xnu-1699.22.81.tar.gz

[apple/xnu.git] / bsd / sys / buf.h

diff --git a/bsd/sys/buf.h b/bsd/sys/buf.h
index 91aa77cf7e01f3629e500b0ce7796b03eb94d48d..f1d7f924b474b119f38b88d392d51d427aea92a1 100644 (file)
--- a/bsd/sys/buf.h
+++ b/bsd/sys/buf.h
@@ -1,23 +1,29 @@
 /*
  * Copyright (c) 2000-2005 Apple Computer, Inc. All rights reserved.
  *
 /*
  * Copyright (c) 2000-2005 Apple Computer, Inc. All rights reserved.
  *

- * @APPLE_LICENSE_HEADER_START@
+ * @APPLE_OSREFERENCE_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 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.

  * 
  * 

- * This Original Code and all software distributed under the License are
- * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
+ * 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,
  * 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.
+ * 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_LICENSE_HEADER_END@
+ * @APPLE_OSREFERENCE_LICENSE_HEADER_END@

  */
 /* Copyright (c) 1995 NeXT Computer, Inc. All Rights Reserved */
 /*
  */
 /* Copyright (c) 1995 NeXT Computer, Inc. All Rights Reserved */
 /*


@@ -65,6 +71,7 @@
 
 #include <sys/cdefs.h>
 #include <sys/kernel_types.h>
 
 #include <sys/cdefs.h>
 #include <sys/kernel_types.h>

+#include <sys/ucred.h>

 #include <mach/memory_object_types.h>
 
 
 #include <mach/memory_object_types.h>
 
 


@@ -78,6 +85,12 @@
 #define B_CLUSTER      0x00000040      /* UPL based I/O generated by cluster layer */
 #define        B_PAGEIO        0x00000080      /* Page in/out */
 #define        B_META          0x00000100      /* buffer contains meta-data. */
 #define B_CLUSTER      0x00000040      /* UPL based I/O generated by cluster layer */
 #define        B_PAGEIO        0x00000080      /* Page in/out */
 #define        B_META          0x00000100      /* buffer contains meta-data. */

+#define        B_RAW           0x00000200      /* Set by physio for raw transfers. */
+#define        B_FUA           0x00000400      /* Write-through disk cache(if supported) */
+#define B_PASSIVE      0x00000800      /* PASSIVE I/Os are ignored by THROTTLE I/O */
+#define        B_IOSTREAMING   0x00001000      /* sequential access pattern detected */
+#define B_THROTTLED_IO 0x00002000      /* low priority I/O */
+#define B_ENCRYPTED_IO 0x00004000      /* Encrypted I/O */

 /*
  * make sure to check when adding flags that
  * that the new flags don't overlap the definitions
 /*
  * make sure to check when adding flags that
  * that the new flags don't overlap the definitions


@@ -86,296 +99,587 @@
 
 __BEGIN_DECLS
 
 
 __BEGIN_DECLS
 

-/*
- * mark the buffer associated with buf_t
- * as AGED with respect to the LRU cache
+/*!
+ @function buf_markaged
+ @abstract Mark a buffer as "aged," i.e. as a good candidate to be discarded and reused after buf_brelse().
+ @param bp Buffer to mark.

  */
 void   buf_markaged(buf_t);
 
  */
 void   buf_markaged(buf_t);
 

-/*
- * mark the buffer associated with buf_t
- * as invalid... on release, it will go
- * directly to the free list
+/*!
+ @function buf_markinvalid
+ @abstract Mark a buffer as not having valid data and being ready for immediate reuse after buf_brelse().
+ @param bp Buffer to mark.

  */
 void   buf_markinvalid(buf_t);
 
  */
 void   buf_markinvalid(buf_t);
 

-/*
- * mark the buffer assoicated with buf_t
- * as a delayed write... 
+/*!
+ @function buf_markdelayed
+ @abstract Mark a buffer as a delayed write: mark it dirty without actually scheduling I/O.
+ @discussion Data will be flushed to disk at some later time, not with brelse(). A sync()/fsync()
+ or pressure necessitating reuse of the buffer will cause it to be written back to disk.
+ @param bp Buffer to mark.

  */
 void   buf_markdelayed(buf_t);
 
  */
 void   buf_markdelayed(buf_t);
 

-/*
- * mark the buffer associated with buf_t
- * as having been interrupted... EINTR
+void   buf_markclean(buf_t);
+
+/*!
+ @function buf_markeintr
+ @abstract Mark a buffer as having been interrupted during I/O.
+ @discussion Waiters for I/O to complete (buf_biowait()) will return with EINTR when woken up.  
+ buf_markeintr does not itself do a wakeup.
+ @param bp Buffer to mark.

  */
 void   buf_markeintr(buf_t);
 
  */
 void   buf_markeintr(buf_t);
 

-/*
- * returns 1 if the buffer associated with buf_t
- * contains valid data... 0 if it does not
+/*!
+ @function buf_markfua
+ @abstract Mark a buffer for write through disk cache, if disk supports it.
+ @param bp Buffer to mark.
+ */
+void   buf_markfua(buf_t);
+
+/*!
+ @function buf_fua
+ @abstract Check if a buffer is marked for write through disk caches.
+ @param bp Buffer to test.
+ @return Nonzero if buffer is marked for write-through, 0 if not.
+ */
+int    buf_fua(buf_t);
+
+/*!
+ @function buf_valid
+ @abstract Check if a buffer contains valid data.
+ @param bp Buffer to test.
+ @return Nonzero if buffer has valid data, 0 if not.

  */
 int    buf_valid(buf_t);
 
  */
 int    buf_valid(buf_t);
 

-/*
- * returns 1 if the buffer was already valid
- * in the cache... i.e. no I/O was performed
- * returns 0 otherwise
+/*!
+ @function buf_fromcache
+ @abstract Check if a buffer's data was found in core.
+ @discussion Will return truth after a buf_getblk that finds a valid buffer in the cache or the relevant
+ data in core (but not in a buffer).
+ @param bp Buffer to test.
+ @return Nonzero if we got this buffer's data without doing I/O, 0 if not.

  */
 int    buf_fromcache(buf_t);
 
  */
 int    buf_fromcache(buf_t);
 

-/*
- * returns the UPL associated with buf_t
+/*!
+ @function buf_upl
+ @abstract Get the upl (Universal Page List) associated with a buffer.
+ @discussion Buffers allocated with buf_alloc() are not returned with a upl, and
+ traditional buffers only have a upl while an I/O is in progress.
+ @param bp Buffer whose upl to grab.
+ @return Buffer's upl if it has one, else NULL.

  */
 void * buf_upl(buf_t);
 
  */
 void * buf_upl(buf_t);
 

-/*
- * returns the offset into the UPL
- * associated with buf_t which is to be
- * used as the base offset for this I/O
+/*!
+ @function buf_uploffset
+ @abstract Get the offset into a UPL at which this buffer begins.
+ @discussion This function should only be called on iobufs, i.e. buffers allocated with buf_alloc().
+ @param bp Buffer whose uploffset to grab.
+ @return Buffer's uploffset--does not check whether that value makes sense for this buffer.

  */
 uint32_t buf_uploffset(buf_t);
 
  */
 uint32_t buf_uploffset(buf_t);
 

-/*
- * returns read credential associated with buf_t
- * a reference is taken which must be explicilty dropped
+/*!
+ @function buf_rcred
+ @abstract Get the credential associated with a buffer for reading.
+ @discussion No reference is taken; if the credential is to be held on to persistently, an additional
+ reference must be taken with kauth_cred_ref.
+ @param bp Buffer whose credential to grab.
+ @return Credential if it exists, else NULL.

  */
  */

-ucred_t buf_rcred(buf_t);
-
-/*
- * returns write credential associated with buf_t
- * a reference is taken which must be explicilty dropped
+kauth_cred_t buf_rcred(buf_t);
+
+/*!
+ @function buf_wcred
+ @abstract Get the credential associated with a buffer for writing.
+ @discussion No reference is taken; if the credential is to be held on to persistently, an additional
+ reference must be taken with kauth_cred_ref.
+ @param bp Buffer whose credential to grab.
+ @return Credential if it exists, else NULL.

  */
  */

-ucred_t buf_wcred(buf_t);
-
-/*
- * returns process handle associated with buf_t
- * i.e identity of task that issued the I/O
+kauth_cred_t buf_wcred(buf_t);
+
+/*!
+ @function buf_proc
+ @abstract Get the process associated with this buffer.
+ @discussion buf_proc() will generally return NULL; a process is currently only associated with
+ a buffer in the event of a physio() call.  
+ @param bp Buffer whose associated process to find.
+ @return Associated process, possibly NULL.

  */
 proc_t buf_proc(buf_t);
 
  */
 proc_t buf_proc(buf_t);
 

+/*!
+ @function buf_dirtyoff
+ @abstract Get the starting offset of the dirty region associated with a buffer.
+ @discussion The dirty offset is zero unless someone explicitly calls buf_setdirtyoff() (which the kernel does not).
+ @param bp Buffer whose dirty offset to get.
+ @return Dirty offset (0 if not explicitly changed).
+ */

 uint32_t buf_dirtyoff(buf_t);
 uint32_t buf_dirtyoff(buf_t);

+
+/*!
+ @function buf_dirtyend
+ @abstract Get the ending offset of the dirty region associated with a buffer.
+ @discussion If the buffer's data was found incore and dirty, the dirty end is the size of the block; otherwise, unless
+ someone outside of xnu explicitly changes it by calling buf_setdirtyend(), it will be zero.
+ @param bp Buffer whose dirty end to get.
+ @return 0 if buffer is found clean; size of buffer if found dirty.  Can be set to any value by callers of buf_setdirtyend().
+ */

 uint32_t buf_dirtyend(buf_t);
 uint32_t buf_dirtyend(buf_t);

+
+/*!
+ @function buf_setdirtyoff
+ @abstract Set the starting offset of the dirty region associated with a buffer.
+ @discussion This value is zero unless someone set it explicitly.
+ @param bp Buffer whose dirty end to set.
+ @return void.
+ */

 void   buf_setdirtyoff(buf_t, uint32_t);
 void   buf_setdirtyoff(buf_t, uint32_t);

+
+/*!
+ @function buf_setdirtyend
+ @abstract Set the ending offset of the dirty region associated with a buffer.
+ @discussion If the buffer's data was found incore and dirty, the dirty end is the size of the block; otherwise, unless
+ someone outside of xnu explicitly changes it by calling buf_setdirtyend(), it will be zero.
+ @param bp Buffer whose dirty end to set.
+ @return void.
+ */

 void   buf_setdirtyend(buf_t, uint32_t);
 
 void   buf_setdirtyend(buf_t, uint32_t);
 

-/*
- * return the errno value associated with buf_t
+/*!
+ @function buf_error
+ @abstract Get the error value associated with a buffer.
+ @discussion Errors are set with buf_seterror().
+ @param bp Buffer whose error value to retrieve.
+ @return Error value, directly.

  */
 errno_t        buf_error(buf_t);
 
  */
 errno_t        buf_error(buf_t);
 

-/*
- * set errno on buf_t
+/*!
+ @function buf_seterror
+ @abstract Set an error value on a buffer.
+ @param bp Buffer whose error value to set.
+ @return void.

  */
 void   buf_seterror(buf_t, errno_t);
 
  */
 void   buf_seterror(buf_t, errno_t);
 

-/*
- * set specified flags on buf_t
- * B_LOCKED/B_NOCACHE/B_ASYNC/B_READ/B_WRITE/B_PAGEIO
+/*!
+ @function buf_setflags
+ @abstract Set flags on a buffer.
+ @discussion: buffer_flags |= flags
+ @param bp Buffer whose flags to set.
+ @param flags Flags to add to buffer's mask. B_LOCKED/B_NOCACHE/B_ASYNC/B_READ/B_WRITE/B_PAGEIO/B_FUA
+ @return void.

  */
 void   buf_setflags(buf_t, int32_t);
 
  */
 void   buf_setflags(buf_t, int32_t);
 

-/*
- * clear specified flags on buf_t
- * B_LOCKED/B_NOCACHE/B_ASYNC/B_READ/B_WRITE/B_PAGEIO
+/*!
+ @function buf_clearflags
+ @abstract Clear flags on a buffer.
+ @discussion: buffer_flags &= ~flags
+ @param bp Buffer whose flags to clear.
+ @param flags Flags to remove from buffer's mask. B_LOCKED/B_NOCACHE/B_ASYNC/B_READ/B_WRITE/B_PAGEIO/B_FUA
+ @return void.

  */
 void   buf_clearflags(buf_t, int32_t);
 
  */
 void   buf_clearflags(buf_t, int32_t);
 

-/*
- * return external flags associated with buf_t
- * B_CLUSTER/B_PHYS/B_LOCKED/B_DELWRI/B_ASYNC/B_READ/B_WRITE/B_META/B_PAGEIO
+/*!
+ @function buf_flags
+ @abstract Get flags set on a buffer.
+ @discussion Valid flags are B_LOCKED/B_NOCACHE/B_ASYNC/B_READ/B_WRITE/B_PAGEIO/B_FUA.
+ @param bp Buffer whose flags to grab.
+ @return flags.

  */
 int32_t        buf_flags(buf_t);
 
  */
 int32_t        buf_flags(buf_t);
 

-/*
- * clears I/O related flags (both internal and
- * external) associated with buf_t and allows
- * the following to be set...
- * B_READ/B_WRITE/B_ASYNC/B_NOCACHE
+/*!
+ @function buf_reset
+ @abstract Reset I/O flag state on a buffer.
+ @discussion Clears current flags on a buffer (internal and external) and allows some new flags to be set.
+ Used perhaps to prepare an iobuf for reuse.
+ @param bp Buffer whose flags to grab.  
+ @param flags Flags to set on buffer: B_READ, B_WRITE, B_ASYNC, B_NOCACHE.
+ @return void.

  */
 void   buf_reset(buf_t, int32_t);
 
  */
 void   buf_reset(buf_t, int32_t);
 

-/*
- * insure that the data storage associated with buf_t
- * is addressable
+/*!
+ @function buf_map
+ @abstract Get virtual mappings for buffer data.
+ @discussion For buffers created through buf_getblk() (i.e. traditional buffer cache usage), 
+ buf_map() just returns the address at which data was mapped by but_getblk().  For a B_CLUSTER buffer, i.e. an iobuf
+ whose upl state is managed manually, there are two possibilities.  If the buffer was created
+ with an underlying "real" buffer through cluster_bp(), the mapping of the "real" buffer is returned.
+ Otherwise, the buffer was created with buf_alloc() and buf_setupl() was subsequently called; buf_map()
+ will call ubc_upl_map() to get a mapping for the buffer's upl and return the start of that mapping
+ plus the buffer's upl offset (set in buf_setupl()).  In the last case, buf_unmap() must later be called
+ to tear down the mapping.  NOTE: buf_map() does not set the buffer data pointer; this must be done with buf_setdataptr().
+ @param bp Buffer whose mapping to find or create.
+ @param io_addr Destination for mapping address.
+ @return 0 for success, ENOMEM if unable to map the buffer.

  */
 errno_t        buf_map(buf_t, caddr_t *);
 
  */
 errno_t        buf_map(buf_t, caddr_t *);
 

-/*
- * release our need to have the storage associated
- * with buf_t in an addressable state
+/*!
+ @function buf_unmap
+ @abstract Release mappings for buffer data.
+ @discussion For buffers created through buf_getblk() (i.e. traditional buffer cache usage), 
+ buf_unmap() does nothing; buf_brelse() will take care of unmapping.  For a B_CLUSTER buffer, i.e. an iobuf
+ whose upl state is managed manually, there are two possibilities.  If the buffer was created
+ with an underlying "real" buffer through cluster_bp(), buf_unmap() does nothing; buf_brelse() on the
+ underlying buffer will tear down the mapping. Otherwise, the buffer was created with buf_alloc() and 
+ buf_setupl() was subsequently called; buf_map() created the mapping.  In this case, buf_unmap() will
+ unmap the buffer.
+ @param bp Buffer whose mapping to find or create.
+ @param io_addr Destination for mapping address.
+ @return 0 for success, EINVAL if unable to unmap buffer.

  */
 errno_t        buf_unmap(buf_t);
 
  */
 errno_t        buf_unmap(buf_t);
 

-/*
- * set driver specific data for buf_t
+/*!
+ @function buf_setdrvdata
+ @abstract Set driver-specific data on a buffer.
+ @param bp Buffer whose driver-data to set.
+ @param drvdata Opaque driver data.
+ @return void.

  */
 void   buf_setdrvdata(buf_t, void *);
 
  */
 void   buf_setdrvdata(buf_t, void *);
 

-/*
- * retrieve driver specific data associated with buf_t
+/*!
+ @function buf_setdrvdata
+ @abstract Get driver-specific data from a buffer.
+ @param bp Buffer whose driver data to get.
+ @return Opaque driver data.

  */
 void * buf_drvdata(buf_t);
 
  */
 void * buf_drvdata(buf_t);
 

-/*
- * set fs specific data for buf_t
+/*!
+ @function buf_setfsprivate
+ @abstract Set filesystem-specific data on a buffer.
+ @param bp Buffer whose filesystem data to set.
+ @param fsprivate Opaque filesystem data.
+ @return void.

  */
 void   buf_setfsprivate(buf_t, void *);
 
  */
 void   buf_setfsprivate(buf_t, void *);
 

-/*
- * retrieve driver specific data associated with buf_t
+/*!
+ @function buf_fsprivate
+ @abstract Get filesystem-specific data from a buffer.
+ @param bp Buffer whose filesystem data to get.
+ @return Opaque filesystem data.

  */
 void * buf_fsprivate(buf_t);
 
  */
 void * buf_fsprivate(buf_t);
 

-/*
- * retrieve the phsyical block number associated with buf_t
+/*!
+ @function buf_blkno
+ @abstract Get physical block number associated with a buffer, in the sense of VNOP_BLOCKMAP.
+ @discussion When a buffer's physical block number is the same is its logical block number, then the physical
+ block number is considered uninitialized.  A physical block number of -1 indicates that there is no valid
+ physical mapping (e.g. the logical block is invalid or corresponds to a sparse region in a file).  Physical
+ block number is normally set by the cluster layer or by buf_getblk().
+ @param bp Buffer whose physical block number to get.
+ @return Block number.

  */
 daddr64_t buf_blkno(buf_t);
 
  */
 daddr64_t buf_blkno(buf_t);
 

-/*
- * retrieve the logical block number associated with buf_t
- * i.e. the block number derived from the file offset
+/*!
+ @function buf_lblkno
+ @abstract Get logical block number associated with a buffer.
+ @discussion Logical block number is set on traditionally-used buffers by an argument passed to buf_getblk(),
+ for example by buf_bread().
+ @param bp Buffer whose logical block number to get.
+ @return Block number.

  */
 daddr64_t buf_lblkno(buf_t);
 
  */
 daddr64_t buf_lblkno(buf_t);
 

-/*
- * set the phsyical block number associated with buf_t
+/*!
+ @function buf_setblkno
+ @abstract Set physical block number associated with a buffer.
+ @discussion Physical block number is generally set by the cluster layer or by buf_getblk().
+ @param bp Buffer whose physical block number to set.
+ @param blkno Block number to set.
+ @return void.

  */
 void   buf_setblkno(buf_t, daddr64_t);
 
  */
 void   buf_setblkno(buf_t, daddr64_t);
 

-/*
- * set the logical block number associated with buf_t
- * i.e. the block number derived from the file offset
+/*!
+ @function buf_setlblkno
+ @abstract Set logical block number associated with a buffer.
+ @discussion Logical block number is set on traditionally-used buffers by an argument passed to buf_getblk(),
+ for example by buf_bread().
+ @param bp Buffer whose logical block number to set.
+ @param lblkno Block number to set.
+ @return void.

  */
 void   buf_setlblkno(buf_t, daddr64_t);
 
  */
 void   buf_setlblkno(buf_t, daddr64_t);
 

-/*
- * retrieve the count of valid bytes associated with buf_t
+/*!
+ @function buf_count
+ @abstract Get count of valid bytes in a buffer.  This may be less than the space allocated to the buffer.
+ @param bp Buffer whose byte count to get.
+ @return Byte count.

  */
 uint32_t buf_count(buf_t);
 
  */
 uint32_t buf_count(buf_t);
 

-/*
- * retrieve the size of the data store assoicated with buf_t
+/*!
+ @function buf_size
+ @abstract Get size of data region allocated to a buffer.
+ @discussion May be larger than amount of valid data in buffer.
+ @param bp Buffer whose size to get.
+ @return Size.

  */
 uint32_t buf_size(buf_t);
 
  */
 uint32_t buf_size(buf_t);
 

-/*
- * retrieve the residual I/O count assoicated with buf_t
- * i.e. number of bytes that have not yet been completed
+/*!
+ @function buf_resid
+ @abstract Get a count of bytes which were not consumed by an I/O on a buffer.
+ @discussion Set when an I/O operations completes.
+ @param bp Buffer whose outstanding count to get.
+ @return Count of unwritten/unread bytes.

  */
 uint32_t buf_resid(buf_t);
 
  */
 uint32_t buf_resid(buf_t);
 

-/*
- * set the count of bytes associated with buf_t
- * typically used to set the size of the I/O to be performed
+/*!
+ @function buf_setcount
+ @abstract Set count of valid bytes in a buffer.  This may be less than the space allocated to the buffer.
+ @param bp Buffer whose byte count to set.
+ @param bcount Count to set.
+ @return void.

  */
 void   buf_setcount(buf_t, uint32_t);
 
  */
 void   buf_setcount(buf_t, uint32_t);
 

-/*
- * set the size of the buffer store associated with buf_t
- * typically used when providing private storage to buf_t
+/*!
+ @function buf_setsize
+ @abstract Set size of data region allocated to a buffer.
+ @discussion May be larger than amount of valid data in buffer.  Should be used by 
+ code which is manually providing storage for an iobuf, one allocated with buf_alloc().
+ @param bp Buffer whose size to set.
+ @return void.

  */
 void   buf_setsize(buf_t, uint32_t);
 
  */
 void   buf_setsize(buf_t, uint32_t);
 

-/*
- * set the size in bytes of the unfinished I/O associated with buf_t
+/*!
+ @function buf_setresid
+ @abstract Set a count of bytes outstanding for I/O in a buffer.
+ @discussion Set when an I/O operations completes.  Examples: called by IOStorageFamily when I/O
+ completes, often called on an "original" buffer when using a manipulated buffer to perform I/O 
+ on behalf of the first.
+ @param bp Buffer whose outstanding count to set.
+ @return Count of unwritten/unread bytes.

  */
 void   buf_setresid(buf_t, uint32_t);
 
  */
 void   buf_setresid(buf_t, uint32_t);
 

-/*
- * associate kernel addressable storage with buf_t
+/*!
+ @function buf_setdataptr
+ @abstract Set the address at which a buffer's data will be stored.
+ @discussion In traditional buffer use, the data pointer will be set automatically. This routine is
+ useful with iobufs (allocated with buf_alloc()).
+ @param bp Buffer whose data pointer to set.
+ @param data Pointer to data region.
+ @return void.

  */
 void   buf_setdataptr(buf_t, uintptr_t);
 
  */
 void   buf_setdataptr(buf_t, uintptr_t);
 

-/*
- * retrieve pointer to buffer associated with buf_t
- * if non-null, than guaranteed to be kernel addressable
- * size of buffer can be retrieved via buf_size
- * size of valid data can be retrieved via buf_count
- * if NULL, than use buf_map/buf_unmap to manage access to the underlying storage
+/*!
+ @function buf_dataptr
+ @abstract Get the address at which a buffer's data is stored; for iobufs, this must
+ be set with buf_setdataptr().  See buf_map().
+ @param bp Buffer whose data pointer to retrieve.
+ @return Data pointer; NULL if unset.

  */
 uintptr_t buf_dataptr(buf_t);
 
  */
 uintptr_t buf_dataptr(buf_t);
 

-/*
- * return the vnode_t associated with buf_t
+/*!
+ @function buf_vnode
+ @abstract Get the vnode associated with a buffer.
+ @discussion Every buffer is associated with a file.  Because there is an I/O in flight,
+ there is an iocount on this vnode; it is returned WITHOUT an extra iocount, and vnode_put()
+ need NOT be called.
+ @param bp Buffer whose vnode to retrieve.
+ @return Buffer's vnode.

  */
 vnode_t        buf_vnode(buf_t);
 
  */
 vnode_t        buf_vnode(buf_t);
 

-/*
- * assign vnode_t to buf_t... the 
- * device currently associated with
- * but_t is not changed.
+/*!
+ @function buf_setvnode
+ @abstract Set the vnode associated with a buffer.
+ @discussion This call need not be used on traditional buffers; it is for use with iobufs.
+ @param bp Buffer whose vnode to set.
+ @param vp The vnode to attach to the buffer.
+ @return void.

  */
 void   buf_setvnode(buf_t, vnode_t);
 
  */
 void   buf_setvnode(buf_t, vnode_t);
 

-/*
- * return the dev_t associated with buf_t
+/*!
+ @function buf_device
+ @abstract Get the device ID associated with a buffer.
+ @discussion In traditional buffer use, this value is NODEV until buf_strategy() is called unless
+ buf_getblk() was passed a device vnode.  It is set on an iobuf if buf_alloc() is passed a device 
+ vnode or if buf_setdevice() is called.
+ @param bp Buffer whose device ID to retrieve.
+ @return Device id.

  */
 dev_t  buf_device(buf_t);
 
  */
 dev_t  buf_device(buf_t);
 

-/*
- * assign the dev_t associated with vnode_t
- * to buf_t
+/*!
+ @function buf_setdevice
+ @abstract Set the device associated with a buffer.
+ @discussion A buffer's device is set in buf_strategy() (or in buf_getblk() if the file is a device).  
+ It is also set on an iobuf if buf_alloc() is passed a device vnode.
+ @param bp Buffer whose device ID to set.
+ @param vp Device to set on the buffer.
+ @return 0 for success, EINVAL if vp is not a device file.

  */
 errno_t        buf_setdevice(buf_t, vnode_t);
 
  */
 errno_t        buf_setdevice(buf_t, vnode_t);
 

+/*!
+ @function buf_strategy
+ @abstract Pass an I/O request for a buffer down to the device layer.
+ @discussion This is one of the most important routines in the buffer cache layer.  For buffers obtained
+ through buf_getblk, it handles finding physical block numbers for the I/O (with VNOP_BLKTOOFF and 
+ VNOP_BLOCKMAP), packaging the I/O into page-sized chunks, and initiating I/O on the disk by calling 
+ the device's strategy routine. If a buffer's UPL has been set manually with buf_setupl(), it assumes 
+ that the request is already correctly configured with a block number and a size divisible by page size
+ and will just call directly to the device.
+ @param devvp Device on which to perform I/O
+ @param ap vnop_strategy_args structure (most importantly, a buffer).
+ @return 0 for success, or errors from filesystem or device layers.
+ */

 errno_t        buf_strategy(vnode_t, void *);
 
 errno_t        buf_strategy(vnode_t, void *);
 

-/*
- * flags for buf_invalblkno
+/* 
+ * Flags for buf_invalblkno() 

  */
 #define        BUF_WAIT        0x01
 
  */
 #define        BUF_WAIT        0x01
 

+/*!
+ @function buf_invalblkno
+ @abstract Invalidate a filesystem logical block in a file.
+ @discussion buf_invalblkno() tries to make the data for a given block in a file
+ invalid; if the buffer for that block is found in core and is not busy, we mark it 
+ invalid and call buf_brelse() (see "flags" param for what happens if the buffer is busy).
+ buf_brelse(), noticing that it is invalid, will 
+ will return the buffer to the empty-buffer list and tell the VM subsystem to abandon 
+ the relevant pages.  Data will not be written to backing store--it will be cast aside.
+ Note that this function will only work if the block in question has been
+ obtained with a buf_getblk().  If data has been read into core without using
+ traditional buffer cache routines, buf_invalblkno() will not be able to invalidate it--this
+ includes the use of iobufs.
+ @param bp Buffer whose block to invalidate.
+ @param lblkno Logical block number.
+ @param flags BUF_WAIT: wait for busy buffers to become unbusy and invalidate them then.  Otherwise,
+ just return EBUSY for busy blocks.
+ @return 0 for success, EINVAL if vp is not a device file.
+ */

 errno_t        buf_invalblkno(vnode_t, daddr64_t, int);
 
 errno_t        buf_invalblkno(vnode_t, daddr64_t, int);
 

-
-/*
- * return the callback function pointer
- * if the callback is still valid
- * returns NULL if a buffer that was not
- * allocated via buf_alloc is specified
- * or if a callback has not been set or
- * it has already fired...
+/*!
+ @function buf_callback
+ @abstract Get the function set to be called when I/O on a buffer completes.
+ @discussion A function returned by buf_callback was originally set with buf_setcallback().
+ @param bp Buffer whose callback to get.
+ @return 0 for success, or errors from filesystem or device layers.

  */
 void * buf_callback(buf_t);
 
  */
 void * buf_callback(buf_t);
 

-/*
- * assign a one-shot callback function (driven from biodone)
- * to a buf_t allocated via buf_alloc... a caller specified
- * arg is passed to the callback function
+/*!
+ @function buf_setcallback
+ @abstract Set a function to be called once when I/O on a buffer completes.
+ @discussion A one-shot callout set with buf_setcallback() will be called from buf_biodone()
+ when I/O completes. It will be passed the "transaction" argument as well as the buffer.
+ buf_setcallback() also marks the buffer as B_ASYNC.
+ @param bp Buffer whose callback to set.
+ @param callback function to use as callback.
+ @param transaction Additional argument to callback function.
+ @return 0; always succeeds.

  */
 errno_t        buf_setcallback(buf_t, void (*)(buf_t, void *), void *);
 
  */
 errno_t        buf_setcallback(buf_t, void (*)(buf_t, void *), void *);
 

-/*
- * add a upl_t to a buffer allocated via buf_alloc
- * and set the offset into the upl_t (must be page
- * aligned).
+/*!
+ @function buf_setupl
+ @abstract Set the UPL (Universal Page List), and offset therein, on a buffer.
+ @discussion buf_setupl() should only be called on buffers allocated with buf_alloc().
+ A subsequent call to buf_map() will map the UPL and give back the address at which data
+ begins. After buf_setupl() is called, a buffer is marked B_CLUSTER; when this is the case,
+ buf_strategy() assumes that a buffer is correctly configured to be passed to the device
+ layer without modification. Passing a NULL upl will clear the upl and the B_CLUSTER flag on the
+ buffer.
+ @param bp Buffer whose upl to set.
+ @param upl UPL to set in the buffer.
+ @parma offset Offset within upl at which relevant data begin.
+ @return 0 for success, EINVAL if the buffer was not allocated with buf_alloc().

  */
 errno_t        buf_setupl(buf_t, upl_t, uint32_t);
 
  */
 errno_t        buf_setupl(buf_t, upl_t, uint32_t);
 

-/*
- * allocate a buf_t that is a clone of the buf_t
- * passed in, but whose I/O range is a subset...
- * if a callback routine is specified, it will
- * be called from buf_biodone with the bp and
- * arg specified.
- * it must be freed via buf_free
+/*!
+ @function buf_clone
+ @abstract Clone a buffer with a restricted range and an optional callback.
+ @discussion Generates a buffer which is identical to its "bp" argument except that
+ it spans a subset of the data of the original.  The buffer to be cloned should
+ have been allocated with buf_alloc().  Checks its arguments to make sure
+ that the data subset is coherent. Optionally, adds a callback function and argument to it
+ to be called when I/O completes (as with buf_setcallback(), but B_ASYNC is not set).  If the original buffer had
+ a upl set through buf_setupl(), this upl is copied to the new buffer; otherwise, the original's
+ data pointer is used raw. The buffer must be released with buf_free().
+ @param bp Buffer to clone.
+ @param io_offset Offset, relative to start of data in original buffer, at which new buffer's data will begin. 
+ @param io_size Size of buffer region in new buffer, in the sense of buf_count().
+ @param iodone Callback to be called from buf_biodone() when I/O completes, in the sense of buf_setcallback().
+ @param arg Argument to pass to iodone() callback.
+ @return NULL if io_offset/io_size combination is invalid for the buffer to be cloned; otherwise, the new buffer.

  */
 buf_t  buf_clone(buf_t, int, int, void (*)(buf_t, void *), void *);
 
  */
 buf_t  buf_clone(buf_t, int, int, void (*)(buf_t, void *), void *);
 

-/*
- * allocate a buf_t associated with vnode_t
- * that has NO storage associated with it
- * but is suitable for use in issuing I/Os
- * after storage has been assigned via buf_setdataptr
- * or buf_addupl
+
+/*!
+ @function buf_create_shadow
+ @abstract Create a shadow buffer with optional private storage and an optional callback.
+ @param bp Buffer to shadow.
+ @param force_copy If TRUE, do not link the shadaow to 'bp' and if 'external_storage' == NULL,
+ force a copy of the data associated with 'bp'.
+ @param external_storage If non-NULL, associate it with the new buffer as its storage instead of the 
+ storage currently associated with 'bp'.
+ @param iodone Callback to be called from buf_biodone() when I/O completes, in the sense of buf_setcallback().
+ @param arg Argument to pass to iodone() callback.
+ @return NULL if the buffer to be shadowed is not B_META or a primary buffer (i.e. not a shadow buffer); otherwise, the new buffer.
+*/
+
+buf_t  buf_create_shadow(buf_t bp, boolean_t force_copy, uintptr_t external_storage, void (*iodone)(buf_t, void *), void *arg);
+
+
+/*!
+ @function buf_shadow
+ @abstract returns true if 'bp' is a shadow of another buffer.
+ @param bp Buffer to query.
+ @return 1 if 'bp' is a shadow, 0 otherwise.
+*/
+int    buf_shadow(buf_t bp);
+
+
+/*!
+ @function buf_alloc
+ @abstract Allocate an uninitialized buffer.
+ @discussion A buffer returned by buf_alloc() is marked as busy and as an iobuf; it has no storage set up and must be
+ set up using buf_setdataptr() or buf_setupl()/buf_map().
+ @param vp vnode to associate with the buffer: optionally NULL.  If vp is a device file, then
+ the buffer's associated device will be set. If vp is NULL, it can be set later with buf_setvnode().
+ @return New buffer.

  */
 buf_t  buf_alloc(vnode_t);
 
  */
 buf_t  buf_alloc(vnode_t);
 

-/*
- * free a buf_t that was allocated via buf_alloc
- * any private storage associated with buf_t is the
- * responsiblity of the caller to release
+/*!
+ @function buf_free
+ @abstract Free a buffer that was allocated with buf_alloc().
+ @discussion The storage (UPL, data pointer) associated with an iobuf must be freed manually.
+ @param bp The buffer to free.
+ @return void.

  */
 void   buf_free(buf_t);
 
  */
 void   buf_free(buf_t);
 


@@ -384,41 +688,265 @@ void     buf_free(buf_t);
  */
 #define        BUF_WRITE_DATA  0x0001          /* write data blocks first */
 #define        BUF_SKIP_META   0x0002          /* skip over metadata blocks */
  */
 #define        BUF_WRITE_DATA  0x0001          /* write data blocks first */
 #define        BUF_SKIP_META   0x0002          /* skip over metadata blocks */

-
+#define BUF_INVALIDATE_LOCKED  0x0004  /* force B_LOCKED blocks to be invalidated */
+
+/*!
+ @function buf_invalidateblks
+ @abstract Invalidate all the blocks associated with a vnode.
+ @discussion This function does for all blocks associated with a vnode what buf_invalblkno does for one block.
+ Again, it will only be able to invalidate data which were populated with traditional buffer cache routines,
+ i.e. by buf_getblk() and callers thereof. Unlike buf_invalblkno(), it can be made to write dirty data to disk
+ rather than casting it aside.
+ @param bp The buffer whose data to invalidate.
+ @param flags BUF_WRITE_DATA: write dirty data to disk with VNOP_BWRITE() before kicking buffer cache entries out.
+ BUF_SKIP_META: do not invalidate metadata blocks.
+ @param slpflag Flags to pass to "msleep" while waiting to acquire busy buffers. 
+ @param slptimeo Timeout in "hz" (1/100 second) to wait for a buffer to become unbusy before waking from sleep
+ and re-starting the scan.
+ @return 0 for success, error values from msleep().
+ */

 int    buf_invalidateblks(vnode_t, int, int, int);
 int    buf_invalidateblks(vnode_t, int, int, int);

+

 /*
  * flags for buf_flushdirtyblks and buf_iterate
  */
 #define BUF_SKIP_NONLOCKED     0x01
 #define BUF_SKIP_LOCKED                0x02
 /*
  * flags for buf_flushdirtyblks and buf_iterate
  */
 #define BUF_SKIP_NONLOCKED     0x01
 #define BUF_SKIP_LOCKED                0x02

+#define BUF_SCAN_CLEAN         0x04    /* scan the clean buffers */
+#define BUF_SCAN_DIRTY         0x08    /* scan the dirty buffers */
+#define BUF_NOTIFY_BUSY                0x10    /* notify the caller about the busy pages during the scan */

 
 

-void   buf_flushdirtyblks(vnode_t, int, int, char *);
-void   buf_iterate(vnode_t, int (*)(buf_t, void *), int, void *);

 
 #define        BUF_RETURNED            0
 #define BUF_RETURNED_DONE      1
 #define BUF_CLAIMED            2
 #define        BUF_CLAIMED_DONE        3
 
 #define        BUF_RETURNED            0
 #define BUF_RETURNED_DONE      1
 #define BUF_CLAIMED            2
 #define        BUF_CLAIMED_DONE        3

+/*!
+ @function buf_flushdirtyblks
+ @abstract Write dirty file blocks to disk.
+ @param vp The vnode whose blocks to flush.
+ @param wait Wait for writes to complete before returning.
+ @param flags Can pass zero, meaning "flush all dirty buffers."  
+ BUF_SKIP_NONLOCKED: Skip buffers which are not busy when we encounter them.
+ BUF_SKIP_LOCKED: Skip buffers which are busy when we encounter them.
+ @param msg String to pass to msleep().
+ @return void.
+ */
+void   buf_flushdirtyblks(vnode_t, int, int, const char *);
+
+/*!
+ @function buf_iterate
+ @abstract Perform some operation on all buffers associated with a vnode.
+ @param vp The vnode whose buffers to scan.
+ @param callout Function to call on each buffer.  Should return one of:
+ BUF_RETURNED: buf_iterate() should call buf_brelse() on the buffer.
+ BUF_RETURNED_DONE: buf_iterate() should call buf_brelse() on the buffer and then stop iterating.
+ BUF_CLAIMED: buf_iterate() should continue iterating (and not call buf_brelse()).
+ BUF_CLAIMED_DONE: buf_iterate() should stop iterating (and not call buf_brelse()).
+ @param flag
+ BUF_SKIP_NONLOCKED: Skip buffers which are not busy when we encounter them. BUF_SKIP_LOCKED: Skip buffers which are busy when we encounter them.
+ BUF_SCAN_CLEAN: Call out on clean buffers.
+ BUF_SCAN_DIRTY: Call out on dirty buffers.
+ BUF_NOTIFY_BUSY: If a buffer cannot be acquired, pass a NULL buffer to callout; otherwise,
+ that buffer will be silently skipped.
+ @param arg Argument to pass to callout in addition to buffer.
+ @return void.
+ */
+void   buf_iterate(vnode_t, int (*)(buf_t, void *), int, void *);

 
 

-/*
- * zero the storage associated with buf_t
+/*!
+ @function buf_clear
+ @abstract Zero out the storage associated with a buffer. 
+ @discussion Calls buf_map() to get the buffer's data address; for a B_CLUSTER
+ buffer (one which has had buf_setupl() called on it), it tries to map the buffer's
+ UPL into memory; should only be called once during the life cycle of an iobuf (one allocated
+ with buf_alloc()).  
+ @param bp The buffer to zero out.
+ @return void.

  */
 void   buf_clear(buf_t);
 
  */
 void   buf_clear(buf_t);
 

+/*!
+ @function buf_bawrite
+ @abstract Start an asychronous write on a buffer.
+ @discussion Calls VNOP_BWRITE to start the process of propagating an asynchronous write down to the device layer.
+ Callers can wait for writes to complete at their discretion using buf_biowait().  When this function is called,
+ data should already have been written to the buffer's data region.
+ @param bp The buffer on which to initiate I/O.
+ @param throttle If "throttle" is nonzero and more than VNODE_ASYNC_THROTTLE writes are in progress on this file,
+ buf_bawrite() will block until the write count drops below VNODE_ASYNC_THROTTLE.  If "throttle" is zero and the write
+ count is high, it will fail with EWOULDBLOCK; the caller can decide whether to make a blocking call or pursue
+ other opportunities.
+ @return EWOULDBLOCK if write count is high and "throttle" is zero; otherwise, errors from VNOP_BWRITE.
+ */

 errno_t        buf_bawrite(buf_t);
 errno_t        buf_bawrite(buf_t);

+
+/*!
+ @function buf_bdwrite
+ @abstract Mark a buffer for delayed write.
+ @discussion Marks a buffer as waiting for delayed write and the current I/O as complete; data will be written to backing store
+ before the buffer is reused, but it will not be queued for I/O immediately.  Note that for buffers allocated
+ with buf_alloc(), there are no such guarantees; you must take care of your own flushing to disk.  If
+ the number of delayed writes pending on the system is greater than an internal limit and the caller has not
+ requested otherwise [see return_error] , buf_bdwrite() will unilaterally launch an asynchronous I/O with buf_bawrite() to keep the pile of
+ delayed writes from getting too large.
+ @param bp The buffer to mark for delayed write.
+ @param return_error If the number of pending delayed writes systemwide is larger than an internal limit,
+ return EAGAIN rather than doing an asynchronous write.
+ @return EAGAIN for return_error != 0 case, 0 for succeess, errors from buf_bawrite.
+ */

 errno_t        buf_bdwrite(buf_t);
 errno_t        buf_bdwrite(buf_t);

+
+/*!
+ @function buf_bwrite
+ @abstract Write a buffer's data to backing store.
+ @discussion Once the data in a buffer has been modified, buf_bwrite() starts sending it to disk by calling
+ VNOP_STRATEGY.  Unless B_ASYNC has been set on the buffer (by buf_setflags() or otherwise), data will have 
+ been written to disk when buf_bwrite() returns.  See Bach (p 56).
+ @param bp The buffer to write to disk.
+ @return 0 for success; errors from buf_biowait().
+ */

 errno_t        buf_bwrite(buf_t);
 
 errno_t        buf_bwrite(buf_t);
 

+/*!
+ @function buf_biodone
+ @abstract Mark an I/O as completed.
+ @discussion buf_biodone() should be called by whosoever decides that an I/O on a buffer is complete; for example,
+ IOStorageFamily.  It clears the dirty flag on a buffer and signals on the vnode that a write has completed
+ with vnode_writedone(). If a callout or filter has been set on the buffer, that function is called.  In the case
+ of a callout, that function is expected to take care of cleaning up and freeing the buffer.
+ Otherwise, if the buffer is marked B_ASYNC (e.g. it was passed to buf_bawrite()), then buf_biodone()
+ considers itself justified in calling buf_brelse() to return it to free lists--no one is waiting for it.  Finally, 
+ waiters on the bp (e.g. in buf_biowait()) are woken up.
+ @param bp The buffer to mark as done with I/O.
+ @return void.
+ */

 void   buf_biodone(buf_t);
 void   buf_biodone(buf_t);

+
+/*!
+ @function buf_biowait
+ @abstract Wait for I/O on a buffer to complete.
+ @discussion Waits for I/O on a buffer to finish, as marked by a buf_biodone() call.  
+ @param bp The buffer to wait on.
+ @return 0 for a successful wait; nonzero the buffer has been marked as EINTR or had an error set on it.
+ */

 errno_t        buf_biowait(buf_t);
 errno_t        buf_biowait(buf_t);

-void   buf_brelse(buf_t);

 
 

-errno_t        buf_bread(vnode_t, daddr64_t, int, ucred_t, buf_t *);
-errno_t        buf_breadn(vnode_t, daddr64_t, int, daddr64_t *, int *, int, ucred_t, buf_t *);
-errno_t        buf_meta_bread(vnode_t, daddr64_t, int, ucred_t, buf_t *);
-errno_t        buf_meta_breadn(vnode_t, daddr64_t, int, daddr64_t *, int *, int, ucred_t, buf_t *);
+/*!
+ @function buf_brelse
+ @abstract Release any claim to a buffer, sending it back to free lists.
+ @discussion buf_brelse() cleans up buffer state and releases a buffer to the free lists.  If the buffer
+ is not marked invalid and its pages are dirty (e.g. a delayed write was made), its data will be commited
+ to backing store. If it is marked invalid, its data will be discarded completely.  
+ A valid, cacheable buffer will be put on a list and kept in the buffer hash so it
+ can be found again; otherwise, it will be dissociated from its vnode and treated as empty.  Which list a valid
+ buffer is placed on depends on the use of buf_markaged(), whether it is metadata, and the B_LOCKED flag.  A
+ B_LOCKED buffer will not be available for reuse by other files, though its data may be paged out.
+ Note that buf_brelse() is intended for use with traditionally allocated buffers.
+ @param bp The buffer to release.
+ @retrn void.
+ */
+void   buf_brelse(buf_t);

 
 

+/*!
+ @function buf_bread
+ @abstract Synchronously read a block of a file.
+ @discussion buf_bread() is the traditional way to read a single logical block of a file through the buffer cache. 
+ It tries to find the buffer and corresponding page(s) in core, calls VNOP_STRATEGY if necessary to bring the data
+ into memory, and waits for I/O to complete.  It should not be used to read blocks of greater than 4K (one VM page) 
+ in size; use cluster routines for large reads.  Indeed, the cluster layer is a more efficient choice for reading DATA
+ unless you need some finely-tuned semantics that it cannot provide.
+ @param vp The file from which to read.
+ @param blkno The logical (filesystem) block number to read.
+ @param size Size of block; do not use for sizes > 4K.
+ @param cred Credential to store and use for reading from disk if data are not already in core.
+ @param bpp Destination pointer for buffer.
+ @return 0 for success, or an error from buf_biowait().
+ */
+errno_t        buf_bread(vnode_t, daddr64_t, int, kauth_cred_t, buf_t *);
+
+/*!
+ @function buf_breadn
+ @abstract Read a block from a file with read-ahead.
+ @discussion buf_breadn() reads one block synchronously in the style of buf_bread() and fires
+ off a specified set of asynchronous reads to improve the likelihood of future cache hits.  
+ It should not be used to read blocks of greater than 4K (one VM page) in size; use cluster 
+ routines for large reads.  Indeed, the cluster layer is a more efficient choice for reading DATA
+ unless you need some finely-tuned semantics that it cannot provide.
+ @param vp The file from which to read.
+ @param blkno The logical (filesystem) block number to read synchronously.
+ @param size Size of block; do not use for sizes > 4K.
+ @param rablks Array of logical block numbers for asynchronous read-aheads.
+ @param rasizes Array of block sizes for asynchronous read-aheads, each index corresponding to same index in "rablks."
+ @param nrablks Number of entries in read-ahead arrays.
+ @param cred Credential to store and use for reading from disk if data are not already in core.
+ @param bpp Destination pointer for buffer.
+ @return 0 for success, or an error from buf_biowait().
+ */
+errno_t        buf_breadn(vnode_t, daddr64_t, int, daddr64_t *, int *, int, kauth_cred_t, buf_t *);
+
+/*!
+ @function buf_meta_bread
+ @abstract Synchronously read a metadata block of a file.
+ @discussion buf_meta_bread() is the traditional way to read a single logical block of a file through the buffer cache. 
+ It tries to find the buffer and corresponding page(s) in core, calls VNOP_STRATEGY if necessary to bring the data
+ into memory, and waits for I/O to complete.  It should not be used to read blocks of greater than 4K (one VM page) 
+ in size; use cluster routines for large reads.  Reading meta-data through the traditional buffer cache, unlike
+ reading data, is efficient and encouraged, especially if the blocks being read are significantly smaller than page size.
+ @param vp The file from which to read.
+ @param blkno The logical (filesystem) block number to read.
+ @param size Size of block; do not use for sizes > 4K.
+ @param cred Credential to store and use for reading from disk if data are not already in core.
+ @param bpp Destination pointer for buffer.
+ @return 0 for success, or an error from buf_biowait().
+ */
+errno_t        buf_meta_bread(vnode_t, daddr64_t, int, kauth_cred_t, buf_t *);
+
+/*!
+ @function buf_meta_breadn
+ @abstract Read a metadata block from a file with read-ahead.
+ @discussion buf_meta_breadn() reads one block synchronously in the style of buf_meta_bread() and fires
+ off a specified set of asynchronous reads to improve the likelihood of future cache hits.  
+ It should not be used to read blocks of greater than 4K (one VM page) in size; use cluster 
+ routines for large reads.
+ @param vp The file from which to read.
+ @param blkno The logical (filesystem) block number to read synchronously.
+ @param size Size of block; do not use for sizes > 4K.
+ @param rablks Array of logical block numbers for asynchronous read-aheads.
+ @param rasizes Array of block sizes for asynchronous read-aheads, each index corresponding to same index in "rablks."
+ @param nrablks Number of entries in read-ahead arrays.
+ @param cred Credential to store and use for reading from disk if data are not already in core.
+ @param bpp Destination pointer for buffer.
+ @return 0 for success, or an error from buf_biowait().
+ */
+errno_t        buf_meta_breadn(vnode_t, daddr64_t, int, daddr64_t *, int *, int, kauth_cred_t, buf_t *);
+
+/*!
+ @function minphys
+ @abstract Adjust a buffer's count to be no more than maximum physical I/O transfer size for the host architecture.
+ @discussion physio() takes as a parameter a function to bound transfer sizes for each VNOP_STRATEGY() call.  minphys()
+ is a default implementation.  It calls buf_setcount() to make the buffer's count the min() of its current count
+ and the max I/O size for the host architecture.
+ @param bp The buffer whose byte count to modify.
+ @return New byte count.
+ */

 u_int  minphys(buf_t bp);
 u_int  minphys(buf_t bp);

+
+/*!
+ @function physio 
+ @abstract Perform I/O on a device to/from target memory described by a uio.
+ @discussion physio() allows I/O directly from a device to user-space memory.  It waits
+ for all I/O to complete before returning.
+ @param f_strategy Strategy routine to call to initiate I/O.
+ @param bp Buffer to configure and pass to strategy routine; can be NULL.
+ @param dev Device on which to perform I/O.
+ @param flags B_READ or B_WRITE.
+ @param f_minphys Function which calls buf_setcount() to set a byte count which is suitably
+ small for the device in question.  Returns byte count that has been set (or unchanged) on the buffer.
+ @param uio UIO describing the I/O operation.
+ @param blocksize Logical block size for this vnode.
+ @return 0 for success; EFAULT for an invalid uio; errors from buf_biowait().
+ */

 int    physio(void (*)(buf_t), buf_t, dev_t, int ,  u_int (*)(buf_t), struct uio *, int );
 
 
 int    physio(void (*)(buf_t), buf_t, dev_t, int ,  u_int (*)(buf_t), struct uio *, int );
 
 


@@ -434,10 +962,91 @@ int       physio(void (*)(buf_t), buf_t, dev_t, int ,  u_int (*)(buf_t), struct uio *,
  */
 #define BLK_ONLYVALID  0x80000000
                                   
  */
 #define BLK_ONLYVALID  0x80000000
                                   

-/* timeout is in msecs */
+/*!
+ @function buf_getblk
+ @abstract Traditional buffer cache routine to get a buffer corresponding to a logical block in a file.
+ @discussion buf_getblk() gets a buffer, not necessarily containing valid data, representing a block in a file.  
+ A metadata buffer will be returned with its own zone-allocated storage, managed by the traditional buffer-cache
+ layer, whereas data buffers will be returned hooked into backing by the UBC (which in fact controls the caching of data).
+ buf_getblk() first looks for the buffer header in cache; if the buffer is in-core but busy, buf_getblk() will wait for it to become
+ unbusy, depending on the slpflag and slptimeo parameters. If the buffer is found unbusy and is a metadata buffer,
+ it must already contain valid data and will be returned directly; data buffers will have a UPL configured to
+ prepare for interaction with the underlying UBC.  If the buffer is found in core, it will be marked as such
+ and buf_fromcache() will return truth. A buffer is allocated and initialized (but not filled with data)
+ if none is found in core. buf_bread(), buf_breadn(), buf_meta_bread(), and buf_meta_breadn() all 
+ return buffers obtained with buf_getblk().
+ @param vp File for which to get block.
+ @param blkno Logical block number.
+ @param size Size of block.
+ @param slpflag Flag to pass to msleep() while waiting for buffer to become unbusy.
+ @param slptimeo Time, in milliseconds, to wait for buffer to become unbusy.  0 means to wait indefinitely.
+ @param operation BLK_READ: want a read buffer.  BLK_WRITE: want a write buffer.  BLK_META: want a metadata buffer.  BLK_ONLYVALID: 
+ only return buffers which are found in core (do not allocate anew), and do not change buffer size.  The last remark means
+ that if a given logical block is found in core with a different size than what is requested, the buffer size will not be modified.
+ @return Buffer found in core or newly allocated, either containing valid data or ready for I/O.
+ */

 buf_t  buf_getblk(vnode_t, daddr64_t, int, int, int, int);
 buf_t  buf_getblk(vnode_t, daddr64_t, int, int, int, int);

+
+/*!
+ @function buf_geteblk
+ @abstract Get a metadata buffer which is marked invalid and not associated with any vnode.
+ @discussion A buffer is returned with zone-allocated storage of the specified size, marked B_META and invalid. 
+ It has no vnode and is not visible in the buffer hash.  
+ @param size Size of buffer.
+ @return Always returns a new buffer.
+ */

 buf_t  buf_geteblk(int);
 
 buf_t  buf_geteblk(int);
 

+/*!
+ @function buf_clear_redundancy_flags
+ @abstract Clear flags on a buffer.
+ @discussion: buffer_redundancy_flags &= ~flags
+ @param bp Buffer whose flags to clear.
+ @param flags Flags to remove from buffer's mask
+ @return void.
+ */
+void   buf_clear_redundancy_flags(buf_t, uint32_t);
+
+/*!
+ @function buf_redundancyflags
+ @abstract Get redundancy flags set on a buffer.
+ @param bp Buffer whose redundancy flags to grab.
+ @return flags.
+ */
+uint32_t       buf_redundancy_flags(buf_t);
+
+/*!
+ @function buf_setredundancyflags
+ @abstract Set redundancy flags on a buffer.
+ @discussion: buffer_redundancy_flags |= flags
+ @param bp Buffer whose flags to set.
+ @param flags Flags to add to buffer's redundancy flags
+ @return void.
+ */
+void   buf_set_redundancy_flags(buf_t, uint32_t);
+
+#ifdef KERNEL_PRIVATE
+void   buf_setfilter(buf_t, void (*)(buf_t, void *), void *, void (**)(buf_t, void *), void **);
+
+
+/*!
+ @function buf_getcpaddr
+ @abstract Set the address of cp_entry on a buffer.
+ @param bp Buffer whose cp entry value has to be set
+ @return void.
+ */
+void buf_setcpaddr(buf_t, void *);
+
+/*!
+ @function buf_getcpaddr
+ @abstract Get the address of cp_entry on a buffer.
+ @param bp Buffer whose error value to set.
+ @return int.
+ */
+void *buf_getcpaddr(buf_t);
+#endif /* KERNEL_PRIVATE */
+
+

 __END_DECLS
 
 
 __END_DECLS