b_addr < wbp->cl_clusters[cl_index].e_addr; cl.b_addr++) {
+                       if (ubc_page_op(vp, (off_t)(cl.b_addr * PAGE_SIZE_64), 0, NULL, &flags) == KERN_SUCCESS) {
+                               if (flags & UPL_POP_DIRTY) {
+                                       cl.e_addr = cl.b_addr + 1;
 
-                       if (ubc_page_op(vp, (off_t)(((off_t)start_pg) * PAGE_SIZE_64), 0, 0, &flags) == KERN_SUCCESS) {
-                               if (flags & UPL_POP_DIRTY)
-                                       sparse_cluster_add(vp, EOF, start_pg, start_pg + 1);
+                                       error = sparse_cluster_add(wbp, &(wbp->cl_scmap), vp, &cl, EOF, callback, callback_arg, vm_initiated);
+
+                                       if (error) {
+                                               break;
+                                       }
+                               }
                        }
                }
        }
-       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 78)) | DBG_FUNC_END, (int)vp, (int)vp->v_scmap, vp->v_scdirty, 0, 0);
+       wbp->cl_number -= cl_index;
+
+       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 78)) | DBG_FUNC_END, kdebug_vnode(vp), wbp->cl_scmap, wbp->cl_number, error, 0);
+
+       return error;
 }
 
 
+/*
+ * sparse_cluster_push must be called with the write-behind lock held if the scmap is
+ * still associated with the write-behind context... however, if the scmap has been disassociated
+ * from the write-behind context (the cluster_push case), the wb lock is not held
+ */
 static int
-sparse_cluster_push(struct vnode *vp, off_t EOF, int push_all)
+sparse_cluster_push(struct cl_writebehind *wbp, void **scmap, vnode_t vp, off_t EOF, int push_flag,
+    int io_flags, int (*callback)(buf_t, void *), void *callback_arg, boolean_t vm_initiated)
 {
-        unsigned int first;
-       unsigned int last;
-        off_t offset;
-       u_int length;
+       struct cl_extent cl;
+       off_t           offset;
+       u_int           length;
+       void            *l_scmap;
+       int error = 0;
 
-       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 79)) | DBG_FUNC_START, (int)vp, (int)vp->v_scmap, vp->v_scdirty, push_all, 0);
+       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 79)) | DBG_FUNC_START, kdebug_vnode(vp), (*scmap), 0, push_flag, 0);
 
-       if (push_all)
-               vfs_drt_control(&(vp->v_scmap), 1);
+       if (push_flag & PUSH_ALL) {
+               vfs_drt_control(scmap, 1);
+       }
+
+       l_scmap = *scmap;
 
        for (;;) {
-               if (vfs_drt_get_cluster(&(vp->v_scmap), &offset, &length) != KERN_SUCCESS) {
-                       vp->v_flag &= ~VHASDIRTY;
-                       vp->v_clen = 0;
+               int retval;
+
+               if (vfs_drt_get_cluster(scmap, &offset, &length) != KERN_SUCCESS) {
                        break;
                }
-               first = (unsigned int)(offset / PAGE_SIZE_64);
-               last  = (unsigned int)((offset + length) / PAGE_SIZE_64);
 
-               cluster_push_x(vp, EOF, first, last, 0);
+               if (vm_initiated == TRUE) {
+                       lck_mtx_unlock(&wbp->cl_lockw);
+               }
+
+               cl.b_addr = (daddr64_t)(offset / PAGE_SIZE_64);
+               cl.e_addr = (daddr64_t)((offset + length) / PAGE_SIZE_64);
+
+               retval = cluster_push_now(vp, &cl, EOF, io_flags, callback, callback_arg, vm_initiated);
+               if (error == 0 && retval) {
+                       error = retval;
+               }
+
+               if (vm_initiated == TRUE) {
+                       lck_mtx_lock(&wbp->cl_lockw);
 
-               vp->v_scdirty -= (last - first);
+                       if (*scmap != l_scmap) {
+                               break;
+                       }
+               }
+
+               if (error) {
+                       if (vfs_drt_mark_pages(scmap, offset, length, NULL) != KERN_SUCCESS) {
+                               panic("Failed to restore dirty state on failure\n");
+                       }
+
+                       break;
+               }
 
-               if (push_all == 0)
-                       break;
+               if (!(push_flag & PUSH_ALL)) {
+                       break;
+               }
        }
-       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 79)) | DBG_FUNC_END, (int)vp, (int)vp->v_scmap, vp->v_scdirty, 0, 0);
+       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 79)) | DBG_FUNC_END, kdebug_vnode(vp), (*scmap), error, 0, 0);
+
+       return error;
 }
 
 
+/*
+ * sparse_cluster_add is called with the write behind lock held
+ */
 static int
-sparse_cluster_add(struct vnode *vp, off_t EOF, daddr_t first, daddr_t last)
+sparse_cluster_add(struct cl_writebehind *wbp, void **scmap, vnode_t vp, struct cl_extent *cl, off_t EOF,
+    int (*callback)(buf_t, void *), void *callback_arg, boolean_t vm_initiated)
 {
-        u_int new_dirty;
-       u_int length;
-       off_t offset;
+       u_int   new_dirty;
+       u_int   length;
+       off_t   offset;
+       int     error;
+       int     push_flag = 0; /* Is this a valid value? */
 
-       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 80)) | DBG_FUNC_START, (int)vp->v_scmap, vp->v_scdirty, first, last, 0);
+       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 80)) | DBG_FUNC_START, (*scmap), 0, cl->b_addr, (int)cl->e_addr, 0);
 
-       offset = (off_t)first * PAGE_SIZE_64;
-       length = (last - first) * PAGE_SIZE;
+       offset = (off_t)(cl->b_addr * PAGE_SIZE_64);
+       length = ((u_int)(cl->e_addr - cl->b_addr)) * PAGE_SIZE;
 
-       while (vfs_drt_mark_pages(&(vp->v_scmap), offset, length, &new_dirty) != KERN_SUCCESS) {
-               /*
+       while (vfs_drt_mark_pages(scmap, offset, length, &new_dirty) != KERN_SUCCESS) {
+               /*
                 * no room left in the map
                 * only a partial update was done
                 * push out some pages and try again
                 */
-               vp->v_scdirty += new_dirty;
 
-               sparse_cluster_push(vp, EOF, 0);
+               if (vfs_get_scmap_push_behavior_internal(scmap, &push_flag)) {
+                       push_flag = 0;
+               }
+
+               error = sparse_cluster_push(wbp, scmap, vp, EOF, push_flag, 0, callback, callback_arg, vm_initiated);
+
+               if (error) {
+                       break;
+               }
 
                offset += (new_dirty * PAGE_SIZE_64);
                length -= (new_dirty * PAGE_SIZE);
        }
-       vp->v_scdirty += new_dirty;
+       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 80)) | DBG_FUNC_END, kdebug_vnode(vp), (*scmap), error, 0, 0);
 
-       KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 80)) | DBG_FUNC_END, (int)vp, (int)vp->v_scmap, vp->v_scdirty, 0, 0);
+       return error;
 }
 
 
 static int
-cluster_align_phys_io(struct vnode *vp, struct uio *uio, addr64_t usr_paddr, int xsize, int devblocksize, int flags)
+cluster_align_phys_io(vnode_t vp, struct uio *uio, addr64_t usr_paddr, u_int32_t xsize, int flags, int (*callback)(buf_t, void *), void *callback_arg)
 {
-        struct iovec     *iov;
-        upl_page_info_t  *pl;
-        upl_t            upl;
-        addr64_t        ubc_paddr;
-        kern_return_t    kret;
-        int              error = 0;
-
-        iov = uio->uio_iov;
-
-        kret = ubc_create_upl(vp,
-                              uio->uio_offset & ~PAGE_MASK_64,
-                              PAGE_SIZE,
-                              &upl,
-                              &pl,
-                              UPL_SET_LITE);
-
-        if (kret != KERN_SUCCESS)
-                return(EINVAL);
-
-        if (!upl_valid_page(pl, 0)) {
-                /*
-                 * issue a synchronous read to cluster_io
-                 */
-                error = cluster_io(vp, upl, 0, uio->uio_offset & ~PAGE_MASK_64, PAGE_SIZE, devblocksize,
-                                  CL_READ, (struct buf *)0, (struct clios *)0);
-                if (error) {
-                          ubc_upl_abort_range(upl, 0, PAGE_SIZE, UPL_ABORT_DUMP_PAGES | UPL_ABORT_FREE_ON_EMPTY);
-
-                          return(error);
-                }
-        }
-        ubc_paddr = ((addr64_t)upl_phys_page(pl, 0) << 12) + (addr64_t)(uio->uio_offset & PAGE_MASK_64);
+       upl_page_info_t  *pl;
+       upl_t            upl;
+       addr64_t         ubc_paddr;
+       kern_return_t    kret;
+       int              error = 0;
+       int              did_read = 0;
+       int              abort_flags;
+       int              upl_flags;
+       int              bflag;
+
+       if (flags & IO_PASSIVE) {
+               bflag = CL_PASSIVE;
+       } else {
+               bflag = 0;
+       }
+
+       if (flags & IO_NOCACHE) {
+               bflag |= CL_NOCACHE;
+       }
+
+       upl_flags = UPL_SET_LITE;
+
+       if (!(flags & CL_READ)) {
+               /*
+                * "write" operation:  let the UPL subsystem know
+                * that we intend to modify the buffer cache pages
+                * we're gathering.
+                */
+               upl_flags |= UPL_WILL_MODIFY;
+       } else {
+               /*
+                * indicate that there is no need to pull the
+                * mapping for this page... we're only going
+                * to read from it, not modify it.
+                */
+               upl_flags |= UPL_FILE_IO;
+       }
+       kret = ubc_create_upl_kernel(vp,
+           uio->uio_offset & ~PAGE_MASK_64,
+           PAGE_SIZE,
+           &upl,
+           &pl,
+           upl_flags,
+           VM_KERN_MEMORY_FILE);
+
+       if (kret != KERN_SUCCESS) {
+               return EINVAL;
+       }
+
+       if (!upl_valid_page(pl, 0)) {
+               /*
+                * issue a synchronous read to cluster_io
+                */
+               error = cluster_io(vp, upl, 0, uio->uio_offset & ~PAGE_MASK_64, PAGE_SIZE,
+                   CL_READ | bflag, (buf_t)NULL, (struct clios *)NULL, callback, callback_arg);
+               if (error) {
+                       ubc_upl_abort_range(upl, 0, PAGE_SIZE, UPL_ABORT_DUMP_PAGES | UPL_ABORT_FREE_ON_EMPTY);
+
+                       return error;
+               }
+               did_read = 1;
+       }
+       ubc_paddr = ((addr64_t)upl_phys_page(pl, 0) << PAGE_SHIFT) + (addr64_t)(uio->uio_offset & PAGE_MASK_64);
 
 /*
  *     NOTE:  There is no prototype for the following in BSD. It, and the definitions
@@ -3821,61 +6444,71 @@ cluster_align_phys_io(struct vnode *vp, struct uio *uio, addr64_t usr_paddr, int
  *     osfmk/ppc/mappings.h.  They are not included here because there appears to be no
  *     way to do so without exporting them to kexts as well.
  */
-       if (flags & CL_READ)
+       if (flags & CL_READ) {
 //             copypv(ubc_paddr, usr_paddr, xsize, cppvPsrc | cppvPsnk | cppvFsnk);    /* Copy physical to physical and flush the destination */
-               copypv(ubc_paddr, usr_paddr, xsize,        2 |        1 |        4);    /* Copy physical to physical and flush the destination */
-       else
+               copypv(ubc_paddr, usr_paddr, xsize, 2 |        1 |        4);           /* Copy physical to physical and flush the destination */
+       } else {
 //             copypv(usr_paddr, ubc_paddr, xsize, cppvPsrc | cppvPsnk | cppvFsrc);    /* Copy physical to physical and flush the source */
-               copypv(usr_paddr, ubc_paddr, xsize,        2 |        1 |        8);    /* Copy physical to physical and flush the source */
-       
-       if ( !(flags & CL_READ) || (upl_valid_page(pl, 0) && upl_dirty_page(pl, 0))) {
-               /*
+               copypv(usr_paddr, ubc_paddr, xsize, 2 |        1 |        8);           /* Copy physical to physical and flush the source */
+       }
+       if (!(flags & CL_READ) || (upl_valid_page(pl, 0) && upl_dirty_page(pl, 0))) {
+               /*
                 * issue a synchronous write to cluster_io
                 */
-               error = cluster_io(vp, upl, 0, uio->uio_offset & ~PAGE_MASK_64, PAGE_SIZE, devblocksize,
-                                       0, (struct buf *)0, (struct clios *)0);
+               error = cluster_io(vp, upl, 0, uio->uio_offset & ~PAGE_MASK_64, PAGE_SIZE,
+                   bflag, (buf_t)NULL, (struct clios *)NULL, callback, callback_arg);
        }
        if (error == 0) {
-               uio->uio_offset += xsize;
-               iov->iov_base   += xsize;
-               iov->iov_len    -= xsize;
-               uio->uio_resid  -= xsize;
-       }
-       ubc_upl_abort_range(upl, 0, PAGE_SIZE, UPL_ABORT_DUMP_PAGES | UPL_ABORT_FREE_ON_EMPTY);
-       
-       return (error);
-}
+               uio_update(uio, (user_size_t)xsize);
+       }
+
+       if (did_read) {
+               abort_flags = UPL_ABORT_FREE_ON_EMPTY;
+       } else {
+               abort_flags = UPL_ABORT_FREE_ON_EMPTY | UPL_ABORT_DUMP_PAGES;
+       }
 
+       ubc_upl_abort_range(upl, 0, PAGE_SIZE, abort_flags);
 
+       return error;
+}
 
 int
-cluster_copy_upl_data(struct uio *uio, upl_t upl, int upl_offset, int xsize)
+cluster_copy_upl_data(struct uio *uio, upl_t upl, int upl_offset, int *io_resid)
 {
-        int       pg_offset;
+       int       pg_offset;
        int       pg_index;
-        int      csize;
+       int       csize;
        int       segflg;
        int       retval = 0;
+       int       xsize;
        upl_page_info_t *pl;
-       boolean_t funnel_state = FALSE;
+       int       dirty_count;
 
+       xsize = *io_resid;
 
        KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 34)) | DBG_FUNC_START,
-                    (int)uio->uio_offset, uio->uio_resid, upl_offset, xsize, 0);
-
-       if (xsize >= (16 * 1024))
-               funnel_state = thread_funnel_set(kernel_flock, FALSE);
+           (int)uio->uio_offset, upl_offset, xsize, 0, 0);
 
        segflg = uio->uio_segflg;
 
-       switch(segflg) {
+       switch (segflg) {
+       case UIO_USERSPACE32:
+       case UIO_USERISPACE32:
+               uio->uio_segflg = UIO_PHYS_USERSPACE32;
+               break;
 
-         case UIO_USERSPACE:
-         case UIO_USERISPACE:
+       case UIO_USERSPACE:
+       case UIO_USERISPACE:
                uio->uio_segflg = UIO_PHYS_USERSPACE;
                break;
 
-         case UIO_SYSSPACE:
+       case UIO_USERSPACE64:
+       case UIO_USERISPACE64:
+               uio->uio_segflg = UIO_PHYS_USERSPACE64;
+               break;
+
+       case UIO_SYSSPACE:
                uio->uio_segflg = UIO_PHYS_SYSSPACE;
                break;
        }
@@ -3885,10 +6518,14 @@ cluster_copy_upl_data(struct uio *uio, upl_t upl, int upl_offset, int xsize)
        pg_offset = upl_offset & PAGE_MASK;
        csize     = min(PAGE_SIZE - pg_offset, xsize);
 
+       dirty_count = 0;
        while (xsize && retval == 0) {
-               addr64_t  paddr;
+               addr64_t  paddr;
 
-               paddr = ((addr64_t)upl_phys_page(pl, pg_index) << 12) + pg_offset;
+               paddr = ((addr64_t)upl_phys_page(pl, pg_index) << PAGE_SHIFT) + pg_offset;
+               if ((uio->uio_rw == UIO_WRITE) && (upl_dirty_page(pl, pg_index) == FALSE)) {
+                       dirty_count++;
+               }
 
                retval = uiomove64(paddr, csize, uio);
 
@@ -3897,112 +6534,109 @@ cluster_copy_upl_data(struct uio *uio, upl_t upl, int upl_offset, int xsize)
                xsize    -= csize;
                csize     = min(PAGE_SIZE, xsize);
        }
-       uio->uio_segflg = segflg;
+       *io_resid = xsize;
 
-       if (funnel_state == TRUE)
-               thread_funnel_set(kernel_flock, TRUE);
+       uio->uio_segflg = segflg;
 
+       task_update_logical_writes(current_task(), (dirty_count * PAGE_SIZE), TASK_WRITE_DEFERRED, upl_lookup_vnode(upl));
        KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 34)) | DBG_FUNC_END,
-                    (int)uio->uio_offset, uio->uio_resid, retval, segflg, 0);
+           (int)uio->uio_offset, xsize, retval, segflg, 0);
 
-       return (retval);
+       return retval;
 }
 
 
 int
-cluster_copy_ubc_data(struct vnode *vp, struct uio *uio, int *io_resid, int mark_dirty)
+cluster_copy_ubc_data(vnode_t vp, struct uio *uio, int *io_resid, int mark_dirty)
+{
+       return cluster_copy_ubc_data_internal(vp, uio, io_resid, mark_dirty, 1);
+}
+
+
+static int
+cluster_copy_ubc_data_internal(vnode_t vp, struct uio *uio, int *io_resid, int mark_dirty, int take_reference)
 {
        int       segflg;
        int       io_size;
        int       xsize;
        int       start_offset;
-       off_t     f_offset;
        int       retval = 0;
-       memory_object_control_t  control;
-        int       op_flags = UPL_POP_SET | UPL_POP_BUSY;
-       boolean_t funnel_state = FALSE;
+       memory_object_control_t  control;
 
+       io_size = *io_resid;
 
        KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 34)) | DBG_FUNC_START,
-                    (int)uio->uio_offset, uio->uio_resid, 0, *io_resid, 0);
+           (int)uio->uio_offset, io_size, mark_dirty, take_reference, 0);
 
        control = ubc_getobject(vp, UBC_FLAGS_NONE);
+
        if (control == MEMORY_OBJECT_CONTROL_NULL) {
                KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 34)) | DBG_FUNC_END,
-                            (int)uio->uio_offset, uio->uio_resid, retval, 3, 0);
+                   (int)uio->uio_offset, io_size, retval, 3, 0);
 
-               return(0);
+               return 0;
        }
-       if (mark_dirty)
-               op_flags |= UPL_POP_DIRTY;
-
        segflg = uio->uio_segflg;
 
-       switch(segflg) {
+       switch (segflg) {
+       case UIO_USERSPACE32:
+       case UIO_USERISPACE32:
+               uio->uio_segflg = UIO_PHYS_USERSPACE32;
+               break;
+
+       case UIO_USERSPACE64:
+       case UIO_USERISPACE64:
+               uio->uio_segflg = UIO_PHYS_USERSPACE64;
+               break;
 
-         case UIO_USERSPACE:
-         case UIO_USERISPACE:
+       case UIO_USERSPACE:
+       case UIO_USERISPACE:
                uio->uio_segflg = UIO_PHYS_USERSPACE;
                break;
 
-         case UIO_SYSSPACE:
+       case UIO_SYSSPACE:
                uio->uio_segflg = UIO_PHYS_SYSSPACE;
                break;
        }
-       io_size      = *io_resid;
-       start_offset = (int)(uio->uio_offset & PAGE_MASK_64);
-       f_offset     = uio->uio_offset - start_offset;
-       xsize        = min(PAGE_SIZE - start_offset, io_size);
-
-       while (io_size && retval == 0) {
-               ppnum_t pgframe;
-
-               if (ubc_page_op_with_control(control, f_offset, op_flags, &pgframe, 0) != KERN_SUCCESS)
-                       break;
-
-               if (funnel_state == FALSE && io_size >= (16 * 1024))
-                       funnel_state = thread_funnel_set(kernel_flock, FALSE);
-
-               retval = uiomove64((addr64_t)(((addr64_t)pgframe << 12) + start_offset), xsize, uio);
 
-               ubc_page_op_with_control(control, f_offset, UPL_POP_CLR | UPL_POP_BUSY, 0, 0);
+       if ((io_size = *io_resid)) {
+               start_offset = (int)(uio->uio_offset & PAGE_MASK_64);
+               xsize = (int)uio_resid(uio);
 
-               io_size     -= xsize;
-               start_offset = 0;
-               f_offset     = uio->uio_offset;
-               xsize        = min(PAGE_SIZE, io_size);
+               retval = memory_object_control_uiomove(control, uio->uio_offset - start_offset, uio,
+                   start_offset, io_size, mark_dirty, take_reference);
+               xsize -= uio_resid(uio);
+               io_size -= xsize;
        }
        uio->uio_segflg = segflg;
        *io_resid       = io_size;
 
-       if (funnel_state == TRUE)
-               thread_funnel_set(kernel_flock, TRUE);
-
        KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, 34)) | DBG_FUNC_END,
-                    (int)uio->uio_offset, uio->uio_resid, retval, 0x80000000 | segflg, 0);
+           (int)uio->uio_offset, io_size, retval, 0x80000000 | segflg, 0);
 
-       return(retval);
+       return retval;
 }
 
 
 int
-is_file_clean(struct vnode *vp, off_t filesize)
+is_file_clean(vnode_t vp, off_t filesize)
 {
-        off_t f_offset;
+       off_t f_offset;
        int   flags;
        int   total_dirty = 0;
 
        for (f_offset = 0; f_offset < filesize; f_offset += PAGE_SIZE_64) {
-               if (ubc_page_op(vp, f_offset, 0, 0, &flags) == KERN_SUCCESS) {
-                       if (flags & UPL_POP_DIRTY) {
-                               total_dirty++;
+               if (ubc_page_op(vp, f_offset, 0, NULL, &flags) == KERN_SUCCESS) {
+                       if (flags & UPL_POP_DIRTY) {
+                               total_dirty++;
                        }
                }
        }
-       if (total_dirty)
-               return(EINVAL);
+       if (total_dirty) {
+               return EINVAL;
+       }
 
-       return (0);
+       return 0;
 }
 
 
@@ -4025,16 +6659,16 @@ is_file_clean(struct vnode *vp, off_t filesize)
  * single hashtable entry.  Each hashtable entry is aligned to this
  * size within the file.
  */
-#define DRT_BITVECTOR_PAGES            256
+#define DRT_BITVECTOR_PAGES             ((1024 * 256) / PAGE_SIZE)
 
 /*
  * File offset handling.
  *
  * DRT_ADDRESS_MASK is dependent on DRT_BITVECTOR_PAGES;
- * the correct formula is  (~(DRT_BITVECTOR_PAGES * PAGE_SIZE) - 1)
+ * the correct formula is  (~((DRT_BITVECTOR_PAGES * PAGE_SIZE) - 1))
  */
-#define DRT_ADDRESS_MASK               (~((1 << 20) - 1))
-#define DRT_ALIGN_ADDRESS(addr)                ((addr) & DRT_ADDRESS_MASK)
+#define DRT_ADDRESS_MASK                (~((DRT_BITVECTOR_PAGES * PAGE_SIZE) - 1))
+#define DRT_ALIGN_ADDRESS(addr)         ((addr) & DRT_ADDRESS_MASK)
 
 /*
  * Hashtable address field handling.
@@ -4046,32 +6680,33 @@ is_file_clean(struct vnode *vp, off_t filesize)
  * 0-DRT_BITVECTOR_PAGES inclusive, as well as have one value
  * to indicate that the bucket is actually unoccupied.
  */
-#define DRT_HASH_GET_ADDRESS(scm, i)   ((scm)->scm_hashtable[(i)].dhe_control & DRT_ADDRESS_MASK)
-#define DRT_HASH_SET_ADDRESS(scm, i, a)                                                                        \
-       do {                                                                                            \
-               (scm)->scm_hashtable[(i)].dhe_control =                                                 \
-                   ((scm)->scm_hashtable[(i)].dhe_control & ~DRT_ADDRESS_MASK) | DRT_ALIGN_ADDRESS(a); \
+#define DRT_HASH_GET_ADDRESS(scm, i)    ((scm)->scm_hashtable[(i)].dhe_control & DRT_ADDRESS_MASK)
+#define DRT_HASH_SET_ADDRESS(scm, i, a)                                                                 \
+       do {                                                                                            \
+               (scm)->scm_hashtable[(i)].dhe_control =                                                 \
+                   ((scm)->scm_hashtable[(i)].dhe_control & ~DRT_ADDRESS_MASK) | DRT_ALIGN_ADDRESS(a); \
        } while (0)
-#define DRT_HASH_COUNT_MASK            0x1ff
-#define DRT_HASH_GET_COUNT(scm, i)     ((scm)->scm_hashtable[(i)].dhe_control & DRT_HASH_COUNT_MASK)
-#define DRT_HASH_SET_COUNT(scm, i, c)                                                                                  \
-       do {                                                                                                            \
-               (scm)->scm_hashtable[(i)].dhe_control =                                                                 \
-                   ((scm)->scm_hashtable[(i)].dhe_control & ~DRT_HASH_COUNT_MASK) | ((c) & DRT_HASH_COUNT_MASK);       \
+#define DRT_HASH_COUNT_MASK             0x1ff
+#define DRT_HASH_GET_COUNT(scm, i)      ((scm)->scm_hashtable[(i)].dhe_control & DRT_HASH_COUNT_MASK)
+#define DRT_HASH_SET_COUNT(scm, i, c)                                                                                   \
+       do {                                                                                                            \
+               (scm)->scm_hashtable[(i)].dhe_control =                                                                 \
+                   ((scm)->scm_hashtable[(i)].dhe_control & ~DRT_HASH_COUNT_MASK) | ((c) & DRT_HASH_COUNT_MASK);       \
        } while (0)
 #define DRT_HASH_CLEAR(scm, i)                                                                                          \
-       do {                                                                                                            \
-               (scm)->scm_hashtable[(i)].dhe_control = 0;                                                              \
+       do {                                                                                                            \
+               (scm)->scm_hashtable[(i)].dhe_control = 0;                                                              \
        } while (0)
-#define DRT_HASH_VACATE(scm, i)                DRT_HASH_SET_COUNT((scm), (i), DRT_HASH_COUNT_MASK)
-#define DRT_HASH_VACANT(scm, i)                (DRT_HASH_GET_COUNT((scm), (i)) == DRT_HASH_COUNT_MASK)
-#define DRT_HASH_COPY(oscm, oi, scm, i)                                                                        \
-       do {                                                                                            \
-               (scm)->scm_hashtable[(i)].dhe_control = (oscm)->scm_hashtable[(oi)].dhe_control;        \
-               DRT_BITVECTOR_COPY(oscm, oi, scm, i);                                                   \
+#define DRT_HASH_VACATE(scm, i)         DRT_HASH_SET_COUNT((scm), (i), DRT_HASH_COUNT_MASK)
+#define DRT_HASH_VACANT(scm, i)         (DRT_HASH_GET_COUNT((scm), (i)) == DRT_HASH_COUNT_MASK)
+#define DRT_HASH_COPY(oscm, oi, scm, i)                                                                 \
+       do {                                                                                            \
+               (scm)->scm_hashtable[(i)].dhe_control = (oscm)->scm_hashtable[(oi)].dhe_control;        \
+               DRT_BITVECTOR_COPY(oscm, oi, scm, i);                                                   \
        } while(0);
 
 
+#if !defined(XNU_TARGET_OS_OSX)
 /*
  * Hash table moduli.
  *
@@ -4080,52 +6715,106 @@ is_file_clean(struct vnode *vp, off_t filesize)
  * both being prime and fitting within the desired allocation
  * size, these values need to be manually determined.
  *
- * For DRT_BITVECTOR_SIZE = 256, the entry size is 40 bytes.
+ * For DRT_BITVECTOR_SIZE = 64, the entry size is 16 bytes.
  *
- * The small hashtable allocation is 1024 bytes, so the modulus is 23.
- * The large hashtable allocation is 16384 bytes, so the modulus is 401.
+ * The small hashtable allocation is 4096 bytes, so the modulus is 251.
+ * The large hashtable allocation is 32768 bytes, so the modulus is 2039.
+ * The xlarge hashtable allocation is 131072 bytes, so the modulus is 8179.
  */
-#define DRT_HASH_SMALL_MODULUS 23
-#define DRT_HASH_LARGE_MODULUS 401
 
-#define DRT_SMALL_ALLOCATION   1024    /* 104 bytes spare */
-#define DRT_LARGE_ALLOCATION   16384   /* 344 bytes spare */
+#define DRT_HASH_SMALL_MODULUS  251
+#define DRT_HASH_LARGE_MODULUS  2039
+#define DRT_HASH_XLARGE_MODULUS  8179
 
-/* *** nothing below here has secret dependencies on DRT_BITVECTOR_PAGES *** */
+/*
+ * Physical memory required before the large hash modulus is permitted.
+ *
+ * On small memory systems, the large hash modulus can lead to phsyical
+ * memory starvation, so we avoid using it there.
+ */
+#define DRT_HASH_LARGE_MEMORY_REQUIRED  (1024LL * 1024LL * 1024LL)      /* 1GiB */
+#define DRT_HASH_XLARGE_MEMORY_REQUIRED  (8 * 1024LL * 1024LL * 1024LL)  /* 8GiB */
+
+#define DRT_SMALL_ALLOCATION    4096    /* 80 bytes spare */
+#define DRT_LARGE_ALLOCATION    32768   /* 144 bytes spare */
+#define DRT_XLARGE_ALLOCATION    131072  /* 208 bytes spare */
 
+#else /* XNU_TARGET_OS_OSX */
 /*
- * Hashtable bitvector handling.
+ * Hash table moduli.
  *
- * Bitvector fields are 32 bits long.
+ * Since the hashtable entry's size is dependent on the size of
+ * the bitvector, and since the hashtable size is constrained to
+ * both being prime and fitting within the desired allocation
+ * size, these values need to be manually determined.
+ *
+ * For DRT_BITVECTOR_SIZE = 64, the entry size is 16 bytes.
+ *
+ * The small hashtable allocation is 16384 bytes, so the modulus is 1019.
+ * The large hashtable allocation is 131072 bytes, so the modulus is 8179.
+ * The xlarge hashtable allocation is 524288 bytes, so the modulus is 32749.
  */
 
-#define DRT_HASH_SET_BIT(scm, i, bit)                          \
-       (scm)->scm_hashtable[(i)].dhe_bitvector[(bit) / 32] |= (1 << ((bit) % 32))
+#define DRT_HASH_SMALL_MODULUS  1019
+#define DRT_HASH_LARGE_MODULUS  8179
+#define DRT_HASH_XLARGE_MODULUS  32749
 
-#define DRT_HASH_CLEAR_BIT(scm, i, bit)                                \
-       (scm)->scm_hashtable[(i)].dhe_bitvector[(bit) / 32] &= ~(1 << ((bit) % 32))
-    
-#define DRT_HASH_TEST_BIT(scm, i, bit)                                 \
-       ((scm)->scm_hashtable[(i)].dhe_bitvector[(bit) / 32] & (1 << ((bit) % 32)))
-    
-#define DRT_BITVECTOR_CLEAR(scm, i)                            \
-       bzero(&(scm)->scm_hashtable[(i)].dhe_bitvector[0], (DRT_BITVECTOR_PAGES / 32) * sizeof(u_int32_t))
+/*
+ * Physical memory required before the large hash modulus is permitted.
+ *
+ * On small memory systems, the large hash modulus can lead to phsyical
+ * memory starvation, so we avoid using it there.
+ */
+#define DRT_HASH_LARGE_MEMORY_REQUIRED  (4 * 1024LL * 1024LL * 1024LL)  /* 4GiB */
+#define DRT_HASH_XLARGE_MEMORY_REQUIRED  (32 * 1024LL * 1024LL * 1024LL)  /* 32GiB */
+
+#define DRT_SMALL_ALLOCATION    16384   /* 80 bytes spare */
+#define DRT_LARGE_ALLOCATION    131072  /* 208 bytes spare */
+#define DRT_XLARGE_ALLOCATION   524288  /* 304 bytes spare */
 
-#define DRT_BITVECTOR_COPY(oscm, oi, scm, i)                   \
-       bcopy(&(oscm)->scm_hashtable[(oi)].dhe_bitvector[0],    \
-           &(scm)->scm_hashtable[(i)].dhe_bitvector[0],        \
-           (DRT_BITVECTOR_PAGES / 32) * sizeof(u_int32_t))
+#endif /* ! XNU_TARGET_OS_OSX */
 
+/* *** nothing below here has secret dependencies on DRT_BITVECTOR_PAGES *** */
 
 /*
  * Hashtable entry.
  */
 struct vfs_drt_hashentry {
-       u_int64_t       dhe_control;
-       u_int32_t       dhe_bitvector[DRT_BITVECTOR_PAGES / 32];
+       u_int64_t       dhe_control;
+/*
+ * dhe_bitvector was declared as dhe_bitvector[DRT_BITVECTOR_PAGES / 32];
+ * DRT_BITVECTOR_PAGES is defined as ((1024 * 256) / PAGE_SIZE)
+ * Since PAGE_SIZE is only known at boot time,
+ *     -define MAX_DRT_BITVECTOR_PAGES for smallest supported page size (4k)
+ *     -declare dhe_bitvector array for largest possible length
+ */
+#define MAX_DRT_BITVECTOR_PAGES (1024 * 256)/( 4 * 1024)
+       u_int32_t       dhe_bitvector[MAX_DRT_BITVECTOR_PAGES / 32];
 };
 
+/*
+ * Hashtable bitvector handling.
+ *
+ * Bitvector fields are 32 bits long.
+ */
+
+#define DRT_HASH_SET_BIT(scm, i, bit)                           \
+       (scm)->scm_hashtable[(i)].dhe_bitvector[(bit) / 32] |= (1 << ((bit) % 32))
+
+#define DRT_HASH_CLEAR_BIT(scm, i, bit)                         \
+       (scm)->scm_hashtable[(i)].dhe_bitvector[(bit) / 32] &= ~(1 << ((bit) % 32))
+
+#define DRT_HASH_TEST_BIT(scm, i, bit)                          \
+       ((scm)->scm_hashtable[(i)].dhe_bitvector[(bit) / 32] & (1 << ((bit) % 32)))
+
+#define DRT_BITVECTOR_CLEAR(scm, i)                             \
+       bzero(&(scm)->scm_hashtable[(i)].dhe_bitvector[0], (MAX_DRT_BITVECTOR_PAGES / 32) * sizeof(u_int32_t))
+
+#define DRT_BITVECTOR_COPY(oscm, oi, scm, i)                    \
+       bcopy(&(oscm)->scm_hashtable[(oi)].dhe_bitvector[0],    \
+           &(scm)->scm_hashtable[(i)].dhe_bitvector[0],        \
+           (MAX_DRT_BITVECTOR_PAGES / 32) * sizeof(u_int32_t))
+
 /*
  * Dirty Region Tracking structure.
  *
@@ -4136,54 +6825,53 @@ struct vfs_drt_hashentry {
  */
 
 struct vfs_drt_clustermap {
-       u_int32_t               scm_magic;      /* sanity/detection */
-#define DRT_SCM_MAGIC          0x12020003
-       u_int32_t               scm_modulus;    /* current ring size */
-       u_int32_t               scm_buckets;    /* number of occupied buckets */
-       u_int32_t               scm_lastclean;  /* last entry we cleaned */
-       u_int32_t               scm_iskips;     /* number of slot skips */
+       u_int32_t               scm_magic;      /* sanity/detection */
+#define DRT_SCM_MAGIC           0x12020003
+       u_int32_t               scm_modulus;    /* current ring size */
+       u_int32_t               scm_buckets;    /* number of occupied buckets */
+       u_int32_t               scm_lastclean;  /* last entry we cleaned */
+       u_int32_t               scm_iskips;     /* number of slot skips */
 
        struct vfs_drt_hashentry scm_hashtable[0];
 };
 
 
-#define DRT_HASH(scm, addr)            ((addr) % (scm)->scm_modulus)
-#define DRT_HASH_NEXT(scm, addr)       (((addr) + 1) % (scm)->scm_modulus)
+#define DRT_HASH(scm, addr)             ((addr) % (scm)->scm_modulus)
+#define DRT_HASH_NEXT(scm, addr)        (((addr) + 1) % (scm)->scm_modulus)
 
 /*
  * Debugging codes and arguments.
  */
-#define DRT_DEBUG_EMPTYFREE    (FSDBG_CODE(DBG_FSRW, 82)) /* nil */
-#define DRT_DEBUG_RETCLUSTER   (FSDBG_CODE(DBG_FSRW, 83)) /* offset, length */
-#define DRT_DEBUG_ALLOC                (FSDBG_CODE(DBG_FSRW, 84)) /* copycount */
-#define DRT_DEBUG_INSERT       (FSDBG_CODE(DBG_FSRW, 85)) /* offset, iskip */
-#define DRT_DEBUG_MARK         (FSDBG_CODE(DBG_FSRW, 86)) /* offset, length,
-                                                           * dirty */
-                                                          /* 0, setcount */
-                                                          /* 1 (clean, no map) */
-                                                          /* 2 (map alloc fail) */
-                                                          /* 3, resid (partial) */
-#define DRT_DEBUG_6            (FSDBG_CODE(DBG_FSRW, 87))
-#define DRT_DEBUG_SCMDATA      (FSDBG_CODE(DBG_FSRW, 88)) /* modulus, buckets,
-                                                           * lastclean, iskips */
-
-
-static void            vfs_drt_sanity(struct vfs_drt_clustermap *cmap);
-static kern_return_t   vfs_drt_alloc_map(struct vfs_drt_clustermap **cmapp);
-static kern_return_t   vfs_drt_free_map(struct vfs_drt_clustermap *cmap);
-static kern_return_t   vfs_drt_search_index(struct vfs_drt_clustermap *cmap,
-       u_int64_t offset, int *indexp);
-static kern_return_t   vfs_drt_get_index(struct vfs_drt_clustermap **cmapp,
-       u_int64_t offset,
-       int *indexp,
-       int recursed);
-static kern_return_t   vfs_drt_do_mark_pages(
-       void            **cmapp,
-       u_int64_t       offset,
-       u_int           length,
-       int             *setcountp,
-       int             dirty);
-static void            vfs_drt_trace(
+#define DRT_DEBUG_EMPTYFREE     (FSDBG_CODE(DBG_FSRW, 82)) /* nil */
+#define DRT_DEBUG_RETCLUSTER    (FSDBG_CODE(DBG_FSRW, 83)) /* offset, length */
+#define DRT_DEBUG_ALLOC         (FSDBG_CODE(DBG_FSRW, 84)) /* copycount */
+#define DRT_DEBUG_INSERT        (FSDBG_CODE(DBG_FSRW, 85)) /* offset, iskip */
+#define DRT_DEBUG_MARK          (FSDBG_CODE(DBG_FSRW, 86)) /* offset, length,
+                                                           * dirty */
+                                                           /* 0, setcount */
+                                                           /* 1 (clean, no map) */
+                                                           /* 2 (map alloc fail) */
+                                                           /* 3, resid (partial) */
+#define DRT_DEBUG_6             (FSDBG_CODE(DBG_FSRW, 87))
+#define DRT_DEBUG_SCMDATA       (FSDBG_CODE(DBG_FSRW, 88)) /* modulus, buckets,
+                                                           * lastclean, iskips */
+
+
+static kern_return_t    vfs_drt_alloc_map(struct vfs_drt_clustermap **cmapp);
+static kern_return_t    vfs_drt_free_map(struct vfs_drt_clustermap *cmap);
+static kern_return_t    vfs_drt_search_index(struct vfs_drt_clustermap *cmap,
+    u_int64_t offset, int *indexp);
+static kern_return_t    vfs_drt_get_index(struct vfs_drt_clustermap **cmapp,
+    u_int64_t offset,
+    int *indexp,
+    int recursed);
+static kern_return_t    vfs_drt_do_mark_pages(
+       void            **cmapp,
+       u_int64_t       offset,
+       u_int           length,
+       u_int           *setcountp,
+       int             dirty);
+static void             vfs_drt_trace(
        struct vfs_drt_clustermap *cmap,
        int code,
        int arg1,
@@ -4203,50 +6891,77 @@ static void             vfs_drt_trace(
 static kern_return_t
 vfs_drt_alloc_map(struct vfs_drt_clustermap **cmapp)
 {
-       struct vfs_drt_clustermap *cmap, *ocmap;
-       kern_return_t   kret;
-       u_int64_t       offset;
-       int             nsize, i, active_buckets, index, copycount;
+       struct vfs_drt_clustermap *cmap = NULL, *ocmap = NULL;
+       kern_return_t   kret = KERN_SUCCESS;
+       u_int64_t       offset = 0;
+       u_int32_t       i = 0;
+       int             modulus_size = 0, map_size = 0, active_buckets = 0, index = 0, copycount = 0;
 
        ocmap = NULL;
-       if (cmapp != NULL)
+       if (cmapp != NULL) {
                ocmap = *cmapp;
-       
+       }
+
        /*
         * Decide on the size of the new map.
         */
        if (ocmap == NULL) {
-               nsize = DRT_HASH_SMALL_MODULUS;
+               modulus_size = DRT_HASH_SMALL_MODULUS;
+               map_size = DRT_SMALL_ALLOCATION;
        } else {
                /* count the number of active buckets in the old map */
                active_buckets = 0;
                for (i = 0; i < ocmap->scm_modulus; i++) {
                        if (!DRT_HASH_VACANT(ocmap, i) &&
-                           (DRT_HASH_GET_COUNT(ocmap, i) != 0))
+                           (DRT_HASH_GET_COUNT(ocmap, i) != 0)) {
                                active_buckets++;
+                       }
                }
                /*
                 * If we're currently using the small allocation, check to
                 * see whether we should grow to the large one.
                 */
                if (ocmap->scm_modulus == DRT_HASH_SMALL_MODULUS) {
-                       /* if the ring is nearly full */
-                       if (active_buckets > (DRT_HASH_SMALL_MODULUS - 5)) {
-                               nsize = DRT_HASH_LARGE_MODULUS;
+                       /*
+                        * If the ring is nearly full and we are allowed to
+                        * use the large modulus, upgrade.
+                        */
+                       if ((active_buckets > (DRT_HASH_SMALL_MODULUS - 5)) &&
+                           (max_mem >= DRT_HASH_LARGE_MEMORY_REQUIRED)) {
+                               modulus_size = DRT_HASH_LARGE_MODULUS;
+                               map_size = DRT_LARGE_ALLOCATION;
+                       } else {
+                               modulus_size = DRT_HASH_SMALL_MODULUS;
+                               map_size = DRT_SMALL_ALLOCATION;
+                       }
+               } else if (ocmap->scm_modulus == DRT_HASH_LARGE_MODULUS) {
+                       if ((active_buckets > (DRT_HASH_LARGE_MODULUS - 5)) &&
+                           (max_mem >= DRT_HASH_XLARGE_MEMORY_REQUIRED)) {
+                               modulus_size = DRT_HASH_XLARGE_MODULUS;
+                               map_size = DRT_XLARGE_ALLOCATION;
                        } else {
-                               nsize = DRT_HASH_SMALL_MODULUS;
+                               /*
+                                * If the ring is completely full and we can't
+                                * expand, there's nothing useful for us to do.
+                                * Behave as though we had compacted into the new
+                                * array and return.
+                                */
+                               return KERN_SUCCESS;
                        }
                } else {
-                       /* already using the large modulus */
-                       nsize = DRT_HASH_LARGE_MODULUS;
+                       /* already using the xlarge modulus */
+                       modulus_size = DRT_HASH_XLARGE_MODULUS;
+                       map_size = DRT_XLARGE_ALLOCATION;
+
                        /*
                         * If the ring is completely full, there's
                         * nothing useful for us to do.  Behave as
                         * though we had compacted into the new
                         * array and return.
                         */
-                       if (active_buckets >= DRT_HASH_LARGE_MODULUS)
-                               return(KERN_SUCCESS);
+                       if (active_buckets >= DRT_HASH_XLARGE_MODULUS) {
+                               return KERN_SUCCESS;
+                       }
                }
        }
 
@@ -4254,17 +6969,17 @@ vfs_drt_alloc_map(struct vfs_drt_clustermap **cmapp)
         * Allocate and initialise the new map.
         */
 
-       kret = kmem_alloc(kernel_map, (vm_offset_t *)&cmap,
-           (nsize == DRT_HASH_SMALL_MODULUS) ? DRT_SMALL_ALLOCATION : DRT_LARGE_ALLOCATION);
-       if (kret != KERN_SUCCESS)
-               return(kret);
+       kret = kmem_alloc(kernel_map, (vm_offset_t *)&cmap, map_size, VM_KERN_MEMORY_FILE);
+       if (kret != KERN_SUCCESS) {
+               return kret;
+       }
        cmap->scm_magic = DRT_SCM_MAGIC;
-       cmap->scm_modulus = nsize;
+       cmap->scm_modulus = modulus_size;
        cmap->scm_buckets = 0;
        cmap->scm_lastclean = 0;
        cmap->scm_iskips = 0;
        for (i = 0; i < cmap->scm_modulus; i++) {
-               DRT_HASH_CLEAR(cmap, i);
+               DRT_HASH_CLEAR(cmap, i);
                DRT_HASH_VACATE(cmap, i);
                DRT_BITVECTOR_CLEAR(cmap, i);
        }
@@ -4277,14 +6992,16 @@ vfs_drt_alloc_map(struct vfs_drt_clustermap **cmapp)
                for (i = 0; i < ocmap->scm_modulus; i++) {
                        /* skip empty buckets */
                        if (DRT_HASH_VACANT(ocmap, i) ||
-                           (DRT_HASH_GET_COUNT(ocmap, i) == 0))
+                           (DRT_HASH_GET_COUNT(ocmap, i) == 0)) {
                                continue;
+                       }
                        /* get new index */
                        offset = DRT_HASH_GET_ADDRESS(ocmap, i);
                        kret = vfs_drt_get_index(&cmap, offset, &index, 1);
                        if (kret != KERN_SUCCESS) {
                                /* XXX need to bail out gracefully here */
                                panic("vfs_drt: new cluster map mysteriously too small");
+                               index = 0;
                        }
                        /* copy */
                        DRT_HASH_COPY(ocmap, i, cmap, index);
@@ -4294,9 +7011,9 @@ vfs_drt_alloc_map(struct vfs_drt_clustermap **cmapp)
 
        /* log what we've done */
        vfs_drt_trace(cmap, DRT_DEBUG_ALLOC, copycount, 0, 0, 0);
-       
+
        /*
-        * It's important to ensure that *cmapp always points to 
+        * It's important to ensure that *cmapp always points to
         * a valid map, so we must overwrite it before freeing
         * the old map.
         */
@@ -4304,14 +7021,14 @@ vfs_drt_alloc_map(struct vfs_drt_clustermap **cmapp)
        if (ocmap != NULL) {
                /* emit stats into trace buffer */
                vfs_drt_trace(ocmap, DRT_DEBUG_SCMDATA,
-                             ocmap->scm_modulus,
-                             ocmap->scm_buckets,
-                             ocmap->scm_lastclean,
-                             ocmap->scm_iskips);
+                   ocmap->scm_modulus,
+                   ocmap->scm_buckets,
+                   ocmap->scm_lastclean,
+                   ocmap->scm_iskips);
 
                vfs_drt_free_map(ocmap);
        }
-       return(KERN_SUCCESS);
+       return KERN_SUCCESS;
 }
 
 
@@ -4321,11 +7038,20 @@ vfs_drt_alloc_map(struct vfs_drt_clustermap **cmapp)
 static kern_return_t
 vfs_drt_free_map(struct vfs_drt_clustermap *cmap)
 {
-       kern_return_t   ret;
+       vm_size_t map_size = 0;
+
+       if (cmap->scm_modulus == DRT_HASH_SMALL_MODULUS) {
+               map_size = DRT_SMALL_ALLOCATION;
+       } else if (cmap->scm_modulus == DRT_HASH_LARGE_MODULUS) {
+               map_size = DRT_LARGE_ALLOCATION;
+       } else if (cmap->scm_modulus == DRT_HASH_XLARGE_MODULUS) {
+               map_size = DRT_XLARGE_ALLOCATION;
+       } else {
+               panic("vfs_drt_free_map: Invalid modulus %d\n", cmap->scm_modulus);
+       }
 
-       kmem_free(kernel_map, (vm_offset_t)cmap, 
-                 (cmap->scm_modulus == DRT_HASH_SMALL_MODULUS) ? DRT_SMALL_ALLOCATION : DRT_LARGE_ALLOCATION);
-       return(KERN_SUCCESS);
+       kmem_free(kernel_map, (vm_offset_t)cmap, map_size);
+       return KERN_SUCCESS;
 }
 
 
@@ -4335,27 +7061,27 @@ vfs_drt_free_map(struct vfs_drt_clustermap *cmap)
 static kern_return_t
 vfs_drt_search_index(struct vfs_drt_clustermap *cmap, u_int64_t offset, int *indexp)
 {
-       kern_return_t   kret;
-       int             index, i, tries;
+       int             index;
+       u_int32_t       i;
 
        offset = DRT_ALIGN_ADDRESS(offset);
        index = DRT_HASH(cmap, offset);
 
        /* traverse the hashtable */
        for (i = 0; i < cmap->scm_modulus; i++) {
-
                /*
                 * If the slot is vacant, we can stop.
                 */
-               if (DRT_HASH_VACANT(cmap, index))
+               if (DRT_HASH_VACANT(cmap, index)) {
                        break;
+               }
 
                /*
                 * If the address matches our offset, we have success.
                 */
                if (DRT_HASH_GET_ADDRESS(cmap, index) == offset) {
                        *indexp = index;
-                       return(KERN_SUCCESS);
+                       return KERN_SUCCESS;
                }
 
                /*
@@ -4366,7 +7092,7 @@ vfs_drt_search_index(struct vfs_drt_clustermap *cmap, u_int64_t offset, int *ind
        /*
         * It's not there.
         */
-       return(KERN_FAILURE);
+       return KERN_FAILURE;
 }
 
 /*
@@ -4379,15 +7105,17 @@ static kern_return_t
 vfs_drt_get_index(struct vfs_drt_clustermap **cmapp, u_int64_t offset, int *indexp, int recursed)
 {
        struct vfs_drt_clustermap *cmap;
-       kern_return_t   kret;
-       int             index, i;
+       kern_return_t   kret;
+       u_int32_t       index;
+       u_int32_t       i;
 
        cmap = *cmapp;
 
        /* look for an existing entry */
        kret = vfs_drt_search_index(cmap, offset, indexp);
-       if (kret == KERN_SUCCESS)
-               return(kret);
+       if (kret == KERN_SUCCESS) {
+               return kret;
+       }
 
        /* need to allocate an entry */
        offset = DRT_ALIGN_ADDRESS(offset);
@@ -4396,16 +7124,17 @@ vfs_drt_get_index(struct vfs_drt_clustermap **cmapp, u_int64_t offset, int *inde
        /* scan from the index forwards looking for a vacant slot */
        for (i = 0; i < cmap->scm_modulus; i++) {
                /* slot vacant? */
-               if (DRT_HASH_VACANT(cmap, index) || DRT_HASH_GET_COUNT(cmap,index) == 0) {
+               if (DRT_HASH_VACANT(cmap, index) || DRT_HASH_GET_COUNT(cmap, index) == 0) {
                        cmap->scm_buckets++;
-                       if (index < cmap->scm_lastclean)
+                       if (index < cmap->scm_lastclean) {
                                cmap->scm_lastclean = index;
+                       }
                        DRT_HASH_SET_ADDRESS(cmap, index, offset);
                        DRT_HASH_SET_COUNT(cmap, index, 0);
                        DRT_BITVECTOR_CLEAR(cmap, index);
                        *indexp = index;
                        vfs_drt_trace(cmap, DRT_DEBUG_INSERT, (int)offset, i, 0, 0);
-                       return(KERN_SUCCESS);
+                       return KERN_SUCCESS;
                }
                cmap->scm_iskips += i;
                index = DRT_HASH_NEXT(cmap, index);
@@ -4415,14 +7144,15 @@ vfs_drt_get_index(struct vfs_drt_clustermap **cmapp, u_int64_t offset, int *inde
         * We haven't found a vacant slot, so the map is full.  If we're not
         * already recursed, try reallocating/compacting it.
         */
-       if (recursed)
-               return(KERN_FAILURE);
+       if (recursed) {
+               return KERN_FAILURE;
+       }
        kret = vfs_drt_alloc_map(cmapp);
        if (kret == KERN_SUCCESS) {
                /* now try to insert again */
                kret = vfs_drt_get_index(cmapp, offset, indexp, 1);
        }
-       return(kret);
+       return kret;
 }
 
 /*
@@ -4432,35 +7162,36 @@ vfs_drt_get_index(struct vfs_drt_clustermap **cmapp, u_int64_t offset, int *inde
  */
 static kern_return_t
 vfs_drt_do_mark_pages(
-       void            **private,
-       u_int64_t       offset,
-       u_int           length,
-       int             *setcountp,
-       int             dirty)
+       void            **private,
+       u_int64_t       offset,
+       u_int           length,
+       u_int           *setcountp,
+       int             dirty)
 {
        struct vfs_drt_clustermap *cmap, **cmapp;
-       kern_return_t   kret;
-       int             i, index, pgoff, pgcount, setcount, ecount;
+       kern_return_t   kret;
+       int             i, index, pgoff, pgcount, setcount, ecount;
 
        cmapp = (struct vfs_drt_clustermap **)private;
        cmap = *cmapp;
 
        vfs_drt_trace(cmap, DRT_DEBUG_MARK | DBG_FUNC_START, (int)offset, (int)length, dirty, 0);
 
-       if (setcountp != NULL)
-               *setcountp = 0;
-       
+       if (setcountp != NULL) {
+               *setcountp = 0;
+       }
+
        /* allocate a cluster map if we don't already have one */
        if (cmap == NULL) {
                /* no cluster map, nothing to clean */
                if (!dirty) {
                        vfs_drt_trace(cmap, DRT_DEBUG_MARK | DBG_FUNC_END, 1, 0, 0, 0);
-                       return(KERN_SUCCESS);
+                       return KERN_SUCCESS;
                }
                kret = vfs_drt_alloc_map(cmapp);
                if (kret != KERN_SUCCESS) {
                        vfs_drt_trace(cmap, DRT_DEBUG_MARK | DBG_FUNC_END, 2, 0, 0, 0);
-                       return(kret);
+                       return kret;
                }
        }
        setcount = 0;
@@ -4476,21 +7207,22 @@ vfs_drt_do_mark_pages(
                 * that hasn't been dirtied.
                 */
                kret = vfs_drt_get_index(cmapp, offset, &index, 0);
-               cmap = *cmapp;  /* may have changed! */
+               cmap = *cmapp;  /* may have changed! */
                /* this may be a partial-success return */
                if (kret != KERN_SUCCESS) {
-                       if (setcountp != NULL)
-                               *setcountp = setcount;
+                       if (setcountp != NULL) {
+                               *setcountp = setcount;
+                       }
                        vfs_drt_trace(cmap, DRT_DEBUG_MARK | DBG_FUNC_END, 3, (int)length, 0, 0);
 
-                       return(kret);
+                       return kret;
                }
 
                /*
                 * Work out how many pages we're modifying in this
                 * hashtable entry.
                 */
-               pgoff = (offset - DRT_ALIGN_ADDRESS(offset)) / PAGE_SIZE;
+               pgoff = (int)((offset - DRT_ALIGN_ADDRESS(offset)) / PAGE_SIZE);
                pgcount = min((length / PAGE_SIZE), (DRT_BITVECTOR_PAGES - pgoff));
 
                /*
@@ -4500,12 +7232,19 @@ vfs_drt_do_mark_pages(
                for (i = 0; i < pgcount; i++) {
                        if (dirty) {
                                if (!DRT_HASH_TEST_BIT(cmap, index, pgoff + i)) {
+                                       if (ecount >= DRT_BITVECTOR_PAGES) {
+                                               panic("ecount >= DRT_BITVECTOR_PAGES, cmap = %p, index = %d, bit = %d", cmap, index, pgoff + i);
+                                       }
                                        DRT_HASH_SET_BIT(cmap, index, pgoff + i);
                                        ecount++;
                                        setcount++;
                                }
                        } else {
                                if (DRT_HASH_TEST_BIT(cmap, index, pgoff + i)) {
+                                       if (ecount <= 0) {
+                                               panic("ecount <= 0, cmap = %p, index = %d, bit = %d", cmap, index, pgoff + i);
+                                       }
+                                       assert(ecount > 0);
                                        DRT_HASH_CLEAR_BIT(cmap, index, pgoff + i);
                                        ecount--;
                                        setcount++;
@@ -4513,16 +7252,17 @@ vfs_drt_do_mark_pages(
                        }
                }
                DRT_HASH_SET_COUNT(cmap, index, ecount);
-next:
+
                offset += pgcount * PAGE_SIZE;
                length -= pgcount * PAGE_SIZE;
        }
-       if (setcountp != NULL)
+       if (setcountp != NULL) {
                *setcountp = setcount;
+       }
 
        vfs_drt_trace(cmap, DRT_DEBUG_MARK | DBG_FUNC_END, 0, setcount, 0, 0);
 
-       return(KERN_SUCCESS);
+       return KERN_SUCCESS;
 }
 
 /*
@@ -4550,17 +7290,19 @@ next:
  * Returns KERN_SUCCESS if all the pages were successfully marked.
  */
 static kern_return_t
-vfs_drt_mark_pages(void **cmapp, off_t offset, u_int length, int *setcountp)
+vfs_drt_mark_pages(void **cmapp, off_t offset, u_int length, u_int *setcountp)
 {
        /* XXX size unused, drop from interface */
-       return(vfs_drt_do_mark_pages(cmapp, offset, length, setcountp, 1));
+       return vfs_drt_do_mark_pages(cmapp, offset, length, setcountp, 1);
 }
 
+#if 0
 static kern_return_t
 vfs_drt_unmark_pages(void **cmapp, off_t offset, u_int length)
 {
-       return(vfs_drt_do_mark_pages(cmapp, offset, length, NULL, 0));
+       return vfs_drt_do_mark_pages(cmapp, offset, length, NULL, 0);
 }
+#endif
 
 /*
  * Get a cluster of dirty pages.
@@ -4586,40 +7328,45 @@ static kern_return_t
 vfs_drt_get_cluster(void **cmapp, off_t *offsetp, u_int *lengthp)
 {
        struct vfs_drt_clustermap *cmap;
-       u_int64_t       offset;
-       u_int           length;
-       int             index, i, j, fs, ls;
+       u_int64_t       offset;
+       u_int           length;
+       u_int32_t       j;
+       int             index, i, fs, ls;
 
        /* sanity */
-       if ((cmapp == NULL) || (*cmapp == NULL))
-               return(KERN_FAILURE);
+       if ((cmapp == NULL) || (*cmapp == NULL)) {
+               return KERN_FAILURE;
+       }
        cmap = *cmapp;
 
        /* walk the hashtable */
        for (offset = 0, j = 0; j < cmap->scm_modulus; offset += (DRT_BITVECTOR_PAGES * PAGE_SIZE), j++) {
-               index = DRT_HASH(cmap, offset);
+               index = DRT_HASH(cmap, offset);
 
-               if (DRT_HASH_VACANT(cmap, index) || (DRT_HASH_GET_COUNT(cmap, index) == 0))
+               if (DRT_HASH_VACANT(cmap, index) || (DRT_HASH_GET_COUNT(cmap, index) == 0)) {
                        continue;
+               }
 
                /* scan the bitfield for a string of bits */
                fs = -1;
 
                for (i = 0; i < DRT_BITVECTOR_PAGES; i++) {
-                       if (DRT_HASH_TEST_BIT(cmap, index, i)) {
-                               fs = i;
+                       if (DRT_HASH_TEST_BIT(cmap, index, i)) {
+                               fs = i;
                                break;
                        }
                }
                if (fs == -1) {
-                       /*  didn't find any bits set */
-                       panic("vfs_drt: entry summary count > 0 but no bits set in map");
+                       /*  didn't find any bits set */
+                       panic("vfs_drt: entry summary count > 0 but no bits set in map, cmap = %p, index = %d, count = %lld",
+                           cmap, index, DRT_HASH_GET_COUNT(cmap, index));
                }
                for (ls = 0; i < DRT_BITVECTOR_PAGES; i++, ls++) {
-                       if (!DRT_HASH_TEST_BIT(cmap, index, i))
-                               break;
+                       if (!DRT_HASH_TEST_BIT(cmap, index, i)) {
+                               break;
+                       }
                }
-               
+
                /* compute offset and length, mark pages clean */
                offset = DRT_HASH_GET_ADDRESS(cmap, index) + (PAGE_SIZE * fs);
                length = ls * PAGE_SIZE;
@@ -4631,7 +7378,7 @@ vfs_drt_get_cluster(void **cmapp, off_t *offsetp, u_int *lengthp)
                *lengthp = length;
 
                vfs_drt_trace(cmap, DRT_DEBUG_RETCLUSTER, (int)offset, (int)length, 0, 0);
-               return(KERN_SUCCESS);
+               return KERN_SUCCESS;
        }
        /*
         * We didn't find anything... hashtable is empty
@@ -4639,15 +7386,15 @@ vfs_drt_get_cluster(void **cmapp, off_t *offsetp, u_int *lengthp)
         * then free it
         */
        vfs_drt_trace(cmap, DRT_DEBUG_SCMDATA,
-                     cmap->scm_modulus,
-                     cmap->scm_buckets,
-                     cmap->scm_lastclean,
-                     cmap->scm_iskips);
-       
+           cmap->scm_modulus,
+           cmap->scm_buckets,
+           cmap->scm_lastclean,
+           cmap->scm_iskips);
+
        vfs_drt_free_map(cmap);
        *cmapp = NULL;
 
-       return(KERN_FAILURE);
+       return KERN_FAILURE;
 }
 
 
@@ -4657,28 +7404,29 @@ vfs_drt_control(void **cmapp, int op_type)
        struct vfs_drt_clustermap *cmap;
 
        /* sanity */
-       if ((cmapp == NULL) || (*cmapp == NULL))
-               return(KERN_FAILURE);
+       if ((cmapp == NULL) || (*cmapp == NULL)) {
+               return KERN_FAILURE;
+       }
        cmap = *cmapp;
 
        switch (op_type) {
        case 0:
                /* emit stats into trace buffer */
                vfs_drt_trace(cmap, DRT_DEBUG_SCMDATA,
-                             cmap->scm_modulus,
-                             cmap->scm_buckets,
-                             cmap->scm_lastclean,
-                             cmap->scm_iskips);
+                   cmap->scm_modulus,
+                   cmap->scm_buckets,
+                   cmap->scm_lastclean,
+                   cmap->scm_iskips);
 
                vfs_drt_free_map(cmap);
                *cmapp = NULL;
-               break;
+               break;
 
        case 1:
-               cmap->scm_lastclean = 0;
-               break;
+               cmap->scm_lastclean = 0;
+               break;
        }
-       return(KERN_SUCCESS);
+       return KERN_SUCCESS;
 }
 
 
@@ -4687,12 +7435,22 @@ vfs_drt_control(void **cmapp, int op_type)
  * Emit a summary of the state of the clustermap into the trace buffer
  * along with some caller-provided data.
  */
+#if KDEBUG
 static void
-vfs_drt_trace(struct vfs_drt_clustermap *cmap, int code, int arg1, int arg2, int arg3, int arg4)
+vfs_drt_trace(__unused struct vfs_drt_clustermap *cmap, int code, int arg1, int arg2, int arg3, int arg4)
 {
        KERNEL_DEBUG(code, arg1, arg2, arg3, arg4, 0);
 }
+#else
+static void
+vfs_drt_trace(__unused struct vfs_drt_clustermap *cmap, __unused int code,
+    __unused int arg1, __unused int arg2, __unused int arg3,
+    __unused int arg4)
+{
+}
+#endif
 
+#if 0
 /*
  * Perform basic sanity check on the hash entry summary count
  * vs. the actual bits set in the entry.
@@ -4700,18 +7458,50 @@ vfs_drt_trace(struct vfs_drt_clustermap *cmap, int code, int arg1, int arg2, int
 static void
 vfs_drt_sanity(struct vfs_drt_clustermap *cmap)
 {
-        int index, i;
+       int index, i;
        int bits_on;
-       
+
        for (index = 0; index < cmap->scm_modulus; index++) {
-               if (DRT_HASH_VACANT(cmap, index))
-                       continue;
+               if (DRT_HASH_VACANT(cmap, index)) {
+                       continue;
+               }
 
                for (bits_on = 0, i = 0; i < DRT_BITVECTOR_PAGES; i++) {
-                       if (DRT_HASH_TEST_BIT(cmap, index, i))
-                               bits_on++;
+                       if (DRT_HASH_TEST_BIT(cmap, index, i)) {
+                               bits_on++;
+                       }
+               }
+               if (bits_on != DRT_HASH_GET_COUNT(cmap, index)) {
+                       panic("bits_on = %d,  index = %d\n", bits_on, index);
                }
-               if (bits_on != DRT_HASH_GET_COUNT(cmap, index))
-                       panic("bits_on = %d,  index = %d\n", bits_on, index);
-       }               
+       }
+}
+#endif
+
+/*
+ * Internal interface only.
+ */
+static kern_return_t
+vfs_get_scmap_push_behavior_internal(void **cmapp, int *push_flag)
+{
+       struct vfs_drt_clustermap *cmap;
+
+       /* sanity */
+       if ((cmapp == NULL) || (*cmapp == NULL) || (push_flag == NULL)) {
+               return KERN_FAILURE;
+       }
+       cmap = *cmapp;
+
+       if (cmap->scm_modulus == DRT_HASH_XLARGE_MODULUS) {
+               /*
+                * If we have a full xlarge sparse cluster,
+                * we push it out all at once so the cluster
+                * map can be available to absorb more I/Os.
+                * This is done on large memory configs so
+                * the small I/Os don't interfere with the
+                * pro workloads.
+                */
+               *push_flag = PUSH_ALL;
+       }
+       return KERN_SUCCESS;
 }