X-Git-Url: https://git.saurik.com/apple/xnu.git/blobdiff_plain/fa4905b191e0d16b0fffd53bd565eca71d01fae0..b7266188b87f3620ec3f9f717e57194a7dd989fe:/bsd/nfs/nfs_bio.c

diff --git a/bsd/nfs/nfs_bio.c b/bsd/nfs/nfs_bio.c
index 926de3419..1c1c19123 100644
--- a/bsd/nfs/nfs_bio.c
+++ b/bsd/nfs/nfs_bio.c
@@ -1,23 +1,29 @@
 /*
- * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
+ * Copyright (c) 2000-2009 Apple 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,
- * 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 */
 /*
@@ -62,1304 +68,3622 @@
 #include <sys/systm.h>
 #include <sys/resourcevar.h>
 #include <sys/signalvar.h>
-#include <sys/proc.h>
-#include <sys/buf.h>
+#include <sys/proc_internal.h>
+#include <sys/kauth.h>
+#include <sys/malloc.h>
 #include <sys/vnode.h>
-#include <sys/mount.h>
+#include <sys/dirent.h>
+#include <sys/mount_internal.h>
 #include <sys/kernel.h>
-#include <sys/sysctl.h>
-#include <sys/ubc.h>
+#include <sys/ubc_internal.h>
+#include <sys/uio_internal.h>
 
 #include <sys/vm.h>
 #include <sys/vmparam.h>
 
 #include <sys/time.h>
 #include <kern/clock.h>
+#include <libkern/OSAtomic.h>
+#include <kern/kalloc.h>
+#include <kern/thread_call.h>
 
 #include <nfs/rpcv2.h>
 #include <nfs/nfsproto.h>
 #include <nfs/nfs.h>
+#include <nfs/nfs_gss.h>
 #include <nfs/nfsmount.h>
-#include <nfs/nqnfs.h>
 #include <nfs/nfsnode.h>
+#include <sys/buf_internal.h>
+#include <libkern/OSAtomic.h>
+
+kern_return_t	thread_terminate(thread_t); /* XXX */
 
-#include <sys/kdebug.h>
+#define	NFSBUFHASH(np, lbn)	\
+	(&nfsbufhashtbl[((long)(np) / sizeof(*(np)) + (int)(lbn)) & nfsbufhash])
+LIST_HEAD(nfsbufhashhead, nfsbuf) *nfsbufhashtbl;
+struct nfsbuffreehead nfsbuffree, nfsbuffreemeta, nfsbufdelwri;
+u_long nfsbufhash;
+int nfsbufcnt, nfsbufmin, nfsbufmax, nfsbufmetacnt, nfsbufmetamax;
+int nfsbuffreecnt, nfsbuffreemetacnt, nfsbufdelwricnt, nfsneedbuffer;
+int nfs_nbdwrite;
+int nfs_buf_timer_on = 0;
+thread_t nfsbufdelwrithd = NULL;
 
-#define FSDBG(A, B, C, D, E) \
-	KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, (A))) | DBG_FUNC_NONE, \
-		(int)(B), (int)(C), (int)(D), (int)(E), 0)
-#define FSDBG_TOP(A, B, C, D, E) \
-	KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, (A))) | DBG_FUNC_START, \
-		(int)(B), (int)(C), (int)(D), (int)(E), 0)
-#define FSDBG_BOT(A, B, C, D, E) \
-	KERNEL_DEBUG((FSDBG_CODE(DBG_FSRW, (A))) | DBG_FUNC_END, \
-		(int)(B), (int)(C), (int)(D), (int)(E), 0)
+lck_grp_t *nfs_buf_lck_grp;
+lck_mtx_t *nfs_buf_mutex;
 
-static struct buf *nfs_getcacheblk __P((struct vnode *vp, daddr_t bn, int size,
-					struct proc *p, int operation));
+#define NFSBUF_FREE_PERIOD	30	/* seconds */
+#define NFSBUF_LRU_STALE	120
+#define NFSBUF_META_STALE	240
 
-extern int nfs_numasync;
-extern struct nfsstats nfsstats;
+/* number of nfsbufs nfs_buf_freeup() should attempt to free from nfsbuffree list */
+#define LRU_TO_FREEUP			6
+/* number of nfsbufs nfs_buf_freeup() should attempt to free from nfsbuffreemeta list */
+#define META_TO_FREEUP			3
+/* total number of nfsbufs nfs_buf_freeup() should attempt to free */
+#define TOTAL_TO_FREEUP			(LRU_TO_FREEUP+META_TO_FREEUP)
+/* fraction of nfsbufs nfs_buf_freeup() should attempt to free from nfsbuffree list when called from timer */
+#define LRU_FREEUP_FRAC_ON_TIMER	8
+/* fraction of nfsbufs nfs_buf_freeup() should attempt to free from nfsbuffreemeta list when called from timer */
+#define META_FREEUP_FRAC_ON_TIMER	16
+/* fraction of total nfsbufs that nfsbuffreecnt should exceed before bothering to call nfs_buf_freeup() */
+#define LRU_FREEUP_MIN_FRAC		4
+/* fraction of total nfsbufs that nfsbuffreemetacnt should exceed before bothering to call nfs_buf_freeup() */
+#define META_FREEUP_MIN_FRAC		2
+
+#define NFS_BUF_FREEUP() \
+	do { \
+		/* only call nfs_buf_freeup() if it has work to do: */ \
+		if (((nfsbuffreecnt > nfsbufcnt/LRU_FREEUP_MIN_FRAC) || \
+		     (nfsbuffreemetacnt > nfsbufcnt/META_FREEUP_MIN_FRAC)) && \
+		    ((nfsbufcnt - TOTAL_TO_FREEUP) > nfsbufmin)) \
+			nfs_buf_freeup(0); \
+	} while (0)
 
 /*
- * Vnode op for read using bio
- * Any similarity to readip() is purely coincidental
+ * Initialize nfsbuf lists
  */
-int
-nfs_bioread(vp, uio, ioflag, cred, getpages)
-	register struct vnode *vp;
-	register struct uio *uio;
-	int ioflag;
-	struct ucred *cred;
-	int getpages;
+void
+nfs_nbinit(void)
 {
-	register struct nfsnode *np = VTONFS(vp);
-	register int biosize, diff, i;
-	struct buf *bp = 0, *rabp;
-	struct vattr vattr;
-	struct proc *p;
-	struct nfsmount *nmp = VFSTONFS(vp->v_mount);
-	daddr_t lbn, rabn;
-	int bufsize;
-	int nra, error = 0, n = 0, on = 0, not_readin;
-	int operation = (getpages? BLK_PAGEIN : BLK_READ);
-
-#if DIAGNOSTIC
-	if (uio->uio_rw != UIO_READ)
-		panic("nfs_read mode");
-#endif
-	if (uio->uio_resid == 0)
-		return (0);
-	if (uio->uio_offset < 0)
-		return (EINVAL);
-	p = uio->uio_procp;
-	if ((nmp->nm_flag & (NFSMNT_NFSV3 | NFSMNT_GOTFSINFO)) == NFSMNT_NFSV3)
-		(void)nfs_fsinfo(nmp, vp, cred, p);
-	/*due to getblk/vm interractions, use vm page size or less values */
-	biosize = min(vp->v_mount->mnt_stat.f_iosize, PAGE_SIZE);
-	/*
-	 * For nfs, cache consistency can only be maintained approximately.
-	 * Although RFC1094 does not specify the criteria, the following is
-	 * believed to be compatible with the reference port.
-	 * For nqnfs, full cache consistency is maintained within the loop.
-	 * For nfs:
-	 * If the file's modify time on the server has changed since the
-	 * last read rpc or you have written to the file,
-	 * you may have lost data cache consistency with the
-	 * server, so flush all of the file's data out of the cache.
-	 * Then force a getattr rpc to ensure that you have up to date
-	 * attributes.
-	 * NB: This implies that cache data can be read when up to
-	 * NFS_ATTRTIMEO seconds out of date. If you find that you need current
-	 * attributes this could be forced by setting n_attrstamp to 0 before
-	 * the VOP_GETATTR() call.
-	 */
-	if ((nmp->nm_flag & NFSMNT_NQNFS) == 0) {
-		if (np->n_flag & NMODIFIED) {
-			if (vp->v_type != VREG) {
-				if (vp->v_type != VDIR)
-					panic("nfs: bioread, not dir");
-				nfs_invaldir(vp);
-				error = nfs_vinvalbuf(vp, V_SAVE, cred, p, 1);
-				if (error)
-					return (error);
-			}
-			np->n_attrstamp = 0;
-			error = VOP_GETATTR(vp, &vattr, cred, p);
-			if (error)
-				return (error);
-			np->n_mtime = vattr.va_mtime.tv_sec;
-		} else {
-			error = VOP_GETATTR(vp, &vattr, cred, p);
-			if (error)
-				return (error);
-			if (np->n_mtime != vattr.va_mtime.tv_sec) {
-				if (vp->v_type == VDIR)
-					nfs_invaldir(vp);
-				error = nfs_vinvalbuf(vp, V_SAVE, cred, p, 1);
-				if (error)
-					return (error);
-				np->n_mtime = vattr.va_mtime.tv_sec;
-			}
-		}
-	}
-	do {
+	nfs_buf_lck_grp = lck_grp_alloc_init("nfs_buf", LCK_GRP_ATTR_NULL);
+	nfs_buf_mutex = lck_mtx_alloc_init(nfs_buf_lck_grp, LCK_ATTR_NULL);
 
-	    /*
-	     * Get a valid lease. If cached data is stale, flush it.
-	     */
-	    if (nmp->nm_flag & NFSMNT_NQNFS) {
-		if (NQNFS_CKINVALID(vp, np, ND_READ)) {
-		    do {
-			error = nqnfs_getlease(vp, ND_READ, cred, p);
-		    } while (error == NQNFS_EXPIRED);
-		    if (error)
-			return (error);
-		    if (np->n_lrev != np->n_brev ||
-			(np->n_flag & NQNFSNONCACHE) ||
-			((np->n_flag & NMODIFIED) && vp->v_type == VDIR)) {
-			if (vp->v_type == VDIR)
-			    nfs_invaldir(vp);
-			error = nfs_vinvalbuf(vp, V_SAVE, cred, p, 1);
-			if (error)
-			    return (error);
-			np->n_brev = np->n_lrev;
-		    }
-		} else if (vp->v_type == VDIR && (np->n_flag & NMODIFIED)) {
-		    nfs_invaldir(vp);
-		    error = nfs_vinvalbuf(vp, V_SAVE, cred, p, 1);
-		    if (error)
-			return (error);
-		}
-	    }
-	    if (np->n_flag & NQNFSNONCACHE) {
-		switch (vp->v_type) {
-		case VREG:
-			return (nfs_readrpc(vp, uio, cred));
-		case VLNK:
-			return (nfs_readlinkrpc(vp, uio, cred));
-		case VDIR:
-			break;
-		default:
-			printf(" NQNFSNONCACHE: type %x unexpected\n",	
-				vp->v_type);
-		};
-	    }
-	    switch (vp->v_type) {
-	    case VREG:
-		nfsstats.biocache_reads++;
-		lbn = uio->uio_offset / biosize;
-		on = uio->uio_offset & (biosize - 1);
-		not_readin = 1;
+	nfsbufcnt = nfsbufmetacnt =
+	nfsbuffreecnt = nfsbuffreemetacnt = nfsbufdelwricnt = 0;
+	nfsbufmin = 128;
+	/* size nfsbufmax to cover at most half sane_size (w/default buf size) */
+	nfsbufmax = (sane_size >> PAGE_SHIFT) / (2 * (NFS_RWSIZE >> PAGE_SHIFT));
+	nfsbufmetamax = nfsbufmax / 4;
+	nfsneedbuffer = 0;
+	nfs_nbdwrite = 0;
 
-		/*
-		 * Start the read ahead(s), as required.
-		 */
-		if (nfs_numasync > 0 && nmp->nm_readahead > 0) {
-		    for (nra = 0; nra < nmp->nm_readahead &&
-				  (off_t)(lbn + 1 + nra) * biosize < np->n_size;
-			 nra++) {
-				rabn = lbn + 1 + nra;
-				if (!incore(vp, rabn)) {
-					rabp = nfs_getcacheblk(vp, rabn, biosize, p, operation);
-					if (!rabp)
-						return (EINTR);
-					if (!ISSET(rabp->b_flags, (B_CACHE|B_DELWRI))) {
-						SET(rabp->b_flags, (B_READ | B_ASYNC));
-						if (nfs_asyncio(rabp, cred)) {
-							SET(rabp->b_flags, (B_INVAL|B_ERROR));
-							rabp->b_error = EIO;
-							brelse(rabp);
-						}
-					} else
-						brelse(rabp);
-				}
-		    }
-		}
+	nfsbufhashtbl = hashinit(nfsbufmax/4, M_TEMP, &nfsbufhash);
+	TAILQ_INIT(&nfsbuffree);
+	TAILQ_INIT(&nfsbuffreemeta);
+	TAILQ_INIT(&nfsbufdelwri);
 
-		/*
-		 * If the block is in the cache and has the required data
-		 * in a valid region, just copy it out.
-		 * Otherwise, get the block and write back/read in,
-		 * as required.
-		 */
-again:
-		bufsize = biosize;
-		if ((off_t)(lbn + 1) * biosize > np->n_size && 
-		    (off_t)(lbn + 1) * biosize - np->n_size < biosize) {
-			bufsize = np->n_size - lbn * biosize;
-			bufsize = (bufsize + DEV_BSIZE - 1) & ~(DEV_BSIZE - 1);
-		}
-		bp = nfs_getcacheblk(vp, lbn, bufsize, p, operation);
-		if (!bp)
-			return (EINTR);
+}
 
-		if (!ISSET(bp->b_flags, B_CACHE)) {
-			SET(bp->b_flags, B_READ);
-			CLR(bp->b_flags, (B_DONE | B_ERROR | B_INVAL));
-			not_readin = 0;
-			error = nfs_doio(bp, cred, p);
-			if (error) {
-			    brelse(bp);
-			    return (error);
-			}
-		}
-		if (bufsize > on) {
-			n = min((unsigned)(bufsize - on), uio->uio_resid);
-		} else {
-			n = 0;
-		}
-		diff = np->n_size - uio->uio_offset;
-		if (diff < n)
-			n = diff;
-		if (not_readin && n > 0) {
-			if (on < bp->b_validoff || (on + n) > bp->b_validend) {
-				SET(bp->b_flags, (B_NOCACHE|B_INVAFTERWRITE));
-				if (bp->b_dirtyend > 0) {
-					if (!ISSET(bp->b_flags, B_DELWRI))
-						panic("nfsbioread");
-					if (VOP_BWRITE(bp) == EINTR)
-						return (EINTR);
-				} else
-					brelse(bp);
-				goto again;
-			}
-		}
-		vp->v_lastr = lbn;
-		diff = (on >= bp->b_validend) ? 0 : (bp->b_validend - on);
-		if (diff < n)
-			n = diff;
-		break;
-	    case VLNK:
-		nfsstats.biocache_readlinks++;
-		bp = nfs_getcacheblk(vp, (daddr_t)0, NFS_MAXPATHLEN, p, operation);
-		if (!bp)
-			return (EINTR);
-		if (!ISSET(bp->b_flags, B_CACHE)) {
-			SET(bp->b_flags, B_READ);
-			error = nfs_doio(bp, cred, p);
-			if (error) {
-				SET(bp->b_flags, B_ERROR);
-				brelse(bp);
-				return (error);
-			}
-		}
-		n = min(uio->uio_resid, NFS_MAXPATHLEN - bp->b_resid);
-		on = 0;
-		break;
-	    case VDIR:
-		nfsstats.biocache_readdirs++;
-		if (np->n_direofoffset
-		    && uio->uio_offset >= np->n_direofoffset) {
-		    return (0);
-		}
-		lbn = uio->uio_offset / NFS_DIRBLKSIZ;
-		on = uio->uio_offset & (NFS_DIRBLKSIZ - 1);
-		bp = nfs_getcacheblk(vp, lbn, NFS_DIRBLKSIZ, p, operation);
-		if (!bp)
-		    return (EINTR);
-		if (!ISSET(bp->b_flags, B_CACHE)) {
-		    SET(bp->b_flags, B_READ);
-		    error = nfs_doio(bp, cred, p);
-		    if (error) {
-			brelse(bp);
-		    }
-		    while (error == NFSERR_BAD_COOKIE) {
-			nfs_invaldir(vp);
-			error = nfs_vinvalbuf(vp, 0, cred, p, 1);
-			/*
-			 * Yuck! The directory has been modified on the
-			 * server. The only way to get the block is by
-			 * reading from the beginning to get all the
-			 * offset cookies.
-			 */
-			for (i = 0; i <= lbn && !error; i++) {
-			    if (np->n_direofoffset
-				&& (i * NFS_DIRBLKSIZ) >= np->n_direofoffset)
-				    return (0);
-			    bp = nfs_getcacheblk(vp, i, NFS_DIRBLKSIZ, p,
-			    			 operation);
-			    if (!bp)
-				    return (EINTR);
-			    if (!ISSET(bp->b_flags, B_CACHE)) {
-				    SET(bp->b_flags, B_READ);
-				    error = nfs_doio(bp, cred, p);
-				    /*
-				     * no error + B_INVAL == directory EOF,
-				     * use the block.
-				     */
-				    if (error == 0 && (bp->b_flags & B_INVAL))
-					    break;
-			    }
-			    /*
-			     * An error will throw away the block and the
-			     * for loop will break out.  If no error and this
-			     * is not the block we want, we throw away the
-			     * block and go for the next one via the for loop.
-			     */
-			    if (error || i < lbn)
-				    brelse(bp);
-			}
-		    }
-		    /*
-		     * The above while is repeated if we hit another cookie
-		     * error.  If we hit an error and it wasn't a cookie error,
-		     * we give up.
-		     */
-		    if (error)
-			return (error);
-		}
+/*
+ * Check periodically for stale/unused nfs bufs
+ */
+void
+nfs_buf_timer(__unused void *param0, __unused void *param1)
+{
+	nfs_buf_freeup(1);
 
-		/*
-		 * If not eof and read aheads are enabled, start one.
-		 * (You need the current block first, so that you have the
-		 *  directory offset cookie of the next block.)
-		 */
-		if (nfs_numasync > 0 && nmp->nm_readahead > 0 &&
-		    (np->n_direofoffset == 0 ||
-		    (lbn + 1) * NFS_DIRBLKSIZ < np->n_direofoffset) &&
-		    !(np->n_flag & NQNFSNONCACHE) &&
-		    !incore(vp, lbn + 1)) {
-			rabp = nfs_getcacheblk(vp, lbn + 1, NFS_DIRBLKSIZ, p,
-					       operation);
-			if (rabp) {
-			    if (!ISSET(rabp->b_flags, (B_CACHE|B_DELWRI))) {
-				SET(rabp->b_flags, (B_READ | B_ASYNC));
-				if (nfs_asyncio(rabp, cred)) {
-				    SET(rabp->b_flags, (B_INVAL|B_ERROR));
-				    rabp->b_error = EIO;
-				    brelse(rabp);
-				}
-			    } else {
-				brelse(rabp);
-			    }
-			}
-		}
-		/*
-		 * Make sure we use a signed variant of min() since
-		 * the second term may be negative.
-		 */
-		n = lmin(uio->uio_resid, NFS_DIRBLKSIZ - bp->b_resid - on);
-		/*
-		 * Unlike VREG files, whos buffer size ( bp->b_bcount ) is
-		 * chopped for the EOF condition, we cannot tell how large
-		 * NFS directories are going to be until we hit EOF.  So
-		 * an NFS directory buffer is *not* chopped to its EOF.  Now,
-		 * it just so happens that b_resid will effectively chop it
-		 * to EOF.  *BUT* this information is lost if the buffer goes
-		 * away and is reconstituted into a B_CACHE state (recovered
-		 * from VM) later.  So we keep track of the directory eof
-		 * in np->n_direofoffset and chop it off as an extra step
-		 * right here.
-		 */
-		if (np->n_direofoffset &&
-		    n > np->n_direofoffset - uio->uio_offset)
-			n = np->n_direofoffset - uio->uio_offset;
-		break;
-	    default:
-		printf(" nfs_bioread: type %x unexpected\n",vp->v_type);
-		break;
-	    };
+	lck_mtx_lock(nfs_buf_mutex);
+	if (nfsbufcnt <= nfsbufmin) {
+		nfs_buf_timer_on = 0;
+		lck_mtx_unlock(nfs_buf_mutex);
+		return;
+	}
+	lck_mtx_unlock(nfs_buf_mutex);
 
-	    if (n > 0) {
-		error = uiomove(bp->b_data + on, (int)n, uio);
-	    }
-	    switch (vp->v_type) {
-	    case VREG:
-		break;
-	    case VLNK:
-		n = 0;
-		break;
-	    case VDIR:
-		if (np->n_flag & NQNFSNONCACHE)
-			SET(bp->b_flags, B_INVAL);
-		break;
-	    default:
-		printf(" nfs_bioread: type %x unexpected\n",vp->v_type);
-	    }
- 	    brelse(bp);
-	} while (error == 0 && uio->uio_resid > 0 && n > 0);
-	return (error);
+	nfs_interval_timer_start(nfs_buf_timer_call,
+		NFSBUF_FREE_PERIOD * 1000);
 }
 
-
 /*
- * Vnode op for write using bio
+ * try to free up some excess, unused nfsbufs
  */
-int
-nfs_write(ap)
-	struct vop_write_args /* {
-		struct vnode *a_vp;
-		struct uio *a_uio;
-		int  a_ioflag;
-		struct ucred *a_cred;
-	} */ *ap;
+void
+nfs_buf_freeup(int timer)
 {
-	register int biosize;
-	register struct uio *uio = ap->a_uio;
-	struct proc *p = uio->uio_procp;
-	register struct vnode *vp = ap->a_vp;
-	struct nfsnode *np = VTONFS(vp);
-	register struct ucred *cred = ap->a_cred;
-	int ioflag = ap->a_ioflag;
-	struct buf *bp;
-	struct vattr vattr;
-	struct nfsmount *nmp = VFSTONFS(vp->v_mount);
-	daddr_t lbn;
-	int bufsize;
-	int n, on, error = 0, iomode, must_commit;
-	off_t boff;
-	struct iovec iov;
-	struct uio auio;
-
-#if DIAGNOSTIC
-	if (uio->uio_rw != UIO_WRITE)
-		panic("nfs_write mode");
-	if (uio->uio_segflg == UIO_USERSPACE && uio->uio_procp != current_proc())
-		panic("nfs_write proc");
-#endif
-	if (vp->v_type != VREG)
-		return (EIO);
-	if (np->n_flag & NWRITEERR) {
-		np->n_flag &= ~NWRITEERR;
-		return (np->n_error);
-	}
-	if ((nmp->nm_flag & (NFSMNT_NFSV3 | NFSMNT_GOTFSINFO)) == NFSMNT_NFSV3)
-		(void)nfs_fsinfo(nmp, vp, cred, p);
-	if (ioflag & (IO_APPEND | IO_SYNC)) {
-		if (np->n_flag & NMODIFIED) {
-			np->n_attrstamp = 0;
-			error = nfs_vinvalbuf(vp, V_SAVE, cred, p, 1);
-			if (error)
-				return (error);
-		}
-		if (ioflag & IO_APPEND) {
-			np->n_attrstamp = 0;
-			error = VOP_GETATTR(vp, &vattr, cred, p);
-			if (error)
-				return (error);
-			uio->uio_offset = np->n_size;
-		}
-	}
-	if (uio->uio_offset < 0)
-		return (EINVAL);
-	if (uio->uio_resid == 0)
-		return (0);
-	/*
-	 * Maybe this should be above the vnode op call, but so long as
-	 * file servers have no limits, i don't think it matters
-	 */
-	if (p && uio->uio_offset + uio->uio_resid >
-	      p->p_rlimit[RLIMIT_FSIZE].rlim_cur) {
-		psignal(p, SIGXFSZ);
-		return (EFBIG);
-	}
-	/*
-	 * I use nm_rsize, not nm_wsize so that all buffer cache blocks
-	 * will be the same size within a filesystem. nfs_writerpc will
-	 * still use nm_wsize when sizing the rpc's.
-	 */
-	/*due to getblk/vm interractions, use vm page size or less values */
-	biosize = min(vp->v_mount->mnt_stat.f_iosize, PAGE_SIZE);
+	struct nfsbuf *fbp;
+	struct timeval now;
+	int count;
+	struct nfsbuffreehead nfsbuffreeup;
 
-	do {
-		/*
-		 * Check for a valid write lease.
-		 */
-		if ((nmp->nm_flag & NFSMNT_NQNFS) &&
-		    NQNFS_CKINVALID(vp, np, ND_WRITE)) {
-			do {
-				error = nqnfs_getlease(vp, ND_WRITE, cred, p);
-			} while (error == NQNFS_EXPIRED);
-			if (error)
-				return (error);
-			if (np->n_lrev != np->n_brev ||
-			    (np->n_flag & NQNFSNONCACHE)) {
-				error = nfs_vinvalbuf(vp, V_SAVE, cred, p, 1);
-				if (error)
-					return (error);
-				np->n_brev = np->n_lrev;
-			}
-		}
-		if ((np->n_flag & NQNFSNONCACHE) && uio->uio_iovcnt == 1) {
-		    iomode = NFSV3WRITE_FILESYNC;
-		    error = nfs_writerpc(vp, uio, cred, &iomode, &must_commit);
-		    if (must_commit)
-			nfs_clearcommit(vp->v_mount);
-		    return (error);
-		}
-		nfsstats.biocache_writes++;
-		lbn = uio->uio_offset / biosize;
-		on = uio->uio_offset & (biosize-1);
-		n = min((unsigned)(biosize - on), uio->uio_resid);
-again:
-		bufsize = biosize;
-#if 0
-/* (removed for UBC) */
-		if ((lbn + 1) * biosize > np->n_size) {
-			bufsize = np->n_size - lbn * biosize;
-			bufsize = (bufsize + DEV_BSIZE - 1) & ~(DEV_BSIZE - 1);
-		}
-#endif
-		/*
-		 * Get a cache block for writing.  The range to be written is
-		 * (off..off+len) within the block.  We ensure that the block
-		 * either has no dirty region or that the given range is
-		 * contiguous with the existing dirty region.
-		 */
-		bp = nfs_getcacheblk(vp, lbn, bufsize, p, BLK_WRITE);
-		if (!bp)
-			return (EINTR);
-		/*
-		 * Resize nfsnode *after* we busy the buffer to prevent
-		 * readers from reading garbage.
-		 * If there was a partial buf at the old eof, validate
-		 * and zero the new bytes. 
-		 */
-		if (uio->uio_offset + n > np->n_size) {
-			struct buf *bp0 = NULL;
-			daddr_t bn = np->n_size / biosize;
-			int off = np->n_size & (biosize - 1);
-
-			if (off && bn < lbn && incore(vp, bn))
-				bp0 = nfs_getcacheblk(vp, bn, biosize, p,
-						      BLK_WRITE);
-			np->n_flag |= NMODIFIED;
-			np->n_size = uio->uio_offset + n;
-			ubc_setsize(vp, (off_t)np->n_size); /* XXX errors */
-			if (bp0) {
-				bzero((char *)bp0->b_data + off, biosize - off);
-				bp0->b_validend = biosize;
-				brelse(bp0);
-			}
-		}
-		/*
-		 * NFS has embedded ucred so crhold() risks zone corruption
-		 */
-		if (bp->b_wcred == NOCRED)
-			bp->b_wcred = crdup(cred);
-		/*
-		 * If dirtyend exceeds file size, chop it down.  This should
-		 * not occur unless there is a race.
-		 */
-		if ((off_t)bp->b_blkno * DEV_BSIZE + bp->b_dirtyend >
-		    np->n_size)
-			bp->b_dirtyend = np->n_size - (off_t)bp->b_blkno *
-						      DEV_BSIZE;
-		/*
-		 * UBC doesn't (yet) handle partial pages so nfs_biowrite was
-		 * hacked to never bdwrite, to start every little write right
-		 * away.  Running IE Avie noticed the performance problem, thus
-		 * this code, which permits those delayed writes by ensuring an
-		 * initial read of the entire page.  The read may hit eof
-		 * ("short read") but that we will handle.
-		 *
-		 * We are quite dependant on the correctness of B_CACHE so check
-		 * that first in case of problems.
-		 */
-		if (!ISSET(bp->b_flags, B_CACHE) && n < PAGE_SIZE) {
-			boff = (off_t)bp->b_blkno * DEV_BSIZE;
-			auio.uio_iov = &iov;
-			auio.uio_iovcnt = 1;
-			auio.uio_offset = boff;
-			auio.uio_resid = PAGE_SIZE;
-			auio.uio_segflg = UIO_SYSSPACE;
-			auio.uio_rw = UIO_READ;
-			auio.uio_procp = p;
-			iov.iov_base = bp->b_data;
-			iov.iov_len = PAGE_SIZE;
-			error = nfs_readrpc(vp, &auio, cred);
-			if (error) {
-				bp->b_error = error;
-				SET(bp->b_flags, B_ERROR);
-				printf("nfs_write: readrpc %d", error);
-			}
-			if (auio.uio_resid > 0)
-				bzero(iov.iov_base, auio.uio_resid);
-			bp->b_validoff = 0;
-			bp->b_validend = PAGE_SIZE - auio.uio_resid;
-			if (np->n_size > boff + bp->b_validend)
-				bp->b_validend = min(np->n_size - boff,
-						     PAGE_SIZE);
-			bp->b_dirtyoff = 0;
-			bp->b_dirtyend = 0;
-		}
-	
-		/*
-		 * If the new write will leave a contiguous dirty
-		 * area, just update the b_dirtyoff and b_dirtyend,
-		 * otherwise try to extend the dirty region.
-		 */
-		if (bp->b_dirtyend > 0 &&
-		    (on > bp->b_dirtyend || (on + n) < bp->b_dirtyoff)) {
-			off_t start, end;
-	
-			boff = (off_t)bp->b_blkno * DEV_BSIZE;
-			if (on > bp->b_dirtyend) {
-				start = boff + bp->b_validend;
-				end = boff + on;
-			} else {
-				start = boff + on + n;
-				end = boff + bp->b_validoff;
-			}
-			
-			/*
-			 * It may be that the valid region in the buffer
-			 * covers the region we want, in which case just
-			 * extend the dirty region.  Otherwise we try to
-			 * extend the valid region.
-			 */
-			if (end > start) {
-				auio.uio_iov = &iov;
-				auio.uio_iovcnt = 1;
-				auio.uio_offset = start;
-				auio.uio_resid = end - start;
-				auio.uio_segflg = UIO_SYSSPACE;
-				auio.uio_rw = UIO_READ;
-				auio.uio_procp = p;
-				iov.iov_base = bp->b_data + (start - boff);
-				iov.iov_len = end - start;
-				error = nfs_readrpc(vp, &auio, cred);
-				/*
-				 * If we couldn't read, do not do a VOP_BWRITE
-				 * as originally coded. That could also error
-				 * and looping back to "again" as it was doing
-				 * could have us stuck trying to write same buf
-				 * again. nfs_write, will get the entire region
-				 * if nfs_readrpc succeeded. If unsuccessful
-				 * we should just error out. Errors like ESTALE
-				 * would keep us looping rather than transient
-				 * errors justifying a retry. We can return here
-				 * instead of altering dirty region later.  We
-				 * did not write old dirty region at this point.
-				 */
-				if (error) {
-					bp->b_error = error;
-					SET(bp->b_flags, B_ERROR);
-					printf("nfs_write: readrpc2 %d", error);
-					brelse(bp);
-					return (error);
-				}
-				/*
-				 * The read worked.
-				 * If there was a short read, just zero fill.
-				 */
-				if (auio.uio_resid > 0)
-					bzero(iov.iov_base, auio.uio_resid);
-				if (on > bp->b_dirtyend)
-					bp->b_validend = on;
-				else
-					bp->b_validoff = on + n;
+	TAILQ_INIT(&nfsbuffreeup);
+
+	lck_mtx_lock(nfs_buf_mutex);
+
+	microuptime(&now);
+
+	FSDBG(320, nfsbufcnt, nfsbuffreecnt, nfsbuffreemetacnt, 0);
+
+	count = timer ? nfsbuffreecnt/LRU_FREEUP_FRAC_ON_TIMER : LRU_TO_FREEUP;
+	while ((nfsbufcnt > nfsbufmin) && (count-- > 0)) {
+		fbp = TAILQ_FIRST(&nfsbuffree);
+		if (!fbp)
+			break;
+		if (fbp->nb_refs)
+			break;
+		if (NBUFSTAMPVALID(fbp) &&
+		    (fbp->nb_timestamp + (2*NFSBUF_LRU_STALE)) > now.tv_sec)
+			break;
+		nfs_buf_remfree(fbp);
+		/* disassociate buffer from any nfsnode */
+		if (fbp->nb_np) {
+			if (fbp->nb_vnbufs.le_next != NFSNOLIST) {
+				LIST_REMOVE(fbp, nb_vnbufs);
+				fbp->nb_vnbufs.le_next = NFSNOLIST;
 			}
-			/*
-			 * We now have a valid region which extends up to the
-			 * dirty region which we want.
-			 */
-			if (on > bp->b_dirtyend)
-				bp->b_dirtyend = on;
-			else
-				bp->b_dirtyoff = on + n;
-		}
-		if (ISSET(bp->b_flags, B_ERROR)) {
-			error = bp->b_error;
-			brelse(bp);
-			return (error);
+			fbp->nb_np = NULL;
 		}
-		/*
-		 * NFS has embedded ucred so crhold() risks zone corruption
-		 */
-		if (bp->b_wcred == NOCRED)
-			bp->b_wcred = crdup(cred);
-		np->n_flag |= NMODIFIED;
+		LIST_REMOVE(fbp, nb_hash);
+		TAILQ_INSERT_TAIL(&nfsbuffreeup, fbp, nb_free);
+		nfsbufcnt--;
+	}
 
-		/*
-		 * Check for valid write lease and get one as required.
-		 * In case getblk() and/or bwrite() delayed us.
-		 */
-		if ((nmp->nm_flag & NFSMNT_NQNFS) &&
-		    NQNFS_CKINVALID(vp, np, ND_WRITE)) {
-			do {
-				error = nqnfs_getlease(vp, ND_WRITE, cred, p);
-			} while (error == NQNFS_EXPIRED);
-			if (error) {
-				brelse(bp);
-				return (error);
-			}
-			if (np->n_lrev != np->n_brev ||
-			    (np->n_flag & NQNFSNONCACHE)) {
-				brelse(bp);
-				error = nfs_vinvalbuf(vp, V_SAVE, cred, p, 1);
-				if (error)
-					return (error);
-				np->n_brev = np->n_lrev;
-				goto again;
+	count = timer ? nfsbuffreemetacnt/META_FREEUP_FRAC_ON_TIMER : META_TO_FREEUP;
+	while ((nfsbufcnt > nfsbufmin) && (count-- > 0)) {
+		fbp = TAILQ_FIRST(&nfsbuffreemeta);
+		if (!fbp)
+			break;
+		if (fbp->nb_refs)
+			break;
+		if (NBUFSTAMPVALID(fbp) &&
+		    (fbp->nb_timestamp + (2*NFSBUF_META_STALE)) > now.tv_sec)
+			break;
+		nfs_buf_remfree(fbp);
+		/* disassociate buffer from any nfsnode */
+		if (fbp->nb_np) {
+			if (fbp->nb_vnbufs.le_next != NFSNOLIST) {
+				LIST_REMOVE(fbp, nb_vnbufs);
+				fbp->nb_vnbufs.le_next = NFSNOLIST;
 			}
+			fbp->nb_np = NULL;
 		}
-		error = uiomove((char *)bp->b_data + on, n, uio);
-		if (error) {
-			SET(bp->b_flags, B_ERROR);
-			brelse(bp);
-			return (error);
-		}
-		if (bp->b_dirtyend > 0) {
-			bp->b_dirtyoff = min(on, bp->b_dirtyoff);
-			bp->b_dirtyend = max((on + n), bp->b_dirtyend);
-		} else {
-			bp->b_dirtyoff = on;
-			bp->b_dirtyend = on + n;
-		}
-		if (bp->b_validend == 0 || bp->b_validend < bp->b_dirtyoff ||
-		    bp->b_validoff > bp->b_dirtyend) {
-			bp->b_validoff = bp->b_dirtyoff;
-			bp->b_validend = bp->b_dirtyend;
-		} else {
-			bp->b_validoff = min(bp->b_validoff, bp->b_dirtyoff);
-			bp->b_validend = max(bp->b_validend, bp->b_dirtyend);
-		}
+		LIST_REMOVE(fbp, nb_hash);
+		TAILQ_INSERT_TAIL(&nfsbuffreeup, fbp, nb_free);
+		nfsbufcnt--;
+		nfsbufmetacnt--;
+	}
 
-		/*
-		 * Since this block is being modified, it must be written
-		 * again and not just committed.
-		 */
-		CLR(bp->b_flags, B_NEEDCOMMIT);
+	FSDBG(320, nfsbufcnt, nfsbuffreecnt, nfsbuffreemetacnt, 0);
+	NFSBUFCNTCHK();
+
+	lck_mtx_unlock(nfs_buf_mutex);
+
+	while ((fbp = TAILQ_FIRST(&nfsbuffreeup))) {
+		TAILQ_REMOVE(&nfsbuffreeup, fbp, nb_free);
+		/* nuke any creds */
+		if (IS_VALID_CRED(fbp->nb_rcred))
+			kauth_cred_unref(&fbp->nb_rcred);
+		if (IS_VALID_CRED(fbp->nb_wcred))
+			kauth_cred_unref(&fbp->nb_wcred);
+		/* if buf was NB_META, dump buffer */
+		if (ISSET(fbp->nb_flags, NB_META) && fbp->nb_data)
+			kfree(fbp->nb_data, fbp->nb_bufsize);
+		FREE(fbp, M_TEMP);
+	}
 
-		/*
-		 * If the lease is non-cachable or IO_SYNC do bwrite().
-		 */
-		if ((np->n_flag & NQNFSNONCACHE) || (ioflag & IO_SYNC)) {
-			bp->b_proc = p;
-			error = VOP_BWRITE(bp);
-			if (error)
-				return (error);
-			if (np->n_flag & NQNFSNONCACHE) {
-				error = nfs_vinvalbuf(vp, V_SAVE, cred, p, 1);
-				if (error)
-					return (error);
-			}
-		} else if ((n + on) == biosize &&
-			(nmp->nm_flag & NFSMNT_NQNFS) == 0) {
-			bp->b_proc = (struct proc *)0;
-			SET(bp->b_flags, B_ASYNC);
-			(void)nfs_writebp(bp, 0);
-		} else
-			bdwrite(bp);
-	} while (uio->uio_resid > 0 && n > 0);
-	return (0);
 }
 
+/*
+ * remove a buffer from the freelist
+ * (must be called with nfs_buf_mutex held)
+ */
+void
+nfs_buf_remfree(struct nfsbuf *bp)
+{
+	if (bp->nb_free.tqe_next == NFSNOLIST)
+		panic("nfsbuf not on free list");
+	if (ISSET(bp->nb_flags, NB_DELWRI)) {
+		nfsbufdelwricnt--;
+		TAILQ_REMOVE(&nfsbufdelwri, bp, nb_free);
+	} else if (ISSET(bp->nb_flags, NB_META)) {
+		nfsbuffreemetacnt--;
+		TAILQ_REMOVE(&nfsbuffreemeta, bp, nb_free);
+	} else {
+		nfsbuffreecnt--;
+		TAILQ_REMOVE(&nfsbuffree, bp, nb_free);
+	}
+	bp->nb_free.tqe_next = NFSNOLIST;
+	NFSBUFCNTCHK();
+}
 
 /*
- * Get an nfs cache block.
- * Allocate a new one if the block isn't currently in the cache
- * and return the block marked busy. If the calling process is
- * interrupted by a signal for an interruptible mount point, return
- * NULL.
+ * check for existence of nfsbuf in cache
  */
-static struct buf *
-nfs_getcacheblk(vp, bn, size, p, operation)
-	struct vnode *vp;
-	daddr_t bn;
-	int size;
-	struct proc *p;
-	int operation;	/* defined in sys/buf.h */
+boolean_t
+nfs_buf_is_incore(nfsnode_t np, daddr64_t blkno)
 {
-	register struct buf *bp;
-	struct nfsmount *nmp = VFSTONFS(vp->v_mount);
-	/*due to getblk/vm interractions, use vm page size or less values */
-	int biosize = min(vp->v_mount->mnt_stat.f_iosize, PAGE_SIZE);
+	boolean_t rv;
+	lck_mtx_lock(nfs_buf_mutex);
+	if (nfs_buf_incore(np, blkno))
+		rv = TRUE;
+	else
+		rv = FALSE;
+	lck_mtx_unlock(nfs_buf_mutex);
+	return (rv);
+}
 
-	if (nmp->nm_flag & NFSMNT_INT) {
-		bp = getblk(vp, bn, size, PCATCH, 0, operation);
-		while (bp == (struct buf *)0) {
-			if (nfs_sigintr(nmp, (struct nfsreq *)0, p))
-				return ((struct buf *)0);
-			bp = getblk(vp, bn, size, 0, 2 * hz, operation);
+/*
+ * return incore buffer (must be called with nfs_buf_mutex held)
+ */
+struct nfsbuf *
+nfs_buf_incore(nfsnode_t np, daddr64_t blkno)
+{
+	/* Search hash chain */
+	struct nfsbuf * bp = NFSBUFHASH(np, blkno)->lh_first;
+	for (; bp != NULL; bp = bp->nb_hash.le_next)
+		if ((bp->nb_lblkno == blkno) && (bp->nb_np == np)) {
+			if (!ISSET(bp->nb_flags, NB_INVAL)) {
+				FSDBG(547, bp, blkno, bp->nb_flags, bp->nb_np);
+				return (bp);
+			}
 		}
-	} else
-		bp = getblk(vp, bn, size, 0, 0, operation);
-
-	if( vp->v_type == VREG)
-		bp->b_blkno = (bn * biosize) / DEV_BSIZE;
-
-	return (bp);
+	return (NULL);
 }
 
 /*
- * Flush and invalidate all dirty buffers. If another process is already
- * doing the flush, just wait for completion.
+ * Check if it's OK to drop a page.
+ *
+ * Called by vnode_pager() on pageout request of non-dirty page.
+ * We need to make sure that it's not part of a delayed write.
+ * If it is, we can't let the VM drop it because we may need it
+ * later when/if we need to write the data (again).
  */
 int
-nfs_vinvalbuf(vp, flags, cred, p, intrflg)
-	struct vnode *vp;
-	int flags;
-	struct ucred *cred;
-	struct proc *p;
-	int intrflg;
+nfs_buf_page_inval(vnode_t vp, off_t offset)
 {
-	register struct nfsnode *np = VTONFS(vp);
-	struct nfsmount *nmp = VFSTONFS(vp->v_mount);
-	int error = 0, slpflag, slptimeo;
-	int didhold = 0;
+	struct nfsmount *nmp = VTONMP(vp);
+	struct nfsbuf *bp;
+	int error = 0;
 
-	if ((nmp->nm_flag & NFSMNT_INT) == 0)
-		intrflg = 0;
-	if (intrflg) {
-		slpflag = PCATCH;
-		slptimeo = 2 * hz;
-	} else {
-		slpflag = 0;
-		slptimeo = 0;
+	if (!nmp)
+		return (ENXIO);
+
+	lck_mtx_lock(nfs_buf_mutex);
+	bp = nfs_buf_incore(VTONFS(vp), (daddr64_t)(offset / nmp->nm_biosize));
+	if (!bp)
+		goto out;
+	FSDBG(325, bp, bp->nb_flags, bp->nb_dirtyoff, bp->nb_dirtyend);
+	if (ISSET(bp->nb_lflags, NBL_BUSY)) {
+		error = EBUSY;
+		goto out;
 	}
 	/*
-	 * First wait for any other process doing a flush to complete.
+	 * If there's a dirty range in the buffer, check to
+	 * see if this page intersects with the dirty range.
+	 * If it does, we can't let the pager drop the page.
 	 */
-	while (np->n_flag & NFLUSHINPROG) {
-		np->n_flag |= NFLUSHWANT;
-		error = tsleep((caddr_t)&np->n_flag, PRIBIO + 2, "nfsvinval",
-			slptimeo);
-		if (error && intrflg && nfs_sigintr(nmp, (struct nfsreq *)0, p))
-			return (EINTR);
+	if (bp->nb_dirtyend > 0) {
+		int start = offset - NBOFF(bp);
+		if ((bp->nb_dirtyend > start) &&
+		    (bp->nb_dirtyoff < (start + PAGE_SIZE))) {
+			/*
+			 * Before returning the bad news, move the
+			 * buffer to the start of the delwri list and
+			 * give the list a push to try to flush the
+			 * buffer out.
+			 */
+			error = EBUSY;
+			nfs_buf_remfree(bp);
+			TAILQ_INSERT_HEAD(&nfsbufdelwri, bp, nb_free);
+			nfsbufdelwricnt++;
+			nfs_buf_delwri_push(1);
+		}
 	}
+out:
+	lck_mtx_unlock(nfs_buf_mutex);
+	return (error);
+}
 
-	/*
-	 * Now, flush as required.
-	 */
-	np->n_flag |= NFLUSHINPROG;
-	error = vinvalbuf(vp, flags, cred, p, slpflag, 0);
-	while (error) {
-		/* we seem to be stuck in a loop here if the thread got aborted.
-		 * nfs_flush will return EINTR. Not sure if that will cause
-		 * other consequences due to EINTR having other meanings in NFS
-		 * To handle, no dirty pages, it seems safe to just return from
-		 * here. But if we did have dirty pages, how would we get them
-		 * written out if thread was aborted? Some other strategy is
-		 * necessary. -- EKN
+/*
+ * set up the UPL for a buffer
+ * (must NOT be called with nfs_buf_mutex held)
+ */
+int
+nfs_buf_upl_setup(struct nfsbuf *bp)
+{
+	kern_return_t kret;
+	upl_t upl;
+	int upl_flags;
+
+	if (ISSET(bp->nb_flags, NB_PAGELIST))
+		return (0);
+
+	upl_flags = UPL_PRECIOUS;
+	if (!ISSET(bp->nb_flags, NB_READ)) {
+		/*
+		 * We're doing a "write", so we intend to modify
+		 * the pages we're gathering.
 		 */
-		if ((intrflg && nfs_sigintr(nmp, (struct nfsreq *)0, p)) ||
-		    (error == EINTR && current_thread_aborted())) {
-			np->n_flag &= ~NFLUSHINPROG;
-			if (np->n_flag & NFLUSHWANT) {
-				np->n_flag &= ~NFLUSHWANT;
-				wakeup((caddr_t)&np->n_flag);
-			}
-			return (EINTR);
-		}
-		error = vinvalbuf(vp, flags, cred, p, 0, slptimeo);
+		upl_flags |= UPL_WILL_MODIFY;
 	}
-	np->n_flag &= ~(NMODIFIED | NFLUSHINPROG);
-	if (np->n_flag & NFLUSHWANT) {
-		np->n_flag &= ~NFLUSHWANT;
-		wakeup((caddr_t)&np->n_flag);
+	kret = ubc_create_upl(NFSTOV(bp->nb_np), NBOFF(bp), bp->nb_bufsize,
+				&upl, NULL, upl_flags);
+	if (kret == KERN_INVALID_ARGUMENT) {
+		/* vm object probably doesn't exist any more */
+		bp->nb_pagelist = NULL;
+		return (EINVAL);
 	}
-	didhold = ubc_hold(vp);
-	if (didhold) {
-		(void) ubc_clean(vp, 1); /* get the pages out of vm also */
-		ubc_rele(vp);
+	if (kret != KERN_SUCCESS) {
+		printf("nfs_buf_upl_setup(): failed to get pagelist %d\n", kret);
+		bp->nb_pagelist = NULL;
+		return (EIO);
 	}
+
+	FSDBG(538, bp, NBOFF(bp), bp->nb_bufsize, bp->nb_np);
+
+	bp->nb_pagelist = upl;
+	SET(bp->nb_flags, NB_PAGELIST);
 	return (0);
 }
 
 /*
- * Initiate asynchronous I/O. Return an error if no nfsiods are available.
- * This is mainly to avoid queueing async I/O requests when the nfsiods
- * are all hung on a dead server.
+ * update buffer's valid/dirty info from UBC
+ * (must NOT be called with nfs_buf_mutex held)
  */
-int
-nfs_asyncio(bp, cred)
-	register struct buf *bp;
-	struct ucred *cred;
+void
+nfs_buf_upl_check(struct nfsbuf *bp)
 {
-	struct nfsmount *nmp;
-	int i;
-	int gotiod;
-	int slpflag = 0;
-	int slptimeo = 0;
-	int error;
+	upl_page_info_t *pl;
+	off_t filesize, fileoffset;
+	int i, npages;
 
-	if (nfs_numasync == 0)
-		return (EIO);
-	
-	nmp = VFSTONFS(bp->b_vp->v_mount);
-again:
-	if (nmp->nm_flag & NFSMNT_INT)
-		slpflag = PCATCH;
-	gotiod = FALSE;
+	if (!ISSET(bp->nb_flags, NB_PAGELIST))
+		return;
 
-	/*
-	 * Find a free iod to process this request.
-	 */
-	for (i = 0; i < NFS_MAXASYNCDAEMON; i++)
-		if (nfs_iodwant[i]) {
-			/*
-			 * Found one, so wake it up and tell it which
-			 * mount to process.
-			 */
-			NFS_DPF(ASYNCIO,
-				("nfs_asyncio: waking iod %d for mount %p\n",
-				 i, nmp));
-			nfs_iodwant[i] = (struct proc *)0;
-			nfs_iodmount[i] = nmp;
-			nmp->nm_bufqiods++;
-			wakeup((caddr_t)&nfs_iodwant[i]);
-			gotiod = TRUE;
-			break;
-		}
+	npages = round_page_32(bp->nb_bufsize) / PAGE_SIZE;
+	filesize = ubc_getsize(NFSTOV(bp->nb_np));
+	fileoffset = NBOFF(bp);
+	if (fileoffset < filesize)
+		SET(bp->nb_flags, NB_CACHE);
+	else
+		CLR(bp->nb_flags, NB_CACHE);
 
-	/*
-	 * If none are free, we may already have an iod working on this mount
-	 * point.  If so, it will process our request.
-	 */
-	if (!gotiod) {
-		if (nmp->nm_bufqiods > 0) {
-			NFS_DPF(ASYNCIO,
-				("nfs_asyncio: %d iods are already processing mount %p\n",
-				 nmp->nm_bufqiods, nmp));
-			gotiod = TRUE;
+	pl = ubc_upl_pageinfo(bp->nb_pagelist);
+	bp->nb_valid = bp->nb_dirty = 0;
+
+	for (i=0; i < npages; i++, fileoffset += PAGE_SIZE_64) {
+		/* anything beyond the end of the file is not valid or dirty */
+		if (fileoffset >= filesize)
+			break;
+		if (!upl_valid_page(pl, i)) {
+			CLR(bp->nb_flags, NB_CACHE);
+			continue;
 		}
+		NBPGVALID_SET(bp,i);
+		if (upl_dirty_page(pl, i))
+			NBPGDIRTY_SET(bp, i);
+	}
+	fileoffset = NBOFF(bp);
+	if (ISSET(bp->nb_flags, NB_CACHE)) {
+		bp->nb_validoff = 0;
+		bp->nb_validend = bp->nb_bufsize;
+		if (fileoffset + bp->nb_validend > filesize)
+			bp->nb_validend = filesize - fileoffset;
+	} else {
+		bp->nb_validoff = bp->nb_validend = -1;
+	}
+	FSDBG(539, bp, fileoffset, bp->nb_valid, bp->nb_dirty);
+	FSDBG(539, bp->nb_validoff, bp->nb_validend, bp->nb_dirtyoff, bp->nb_dirtyend);
+}
+
+/*
+ * make sure that a buffer is mapped
+ * (must NOT be called with nfs_buf_mutex held)
+ */
+int
+nfs_buf_map(struct nfsbuf *bp)
+{
+	kern_return_t kret;
+
+	if (bp->nb_data)
+		return (0);
+	if (!ISSET(bp->nb_flags, NB_PAGELIST))
+		return (EINVAL);
+
+	kret = ubc_upl_map(bp->nb_pagelist, (vm_offset_t *)&(bp->nb_data));
+	if (kret != KERN_SUCCESS)
+		panic("nfs_buf_map: ubc_upl_map() failed with (%d)", kret);
+	if (bp->nb_data == 0)
+		panic("ubc_upl_map mapped 0");
+	FSDBG(540, bp, bp->nb_flags, NBOFF(bp), bp->nb_data);
+	return (0);
+}
+
+/*
+ * normalize an nfsbuf's valid range
+ *
+ * the read/write code guarantees that we'll always have a valid
+ * region that is an integral number of pages.  If either end
+ * of the valid range isn't page-aligned, it gets corrected
+ * here as we extend the valid range through all of the
+ * contiguous valid pages.
+ */
+void
+nfs_buf_normalize_valid_range(nfsnode_t np, struct nfsbuf *bp)
+{
+	int pg, npg;
+	/* pull validoff back to start of contiguous valid page range */
+	pg = bp->nb_validoff/PAGE_SIZE;
+	while (pg >= 0 && NBPGVALID(bp,pg))
+		pg--;
+	bp->nb_validoff = (pg+1) * PAGE_SIZE;
+	/* push validend forward to end of contiguous valid page range */
+	npg = bp->nb_bufsize/PAGE_SIZE;
+	pg = bp->nb_validend/PAGE_SIZE;
+	while (pg < npg && NBPGVALID(bp,pg))
+		pg++;
+	bp->nb_validend = pg * PAGE_SIZE;
+	/* clip to EOF */
+	if (NBOFF(bp) + bp->nb_validend > (off_t)np->n_size)
+		bp->nb_validend = np->n_size % bp->nb_bufsize;
+}
+
+/*
+ * process some entries on the delayed write queue
+ * (must be called with nfs_buf_mutex held)
+ */
+void
+nfs_buf_delwri_service(void)
+{
+	struct nfsbuf *bp;
+	nfsnode_t np;
+	int error, i = 0;
+
+	while (i < 8 && (bp = TAILQ_FIRST(&nfsbufdelwri)) != NULL) {
+		np = bp->nb_np;
+		nfs_buf_remfree(bp);
+		nfs_buf_refget(bp);
+		while ((error = nfs_buf_acquire(bp, 0, 0, 0)) == EAGAIN);
+		nfs_buf_refrele(bp);
+		if (error)
+			break;
+		if (!bp->nb_np) {
+			/* buffer is no longer valid */
+			nfs_buf_drop(bp);
+			continue;
+		}
+		if (ISSET(bp->nb_flags, NB_NEEDCOMMIT))
+			nfs_buf_check_write_verifier(np, bp);
+		if (ISSET(bp->nb_flags, NB_NEEDCOMMIT)) {
+			/* put buffer at end of delwri list */
+			TAILQ_INSERT_TAIL(&nfsbufdelwri, bp, nb_free);
+			nfsbufdelwricnt++;
+			nfs_buf_drop(bp);
+			lck_mtx_unlock(nfs_buf_mutex);
+			nfs_flushcommits(np, 1);
+		} else {
+			SET(bp->nb_flags, NB_ASYNC);
+			lck_mtx_unlock(nfs_buf_mutex);
+			nfs_buf_write(bp);
+		}
+		i++;
+		lck_mtx_lock(nfs_buf_mutex);
+	}
+}
+
+/*
+ * thread to service the delayed write queue when asked
+ */
+void
+nfs_buf_delwri_thread(__unused void *arg, __unused wait_result_t wr)
+{
+	struct timespec ts = { 30, 0 };
+	int error = 0;
+
+	lck_mtx_lock(nfs_buf_mutex);
+	while (!error) {
+		nfs_buf_delwri_service();
+		error = msleep(&nfsbufdelwrithd, nfs_buf_mutex, 0, "nfsbufdelwri", &ts);
+	}
+	nfsbufdelwrithd = NULL;
+	lck_mtx_unlock(nfs_buf_mutex);
+	thread_terminate(nfsbufdelwrithd);
+}
+
+/*
+ * try to push out some delayed/uncommitted writes
+ * ("locked" indicates whether nfs_buf_mutex is already held)
+ */
+void
+nfs_buf_delwri_push(int locked)
+{
+	if (TAILQ_EMPTY(&nfsbufdelwri))
+		return;
+	if (!locked)
+		lck_mtx_lock(nfs_buf_mutex);
+	/* wake up the delayed write service thread */
+	if (nfsbufdelwrithd)
+		wakeup(&nfsbufdelwrithd);
+	else if (kernel_thread_start(nfs_buf_delwri_thread, NULL, &nfsbufdelwrithd) == KERN_SUCCESS)
+		thread_deallocate(nfsbufdelwrithd);
+	/* otherwise, try to do some of the work ourselves */
+	if (!nfsbufdelwrithd)
+		nfs_buf_delwri_service();
+	if (!locked)
+		lck_mtx_unlock(nfs_buf_mutex);
+}
+
+/*
+ * Get an nfs buffer.
+ *
+ * Returns errno on error, 0 otherwise.
+ * Any buffer is returned in *bpp.
+ *
+ * If NBLK_ONLYVALID is set, only return buffer if found in cache.
+ * If NBLK_NOWAIT is set, don't wait for the buffer if it's marked BUSY.
+ *
+ * Check for existence of buffer in cache.
+ * Or attempt to reuse a buffer from one of the free lists.
+ * Or allocate a new buffer if we haven't already hit max allocation.
+ * Or wait for a free buffer.
+ *
+ * If available buffer found, prepare it, and return it.
+ *
+ * If the calling process is interrupted by a signal for
+ * an interruptible mount point, return EINTR.
+ */
+int
+nfs_buf_get(
+	nfsnode_t np,
+	daddr64_t blkno,
+	uint32_t size,
+	thread_t thd,
+	int flags,
+	struct nfsbuf **bpp)
+{
+	vnode_t vp = NFSTOV(np);
+	struct nfsmount *nmp = VTONMP(vp);
+	struct nfsbuf *bp;
+	uint32_t bufsize;
+	int slpflag = PCATCH;
+	int operation = (flags & NBLK_OPMASK);
+	int error = 0;
+	struct timespec ts;
+
+	FSDBG_TOP(541, np, blkno, size, flags);
+	*bpp = NULL;
+
+	bufsize = size;
+	if (bufsize > NFS_MAXBSIZE)
+		panic("nfs_buf_get: buffer larger than NFS_MAXBSIZE requested");
+
+	if (!nmp) {
+		FSDBG_BOT(541, np, blkno, 0, ENXIO);
+		return (ENXIO);
+	}
+
+	if (!UBCINFOEXISTS(vp)) {
+		operation = NBLK_META;
+	} else if (bufsize < (uint32_t)nmp->nm_biosize) {
+		/* reg files should always have biosize blocks */
+		bufsize = nmp->nm_biosize;
+	}
+
+	/* if NBLK_WRITE, check for too many delayed/uncommitted writes */
+	if ((operation == NBLK_WRITE) && (nfs_nbdwrite > NFS_A_LOT_OF_DELAYED_WRITES)) {
+		FSDBG_TOP(542, np, blkno, nfs_nbdwrite, NFS_A_LOT_OF_DELAYED_WRITES);
+
+		/* poke the delwri list */
+		nfs_buf_delwri_push(0);
+
+		/* sleep to let other threads run... */
+		tsleep(&nfs_nbdwrite, PCATCH, "nfs_nbdwrite", 1);
+		FSDBG_BOT(542, np, blkno, nfs_nbdwrite, NFS_A_LOT_OF_DELAYED_WRITES);
+	}
+
+loop:
+	lck_mtx_lock(nfs_buf_mutex);
+
+	/* check for existence of nfsbuf in cache */
+	if ((bp = nfs_buf_incore(np, blkno))) {
+		/* if busy, set wanted and wait */
+		if (ISSET(bp->nb_lflags, NBL_BUSY)) {
+			if (flags & NBLK_NOWAIT) {
+				lck_mtx_unlock(nfs_buf_mutex);
+				FSDBG_BOT(541, np, blkno, bp, 0xbcbcbcbc);
+				return (0);
+			}
+			FSDBG_TOP(543, np, blkno, bp, bp->nb_flags);
+			SET(bp->nb_lflags, NBL_WANTED);
+
+			ts.tv_sec = 2;
+			ts.tv_nsec = 0;
+			msleep(bp, nfs_buf_mutex, slpflag|(PRIBIO+1)|PDROP,
+					"nfsbufget", (slpflag == PCATCH) ? NULL : &ts);
+			slpflag = 0;
+			FSDBG_BOT(543, np, blkno, bp, bp->nb_flags);
+			if ((error = nfs_sigintr(VTONMP(vp), NULL, thd, 0))) {
+				FSDBG_BOT(541, np, blkno, 0, error);
+				return (error);
+			}
+			goto loop;
+		}
+		if (bp->nb_bufsize != bufsize)
+			panic("nfsbuf size mismatch");
+		SET(bp->nb_lflags, NBL_BUSY);
+		SET(bp->nb_flags, NB_CACHE);
+		nfs_buf_remfree(bp);
+		/* additional paranoia: */
+		if (ISSET(bp->nb_flags, NB_PAGELIST))
+			panic("pagelist buffer was not busy");
+		goto buffer_setup;
+	}
+
+	if (flags & NBLK_ONLYVALID) {
+		lck_mtx_unlock(nfs_buf_mutex);
+		FSDBG_BOT(541, np, blkno, 0, 0x0000cace);
+		return (0);
+	}
+
+	/*
+	 * where to get a free buffer:
+	 * - if meta and maxmeta reached, must reuse meta
+	 * - alloc new if we haven't reached min bufs
+	 * - if free lists are NOT empty
+	 *   - if free list is stale, use it
+	 *   - else if freemeta list is stale, use it
+	 *   - else if max bufs allocated, use least-time-to-stale
+	 * - alloc new if we haven't reached max allowed
+	 * - start clearing out delwri list and try again
+	 */
+
+	if ((operation == NBLK_META) && (nfsbufmetacnt >= nfsbufmetamax)) {
+		/* if we've hit max meta buffers, must reuse a meta buffer */
+		bp = TAILQ_FIRST(&nfsbuffreemeta);
+	} else if ((nfsbufcnt > nfsbufmin) &&
+	    (!TAILQ_EMPTY(&nfsbuffree) || !TAILQ_EMPTY(&nfsbuffreemeta))) {
+		/* try to pull an nfsbuf off a free list */
+		struct nfsbuf *lrubp, *metabp;
+		struct timeval now;
+		microuptime(&now);
+
+		/* if the next LRU or META buffer is invalid or stale, use it */
+		lrubp = TAILQ_FIRST(&nfsbuffree);
+		if (lrubp && (!NBUFSTAMPVALID(lrubp) ||
+		    ((lrubp->nb_timestamp + NFSBUF_LRU_STALE) < now.tv_sec)))
+			bp = lrubp;
+		metabp = TAILQ_FIRST(&nfsbuffreemeta);
+		if (!bp && metabp && (!NBUFSTAMPVALID(metabp) ||
+		    ((metabp->nb_timestamp + NFSBUF_META_STALE) < now.tv_sec)))
+			bp = metabp;
+
+		if (!bp && (nfsbufcnt >= nfsbufmax)) {
+			/* we've already allocated all bufs, so */
+			/* choose the buffer that'll go stale first */
+			if (!metabp)
+				bp = lrubp;
+			else if (!lrubp)
+				bp = metabp;
+			else {
+				int32_t lru_stale_time, meta_stale_time;
+				lru_stale_time = lrubp->nb_timestamp + NFSBUF_LRU_STALE;
+				meta_stale_time = metabp->nb_timestamp + NFSBUF_META_STALE;
+				if (lru_stale_time <= meta_stale_time)
+					bp = lrubp;
+				else
+					bp = metabp;
+			}
+		}
+	}
+
+	if (bp) {
+		/* we have a buffer to reuse */
+		FSDBG(544, np, blkno, bp, bp->nb_flags);
+		nfs_buf_remfree(bp);
+		if (ISSET(bp->nb_flags, NB_DELWRI))
+			panic("nfs_buf_get: delwri");
+		SET(bp->nb_lflags, NBL_BUSY);
+		/* disassociate buffer from previous nfsnode */
+		if (bp->nb_np) {
+			if (bp->nb_vnbufs.le_next != NFSNOLIST) {
+				LIST_REMOVE(bp, nb_vnbufs);
+				bp->nb_vnbufs.le_next = NFSNOLIST;
+			}
+			bp->nb_np = NULL;
+		}
+		LIST_REMOVE(bp, nb_hash);
+		/* nuke any creds we're holding */
+		if (IS_VALID_CRED(bp->nb_rcred))
+			kauth_cred_unref(&bp->nb_rcred);
+		if (IS_VALID_CRED(bp->nb_wcred))
+			kauth_cred_unref(&bp->nb_wcred);
+		/* if buf will no longer be NB_META, dump old buffer */
+		if (operation == NBLK_META) {
+			if (!ISSET(bp->nb_flags, NB_META))
+				nfsbufmetacnt++;
+		} else if (ISSET(bp->nb_flags, NB_META)) {
+			if (bp->nb_data) {
+				kfree(bp->nb_data, bp->nb_bufsize);
+				bp->nb_data = NULL;
+			}
+			nfsbufmetacnt--;
+		}
+		/* re-init buf fields */
+		bp->nb_error = 0;
+		bp->nb_validoff = bp->nb_validend = -1;
+		bp->nb_dirtyoff = bp->nb_dirtyend = 0;
+		bp->nb_valid = 0;
+		bp->nb_dirty = 0;
+		bp->nb_verf = 0;
+	} else {
+		/* no buffer to reuse */
+		if ((nfsbufcnt < nfsbufmax) &&
+		    ((operation != NBLK_META) || (nfsbufmetacnt < nfsbufmetamax))) {
+			/* just alloc a new one */
+			MALLOC(bp, struct nfsbuf *, sizeof(struct nfsbuf), M_TEMP, M_WAITOK);
+			if (!bp) {
+				lck_mtx_unlock(nfs_buf_mutex);
+				FSDBG_BOT(541, np, blkno, 0, error);
+				return (ENOMEM);
+			}
+			nfsbufcnt++;
+
+			/*
+			 * If any excess bufs, make sure the timer
+			 * is running to free them up later.
+			 */
+			if (nfsbufcnt > nfsbufmin && !nfs_buf_timer_on) {
+				nfs_buf_timer_on = 1;
+				nfs_interval_timer_start(nfs_buf_timer_call,
+					NFSBUF_FREE_PERIOD * 1000);
+			}
+
+			if (operation == NBLK_META)
+				nfsbufmetacnt++;
+			NFSBUFCNTCHK();
+			/* init nfsbuf */
+			bzero(bp, sizeof(*bp));
+			bp->nb_free.tqe_next = NFSNOLIST;
+			bp->nb_validoff = bp->nb_validend = -1;
+			FSDBG(545, np, blkno, bp, 0);
+		} else {
+			/* too many bufs... wait for buffers to free up */
+			FSDBG_TOP(546, np, blkno, nfsbufcnt, nfsbufmax);
+
+			/* poke the delwri list */
+			nfs_buf_delwri_push(1);
+
+			nfsneedbuffer = 1;
+			msleep(&nfsneedbuffer, nfs_buf_mutex, PCATCH|PDROP, "nfsbufget", NULL);
+			FSDBG_BOT(546, np, blkno, nfsbufcnt, nfsbufmax);
+			if ((error = nfs_sigintr(VTONMP(vp), NULL, thd, 0))) {
+				FSDBG_BOT(541, np, blkno, 0, error);
+				return (error);
+			}
+			goto loop;
+		}
+	}
+
+	/* set up nfsbuf */
+	SET(bp->nb_lflags, NBL_BUSY);
+	bp->nb_flags = 0;
+	bp->nb_lblkno = blkno;
+	/* insert buf in hash */
+	LIST_INSERT_HEAD(NFSBUFHASH(np, blkno), bp, nb_hash);
+	/* associate buffer with new nfsnode */
+	bp->nb_np = np;
+	LIST_INSERT_HEAD(&np->n_cleanblkhd, bp, nb_vnbufs);
+
+buffer_setup:
+
+	/* unlock hash */
+	lck_mtx_unlock(nfs_buf_mutex);
+
+	switch (operation) {
+	case NBLK_META:
+		SET(bp->nb_flags, NB_META);
+		if ((bp->nb_bufsize != bufsize) && bp->nb_data) {
+			kfree(bp->nb_data, bp->nb_bufsize);
+			bp->nb_data = NULL;
+			bp->nb_validoff = bp->nb_validend = -1;
+			bp->nb_dirtyoff = bp->nb_dirtyend = 0;
+			bp->nb_valid = 0;
+			bp->nb_dirty = 0;
+			CLR(bp->nb_flags, NB_CACHE);
+		}
+		if (!bp->nb_data)
+			bp->nb_data = kalloc(bufsize);
+		if (!bp->nb_data) {
+			/* Ack! couldn't allocate the data buffer! */
+			/* clean up buffer and return error */
+			lck_mtx_lock(nfs_buf_mutex);
+			LIST_REMOVE(bp, nb_vnbufs);
+			bp->nb_vnbufs.le_next = NFSNOLIST;
+			bp->nb_np = NULL;
+			/* invalidate usage timestamp to allow immediate freeing */
+			NBUFSTAMPINVALIDATE(bp);
+			if (bp->nb_free.tqe_next != NFSNOLIST)
+				panic("nfsbuf on freelist");
+			TAILQ_INSERT_HEAD(&nfsbuffree, bp, nb_free);
+			nfsbuffreecnt++;
+			lck_mtx_unlock(nfs_buf_mutex);
+			FSDBG_BOT(541, np, blkno, 0xb00, ENOMEM);
+			return (ENOMEM);
+		}
+		bp->nb_bufsize = bufsize;
+		break;
+
+	case NBLK_READ:
+	case NBLK_WRITE:
+		/*
+		 * Set or clear NB_READ now to let the UPL subsystem know
+		 * if we intend to modify the pages or not.
+		 */
+		if (operation == NBLK_READ) {
+			SET(bp->nb_flags, NB_READ);
+		} else {
+			CLR(bp->nb_flags, NB_READ);
+		}
+		if (bufsize < PAGE_SIZE)
+			bufsize = PAGE_SIZE;
+		bp->nb_bufsize = bufsize;
+		bp->nb_validoff = bp->nb_validend = -1;
+
+		if (UBCINFOEXISTS(vp)) {
+			/* set up upl */
+			if (nfs_buf_upl_setup(bp)) {
+				/* unable to create upl */
+				/* vm object must no longer exist */
+				/* clean up buffer and return error */
+				lck_mtx_lock(nfs_buf_mutex);
+				LIST_REMOVE(bp, nb_vnbufs);
+				bp->nb_vnbufs.le_next = NFSNOLIST;
+				bp->nb_np = NULL;
+				/* invalidate usage timestamp to allow immediate freeing */
+				NBUFSTAMPINVALIDATE(bp);
+				if (bp->nb_free.tqe_next != NFSNOLIST)
+					panic("nfsbuf on freelist");
+				TAILQ_INSERT_HEAD(&nfsbuffree, bp, nb_free);
+				nfsbuffreecnt++;
+				lck_mtx_unlock(nfs_buf_mutex);
+				FSDBG_BOT(541, np, blkno, 0x2bc, EIO);
+				return (EIO);
+			}
+			nfs_buf_upl_check(bp);
+		}
+		break;
+
+	default:
+		panic("nfs_buf_get: %d unknown operation", operation);
+	}
+
+	*bpp = bp;
+
+	FSDBG_BOT(541, np, blkno, bp, bp->nb_flags);
+
+	return (0);
+}
+
+void
+nfs_buf_release(struct nfsbuf *bp, int freeup)
+{
+	nfsnode_t np = bp->nb_np;
+	vnode_t vp;
+	struct timeval now;
+	int wakeup_needbuffer, wakeup_buffer, wakeup_nbdwrite;
+
+	FSDBG_TOP(548, bp, NBOFF(bp), bp->nb_flags, bp->nb_data);
+	FSDBG(548, bp->nb_validoff, bp->nb_validend, bp->nb_dirtyoff, bp->nb_dirtyend);
+	FSDBG(548, bp->nb_valid, 0, bp->nb_dirty, 0);
+
+	vp = np ? NFSTOV(np) : NULL;
+	if (vp && UBCINFOEXISTS(vp) && bp->nb_bufsize) {
+		int upl_flags, rv;
+		upl_t upl;
+		uint32_t i;
+
+		if (!ISSET(bp->nb_flags, NB_PAGELIST) && !ISSET(bp->nb_flags, NB_INVAL)) {
+			rv = nfs_buf_upl_setup(bp);
+			if (rv)
+				printf("nfs_buf_release: upl create failed %d\n", rv);
+			else
+				nfs_buf_upl_check(bp);
+		}
+		upl = bp->nb_pagelist;
+		if (!upl)
+			goto pagelist_cleanup_done;
+		if (bp->nb_data) {
+			if (ubc_upl_unmap(upl) != KERN_SUCCESS)
+				panic("ubc_upl_unmap failed");
+			bp->nb_data = NULL;
+		}
+		/*
+		 * Abort the pages on error or: if this is an invalid or
+		 * non-needcommit nocache buffer AND no pages are dirty.
+		 */
+		if (ISSET(bp->nb_flags, NB_ERROR) || (!bp->nb_dirty && (ISSET(bp->nb_flags, NB_INVAL) ||
+		    (ISSET(bp->nb_flags, NB_NOCACHE) && !ISSET(bp->nb_flags, (NB_NEEDCOMMIT | NB_DELWRI)))))) {
+			if (ISSET(bp->nb_flags, (NB_READ | NB_INVAL | NB_NOCACHE)))
+				upl_flags = UPL_ABORT_DUMP_PAGES;
+			else
+				upl_flags = 0;
+			ubc_upl_abort(upl, upl_flags);
+			goto pagelist_cleanup_done;
+		}
+		for (i=0; i <= (bp->nb_bufsize - 1)/PAGE_SIZE; i++) {
+			if (!NBPGVALID(bp,i))
+				ubc_upl_abort_range(upl,
+					i*PAGE_SIZE, PAGE_SIZE,
+					UPL_ABORT_DUMP_PAGES |
+					UPL_ABORT_FREE_ON_EMPTY);
+			else {
+				if (NBPGDIRTY(bp,i))
+					upl_flags = UPL_COMMIT_SET_DIRTY;
+				else
+					upl_flags = UPL_COMMIT_CLEAR_DIRTY;
+				
+				if (!ISSET(bp->nb_flags, (NB_NEEDCOMMIT | NB_DELWRI)))
+					upl_flags |= UPL_COMMIT_CLEAR_PRECIOUS;
+
+				ubc_upl_commit_range(upl,
+					i*PAGE_SIZE, PAGE_SIZE,
+					upl_flags |
+					UPL_COMMIT_INACTIVATE |
+					UPL_COMMIT_FREE_ON_EMPTY);
+			}
+		}
+pagelist_cleanup_done:
+		/* invalidate any pages past EOF */
+		if (NBOFF(bp) + bp->nb_bufsize > (off_t)(np->n_size)) {
+			off_t start, end;
+			start = trunc_page_64(np->n_size) + PAGE_SIZE_64;
+			end = trunc_page_64(NBOFF(bp) + bp->nb_bufsize);
+			if (start < NBOFF(bp))
+				start = NBOFF(bp);
+			if (end > start) {
+				if (!(rv = ubc_sync_range(vp, start, end, UBC_INVALIDATE)))
+					printf("nfs_buf_release(): ubc_sync_range failed!\n");
+			}
+		}
+		CLR(bp->nb_flags, NB_PAGELIST);
+		bp->nb_pagelist = NULL;
+	}
+
+	lck_mtx_lock(nfs_buf_mutex);
+
+	wakeup_needbuffer = wakeup_buffer = wakeup_nbdwrite = 0;
+
+	/* Wake up any processes waiting for any buffer to become free. */
+	if (nfsneedbuffer) {
+		nfsneedbuffer = 0;
+		wakeup_needbuffer = 1;
+	}
+	/* Wake up any processes waiting for _this_ buffer to become free. */
+	if (ISSET(bp->nb_lflags, NBL_WANTED)) {
+		CLR(bp->nb_lflags, NBL_WANTED);
+		wakeup_buffer = 1;
+	}
+
+	/* If it's non-needcommit nocache, or an error, mark it invalid. */
+	if (ISSET(bp->nb_flags, NB_ERROR) ||
+	    (ISSET(bp->nb_flags, NB_NOCACHE) && !ISSET(bp->nb_flags, (NB_NEEDCOMMIT | NB_DELWRI))))
+		SET(bp->nb_flags, NB_INVAL);
+
+	if ((bp->nb_bufsize <= 0) || ISSET(bp->nb_flags, NB_INVAL)) {
+		/* If it's invalid or empty, dissociate it from its nfsnode */
+		if (bp->nb_vnbufs.le_next != NFSNOLIST) {
+			LIST_REMOVE(bp, nb_vnbufs);
+			bp->nb_vnbufs.le_next = NFSNOLIST;
+		}
+		bp->nb_np = NULL;
+		/* if this was a delayed write, wakeup anyone */
+		/* waiting for delayed writes to complete */
+		if (ISSET(bp->nb_flags, NB_DELWRI)) {
+			CLR(bp->nb_flags, NB_DELWRI);
+			nfs_nbdwrite--;
+			NFSBUFCNTCHK();
+			wakeup_nbdwrite = 1;
+		}
+		/* invalidate usage timestamp to allow immediate freeing */
+		NBUFSTAMPINVALIDATE(bp);
+		/* put buffer at head of free list */
+		if (bp->nb_free.tqe_next != NFSNOLIST)
+			panic("nfsbuf on freelist");
+		SET(bp->nb_flags, NB_INVAL);
+		if (ISSET(bp->nb_flags, NB_META)) {
+			TAILQ_INSERT_HEAD(&nfsbuffreemeta, bp, nb_free);
+			nfsbuffreemetacnt++;
+		} else {
+			TAILQ_INSERT_HEAD(&nfsbuffree, bp, nb_free);
+			nfsbuffreecnt++;
+		}
+	} else if (ISSET(bp->nb_flags, NB_DELWRI)) {
+		/* put buffer at end of delwri list */
+		if (bp->nb_free.tqe_next != NFSNOLIST)
+			panic("nfsbuf on freelist");
+		TAILQ_INSERT_TAIL(&nfsbufdelwri, bp, nb_free);
+		nfsbufdelwricnt++;
+		freeup = 0;
+	} else {
+		/* update usage timestamp */
+		microuptime(&now);
+		bp->nb_timestamp = now.tv_sec;
+		/* put buffer at end of free list */
+		if (bp->nb_free.tqe_next != NFSNOLIST)
+			panic("nfsbuf on freelist");
+		if (ISSET(bp->nb_flags, NB_META)) {
+			TAILQ_INSERT_TAIL(&nfsbuffreemeta, bp, nb_free);
+			nfsbuffreemetacnt++;
+		} else {
+			TAILQ_INSERT_TAIL(&nfsbuffree, bp, nb_free);
+			nfsbuffreecnt++;
+		}
+	}
+
+	NFSBUFCNTCHK();
+
+	/* Unlock the buffer. */
+	CLR(bp->nb_flags, (NB_ASYNC | NB_STABLE));
+	CLR(bp->nb_lflags, NBL_BUSY);
+
+	FSDBG_BOT(548, bp, NBOFF(bp), bp->nb_flags, bp->nb_data);
+
+	lck_mtx_unlock(nfs_buf_mutex);
+
+	if (wakeup_needbuffer)
+		wakeup(&nfsneedbuffer);
+	if (wakeup_buffer)
+		wakeup(bp);
+	if (wakeup_nbdwrite)
+		wakeup(&nfs_nbdwrite);
+	if (freeup)
+		NFS_BUF_FREEUP();
+}
+
+/*
+ * Wait for operations on the buffer to complete.
+ * When they do, extract and return the I/O's error value.
+ */
+int
+nfs_buf_iowait(struct nfsbuf *bp)
+{
+	FSDBG_TOP(549, bp, NBOFF(bp), bp->nb_flags, bp->nb_error);
+
+	lck_mtx_lock(nfs_buf_mutex);
+
+	while (!ISSET(bp->nb_flags, NB_DONE))
+		msleep(bp, nfs_buf_mutex, PRIBIO + 1, "nfs_buf_iowait", NULL);
+
+	lck_mtx_unlock(nfs_buf_mutex);
+
+	FSDBG_BOT(549, bp, NBOFF(bp), bp->nb_flags, bp->nb_error);
+
+	/* check for interruption of I/O, then errors. */
+	if (ISSET(bp->nb_flags, NB_EINTR)) {
+		CLR(bp->nb_flags, NB_EINTR);
+		return (EINTR);
+	} else if (ISSET(bp->nb_flags, NB_ERROR))
+		return (bp->nb_error ? bp->nb_error : EIO);
+	return (0);
+}
+
+/*
+ * Mark I/O complete on a buffer.
+ */
+void
+nfs_buf_iodone(struct nfsbuf *bp)
+{
+
+	FSDBG_TOP(550, bp, NBOFF(bp), bp->nb_flags, bp->nb_error);
+
+	if (ISSET(bp->nb_flags, NB_DONE))
+		panic("nfs_buf_iodone already");
+
+	if (!ISSET(bp->nb_flags, NB_READ)) {
+		CLR(bp->nb_flags, NB_WRITEINPROG);
+		/*
+		 * vnode_writedone() takes care of waking up
+		 * any throttled write operations
+		 */
+		vnode_writedone(NFSTOV(bp->nb_np));
+		nfs_node_lock_force(bp->nb_np);
+		bp->nb_np->n_numoutput--;
+		nfs_node_unlock(bp->nb_np);
+	}
+	if (ISSET(bp->nb_flags, NB_ASYNC)) {	/* if async, release it */
+		SET(bp->nb_flags, NB_DONE);		/* note that it's done */
+		nfs_buf_release(bp, 1);
+	} else {		                        /* or just wakeup the buffer */	
+	        lck_mtx_lock(nfs_buf_mutex);
+		SET(bp->nb_flags, NB_DONE);		/* note that it's done */
+		CLR(bp->nb_lflags, NBL_WANTED);
+	        lck_mtx_unlock(nfs_buf_mutex);
+		wakeup(bp);
+	}
+
+	FSDBG_BOT(550, bp, NBOFF(bp), bp->nb_flags, bp->nb_error);
+}
+
+void
+nfs_buf_write_delayed(struct nfsbuf *bp)
+{
+	nfsnode_t np = bp->nb_np;
+
+	FSDBG_TOP(551, bp, NBOFF(bp), bp->nb_flags, 0);
+	FSDBG(551, bp, bp->nb_dirtyoff, bp->nb_dirtyend, bp->nb_dirty);
+
+	/*
+	 * If the block hasn't been seen before:
+	 *	(1) Mark it as having been seen,
+	 *	(2) Make sure it's on its node's correct block list,
+	 */
+	if (!ISSET(bp->nb_flags, NB_DELWRI)) {
+		SET(bp->nb_flags, NB_DELWRI);
+		/* move to dirty list */
+		lck_mtx_lock(nfs_buf_mutex);
+		nfs_nbdwrite++;
+		NFSBUFCNTCHK();
+		if (bp->nb_vnbufs.le_next != NFSNOLIST)
+			LIST_REMOVE(bp, nb_vnbufs);
+		LIST_INSERT_HEAD(&np->n_dirtyblkhd, bp, nb_vnbufs);
+		lck_mtx_unlock(nfs_buf_mutex);
+	}
+
+	/*
+	 * If the vnode has "too many" write operations in progress
+	 * wait for them to finish the IO
+	 */
+	vnode_waitforwrites(NFSTOV(np), VNODE_ASYNC_THROTTLE, 0, 0, "nfs_buf_write_delayed");
+
+	/* the file is in a modified state, so make sure the flag's set */
+	nfs_node_lock_force(np);
+	np->n_flag |= NMODIFIED;
+	nfs_node_unlock(np);
+
+	/*
+	 * If we have too many delayed write buffers,
+	 * just fall back to doing the async write.
+	 */
+	if (nfs_nbdwrite < 0)
+		panic("nfs_buf_write_delayed: Negative nfs_nbdwrite");
+	if (nfs_nbdwrite > NFS_A_LOT_OF_DELAYED_WRITES) {
+		/* issue async write */
+		SET(bp->nb_flags, NB_ASYNC);
+		nfs_buf_write(bp);
+		FSDBG_BOT(551, bp, NBOFF(bp), bp->nb_flags, bp->nb_error);
+		return;
+	}
+
+	/* Otherwise, the "write" is done, so mark and release the buffer. */
+	SET(bp->nb_flags, NB_DONE);
+	nfs_buf_release(bp, 1);
+	FSDBG_BOT(551, bp, NBOFF(bp), bp->nb_flags, 0);
+	return;
+}
+
+/*
+ * Check that a "needcommit" buffer can still be committed.
+ * If the write verifier has changed, we need to clear the
+ * the needcommit flag.
+ */
+void
+nfs_buf_check_write_verifier(nfsnode_t np, struct nfsbuf *bp)
+{
+	struct nfsmount *nmp;
+
+	if (!ISSET(bp->nb_flags, NB_NEEDCOMMIT))
+		return;
+
+	nmp = NFSTONMP(np);
+	if (!nmp)
+		return;
+	if (!ISSET(bp->nb_flags, NB_STALEWVERF) && (bp->nb_verf == nmp->nm_verf))
+		return;
+
+	/* write verifier changed, clear commit/wverf flags */
+	CLR(bp->nb_flags, (NB_NEEDCOMMIT | NB_STALEWVERF));
+	bp->nb_verf = 0;
+	nfs_node_lock_force(np);
+	np->n_needcommitcnt--;
+	CHECK_NEEDCOMMITCNT(np);
+	nfs_node_unlock(np);
+}
+
+/*
+ * add a reference to a buffer so it doesn't disappear while being used
+ * (must be called with nfs_buf_mutex held)
+ */
+void
+nfs_buf_refget(struct nfsbuf *bp)
+{
+	bp->nb_refs++;
+}
+/*
+ * release a reference on a buffer
+ * (must be called with nfs_buf_mutex held)
+ */
+void
+nfs_buf_refrele(struct nfsbuf *bp)
+{
+	bp->nb_refs--;
+}
+
+/*
+ * mark a particular buffer as BUSY
+ * (must be called with nfs_buf_mutex held)
+ */
+errno_t
+nfs_buf_acquire(struct nfsbuf *bp, int flags, int slpflag, int slptimeo)
+{
+	errno_t error;
+	struct timespec ts;
+
+	if (ISSET(bp->nb_lflags, NBL_BUSY)) {
+		/*	
+		 * since the lck_mtx_lock may block, the buffer
+		 * may become BUSY, so we need to recheck for
+		 * a NOWAIT request
+		 */
+	        if (flags & NBAC_NOWAIT)
+			return (EBUSY);
+	        SET(bp->nb_lflags, NBL_WANTED);
+
+		ts.tv_sec = (slptimeo/100);
+		/* the hz value is 100; which leads to 10ms */
+		ts.tv_nsec = (slptimeo % 100) * 10  * NSEC_PER_USEC * 1000;
+
+		error = msleep(bp, nfs_buf_mutex, slpflag | (PRIBIO + 1),
+			"nfs_buf_acquire", &ts);
+		if (error)
+			return (error);
+		return (EAGAIN);
+	}
+	if (flags & NBAC_REMOVE)
+	        nfs_buf_remfree(bp);
+	SET(bp->nb_lflags, NBL_BUSY);
+
+	return (0);
+}
+
+/*
+ * simply drop the BUSY status of a buffer
+ * (must be called with nfs_buf_mutex held)
+ */
+void
+nfs_buf_drop(struct nfsbuf *bp)
+{
+	int need_wakeup = 0;
+
+	if (!ISSET(bp->nb_lflags, NBL_BUSY))
+		panic("nfs_buf_drop: buffer not busy!");
+	if (ISSET(bp->nb_lflags, NBL_WANTED)) {
+	        /* delay the actual wakeup until after we clear NBL_BUSY */
+		need_wakeup = 1;
+	}
+	/* Unlock the buffer. */
+	CLR(bp->nb_lflags, (NBL_BUSY | NBL_WANTED));
+
+	if (need_wakeup)
+	        wakeup(bp);
+}
+
+/*
+ * prepare for iterating over an nfsnode's buffer list
+ * this lock protects the queue manipulation
+ * (must be called with nfs_buf_mutex held)
+ */
+int
+nfs_buf_iterprepare(nfsnode_t np, struct nfsbuflists *iterheadp, int flags)
+{
+	struct nfsbuflists *listheadp;
+
+	if (flags & NBI_DIRTY)
+		listheadp = &np->n_dirtyblkhd;
+	else
+		listheadp = &np->n_cleanblkhd;
+
+	if ((flags & NBI_NOWAIT) && (np->n_bufiterflags & NBI_ITER)) {
+	        LIST_INIT(iterheadp);
+		return(EWOULDBLOCK);
+	}
+
+	while (np->n_bufiterflags & NBI_ITER) 	{
+	        np->n_bufiterflags |= NBI_ITERWANT;
+		msleep(&np->n_bufiterflags, nfs_buf_mutex, 0, "nfs_buf_iterprepare", NULL);
+	}
+	if (LIST_EMPTY(listheadp)) {
+	        LIST_INIT(iterheadp);
+		return(EINVAL);
+	}
+	np->n_bufiterflags |= NBI_ITER;
+
+	iterheadp->lh_first = listheadp->lh_first;
+	listheadp->lh_first->nb_vnbufs.le_prev = &iterheadp->lh_first;	
+	LIST_INIT(listheadp);
+
+	return(0);
+}
+
+/*
+ * clean up after iterating over an nfsnode's buffer list
+ * this lock protects the queue manipulation
+ * (must be called with nfs_buf_mutex held)
+ */
+void
+nfs_buf_itercomplete(nfsnode_t np, struct nfsbuflists *iterheadp, int flags)
+{
+	struct nfsbuflists * listheadp;
+	struct nfsbuf *bp;
+
+	if (flags & NBI_DIRTY)
+		listheadp = &np->n_dirtyblkhd;
+	else
+		listheadp = &np->n_cleanblkhd;
+
+	while (!LIST_EMPTY(iterheadp)) {
+		bp = LIST_FIRST(iterheadp);
+		LIST_REMOVE(bp, nb_vnbufs);
+		LIST_INSERT_HEAD(listheadp, bp, nb_vnbufs);
+	}
+
+	np->n_bufiterflags &= ~NBI_ITER;
+	if (np->n_bufiterflags & NBI_ITERWANT) {
+		np->n_bufiterflags &= ~NBI_ITERWANT;
+		wakeup(&np->n_bufiterflags);
+	}
+}
+
+
+/*
+ * Read an NFS buffer for a file.
+ */
+int
+nfs_buf_read(struct nfsbuf *bp)
+{
+	int error = 0;
+	nfsnode_t np;
+	thread_t thd;
+	kauth_cred_t cred;
+
+	np = bp->nb_np;
+	cred = bp->nb_rcred;
+	if (IS_VALID_CRED(cred))
+		kauth_cred_ref(cred);
+	thd = ISSET(bp->nb_flags, NB_ASYNC) ? NULL : current_thread();
+
+	/* sanity checks */
+	if (!ISSET(bp->nb_flags, NB_READ))
+		panic("nfs_buf_read: !NB_READ");
+	if (ISSET(bp->nb_flags, NB_DONE))
+		CLR(bp->nb_flags, NB_DONE);
+
+	NFS_BUF_MAP(bp);
+
+	OSAddAtomic(1, &nfsstats.read_bios);
+
+	error = nfs_buf_read_rpc(bp, thd, cred);
+	/*
+	 * For async I/O, the callbacks will finish up the
+	 * read.  Otherwise, the read has already been finished.
+	 */
+
+	if (IS_VALID_CRED(cred))
+		kauth_cred_unref(&cred);
+	return (error);
+}
+
+/*
+ * finish the reading of a buffer
+ */
+void
+nfs_buf_read_finish(struct nfsbuf *bp)
+{
+	nfsnode_t np = bp->nb_np;
+	struct nfsmount *nmp;
+
+	if (!ISSET(bp->nb_flags, NB_ERROR)) {
+		/* update valid range */
+		bp->nb_validoff = 0;
+		bp->nb_validend = bp->nb_endio;
+		if (bp->nb_endio < (int)bp->nb_bufsize) { 
+			/*
+			 * The read may be short because we have unflushed writes
+			 * that are extending the file size and the reads hit the
+			 * (old) EOF on the server.  So, just make sure nb_validend
+			 * correctly tracks EOF.
+			 * Note that the missing data should have already been zeroed
+			 * in nfs_buf_read_rpc_finish().
+			 */
+			off_t boff = NBOFF(bp);
+			if ((off_t)np->n_size >= (boff + bp->nb_bufsize))
+				bp->nb_validend = bp->nb_bufsize;
+			else if ((off_t)np->n_size >= boff)
+				bp->nb_validend = np->n_size - boff;
+			else
+				bp->nb_validend = 0;
+		}
+		if ((nmp = NFSTONMP(np)) && (nmp->nm_vers == NFS_VER2) &&
+		    ((NBOFF(bp) + bp->nb_validend) > 0x100000000LL))
+			bp->nb_validend = 0x100000000LL - NBOFF(bp);
+		bp->nb_valid = (1 << (round_page_32(bp->nb_validend) / PAGE_SIZE)) - 1;
+		if (bp->nb_validend & PAGE_MASK) {
+			/* zero-fill remainder of last page */
+			bzero(bp->nb_data + bp->nb_validend, bp->nb_bufsize - bp->nb_validend);
+		}
+	}
+	nfs_buf_iodone(bp);
+}
+
+/*
+ * initiate the NFS READ RPC(s) for a buffer
+ */
+int
+nfs_buf_read_rpc(struct nfsbuf *bp, thread_t thd, kauth_cred_t cred)
+{
+	struct nfsmount *nmp;
+	nfsnode_t np = bp->nb_np;
+	int error = 0, nfsvers, async;
+	int offset, nrpcs;
+	uint32_t nmrsize, length, len;
+	off_t boff;
+	struct nfsreq *req;
+	struct nfsreq_cbinfo cb;
+
+	nmp = NFSTONMP(np);
+	if (!nmp) {
+		bp->nb_error = error = ENXIO;
+		SET(bp->nb_flags, NB_ERROR);
+		nfs_buf_iodone(bp);
+		return (error);
+	}
+	nfsvers = nmp->nm_vers;
+	nmrsize = nmp->nm_rsize;
+
+	boff = NBOFF(bp);
+	offset = 0;
+	length = bp->nb_bufsize;
+
+	if (nfsvers == NFS_VER2) {
+		if (boff > 0xffffffffLL) {
+			bp->nb_error = error = EFBIG;
+			SET(bp->nb_flags, NB_ERROR);
+			nfs_buf_iodone(bp);
+			return (error);
+		}
+		if ((boff + length - 1) > 0xffffffffLL)
+			length = 0x100000000LL - boff;
+	}
+
+	/* Note: Can only do async I/O if nfsiods are configured. */
+	async = (bp->nb_flags & NB_ASYNC);
+	cb.rcb_func = async ? nfs_buf_read_rpc_finish : NULL;
+	cb.rcb_bp = bp;
+
+	bp->nb_offio = bp->nb_endio = 0;
+	bp->nb_rpcs = nrpcs = (length + nmrsize - 1) / nmrsize;
+	if (async && (nrpcs > 1)) {
+		SET(bp->nb_flags, NB_MULTASYNCRPC);
+	} else {
+		CLR(bp->nb_flags, NB_MULTASYNCRPC);
+	}
+
+	while (length > 0) {
+		if (ISSET(bp->nb_flags, NB_ERROR)) {
+			error = bp->nb_error;
+			break;
+		}
+		len = (length > nmrsize) ? nmrsize : length;
+		cb.rcb_args[0] = offset;
+		cb.rcb_args[1] = len;
+		if (nmp->nm_vers >= NFS_VER4)
+			cb.rcb_args[2] = nmp->nm_stategenid;
+		req = NULL;
+		error = nmp->nm_funcs->nf_read_rpc_async(np, boff + offset, len, thd, cred, &cb, &req);
+		if (error)
+			break;
+		offset += len;
+		length -= len;
+		if (async)
+			continue;
+		nfs_buf_read_rpc_finish(req);
+		if (ISSET(bp->nb_flags, NB_ERROR)) {
+			error = bp->nb_error;
+			break;
+		}
+	}
+
+	if (length > 0) {
+		/*
+		 * Something bad happened while trying to send the RPC(s).
+		 * Wait for any outstanding requests to complete.
+		 */
+		bp->nb_error = error;
+		SET(bp->nb_flags, NB_ERROR);
+		if (ISSET(bp->nb_flags, NB_MULTASYNCRPC)) {
+			nrpcs = (length + nmrsize - 1) / nmrsize;
+			lck_mtx_lock(nfs_buf_mutex);
+			bp->nb_rpcs -= nrpcs;
+			if (bp->nb_rpcs == 0) {
+				/* No RPCs left, so the buffer's done */
+				lck_mtx_unlock(nfs_buf_mutex);
+				nfs_buf_iodone(bp);
+			} else {
+				/* wait for the last RPC to mark it done */
+				while (bp->nb_rpcs > 0)
+					msleep(&bp->nb_rpcs, nfs_buf_mutex, 0,
+						"nfs_buf_read_rpc_cancel", NULL);
+				lck_mtx_unlock(nfs_buf_mutex);
+			}
+		} else {
+			nfs_buf_iodone(bp);
+		}
+	}
+
+	return (error);
+}
+
+/*
+ * finish up an NFS READ RPC on a buffer
+ */
+void
+nfs_buf_read_rpc_finish(struct nfsreq *req)
+{
+	struct nfsmount *nmp;
+	size_t rlen;
+	struct nfsreq_cbinfo cb;
+	struct nfsbuf *bp;
+	int error = 0, nfsvers, offset, length, eof = 0, multasyncrpc, finished;
+	void *wakeme = NULL;
+	struct nfsreq *rreq = NULL;
+	nfsnode_t np;
+	thread_t thd;
+	kauth_cred_t cred;
+	uio_t auio;
+	char uio_buf [ UIO_SIZEOF(1) ];
+
+finish:
+	np = req->r_np;
+	thd = req->r_thread;
+	cred = req->r_cred;
+	if (IS_VALID_CRED(cred))
+		kauth_cred_ref(cred);
+	cb = req->r_callback;
+	bp = cb.rcb_bp;
+
+	nmp = NFSTONMP(np);
+	if (!nmp) {
+		SET(bp->nb_flags, NB_ERROR);
+		bp->nb_error = error = ENXIO;
+	}
+	if (error || ISSET(bp->nb_flags, NB_ERROR)) {
+		/* just drop it */
+		nfs_request_async_cancel(req);
+		goto out;
+	}
+
+	nfsvers = nmp->nm_vers;
+	offset = cb.rcb_args[0];
+	rlen = length = cb.rcb_args[1];
+
+	auio = uio_createwithbuffer(1, NBOFF(bp) + offset, UIO_SYSSPACE,
+                                UIO_READ, &uio_buf, sizeof(uio_buf));
+	uio_addiov(auio, CAST_USER_ADDR_T(bp->nb_data + offset), length);
+
+	/* finish the RPC */
+	error = nmp->nm_funcs->nf_read_rpc_async_finish(np, req, auio, &rlen, &eof);
+	if ((error == EINPROGRESS) && cb.rcb_func) {
+		/* async request restarted */
+		if (IS_VALID_CRED(cred))
+			kauth_cred_unref(&cred);
+		return;
+	}
+	if ((nmp->nm_vers >= NFS_VER4) && nfs_mount_state_error_should_restart(error) && !ISSET(bp->nb_flags, NB_ERROR)) {
+		lck_mtx_lock(&nmp->nm_lock);
+		if ((error != NFSERR_GRACE) && (cb.rcb_args[2] == nmp->nm_stategenid) && !(nmp->nm_state & NFSSTA_RECOVER)) {
+			printf("nfs_buf_read_rpc_finish: error %d, initiating recovery\n", error);
+			nmp->nm_state |= NFSSTA_RECOVER;
+			nfs_mount_sock_thread_wake(nmp);
+		}
+		lck_mtx_unlock(&nmp->nm_lock);
+		if (error == NFSERR_GRACE)
+			tsleep(&nmp->nm_state, (PZERO-1), "nfsgrace", 2*hz);
+		if (!(error = nfs_mount_state_wait_for_recovery(nmp))) {
+			rlen = 0;
+			goto readagain;
+		}
+	}
+	if (error) {
+		SET(bp->nb_flags, NB_ERROR);
+		bp->nb_error = error;
+		goto out;
+	}
+
+	if ((rlen > 0) && (bp->nb_endio < (offset + (int)rlen)))
+		bp->nb_endio = offset + rlen;
+
+	if ((nfsvers == NFS_VER2) || eof || (rlen == 0)) {
+		/* zero out the remaining data (up to EOF) */
+		off_t rpcrem, eofrem, rem;
+		rpcrem = (length - rlen);
+		eofrem = np->n_size - (NBOFF(bp) + offset + rlen);
+		rem = (rpcrem < eofrem) ? rpcrem : eofrem;
+		if (rem > 0)
+			bzero(bp->nb_data + offset + rlen, rem);
+	} else if (((int)rlen < length) && !ISSET(bp->nb_flags, NB_ERROR)) {
+		/*
+		 * short read
+		 *
+		 * We haven't hit EOF and we didn't get all the data
+		 * requested, so we need to issue another read for the rest.
+		 * (Don't bother if the buffer already hit an error.)
+		 */
+readagain:
+		offset += rlen;
+		length -= rlen;
+		cb.rcb_args[0] = offset;
+		cb.rcb_args[1] = length;
+		if (nmp->nm_vers >= NFS_VER4)
+			cb.rcb_args[2] = nmp->nm_stategenid;
+		error = nmp->nm_funcs->nf_read_rpc_async(np, NBOFF(bp) + offset, length, thd, cred, &cb, &rreq);
+		if (!error) {
+			if (IS_VALID_CRED(cred))
+				kauth_cred_unref(&cred);
+			if (!cb.rcb_func) {
+				/* if !async we'll need to wait for this RPC to finish */
+				req = rreq;
+				rreq = NULL;
+				goto finish;
+			}
+			/*
+			 * We're done here.
+			 * Outstanding RPC count is unchanged.
+			 * Callback will be called when RPC is done.
+			 */
+			return;
+		}
+		SET(bp->nb_flags, NB_ERROR);
+		bp->nb_error = error;
+	}
+
+out:
+	if (IS_VALID_CRED(cred))
+		kauth_cred_unref(&cred);
+
+	/*
+	 * Decrement outstanding RPC count on buffer
+	 * and call nfs_buf_read_finish on last RPC.
+	 *
+	 * (Note: when there are multiple async RPCs issued for a
+	 * buffer we need nfs_buffer_mutex to avoid problems when
+	 * aborting a partially-initiated set of RPCs)
+	 */
+
+	multasyncrpc = ISSET(bp->nb_flags, NB_MULTASYNCRPC);
+	if (multasyncrpc)
+		lck_mtx_lock(nfs_buf_mutex);
+
+	bp->nb_rpcs--;
+	finished = (bp->nb_rpcs == 0);
+
+	if (multasyncrpc)
+		lck_mtx_unlock(nfs_buf_mutex);
+
+	if (finished) {
+		if (multasyncrpc)
+			wakeme = &bp->nb_rpcs;
+		nfs_buf_read_finish(bp);
+		if (wakeme)
+			wakeup(wakeme);
+	}
+}
+
+/*
+ * Do buffer readahead.
+ * Initiate async I/O to read buffers not in cache.
+ */
+int
+nfs_buf_readahead(nfsnode_t np, int ioflag, daddr64_t *rabnp, daddr64_t lastrabn, thread_t thd, kauth_cred_t cred)
+{
+	struct nfsmount *nmp = NFSTONMP(np);
+	struct nfsbuf *bp;
+	int error = 0, nra;
+
+	if (!nmp)
+		return (ENXIO);
+	if (nmp->nm_readahead <= 0)
+		return (0);
+	if (*rabnp > lastrabn)
+		return (0);
+
+	for (nra = 0; (nra < nmp->nm_readahead) && (*rabnp <= lastrabn); nra++, *rabnp = *rabnp + 1) {
+		/* check if block exists and is valid. */
+		if ((*rabnp * nmp->nm_biosize) >= (off_t)np->n_size) {
+			/* stop reading ahead if we're beyond EOF */
+			*rabnp = lastrabn;
+			break;
+		}
+		error = nfs_buf_get(np, *rabnp, nmp->nm_biosize, thd, NBLK_READ|NBLK_NOWAIT, &bp);
+		if (error)
+			break;
+		nfs_node_lock_force(np);
+		np->n_lastrahead = *rabnp;
+		nfs_node_unlock(np);
+		if (!bp)
+			continue;
+		if ((ioflag & IO_NOCACHE) && ISSET(bp->nb_flags, NB_CACHE) &&
+		    !bp->nb_dirty && !ISSET(bp->nb_flags, (NB_DELWRI|NB_NCRDAHEAD))) {
+			CLR(bp->nb_flags, NB_CACHE);
+			bp->nb_valid = 0;
+			bp->nb_validoff = bp->nb_validend = -1;
+		}
+		if ((bp->nb_dirtyend <= 0) && !bp->nb_dirty &&
+		    !ISSET(bp->nb_flags, (NB_CACHE|NB_DELWRI))) {
+			SET(bp->nb_flags, (NB_READ|NB_ASYNC));
+			if (ioflag & IO_NOCACHE)
+				SET(bp->nb_flags, NB_NCRDAHEAD);
+			if (!IS_VALID_CRED(bp->nb_rcred) && IS_VALID_CRED(cred)) {
+				kauth_cred_ref(cred);
+				bp->nb_rcred = cred;
+			}
+			if ((error = nfs_buf_read(bp)))
+				break;
+			continue;
+		}
+		nfs_buf_release(bp, 1);
+	}
+	return (error);
+}
+
+/*
+ * NFS buffer I/O for reading files.
+ */
+int
+nfs_bioread(nfsnode_t np, uio_t uio, int ioflag, vfs_context_t ctx)
+{
+	vnode_t vp = NFSTOV(np);
+	struct nfsbuf *bp = NULL;
+	struct nfs_vattr nvattr;
+	struct nfsmount *nmp = VTONMP(vp);
+	daddr64_t lbn, rabn = 0, lastrabn, maxrabn = -1;
+	off_t diff;
+	int error = 0, n = 0, on = 0;
+	int nfsvers, biosize, modified, readaheads = 0;
+	thread_t thd;
+	kauth_cred_t cred;
+	int64_t io_resid;
+
+	FSDBG_TOP(514, np, uio_offset(uio), uio_resid(uio), ioflag);
+
+	nfsvers = nmp->nm_vers;
+	biosize = nmp->nm_biosize;
+	thd = vfs_context_thread(ctx);
+	cred = vfs_context_ucred(ctx);
+
+	if (vnode_vtype(vp) != VREG) {
+		printf("nfs_bioread: type %x unexpected\n", vnode_vtype(vp));
+		FSDBG_BOT(514, np, 0xd1e0016, 0, EINVAL);
+		return (EINVAL);
+	}
+
+	/*
+	 * For NFS, cache consistency can only be maintained approximately.
+	 * Although RFC1094 does not specify the criteria, the following is
+	 * believed to be compatible with the reference port.
+	 * 
+	 * If the file has changed since the last read RPC or you have
+	 * written to the file, you may have lost data cache consistency
+	 * with the server.  So, check for a change, and flush all of the
+	 * file's data out of the cache.
+	 * NB: This implies that cache data can be read when up to
+	 * NFS_MAXATTRTIMO seconds out of date. If you find that you
+	 * need current attributes, nfs_getattr() can be forced to fetch
+	 * new attributes (via NATTRINVALIDATE() or NGA_UNCACHED).
+	 */
+
+	if (ISSET(np->n_flag, NUPDATESIZE))
+		nfs_data_update_size(np, 0);
+
+	if ((error = nfs_node_lock(np))) {
+		FSDBG_BOT(514, np, 0xd1e0222, 0, error);
+		return (error);
+	}
+
+	if (np->n_flag & NNEEDINVALIDATE) {
+		np->n_flag &= ~NNEEDINVALIDATE;
+		nfs_node_unlock(np);
+		error = nfs_vinvalbuf(vp, V_SAVE|V_IGNORE_WRITEERR, ctx, 1);
+		if (!error)
+			error = nfs_node_lock(np);
+		if (error) {
+			FSDBG_BOT(514, np, 0xd1e0322, 0, error);
+			return (error);
+		}
+	}
+
+	modified = (np->n_flag & NMODIFIED);
+	nfs_node_unlock(np);
+	/* nfs_getattr() will check changed and purge caches */
+	error = nfs_getattr(np, &nvattr, ctx, modified ? NGA_UNCACHED : NGA_CACHED);
+	if (error) {
+		FSDBG_BOT(514, np, 0xd1e0004, 0, error);
+		return (error);
+	}
+
+	if (uio_resid(uio) == 0) {
+		FSDBG_BOT(514, np, 0xd1e0001, 0, 0);
+		return (0);
+	}
+	if (uio_offset(uio) < 0) {
+		FSDBG_BOT(514, np, 0xd1e0002, 0, EINVAL);
+		return (EINVAL);
+	}
+
+	/*
+	 * set up readahead - which may be limited by:
+	 * + current request length (for IO_NOCACHE)
+	 * + readahead setting
+	 * + file size
+	 */
+	if (nmp->nm_readahead > 0) {
+		off_t end = uio_offset(uio) + uio_resid(uio);
+		if (end > (off_t)np->n_size)
+			end = np->n_size;
+		rabn = uio_offset(uio) / biosize;
+		maxrabn = (end - 1) / biosize;
+		nfs_node_lock_force(np);
+		if (!(ioflag & IO_NOCACHE) &&
+		    (!rabn || (rabn == np->n_lastread) || (rabn == (np->n_lastread+1)))) {
+			maxrabn += nmp->nm_readahead;
+			if ((maxrabn * biosize) >= (off_t)np->n_size)
+				maxrabn = ((off_t)np->n_size - 1)/biosize;
+		}
+		if (maxrabn < np->n_lastrahead)
+			np->n_lastrahead = -1;
+		if (rabn < np->n_lastrahead)
+			rabn = np->n_lastrahead + 1;
+		nfs_node_unlock(np);
+	} else {
+		rabn = maxrabn = 0;
+	}
+
+	do {
+
+		nfs_data_lock(np, NFS_DATA_LOCK_SHARED);
+		lbn = uio_offset(uio) / biosize;
+
+		/*
+		 * Copy directly from any cached pages without grabbing the bufs.
+		 * (If we are NOCACHE and we've issued readahead requests, we need
+		 * to grab the NB_NCRDAHEAD bufs to drop them.)
+		 */
+		if ((!(ioflag & IO_NOCACHE) || !readaheads) &&
+		    ((uio->uio_segflg == UIO_USERSPACE32 ||
+		      uio->uio_segflg == UIO_USERSPACE64 ||
+		      uio->uio_segflg == UIO_USERSPACE))) {
+			io_resid = uio_resid(uio);
+			diff = np->n_size - uio_offset(uio);
+			if (diff < io_resid)
+				io_resid = diff;
+			if (io_resid > 0) {
+				int count = (io_resid > INT_MAX) ? INT_MAX : io_resid;
+				error = cluster_copy_ubc_data(vp, uio, &count, 0);
+				if (error) {
+					nfs_data_unlock(np);
+					FSDBG_BOT(514, np, uio_offset(uio), 0xcacefeed, error);
+					return (error);
+				}
+			}
+			/* count any biocache reads that we just copied directly */
+			if (lbn != (uio_offset(uio)/biosize)) {
+				OSAddAtomic((uio_offset(uio)/biosize) - lbn, &nfsstats.biocache_reads);
+				FSDBG(514, np, 0xcacefeed, uio_offset(uio), error);
+			}
+		}
+
+		lbn = uio_offset(uio) / biosize;
+		on = uio_offset(uio) % biosize;
+		nfs_node_lock_force(np);
+		np->n_lastread = (uio_offset(uio) - 1) / biosize;
+		nfs_node_unlock(np);
+
+		/* adjust readahead block number, if necessary */
+		if (rabn < lbn)
+			rabn = lbn;
+		lastrabn = MIN(maxrabn, lbn + nmp->nm_readahead);
+		if (rabn <= lastrabn) { /* start readaheads */
+			error = nfs_buf_readahead(np, ioflag, &rabn, lastrabn, thd, cred);
+			if (error) {
+				nfs_data_unlock(np);
+				FSDBG_BOT(514, np, 0xd1e000b, 1, error);
+				return (error);
+			}
+			readaheads = 1;
+		}
+
+		if ((uio_resid(uio) <= 0) || (uio_offset(uio) >= (off_t)np->n_size)) {
+			nfs_data_unlock(np);
+			FSDBG_BOT(514, np, uio_offset(uio), uio_resid(uio), 0xaaaaaaaa);
+			return (0);
+		}
+
+		OSAddAtomic(1, &nfsstats.biocache_reads);
+
+		/*
+		 * If the block is in the cache and has the required data
+		 * in a valid region, just copy it out.
+		 * Otherwise, get the block and write back/read in,
+		 * as required.
+		 */
+again:
+		io_resid = uio_resid(uio);
+		n = (io_resid > (biosize - on)) ? (biosize - on) : io_resid;
+		diff = np->n_size - uio_offset(uio);
+		if (diff < n)
+			n = diff;
+
+		error = nfs_buf_get(np, lbn, biosize, thd, NBLK_READ, &bp);
+		if (error) {
+			nfs_data_unlock(np);
+			FSDBG_BOT(514, np, 0xd1e000c, 0, error);
+			return (error);
+		}
+
+		if ((ioflag & IO_NOCACHE) && ISSET(bp->nb_flags, NB_CACHE)) {
+			/*
+			 * IO_NOCACHE found a cached buffer.
+			 * Flush the buffer if it's dirty.
+			 * Invalidate the data if it wasn't just read
+			 * in as part of a "nocache readahead".
+			 */
+			if (bp->nb_dirty || (bp->nb_dirtyend > 0)) {
+				/* so write the buffer out and try again */
+				SET(bp->nb_flags, NB_NOCACHE);
+				goto flushbuffer;
+			}
+			if (ISSET(bp->nb_flags, NB_NCRDAHEAD)) {
+				CLR(bp->nb_flags, NB_NCRDAHEAD);
+				SET(bp->nb_flags, NB_NOCACHE);
+			}
+		}
+
+		/* if any pages are valid... */
+		if (bp->nb_valid) {
+			/* ...check for any invalid pages in the read range */
+			int pg, firstpg, lastpg, dirtypg;
+			dirtypg = firstpg = lastpg = -1;
+			pg = on/PAGE_SIZE;
+			while (pg <= (on + n - 1)/PAGE_SIZE) {
+				if (!NBPGVALID(bp,pg)) {
+					if (firstpg < 0)
+						firstpg = pg;
+					lastpg = pg;
+				} else if (firstpg >= 0 && dirtypg < 0 && NBPGDIRTY(bp,pg))
+					dirtypg = pg;
+				pg++;
+			}
+
+			/* if there are no invalid pages, we're all set */
+			if (firstpg < 0) {
+				if (bp->nb_validoff < 0) {
+					/* valid range isn't set up, so */
+					/* set it to what we know is valid */
+					bp->nb_validoff = trunc_page(on);
+					bp->nb_validend = round_page(on+n);
+					nfs_buf_normalize_valid_range(np, bp);
+				}
+				goto buffer_ready;
+			}
+
+			/* there are invalid pages in the read range */
+			if (((dirtypg > firstpg) && (dirtypg < lastpg)) ||
+			    (((firstpg*PAGE_SIZE) < bp->nb_dirtyend) && (((lastpg+1)*PAGE_SIZE) > bp->nb_dirtyoff))) {
+				/* there are also dirty page(s) (or range) in the read range, */
+				/* so write the buffer out and try again */
+flushbuffer:
+				CLR(bp->nb_flags, (NB_DONE | NB_ERROR | NB_INVAL));
+				SET(bp->nb_flags, NB_ASYNC);
+				if (!IS_VALID_CRED(bp->nb_wcred)) {
+					kauth_cred_ref(cred);
+					bp->nb_wcred = cred;
+				}
+				error = nfs_buf_write(bp);
+				if (error) {
+					nfs_data_unlock(np);
+					FSDBG_BOT(514, np, 0xd1e000d, 0, error);
+					return (error);
+				}
+				goto again;
+			}
+			if (!bp->nb_dirty && bp->nb_dirtyend <= 0 &&
+			    (lastpg - firstpg + 1) > (biosize/PAGE_SIZE)/2) {
+				/* we need to read in more than half the buffer and the */
+				/* buffer's not dirty, so just fetch the whole buffer */
+				bp->nb_valid = 0;
+			} else {
+				/* read the page range in */
+				uio_t auio;
+				char uio_buf[ UIO_SIZEOF(1) ];
+				
+				NFS_BUF_MAP(bp);
+				auio = uio_createwithbuffer(1, (NBOFF(bp) + firstpg * PAGE_SIZE_64),
+						UIO_SYSSPACE, UIO_READ, &uio_buf[0], sizeof(uio_buf));
+				if (!auio) {
+					error = ENOMEM;
+				} else {
+					uio_addiov(auio, CAST_USER_ADDR_T(bp->nb_data + (firstpg * PAGE_SIZE)),
+							((lastpg - firstpg + 1) * PAGE_SIZE));
+					error = nfs_read_rpc(np, auio, ctx);
+				}
+				if (error) {
+					if (ioflag & IO_NOCACHE)
+						SET(bp->nb_flags, NB_NOCACHE);
+					nfs_buf_release(bp, 1);
+					nfs_data_unlock(np);
+					FSDBG_BOT(514, np, 0xd1e000e, 0, error);
+					return (error);
+				}
+				/* Make sure that the valid range is set to cover this read. */
+				bp->nb_validoff = trunc_page_32(on);
+				bp->nb_validend = round_page_32(on+n);
+				nfs_buf_normalize_valid_range(np, bp);
+				if (uio_resid(auio) > 0) {
+					/* if short read, must have hit EOF, */
+					/* so zero the rest of the range */
+					bzero(CAST_DOWN(caddr_t, uio_curriovbase(auio)), uio_resid(auio));
+				}
+				/* mark the pages (successfully read) as valid */
+				for (pg=firstpg; pg <= lastpg; pg++)
+					NBPGVALID_SET(bp,pg);
+			}
+		}
+		/* if no pages are valid, read the whole block */
+		if (!bp->nb_valid) {
+			if (!IS_VALID_CRED(bp->nb_rcred) && IS_VALID_CRED(cred)) {
+				kauth_cred_ref(cred);
+				bp->nb_rcred = cred;
+			}
+			SET(bp->nb_flags, NB_READ);
+			CLR(bp->nb_flags, (NB_DONE | NB_ERROR | NB_INVAL));
+			error = nfs_buf_read(bp);
+			if (ioflag & IO_NOCACHE)
+				SET(bp->nb_flags, NB_NOCACHE);
+			if (error) {
+				nfs_data_unlock(np);
+				nfs_buf_release(bp, 1);
+				FSDBG_BOT(514, np, 0xd1e000f, 0, error);
+				return (error);
+			}
+		}
+buffer_ready:
+		/* validate read range against valid range and clip */
+		if (bp->nb_validend > 0) {
+			diff = (on >= bp->nb_validend) ? 0 : (bp->nb_validend - on);
+			if (diff < n)
+				n = diff;
+		}
+		if (n > 0) {
+			NFS_BUF_MAP(bp);
+			error = uiomove(bp->nb_data + on, n, uio);
+		}
+
+		nfs_buf_release(bp, 1);
+		nfs_data_unlock(np);
+		nfs_node_lock_force(np);
+		np->n_lastread = (uio_offset(uio) - 1) / biosize;
+		nfs_node_unlock(np);
+	} while (error == 0 && uio_resid(uio) > 0 && n > 0);
+	FSDBG_BOT(514, np, uio_offset(uio), uio_resid(uio), error);
+	return (error);
+}
+
+/*
+ * limit the number of outstanding async I/O writes
+ */
+int
+nfs_async_write_start(struct nfsmount *nmp)
+{
+	int error = 0, slpflag = (nmp->nm_flag & NFSMNT_INT) ? PCATCH : 0;
+	struct timespec ts = {1, 0};
+
+	if (nfs_max_async_writes <= 0)
+		return (0);
+	lck_mtx_lock(&nmp->nm_lock);
+	while ((nfs_max_async_writes > 0) && (nmp->nm_asyncwrites >= nfs_max_async_writes)) {
+		if ((error = nfs_sigintr(nmp, NULL, current_thread(), 1)))
+			break;
+		msleep(&nmp->nm_asyncwrites, &nmp->nm_lock, slpflag|(PZERO-1), "nfsasyncwrites", &ts);
+		slpflag = 0;
+	}
+	if (!error)
+		nmp->nm_asyncwrites++;
+	lck_mtx_unlock(&nmp->nm_lock);
+	return (error);
+}
+void
+nfs_async_write_done(struct nfsmount *nmp)
+{
+	if (nmp->nm_asyncwrites <= 0)
+		return;
+	lck_mtx_lock(&nmp->nm_lock);
+	if (nmp->nm_asyncwrites-- >= nfs_max_async_writes)
+		wakeup(&nmp->nm_asyncwrites);
+	lck_mtx_unlock(&nmp->nm_lock);
+}
+
+/*
+ * write (or commit) the given NFS buffer
+ *
+ * Commit the buffer if we can.
+ * Write out any dirty range.
+ * If any dirty pages remain, write them out.
+ * Mark buffer done.
+ *
+ * For async requests, all the work beyond sending the initial
+ * write RPC is handled in the RPC callback(s).
+ */
+int
+nfs_buf_write(struct nfsbuf *bp)
+{
+	int error = 0, oldflags, async;
+	nfsnode_t np;
+	thread_t thd;
+	kauth_cred_t cred;
+	proc_t p = current_proc();
+	int iomode, doff, dend, firstpg, lastpg;
+	uint32_t pagemask;
+
+	FSDBG_TOP(553, bp, NBOFF(bp), bp->nb_flags, 0);
+
+	if (!ISSET(bp->nb_lflags, NBL_BUSY))
+		panic("nfs_buf_write: buffer is not busy???");
+
+	np = bp->nb_np;
+	async = ISSET(bp->nb_flags, NB_ASYNC);
+	oldflags = bp->nb_flags;
+
+	CLR(bp->nb_flags, (NB_READ|NB_DONE|NB_ERROR|NB_DELWRI));
+	if (ISSET(oldflags, NB_DELWRI)) {
+		lck_mtx_lock(nfs_buf_mutex);
+		nfs_nbdwrite--;
+		NFSBUFCNTCHK();
+		lck_mtx_unlock(nfs_buf_mutex);
+		wakeup(&nfs_nbdwrite);
+	}
+
+	/* move to clean list */
+	if (ISSET(oldflags, (NB_ASYNC|NB_DELWRI))) {
+		lck_mtx_lock(nfs_buf_mutex);
+		if (bp->nb_vnbufs.le_next != NFSNOLIST)
+			LIST_REMOVE(bp, nb_vnbufs);
+		LIST_INSERT_HEAD(&np->n_cleanblkhd, bp, nb_vnbufs);
+		lck_mtx_unlock(nfs_buf_mutex);
+	}
+	nfs_node_lock_force(np);
+	np->n_numoutput++;
+	nfs_node_unlock(np);
+	vnode_startwrite(NFSTOV(np));
+
+	if (p && p->p_stats)
+		OSIncrementAtomicLong(&p->p_stats->p_ru.ru_oublock);
+
+	cred = bp->nb_wcred;
+	if (!IS_VALID_CRED(cred) && ISSET(bp->nb_flags, NB_READ))
+		cred = bp->nb_rcred;  /* shouldn't really happen, but... */
+	if (IS_VALID_CRED(cred))
+		kauth_cred_ref(cred);
+	thd = async ? NULL : current_thread();
+
+	/* We need to make sure the pages are locked before doing I/O.  */
+	if (!ISSET(bp->nb_flags, NB_META) && UBCINFOEXISTS(NFSTOV(np))) {
+		if (!ISSET(bp->nb_flags, NB_PAGELIST)) {
+			error = nfs_buf_upl_setup(bp);
+			if (error) {
+				printf("nfs_buf_write: upl create failed %d\n", error);
+				SET(bp->nb_flags, NB_ERROR);
+				bp->nb_error = error = EIO;
+				nfs_buf_iodone(bp);
+				goto out;
+			}
+			nfs_buf_upl_check(bp);
+		}
+	}
+
+	/* If NB_NEEDCOMMIT is set, a commit RPC may do the trick. */
+	if (ISSET(bp->nb_flags, NB_NEEDCOMMIT))
+		nfs_buf_check_write_verifier(np, bp);
+	if (ISSET(bp->nb_flags, NB_NEEDCOMMIT)) {
+		struct nfsmount *nmp = NFSTONMP(np);
+		if (!nmp) {
+			SET(bp->nb_flags, NB_ERROR);
+			bp->nb_error = error = EIO;
+			nfs_buf_iodone(bp);
+			goto out;
+		}
+		SET(bp->nb_flags, NB_WRITEINPROG);
+		error = nmp->nm_funcs->nf_commit_rpc(np, NBOFF(bp) + bp->nb_dirtyoff,
+				bp->nb_dirtyend - bp->nb_dirtyoff, bp->nb_wcred);
+		CLR(bp->nb_flags, NB_WRITEINPROG);
+		if (error) {
+			if (error != NFSERR_STALEWRITEVERF) {
+				SET(bp->nb_flags, NB_ERROR);
+				bp->nb_error = error;
+			}
+			nfs_buf_iodone(bp);
+			goto out;
+		}
+		bp->nb_dirtyoff = bp->nb_dirtyend = 0;
+		CLR(bp->nb_flags, NB_NEEDCOMMIT);
+		nfs_node_lock_force(np);
+		np->n_needcommitcnt--;
+		CHECK_NEEDCOMMITCNT(np);
+		nfs_node_unlock(np);
+	}
+	if (!error && (bp->nb_dirtyend > 0)) {
+		/* sanity check the dirty range */
+		if (NBOFF(bp) + bp->nb_dirtyend > (off_t) np->n_size) {
+			bp->nb_dirtyend = np->n_size - NBOFF(bp);
+			if (bp->nb_dirtyoff >= bp->nb_dirtyend)
+				bp->nb_dirtyoff = bp->nb_dirtyend = 0;
+		}
+	}
+	if (!error && (bp->nb_dirtyend > 0)) {
+		/* there's a dirty range that needs to be written out */
+		NFS_BUF_MAP(bp);
+
+		doff = bp->nb_dirtyoff;
+		dend = bp->nb_dirtyend;
+
+		/* if doff page is dirty, move doff to start of page */
+		if (NBPGDIRTY(bp, doff / PAGE_SIZE))
+			doff -= doff & PAGE_MASK;
+		/* try to expand write range to include preceding dirty pages */
+		if (!(doff & PAGE_MASK))
+			while ((doff > 0) && NBPGDIRTY(bp, (doff - 1) / PAGE_SIZE))
+				doff -= PAGE_SIZE;
+		/* if dend page is dirty, move dend to start of next page */
+		if ((dend & PAGE_MASK) && NBPGDIRTY(bp, dend / PAGE_SIZE))
+			dend = round_page_32(dend);
+		/* try to expand write range to include trailing dirty pages */
+		if (!(dend & PAGE_MASK))
+			while ((dend < (int)bp->nb_bufsize) && NBPGDIRTY(bp, dend / PAGE_SIZE))
+				dend += PAGE_SIZE;
+		/* make sure to keep dend clipped to EOF */
+		if ((NBOFF(bp) + dend) > (off_t) np->n_size)
+			dend = np->n_size - NBOFF(bp);
+		/* calculate range of complete pages being written */
+		firstpg = round_page_32(doff) / PAGE_SIZE;
+		lastpg = (trunc_page_32(dend) - 1) / PAGE_SIZE;
+		/* calculate mask for that page range */
+		pagemask = ((1 << (lastpg + 1)) - 1) & ~((1 << firstpg) - 1);
+
+		/*
+		 * compare page mask to nb_dirty; if there are other dirty pages
+		 * then write FILESYNC; otherwise, write UNSTABLE if async and
+		 * not needcommit/stable; otherwise write FILESYNC
+		 */
+		if (bp->nb_dirty & ~pagemask)
+			iomode = NFS_WRITE_FILESYNC;
+		else if ((bp->nb_flags & (NB_ASYNC | NB_NEEDCOMMIT | NB_STABLE)) == NB_ASYNC)
+			iomode = NFS_WRITE_UNSTABLE;
+		else
+			iomode = NFS_WRITE_FILESYNC;
+
+		/* write the whole contiguous dirty range */
+		bp->nb_offio = doff;
+		bp->nb_endio = dend;
+
+		OSAddAtomic(1, &nfsstats.write_bios);
+
+		SET(bp->nb_flags, NB_WRITEINPROG);
+		error = nfs_buf_write_rpc(bp, iomode, thd, cred);
+		/*
+		 * For async I/O, the callbacks will finish up the
+		 * write and push out any dirty pages.  Otherwise,
+		 * the write has already been finished and any dirty
+		 * pages pushed out.
+		 */
+	} else {
+		if (!error && bp->nb_dirty) /* write out any dirty pages */
+			error = nfs_buf_write_dirty_pages(bp, thd, cred);
+		nfs_buf_iodone(bp);
+	}
+	/* note: bp is still valid only for !async case */
+out:
+	if (!async) {
+		error = nfs_buf_iowait(bp);
+		/* move to clean list */
+		if (oldflags & NB_DELWRI) {
+			lck_mtx_lock(nfs_buf_mutex);
+			if (bp->nb_vnbufs.le_next != NFSNOLIST)
+				LIST_REMOVE(bp, nb_vnbufs);
+			LIST_INSERT_HEAD(&np->n_cleanblkhd, bp, nb_vnbufs);
+			lck_mtx_unlock(nfs_buf_mutex);
+		}
+		FSDBG_BOT(553, bp, NBOFF(bp), bp->nb_flags, error);
+		nfs_buf_release(bp, 1);
+		/* check if we need to invalidate (and we can) */
+		if ((np->n_flag & NNEEDINVALIDATE) &&
+		    !(np->n_bflag & (NBINVALINPROG|NBFLUSHINPROG))) {
+			int invalidate = 0;
+			nfs_node_lock_force(np);
+			if (np->n_flag & NNEEDINVALIDATE) {
+				invalidate = 1;
+				np->n_flag &= ~NNEEDINVALIDATE;
+			}
+			nfs_node_unlock(np);
+			if (invalidate) {
+				/*
+				 * There was a write error and we need to
+				 * invalidate attrs and flush buffers in
+				 * order to sync up with the server.
+				 * (if this write was extending the file,
+				 * we may no longer know the correct size)
+				 *
+				 * But we couldn't call vinvalbuf while holding
+				 * the buffer busy.  So we call vinvalbuf() after
+				 * releasing the buffer.
+				 */
+				nfs_vinvalbuf2(NFSTOV(np), V_SAVE|V_IGNORE_WRITEERR, thd, cred, 1);
+			}
+		}
+	}
+
+	if (IS_VALID_CRED(cred))
+		kauth_cred_unref(&cred);
+	return (error);
+}
+
+/*
+ * finish the writing of a buffer
+ */
+void
+nfs_buf_write_finish(struct nfsbuf *bp, thread_t thd, kauth_cred_t cred)
+{
+	nfsnode_t np = bp->nb_np;
+	int error = (bp->nb_flags & NB_ERROR) ? bp->nb_error : 0;
+	int firstpg, lastpg;
+	uint32_t pagemask;
+
+	if ((error == EINTR) || (error == ERESTART)) {
+		CLR(bp->nb_flags, NB_ERROR);
+		SET(bp->nb_flags, NB_EINTR);
+	}
+
+	if (!error) {
+		/* calculate range of complete pages being written */
+		firstpg = round_page_32(bp->nb_offio) / PAGE_SIZE;
+		lastpg = (trunc_page_32(bp->nb_endio) - 1) / PAGE_SIZE;
+		/* calculate mask for that page range written */
+		pagemask = ((1 << (lastpg + 1)) - 1) & ~((1 << firstpg) - 1);
+		/* clear dirty bits for pages we've written */
+		bp->nb_dirty &= ~pagemask;
+	}
+
+	/* manage needcommit state */
+	if (!error && (bp->nb_commitlevel == NFS_WRITE_UNSTABLE)) {
+		if (!ISSET(bp->nb_flags, NB_NEEDCOMMIT)) {
+			nfs_node_lock_force(np);
+			np->n_needcommitcnt++;
+			nfs_node_unlock(np);
+			SET(bp->nb_flags, NB_NEEDCOMMIT);
+		}
+		/* make sure nb_dirtyoff/nb_dirtyend reflect actual range written */
+		bp->nb_dirtyoff = bp->nb_offio;
+		bp->nb_dirtyend = bp->nb_endio;
+	} else if (ISSET(bp->nb_flags, NB_NEEDCOMMIT)) {
+		nfs_node_lock_force(np);
+		np->n_needcommitcnt--;
+		CHECK_NEEDCOMMITCNT(np);
+		nfs_node_unlock(np);
+		CLR(bp->nb_flags, NB_NEEDCOMMIT);
+	}
+
+	CLR(bp->nb_flags, NB_WRITEINPROG);
+
+	/*
+	 * For an unstable write, the buffer is still treated as dirty until
+	 * a commit (or stable (re)write) is performed.  Buffers needing only
+	 * a commit are marked with the NB_DELWRI and NB_NEEDCOMMIT flags.
+	 *
+	 * If the write was interrupted we set NB_EINTR.  Don't set NB_ERROR
+	 * because that would cause the buffer to be dropped.  The buffer is
+	 * still valid and simply needs to be written again.
+	 */
+	if ((error == EINTR) || (error == ERESTART) || (!error && (bp->nb_flags & NB_NEEDCOMMIT))) {
+		CLR(bp->nb_flags, NB_INVAL);
+		if (!ISSET(bp->nb_flags, NB_DELWRI)) {
+			SET(bp->nb_flags, NB_DELWRI);
+			lck_mtx_lock(nfs_buf_mutex);
+			nfs_nbdwrite++;
+			NFSBUFCNTCHK();
+			lck_mtx_unlock(nfs_buf_mutex);
+		}
+		/*
+		 * Since for the NB_ASYNC case, we've reassigned the buffer to the
+		 * clean list, we have to reassign it back to the dirty one. Ugh.
+		 */
+		if (ISSET(bp->nb_flags, NB_ASYNC)) {
+			/* move to dirty list */
+			lck_mtx_lock(nfs_buf_mutex);
+			if (bp->nb_vnbufs.le_next != NFSNOLIST)
+				LIST_REMOVE(bp, nb_vnbufs);
+			LIST_INSERT_HEAD(&np->n_dirtyblkhd, bp, nb_vnbufs);
+			lck_mtx_unlock(nfs_buf_mutex);
+		}
+	} else {
+		/* either there's an error or we don't need to commit */
+		if (error) {
+			/*
+			 * There was a write error and we need to invalidate
+			 * attrs and flush buffers in order to sync up with the
+			 * server.  (if this write was extending the file, we
+			 * may no longer know the correct size)
+			 *
+			 * But we can't call vinvalbuf while holding this
+			 * buffer busy.  Set a flag to do it after releasing
+			 * the buffer.
+			 */
+			nfs_node_lock_force(np);
+			np->n_error = error;
+			np->n_flag |= (NWRITEERR | NNEEDINVALIDATE);
+			NATTRINVALIDATE(np);
+			nfs_node_unlock(np);
+		}
+		/* clear the dirty range */
+		bp->nb_dirtyoff = bp->nb_dirtyend = 0;
+	}
+
+	if (!error && bp->nb_dirty)
+		nfs_buf_write_dirty_pages(bp, thd, cred);
+	nfs_buf_iodone(bp);
+}
+
+/*
+ * write out any pages marked dirty in a buffer
+ *
+ * We do use unstable writes and follow up with a commit.
+ * If we catch the write verifier changing we'll restart
+ * do the writes filesync.
+ */
+int
+nfs_buf_write_dirty_pages(struct nfsbuf *bp, thread_t thd, kauth_cred_t cred)
+{
+	nfsnode_t np = bp->nb_np;
+	struct nfsmount *nmp = NFSTONMP(np);
+	int error = 0, commit, iomode, iomode2, len, pg, count, npages, off;
+	uint32_t dirty = bp->nb_dirty;
+	uint64_t wverf;
+	uio_t auio;
+	char uio_buf [ UIO_SIZEOF(1) ];
+
+	if (!bp->nb_dirty)
+		return (0);
+
+	/* there are pages marked dirty that need to be written out */
+	OSAddAtomic(1, &nfsstats.write_bios);
+	NFS_BUF_MAP(bp);
+	SET(bp->nb_flags, NB_WRITEINPROG);
+	npages = bp->nb_bufsize / PAGE_SIZE;
+	iomode = NFS_WRITE_UNSTABLE;
+
+	auio = uio_createwithbuffer(1, 0, UIO_SYSSPACE, UIO_WRITE,
+		&uio_buf, sizeof(uio_buf));
+
+again:
+	dirty = bp->nb_dirty;
+	wverf = bp->nb_verf;
+	commit = NFS_WRITE_FILESYNC;
+	for (pg = 0; pg < npages; pg++) {
+		if (!NBPGDIRTY(bp, pg))
+			continue;
+		count = 1;
+		while (((pg + count) < npages) && NBPGDIRTY(bp, pg + count))
+			count++;
+		/* write count pages starting with page pg */
+		off = pg * PAGE_SIZE;
+		len = count * PAGE_SIZE;
+		/* clip writes to EOF */
+		if (NBOFF(bp) + off + len > (off_t) np->n_size)
+			len -= (NBOFF(bp) + off + len) - np->n_size;
+		if (len > 0) {
+			iomode2 = iomode;
+			uio_reset(auio, NBOFF(bp) + off, UIO_SYSSPACE, UIO_WRITE);
+			uio_addiov(auio, CAST_USER_ADDR_T(bp->nb_data + off), len);
+			error = nfs_write_rpc2(np, auio, thd, cred, &iomode2, &bp->nb_verf);
+			if (error)
+				break;
+			if (iomode2 < commit) /* Retain the lowest commitment level returned. */
+				commit = iomode2;
+			if ((commit != NFS_WRITE_FILESYNC) && (wverf != bp->nb_verf)) {
+				/* verifier changed, redo all the writes filesync */
+				iomode = NFS_WRITE_FILESYNC;
+				goto again;
+			}
+		}
+		/* clear dirty bits */
+		while (count--) {
+			dirty &= ~(1 << pg);
+			if (count) /* leave pg on last page */
+				pg++;
+		}
+	}
+	CLR(bp->nb_flags, NB_WRITEINPROG);
+
+	if (!error && (commit != NFS_WRITE_FILESYNC)) {
+		error = nmp->nm_funcs->nf_commit_rpc(np, NBOFF(bp), bp->nb_bufsize, cred);
+		if (error == NFSERR_STALEWRITEVERF) {
+			/* verifier changed, so we need to restart all the writes */
+			iomode = NFS_WRITE_FILESYNC;
+			goto again;
+		}
+	}
+	if (!error) {
+		bp->nb_dirty = dirty;
+	} else {
+		SET(bp->nb_flags, NB_ERROR);
+		bp->nb_error = error;
+	}
+	return (error);
+}
+
+/*
+ * initiate the NFS WRITE RPC(s) for a buffer
+ */
+int
+nfs_buf_write_rpc(struct nfsbuf *bp, int iomode, thread_t thd, kauth_cred_t cred)
+{
+	struct nfsmount *nmp;
+	nfsnode_t np = bp->nb_np;
+	int error = 0, nfsvers, async;
+	int offset, nrpcs;
+	uint32_t nmwsize, length, len;
+	struct nfsreq *req;
+	struct nfsreq_cbinfo cb;
+	uio_t auio;
+	char uio_buf [ UIO_SIZEOF(1) ];
+
+	nmp = NFSTONMP(np);
+	if (!nmp) {
+		bp->nb_error = error = ENXIO;
+		SET(bp->nb_flags, NB_ERROR);
+		nfs_buf_iodone(bp);
+		return (error);
+	}
+	nfsvers = nmp->nm_vers;
+	nmwsize = nmp->nm_wsize;
+
+	offset = bp->nb_offio;
+	length = bp->nb_endio - bp->nb_offio;
+
+	/* Note: Can only do async I/O if nfsiods are configured. */
+	async = (bp->nb_flags & NB_ASYNC) && (NFSIOD_MAX > 0);
+	bp->nb_commitlevel = NFS_WRITE_FILESYNC;
+	cb.rcb_func = async ? nfs_buf_write_rpc_finish : NULL;
+	cb.rcb_bp = bp;
+
+	if ((nfsvers == NFS_VER2) && ((NBOFF(bp) + bp->nb_endio) > 0xffffffffLL)) {
+		bp->nb_error = error = EFBIG;
+		SET(bp->nb_flags, NB_ERROR);
+		nfs_buf_iodone(bp);
+		return (error);
+	}
+
+	auio = uio_createwithbuffer(1, NBOFF(bp) + offset, UIO_SYSSPACE,
+		UIO_WRITE, &uio_buf, sizeof(uio_buf));
+	uio_addiov(auio, CAST_USER_ADDR_T(bp->nb_data + offset), length);
+
+	bp->nb_rpcs = nrpcs = (length + nmwsize - 1) / nmwsize;
+	if (async && (nrpcs > 1)) {
+		SET(bp->nb_flags, NB_MULTASYNCRPC);
+	} else {
+		CLR(bp->nb_flags, NB_MULTASYNCRPC);
+	}
+
+	while (length > 0) {
+		if (ISSET(bp->nb_flags, NB_ERROR)) {
+			error = bp->nb_error;
+			break;
+		}
+		len = (length > nmwsize) ? nmwsize : length;
+		cb.rcb_args[0] = offset;
+		cb.rcb_args[1] = len;
+		if (nmp->nm_vers >= NFS_VER4)
+			cb.rcb_args[2] = nmp->nm_stategenid;
+		if (async && ((error = nfs_async_write_start(nmp))))
+			break;
+		req = NULL;
+		error = nmp->nm_funcs->nf_write_rpc_async(np, auio, len, thd, cred,
+				iomode, &cb, &req);
+		if (error) {
+			if (async)
+				nfs_async_write_done(nmp);
+			break;
+		}
+		offset += len;
+		length -= len;
+		if (async)
+			continue;
+		nfs_buf_write_rpc_finish(req);
+	}
+
+	if (length > 0) {
+		/*
+		 * Something bad happened while trying to send the RPCs.
+		 * Wait for any outstanding requests to complete.
+		 */
+		bp->nb_error = error;
+		SET(bp->nb_flags, NB_ERROR);
+		if (ISSET(bp->nb_flags, NB_MULTASYNCRPC)) {
+			nrpcs = (length + nmwsize - 1) / nmwsize;
+			lck_mtx_lock(nfs_buf_mutex);
+			bp->nb_rpcs -= nrpcs;
+			if (bp->nb_rpcs == 0) {
+				/* No RPCs left, so the buffer's done */
+				lck_mtx_unlock(nfs_buf_mutex);
+				nfs_buf_write_finish(bp, thd, cred);
+			} else {
+				/* wait for the last RPC to mark it done */
+				while (bp->nb_rpcs > 0)
+					msleep(&bp->nb_rpcs, nfs_buf_mutex, 0,
+						"nfs_buf_write_rpc_cancel", NULL);
+				lck_mtx_unlock(nfs_buf_mutex);
+			}
+		} else {
+			nfs_buf_write_finish(bp, thd, cred);
+		}
+	}
+
+	return (error);
+}
+
+/*
+ * finish up an NFS WRITE RPC on a buffer
+ */
+void
+nfs_buf_write_rpc_finish(struct nfsreq *req)
+{
+	int error = 0, nfsvers, offset, length, multasyncrpc, finished;
+	int committed = NFS_WRITE_FILESYNC;
+	uint64_t wverf = 0;
+	size_t rlen;
+	void *wakeme = NULL;
+	struct nfsreq_cbinfo cb;
+	struct nfsreq *wreq = NULL;
+	struct nfsbuf *bp;
+	struct nfsmount *nmp;
+	nfsnode_t np;
+	thread_t thd;
+	kauth_cred_t cred;
+	uio_t auio;
+	char uio_buf [ UIO_SIZEOF(1) ];
+
+finish:
+	np = req->r_np;
+	thd = req->r_thread;
+	cred = req->r_cred;
+	if (IS_VALID_CRED(cred))
+		kauth_cred_ref(cred);
+	cb = req->r_callback;
+	bp = cb.rcb_bp;
+
+	nmp = NFSTONMP(np);
+	if (!nmp) {
+		SET(bp->nb_flags, NB_ERROR);
+		bp->nb_error = error = ENXIO;
+	}
+	if (error || ISSET(bp->nb_flags, NB_ERROR)) {
+		/* just drop it */
+		nfs_request_async_cancel(req);
+		goto out;
+	}
+	nfsvers = nmp->nm_vers;
+
+	offset = cb.rcb_args[0];
+	rlen = length = cb.rcb_args[1];
+
+	/* finish the RPC */
+	error = nmp->nm_funcs->nf_write_rpc_async_finish(np, req, &committed, &rlen, &wverf);
+	if ((error == EINPROGRESS) && cb.rcb_func) {
+		/* async request restarted */
+		if (IS_VALID_CRED(cred))
+			kauth_cred_unref(&cred);
+		return;
+	}
+	if ((nmp->nm_vers >= NFS_VER4) && nfs_mount_state_error_should_restart(error) && !ISSET(bp->nb_flags, NB_ERROR)) {
+		lck_mtx_lock(&nmp->nm_lock);
+		if ((error != NFSERR_GRACE) && (cb.rcb_args[2] == nmp->nm_stategenid) && !(nmp->nm_state & NFSSTA_RECOVER)) {
+			printf("nfs_buf_write_rpc_finish: error %d, initiating recovery\n", error);
+			nmp->nm_state |= NFSSTA_RECOVER;
+			nfs_mount_sock_thread_wake(nmp);
+		}
+		lck_mtx_unlock(&nmp->nm_lock);
+		if (error == NFSERR_GRACE)
+			tsleep(&nmp->nm_state, (PZERO-1), "nfsgrace", 2*hz);
+		if (!(error = nfs_mount_state_wait_for_recovery(nmp))) {
+			rlen = 0;
+			goto writeagain;
+		}
+	}
+	if (error) {
+		SET(bp->nb_flags, NB_ERROR);
+		bp->nb_error = error;
+	}
+	if (error || (nfsvers == NFS_VER2))
+		goto out;
+	if (rlen <= 0) {
+		SET(bp->nb_flags, NB_ERROR);
+		bp->nb_error = error = EIO;
+		goto out;
+	}
+
+	/* save lowest commit level returned */
+	if (committed < bp->nb_commitlevel)
+		bp->nb_commitlevel = committed;
+
+	/* check the write verifier */
+	if (!bp->nb_verf) {
+		bp->nb_verf = wverf;
+	} else if (bp->nb_verf != wverf) {
+		/* verifier changed, so buffer will need to be rewritten */
+		bp->nb_flags |= NB_STALEWVERF;
+		bp->nb_commitlevel = NFS_WRITE_UNSTABLE;
+		bp->nb_verf = wverf;
 	}
 
 	/*
-	 * If we have an iod which can process the request, then queue
-	 * the buffer.
+	 * check for a short write
+	 *
+	 * If the server didn't write all the data, then we
+	 * need to issue another write for the rest of it.
+	 * (Don't bother if the buffer hit an error or stale wverf.)
 	 */
-	if (gotiod) {
-		/*
-		 * Ensure that the queue never grows too large.
-		 */
-		while (nmp->nm_bufqlen >= 2*nfs_numasync) {
-			NFS_DPF(ASYNCIO,
-				("nfs_asyncio: waiting for mount %p queue to drain\n", nmp));
-			nmp->nm_bufqwant = TRUE;
-			error = tsleep(&nmp->nm_bufq, slpflag | PRIBIO,
-				       "nfsaio", slptimeo);
-			if (error) {
-				if (nfs_sigintr(nmp, NULL, bp->b_proc))
-					return (EINTR);
-				if (slpflag == PCATCH) {
-					slpflag = 0;
-					slptimeo = 2 * hz;
-				}
+	if (((int)rlen < length) && !(bp->nb_flags & (NB_STALEWVERF|NB_ERROR))) {
+writeagain:
+		offset += rlen;
+		length -= rlen;
+
+		auio = uio_createwithbuffer(1, NBOFF(bp) + offset, UIO_SYSSPACE,
+			UIO_WRITE, &uio_buf, sizeof(uio_buf));
+		uio_addiov(auio, CAST_USER_ADDR_T(bp->nb_data + offset), length);
+
+		cb.rcb_args[0] = offset;
+		cb.rcb_args[1] = length;
+		if (nmp->nm_vers >= NFS_VER4)
+			cb.rcb_args[2] = nmp->nm_stategenid;
+
+		// XXX iomode should really match the original request
+		error = nmp->nm_funcs->nf_write_rpc_async(np, auio, length, thd, cred,
+				NFS_WRITE_FILESYNC, &cb, &wreq);
+		if (!error) {
+			if (IS_VALID_CRED(cred))
+				kauth_cred_unref(&cred);
+			if (!cb.rcb_func) {
+				/* if !async we'll need to wait for this RPC to finish */
+				req = wreq;
+				wreq = NULL;
+				goto finish;
 			}
 			/*
-			 * We might have lost our iod while sleeping,
-			 * so check and loop if nescessary.
+			 * We're done here.
+			 * Outstanding RPC count is unchanged.
+			 * Callback will be called when RPC is done.
 			 */
-			if (nmp->nm_bufqiods == 0) {
-				NFS_DPF(ASYNCIO,
-					("nfs_asyncio: no iods after mount %p queue was drained, looping\n", nmp));
-				goto again;
-			}
-		}
-
-		if (ISSET(bp->b_flags, B_READ)) {
-			if (bp->b_rcred == NOCRED && cred != NOCRED) {
-				/*
-				 * NFS has embedded ucred.
-				 * Can not crhold() here as that causes zone corruption
-				 */
-				bp->b_rcred = crdup(cred);
-			}
-		} else {
-			SET(bp->b_flags, B_WRITEINPROG);
-			if (bp->b_wcred == NOCRED && cred != NOCRED) {
-				/*
-				 * NFS has embedded ucred.
-				 * Can not crhold() here as that causes zone corruption
-				 */
-				bp->b_wcred = crdup(cred);
-			}
+			return;
 		}
-
-		TAILQ_INSERT_TAIL(&nmp->nm_bufq, bp, b_freelist);
-		nmp->nm_bufqlen++;
-		return (0);
+		SET(bp->nb_flags, NB_ERROR);
+		bp->nb_error = error;
 	}
 
+out:
+	if (cb.rcb_func)
+		nfs_async_write_done(nmp);
 	/*
-	 * All the iods are busy on other mounts, so return EIO to
-	 * force the caller to process the i/o synchronously.
+	 * Decrement outstanding RPC count on buffer
+	 * and call nfs_buf_write_finish on last RPC.
+	 *
+	 * (Note: when there are multiple async RPCs issued for a
+	 * buffer we need nfs_buffer_mutex to avoid problems when
+	 * aborting a partially-initiated set of RPCs)
 	 */
-	NFS_DPF(ASYNCIO, ("nfs_asyncio: no iods available, i/o is synchronous\n"));
-	return (EIO);
+	multasyncrpc = ISSET(bp->nb_flags, NB_MULTASYNCRPC);
+	if (multasyncrpc)
+		lck_mtx_lock(nfs_buf_mutex);
+
+	bp->nb_rpcs--;
+	finished = (bp->nb_rpcs == 0);
+
+	if (multasyncrpc)
+		lck_mtx_unlock(nfs_buf_mutex);
+
+	if (finished) {
+		if (multasyncrpc)
+			wakeme = &bp->nb_rpcs;
+		nfs_buf_write_finish(bp, thd, cred);
+		if (wakeme)
+			wakeup(wakeme);
+	}
+
+	if (IS_VALID_CRED(cred))
+		kauth_cred_unref(&cred);
 }
 
 /*
- * Do an I/O operation to/from a cache block. This may be called
- * synchronously or from an nfsiod.
+ * Send commit(s) for the given node's "needcommit" buffers 
  */
 int
-nfs_doio(bp, cr, p)
-	register struct buf *bp;
-	struct ucred *cr;
-	struct proc *p;
+nfs_flushcommits(nfsnode_t np, int nowait)
 {
-	register struct uio *uiop;
-	register struct vnode *vp;
-	struct nfsnode *np;
 	struct nfsmount *nmp;
-	int error = 0, diff, len, iomode, must_commit = 0;
-	struct uio uio;
-	struct iovec io;
-
-	vp = bp->b_vp;
-	np = VTONFS(vp);
-	nmp = VFSTONFS(vp->v_mount);
-	uiop = &uio;
-	uiop->uio_iov = &io;
-	uiop->uio_iovcnt = 1;
-	uiop->uio_segflg = UIO_SYSSPACE;
-	uiop->uio_procp = p;
-
-	/* 
-	 * With UBC, getblk() can return a buf with B_DONE set.
-	 * This indicates that the VM has valid data for that page.
-	 * NFS being stateless, this case poses a problem.
-	 * By definition, the NFS server should always be consulted
-	 * for the data in that page.
-	 * So we choose to clear the B_DONE and to do the IO.
-	 *
-	 * XXX revisit this if there is a performance issue.
-	 * XXX In that case, we could play the attribute cache games ...
-	 */
-	 if (ISSET(bp->b_flags, B_DONE)) {
-		if (!ISSET(bp->b_flags, B_ASYNC))
-			panic("nfs_doio: done and not async");
-		CLR(bp->b_flags, B_DONE);
-	}
-	FSDBG_TOP(256, np->n_size, bp->b_blkno * DEV_BSIZE, bp->b_bcount,
-		  bp->b_flags);
-	FSDBG(257, bp->b_validoff, bp->b_validend, bp->b_dirtyoff,
-	      bp->b_dirtyend);
+	struct nfsbuf *bp, *prevlbp, *lbp;
+	struct nfsbuflists blist, commitlist;
+	int error = 0, retv, wcred_set, flags, dirty;
+	u_quad_t off, endoff, toff;
+	u_int32_t count;
+	kauth_cred_t wcred = NULL;
+
+	FSDBG_TOP(557, np, 0, 0, 0);
+
 	/*
-	 * Historically, paging was done with physio, but no more.
+	 * A nb_flags == (NB_DELWRI | NB_NEEDCOMMIT) block has been written to the
+	 * server, but nas not been committed to stable storage on the server
+	 * yet. The byte range is worked out for as many nfsbufs as we can handle
+	 * and the commit rpc is done.
 	 */
-	if (ISSET(bp->b_flags, B_PHYS)) {
-	    /*
-	     * ...though reading /dev/drum still gets us here.
-	     */
-	    io.iov_len = uiop->uio_resid = bp->b_bcount;
-	    /* mapping was done by vmapbuf() */
-	    io.iov_base = bp->b_data;
-	    uiop->uio_offset = (off_t)bp->b_blkno * DEV_BSIZE;
-	    if (ISSET(bp->b_flags, B_READ)) {
-			uiop->uio_rw = UIO_READ;
-			nfsstats.read_physios++;
-			error = nfs_readrpc(vp, uiop, cr);
-	    } else {
-			int com;
-
-			iomode = NFSV3WRITE_DATASYNC;
-			uiop->uio_rw = UIO_WRITE;
-			nfsstats.write_physios++;
-			error = nfs_writerpc(vp, uiop, cr, &iomode, &com);
-	    }
-	    if (error) {
-			SET(bp->b_flags, B_ERROR);
-			bp->b_error = error;
-	    }
-	} else if (ISSET(bp->b_flags, B_READ)) {
-	    io.iov_len = uiop->uio_resid = bp->b_bcount;
-	    io.iov_base = bp->b_data;
-	    uiop->uio_rw = UIO_READ;
-	    switch (vp->v_type) {
-	    case VREG:
-		uiop->uio_offset = (off_t)bp->b_blkno * DEV_BSIZE;
-		nfsstats.read_bios++;
-		error = nfs_readrpc(vp, uiop, cr);
-		FSDBG(262, np->n_size, bp->b_blkno * DEV_BSIZE,
-		      uiop->uio_resid, error);
-		if (!error) {
-		    bp->b_validoff = 0;
-		    if (uiop->uio_resid) {
+	if (!LIST_EMPTY(&np->n_dirtyblkhd)) {
+		error = nfs_node_lock(np);
+		if (error)
+			goto done;
+		np->n_flag |= NMODIFIED;
+		nfs_node_unlock(np);
+	}
+
+	off = (u_quad_t)-1;
+	endoff = 0;
+	wcred_set = 0;
+	LIST_INIT(&commitlist);
+
+	nmp = NFSTONMP(np);
+	if (!nmp) {
+		error = ENXIO;
+		goto done;
+	}
+	if (nmp->nm_vers == NFS_VER2) {
+		error = EINVAL;
+		goto done;
+	}
+
+	flags = NBI_DIRTY;
+	if (nowait)
+		flags |= NBI_NOWAIT;
+	lck_mtx_lock(nfs_buf_mutex);
+	if (!nfs_buf_iterprepare(np, &blist, flags)) {
+		while ((bp = LIST_FIRST(&blist))) {
+			LIST_REMOVE(bp, nb_vnbufs);
+			LIST_INSERT_HEAD(&np->n_dirtyblkhd, bp, nb_vnbufs);
+			error = nfs_buf_acquire(bp, NBAC_NOWAIT, 0, 0);
+			if (error)
+				continue;
+			if (ISSET(bp->nb_flags, NB_NEEDCOMMIT))
+				nfs_buf_check_write_verifier(np, bp);
+			if (((bp->nb_flags & (NB_DELWRI | NB_NEEDCOMMIT))
+				!= (NB_DELWRI | NB_NEEDCOMMIT))) {
+				nfs_buf_drop(bp);
+				continue;
+			}
+			nfs_buf_remfree(bp);
+
+			/* buffer UPLs will be grabbed *in order* below */
+
+			FSDBG(557, bp, bp->nb_flags, bp->nb_valid, bp->nb_dirty);
+			FSDBG(557, bp->nb_validoff, bp->nb_validend,
+			      bp->nb_dirtyoff, bp->nb_dirtyend);
+
+			/*
+			 * Work out if all buffers are using the same cred
+			 * so we can deal with them all with one commit.
+			 *
+			 * Note: creds in bp's must be obtained by kauth_cred_ref
+			 * on the same original cred in order for them to be equal.
+			 */
+			if (wcred_set == 0) {
+				wcred = bp->nb_wcred;
+				if (!IS_VALID_CRED(wcred))
+					panic("nfs: needcommit w/out wcred");
+				wcred_set = 1;
+			} else if ((wcred_set == 1) && wcred != bp->nb_wcred) {
+				wcred_set = -1;
+			}
+			SET(bp->nb_flags, NB_WRITEINPROG);
+
 			/*
-			 * If len > 0, there is a hole in the file and
-			 * no writes after the hole have been pushed to
-			 * the server yet.
-			 * Just zero fill the rest of the valid area.
+			 * Add this buffer to the list of buffers we are committing.
+			 * Buffers are inserted into the list in ascending order so that
+			 * we can take the UPLs in order after the list is complete.
 			 */
-			diff = bp->b_bcount - uiop->uio_resid;
-			len = np->n_size - ((u_quad_t)bp->b_blkno * DEV_BSIZE +
-					    diff);
-			if (len > 0) {
-				len = min(len, uiop->uio_resid);
-				bzero((char *)bp->b_data + diff, len);
-				bp->b_validend = diff + len;
-				FSDBG(258, diff, len, 0, 1);
-			} else
-				bp->b_validend = diff;
-		    } else
-				bp->b_validend = bp->b_bcount;
-#if 1 /* USV + JOE [ */
-		    if (bp->b_validend < bp->b_bufsize) {
-			    /*
-			     * we're about to release a partial buffer after a
-			     * read... the only way we should get here is if
-			     * this buffer contains the EOF before releasing it,
-			     * we'll zero out to the end of the buffer so that
-			     * if a mmap of this page occurs, we'll see zero's
-			     * even if a ftruncate extends the file in the
-			     * meantime
-			     */
-			    bzero((caddr_t)(bp->b_data + bp->b_validend),
-			          bp->b_bufsize - bp->b_validend);
-			    FSDBG(258, bp->b_validend,
-			          bp->b_bufsize - bp->b_validend, 0, 2);
-		    }
-#endif /* ] USV + JOE */
-		}
-		if (p && (vp->v_flag & VTEXT) &&
-			(((nmp->nm_flag & NFSMNT_NQNFS) &&
-			  NQNFS_CKINVALID(vp, np, ND_READ) &&
-			  np->n_lrev != np->n_brev) ||
-			 (!(nmp->nm_flag & NFSMNT_NQNFS) &&
-			  np->n_mtime != np->n_vattr.va_mtime.tv_sec))) {
-			uprintf("Process killed due to text file modification\n");
-			psignal(p, SIGKILL);
-			p->p_flag |= P_NOSWAP;
+			prevlbp = NULL;
+			LIST_FOREACH(lbp, &commitlist, nb_vnbufs) {
+				if (bp->nb_lblkno < lbp->nb_lblkno)
+					break;
+				prevlbp = lbp;
+			}
+			LIST_REMOVE(bp, nb_vnbufs);
+			if (prevlbp)
+				LIST_INSERT_AFTER(prevlbp, bp, nb_vnbufs);
+			else
+				LIST_INSERT_HEAD(&commitlist, bp, nb_vnbufs);
+
+			/* update commit range start, end */
+			toff = NBOFF(bp) + bp->nb_dirtyoff;
+			if (toff < off)
+				off = toff;
+			toff += (u_quad_t)(bp->nb_dirtyend - bp->nb_dirtyoff);
+			if (toff > endoff)
+				endoff = toff;
 		}
-		break;
-	    case VLNK:
-		uiop->uio_offset = (off_t)0;
-		nfsstats.readlink_bios++;
-		error = nfs_readlinkrpc(vp, uiop, cr);
-		break;
-	    case VDIR:
-		nfsstats.readdir_bios++;
-		uiop->uio_offset = ((u_quad_t)bp->b_lblkno) * NFS_DIRBLKSIZ;
-		if (!(nmp->nm_flag & NFSMNT_NFSV3))
-			nmp->nm_flag &= ~NFSMNT_RDIRPLUS; /* dk@farm.org */
-		if (nmp->nm_flag & NFSMNT_RDIRPLUS) {
-			error = nfs_readdirplusrpc(vp, uiop, cr);
-			if (error == NFSERR_NOTSUPP)
-				nmp->nm_flag &= ~NFSMNT_RDIRPLUS;
-		}
-		if ((nmp->nm_flag & NFSMNT_RDIRPLUS) == 0)
-			error = nfs_readdirrpc(vp, uiop, cr);
-		break;
-	    default:
-		printf("nfs_doio: type %x unexpected\n", vp->v_type);
-		break;
-	    };
-	    if (error) {
-		SET(bp->b_flags, B_ERROR);
-		bp->b_error = error;
-	    }
-	} else {
-	    /*
-	     * mapped I/O may have altered any bytes, so we extend
-	     * the dirty zone to the valid zone.  For best performance
-	     * a better solution would be to save & restore page dirty bits
-	     * around the uiomove which brings write-data into the buffer.
-	     * Then here we'd check if the page is dirty rather than WASMAPPED
-	     * Also vnode_pager would change - if a page is clean it might
-	     * still need to be written due to DELWRI.
-	     */
-	    if (UBCINFOEXISTS(vp) && ubc_issetflags(vp, UI_WASMAPPED)) {
-		bp->b_dirtyoff = min(bp->b_dirtyoff, bp->b_validoff);
-		bp->b_dirtyend = max(bp->b_dirtyend, bp->b_validend);
-	    }
-	    if ((off_t)bp->b_blkno * DEV_BSIZE + bp->b_dirtyend > np->n_size)
-		bp->b_dirtyend = np->n_size - (off_t)bp->b_blkno * DEV_BSIZE;
-
-	    if (bp->b_dirtyend > bp->b_dirtyoff) {
-		io.iov_len = uiop->uio_resid = bp->b_dirtyend - bp->b_dirtyoff;
-		uiop->uio_offset = (off_t)bp->b_blkno * DEV_BSIZE +
-				   bp->b_dirtyoff;
-		io.iov_base = (char *)bp->b_data + bp->b_dirtyoff;
-		uiop->uio_rw = UIO_WRITE;
-
-		nfsstats.write_bios++;
-		if ((bp->b_flags & (B_ASYNC | B_NEEDCOMMIT | B_NOCACHE)) ==
-		    B_ASYNC)
-		    iomode = NFSV3WRITE_UNSTABLE;
+		nfs_buf_itercomplete(np, &blist, NBI_DIRTY);
+	}
+	lck_mtx_unlock(nfs_buf_mutex);
+
+	if (LIST_EMPTY(&commitlist)) {
+		error = ENOBUFS;
+		goto done;
+	}
+
+	/*
+	 * We need a UPL to prevent others from accessing the buffers during
+	 * our commit RPC(s).
+	 *
+	 * We used to also check for dirty pages here; if there were any we'd
+	 * abort the commit and force the entire buffer to be written again.
+	 * Instead of doing that, we just go ahead and commit the dirty range,
+	 * and then leave the buffer around with dirty pages that will be
+	 * written out later.
+	 */
+	LIST_FOREACH(bp, &commitlist, nb_vnbufs) {
+		if (!ISSET(bp->nb_flags, NB_PAGELIST)) {
+			retv = nfs_buf_upl_setup(bp);
+			if (retv) {
+				/* Unable to create the UPL, the VM object probably no longer exists. */
+				printf("nfs_flushcommits: upl create failed %d\n", retv);
+				bp->nb_valid = bp->nb_dirty = 0;
+			}
+		}
+		nfs_buf_upl_check(bp);
+	}
+
+	/*
+	 * Commit data on the server, as required.
+	 * If all bufs are using the same wcred, then use that with
+	 * one call for all of them, otherwise commit each one
+	 * separately.
+	 */
+	if (wcred_set == 1) {
+		/*
+		 * Note, it's possible the commit range could be >2^32-1.
+		 * If it is, we'll send one commit that covers the whole file.
+		 */
+		if ((endoff - off) > 0xffffffff)
+			count = 0;
 		else
-		    iomode = NFSV3WRITE_FILESYNC;
-		SET(bp->b_flags, B_WRITEINPROG);
-		error = nfs_writerpc(vp, uiop, cr, &iomode, &must_commit);
-		if (!error && iomode == NFSV3WRITE_UNSTABLE)
-		    SET(bp->b_flags, B_NEEDCOMMIT);
+			count = (endoff - off);
+		retv = nmp->nm_funcs->nf_commit_rpc(np, off, count, wcred);
+	} else {
+		retv = 0;
+		LIST_FOREACH(bp, &commitlist, nb_vnbufs) {
+			toff = NBOFF(bp) + bp->nb_dirtyoff;
+			count = bp->nb_dirtyend - bp->nb_dirtyoff;
+			retv = nmp->nm_funcs->nf_commit_rpc(np, toff, count, bp->nb_wcred);
+			if (retv)
+				break;
+		}
+	}
+
+	/*
+	 * Now, either mark the blocks I/O done or mark the
+	 * blocks dirty, depending on whether the commit
+	 * succeeded.
+	 */
+	while ((bp = LIST_FIRST(&commitlist))) {
+		LIST_REMOVE(bp, nb_vnbufs);
+		FSDBG(557, bp, retv, bp->nb_flags, bp->nb_dirty);
+		nfs_node_lock_force(np);
+		CLR(bp->nb_flags, (NB_NEEDCOMMIT | NB_WRITEINPROG));
+		np->n_needcommitcnt--;
+		CHECK_NEEDCOMMITCNT(np);
+		nfs_node_unlock(np);
+
+		if (retv) {
+			/* move back to dirty list */
+			lck_mtx_lock(nfs_buf_mutex);
+			LIST_INSERT_HEAD(&np->n_dirtyblkhd, bp, nb_vnbufs);
+			lck_mtx_unlock(nfs_buf_mutex);
+			nfs_buf_release(bp, 1);
+			continue;
+		}
+
+		nfs_node_lock_force(np);
+		np->n_numoutput++;
+		nfs_node_unlock(np);
+		vnode_startwrite(NFSTOV(np));
+		if (ISSET(bp->nb_flags, NB_DELWRI)) {
+			lck_mtx_lock(nfs_buf_mutex);
+			nfs_nbdwrite--;
+			NFSBUFCNTCHK();
+			lck_mtx_unlock(nfs_buf_mutex);
+			wakeup(&nfs_nbdwrite);
+		}
+		CLR(bp->nb_flags, (NB_READ|NB_DONE|NB_ERROR|NB_DELWRI));
+		/* if block still has dirty pages, we don't want it to */
+		/* be released in nfs_buf_iodone().  So, don't set NB_ASYNC. */
+		if (!(dirty = bp->nb_dirty))
+			SET(bp->nb_flags, NB_ASYNC);
 		else
-		    CLR(bp->b_flags, B_NEEDCOMMIT);
-		CLR(bp->b_flags, B_WRITEINPROG);
+			CLR(bp->nb_flags, NB_ASYNC);
+
+		/* move to clean list */
+		lck_mtx_lock(nfs_buf_mutex);
+		LIST_INSERT_HEAD(&np->n_cleanblkhd, bp, nb_vnbufs);
+		lck_mtx_unlock(nfs_buf_mutex);
+
+		bp->nb_dirtyoff = bp->nb_dirtyend = 0;
+
+		nfs_buf_iodone(bp);
+		if (dirty) {
+			/* throw it back in as a delayed write buffer */
+			CLR(bp->nb_flags, NB_DONE);
+			nfs_buf_write_delayed(bp);
+		}
+	}
+
+done:
+	FSDBG_BOT(557, np, 0, 0, error);
+	return (error);
+}
+
+/*
+ * Flush all the blocks associated with a vnode.
+ * 	Walk through the buffer pool and push any dirty pages
+ *	associated with the vnode.
+ */
+int
+nfs_flush(nfsnode_t np, int waitfor, thread_t thd, int ignore_writeerr)
+{
+	struct nfsbuf *bp;
+	struct nfsbuflists blist;
+	struct nfsmount *nmp = NFSTONMP(np);
+	int error = 0, error2, slptimeo = 0, slpflag = 0;
+	int nfsvers, flags, passone = 1;
+
+	FSDBG_TOP(517, np, waitfor, ignore_writeerr, 0);
+
+	if (!nmp) {
+		error = ENXIO;
+		goto out;
+	}
+	nfsvers = nmp->nm_vers;
+	if (nmp->nm_flag & NFSMNT_INT)
+		slpflag = PCATCH;
+
+	if (!LIST_EMPTY(&np->n_dirtyblkhd)) {
+		nfs_node_lock_force(np);
+		np->n_flag |= NMODIFIED;
+		nfs_node_unlock(np);
+	}
+
+	lck_mtx_lock(nfs_buf_mutex);
+	while (np->n_bflag & NBFLUSHINPROG) {
+		np->n_bflag |= NBFLUSHWANT;
+		msleep(&np->n_bflag, nfs_buf_mutex, slpflag, "nfs_flush", NULL);
+		if ((error = nfs_sigintr(NFSTONMP(np), NULL, thd, 0))) {
+			lck_mtx_unlock(nfs_buf_mutex);
+			goto out;
+		}
+	}
+	np->n_bflag |= NBFLUSHINPROG;
+
+	/*
+	 * On the first pass, start async/unstable writes on all
+	 * delayed write buffers.  Then wait for all writes to complete
+	 * and call nfs_flushcommits() to commit any uncommitted buffers.
+	 * On all subsequent passes, start STABLE writes on any remaining
+	 * dirty buffers.  Then wait for all writes to complete.
+	 */
+again:
+	FSDBG(518, LIST_FIRST(&np->n_dirtyblkhd), np->n_flag, 0, 0);
+	if (!NFSTONMP(np)) {
+		lck_mtx_unlock(nfs_buf_mutex);
+		error = ENXIO;
+		goto done;
+	}
+
+	/* Start/do any write(s) that are required. */
+	if (!nfs_buf_iterprepare(np, &blist, NBI_DIRTY)) {
+		while ((bp = LIST_FIRST(&blist))) {
+			LIST_REMOVE(bp, nb_vnbufs);
+			LIST_INSERT_HEAD(&np->n_dirtyblkhd, bp, nb_vnbufs);
+			flags = (passone || !(waitfor == MNT_WAIT || waitfor == MNT_DWAIT)) ? NBAC_NOWAIT : 0;
+			if (flags != NBAC_NOWAIT)
+				nfs_buf_refget(bp);
+			while ((error = nfs_buf_acquire(bp, flags, slpflag, slptimeo))) {
+				FSDBG(524, bp, flags, bp->nb_lflags, bp->nb_flags);
+				if (error == EBUSY)
+					break;
+				if (error) {
+					error2 = nfs_sigintr(NFSTONMP(np), NULL, thd, 0);
+					if (error2) {
+						if (flags != NBAC_NOWAIT)
+							nfs_buf_refrele(bp);
+						nfs_buf_itercomplete(np, &blist, NBI_DIRTY);
+						lck_mtx_unlock(nfs_buf_mutex);
+						error = error2;
+						goto done;
+					}
+					if (slpflag == PCATCH) {
+						slpflag = 0;
+						slptimeo = 2 * hz;
+					}
+				}
+			}
+			if (flags != NBAC_NOWAIT)
+				nfs_buf_refrele(bp);
+			if (error == EBUSY)
+				continue;
+			if (!bp->nb_np) {
+				/* buffer is no longer valid */
+				nfs_buf_drop(bp);
+				continue;
+			}
+			if (ISSET(bp->nb_flags, NB_NEEDCOMMIT))
+				nfs_buf_check_write_verifier(np, bp);
+			if (!ISSET(bp->nb_flags, NB_DELWRI)) {
+				/* buffer is no longer dirty */
+				nfs_buf_drop(bp);
+				continue;
+			}
+			FSDBG(525, bp, passone, bp->nb_lflags, bp->nb_flags);
+			if ((passone || !(waitfor == MNT_WAIT || waitfor == MNT_DWAIT)) &&
+			    ISSET(bp->nb_flags, NB_NEEDCOMMIT)) {
+				nfs_buf_drop(bp);
+				continue;
+			}
+			nfs_buf_remfree(bp);
+			lck_mtx_unlock(nfs_buf_mutex);
+			if (ISSET(bp->nb_flags, NB_ERROR)) {
+				nfs_node_lock_force(np);
+				np->n_error = bp->nb_error ? bp->nb_error : EIO;
+				np->n_flag |= NWRITEERR;
+				nfs_node_unlock(np);
+				nfs_buf_release(bp, 1);
+				lck_mtx_lock(nfs_buf_mutex);
+				continue;
+			}
+			SET(bp->nb_flags, NB_ASYNC);
+			if (!passone) {
+				/* NB_STABLE forces this to be written FILESYNC */
+				SET(bp->nb_flags, NB_STABLE);
+			}
+			nfs_buf_write(bp);
+			lck_mtx_lock(nfs_buf_mutex);
+		}
+		nfs_buf_itercomplete(np, &blist, NBI_DIRTY);
+	}
+	lck_mtx_unlock(nfs_buf_mutex);
+
+	if (waitfor == MNT_WAIT || waitfor == MNT_DWAIT) {
+	        while ((error = vnode_waitforwrites(NFSTOV(np), 0, slpflag, slptimeo, "nfsflush"))) {
+		        error2 = nfs_sigintr(NFSTONMP(np), NULL, thd, 0);
+			if (error2) {
+			        error = error2;
+				goto done;
+			}
+			if (slpflag == PCATCH) {
+				slpflag = 0;
+				slptimeo = 2 * hz;
+			}
+		}
+	}
+
+	if (nfsvers != NFS_VER2) {
+		/* loop while it looks like there are still buffers to be */
+		/* commited and nfs_flushcommits() seems to be handling them. */
+		while (np->n_needcommitcnt)
+			if (nfs_flushcommits(np, 0))
+				break;
+	}
+
+	if (passone) {
+		passone = 0;
+		if (!LIST_EMPTY(&np->n_dirtyblkhd)) {
+			nfs_node_lock_force(np);
+			np->n_flag |= NMODIFIED;
+			nfs_node_unlock(np);
+		}
+		lck_mtx_lock(nfs_buf_mutex);
+		goto again;
+	}
+
+	if (waitfor == MNT_WAIT || waitfor == MNT_DWAIT) {
+		if (!LIST_EMPTY(&np->n_dirtyblkhd)) {
+			nfs_node_lock_force(np);
+			np->n_flag |= NMODIFIED;
+			nfs_node_unlock(np);
+		}
+		lck_mtx_lock(nfs_buf_mutex);
+		if (!LIST_EMPTY(&np->n_dirtyblkhd))
+			goto again;
+		lck_mtx_unlock(nfs_buf_mutex);
+		nfs_node_lock_force(np);
 		/*
-		 * For an interrupted write, the buffer is still valid
-		 * and the write hasn't been pushed to the server yet,
-		 * so we can't set B_ERROR and report the interruption
-		 * by setting B_EINTR. For the B_ASYNC case, B_EINTR
-		 * is not relevant, so the rpc attempt is essentially
-		 * a noop.  For the case of a V3 write rpc not being
-		 * committed to stable storage, the block is still
-		 * dirty and requires either a commit rpc or another
-		 * write rpc with iomode == NFSV3WRITE_FILESYNC before
-		 * the block is reused. This is indicated by setting
-		 * the B_DELWRI and B_NEEDCOMMIT flags.
+		 * OK, it looks like there are no dirty blocks.  If we have no
+		 * writes in flight and no one in the write code, we can clear
+		 * the modified flag.  In order to make sure we see the latest
+		 * attributes and size, we also invalidate the attributes and
+		 * advance the attribute cache XID to guarantee that attributes
+		 * newer than our clearing of NMODIFIED will get loaded next.
+		 * (If we don't do this, it's possible for the flush's final
+		 * write/commit (xid1) to be executed in parallel with a subsequent
+		 * getattr request (xid2).  The getattr could return attributes
+		 * from *before* the write/commit completed but the stale attributes
+		 * would be preferred because of the xid ordering.)
 		 */
-		if (error == EINTR || (!error && bp->b_flags & B_NEEDCOMMIT)) {
-			int s;
+		if (!np->n_wrbusy && !np->n_numoutput) {
+			np->n_flag &= ~NMODIFIED;
+			NATTRINVALIDATE(np);
+			nfs_get_xid(&np->n_xid);
+		}
+	} else {
+		nfs_node_lock_force(np);
+	}
 
-			CLR(bp->b_flags, B_INVAL | B_NOCACHE);
-			SET(bp->b_flags, B_DELWRI);
-			FSDBG(261, bp->b_validoff, bp->b_validend,
-			      bp->b_bufsize, bp->b_bcount);
-			/*
-			 * Since for the B_ASYNC case, nfs_bwrite() has
-			 * reassigned the buffer to the clean list, we have to
-			 * reassign it back to the dirty one. Ugh.
-			 */
-			if (ISSET(bp->b_flags, B_ASYNC)) {
-				s = splbio();
-				reassignbuf(bp, vp);
-				splx(s);
-			} else {
-				SET(bp->b_flags, B_EINTR);
+	FSDBG(526, np->n_flag, np->n_error, 0, 0);
+	if (!ignore_writeerr && (np->n_flag & NWRITEERR)) {
+		error = np->n_error;
+		np->n_flag &= ~NWRITEERR;
+	}
+	nfs_node_unlock(np);
+done:
+	lck_mtx_lock(nfs_buf_mutex);
+	flags = np->n_bflag;
+	np->n_bflag &= ~(NBFLUSHINPROG|NBFLUSHWANT);
+	lck_mtx_unlock(nfs_buf_mutex);
+	if (flags & NBFLUSHWANT)
+		wakeup(&np->n_bflag);
+out:
+	FSDBG_BOT(517, np, error, ignore_writeerr, 0);
+	return (error);
+}
+
+/*
+ * Flush out and invalidate all buffers associated with a vnode.
+ * Called with the underlying object locked.
+ */
+int
+nfs_vinvalbuf_internal(
+	nfsnode_t np,
+	int flags,
+	thread_t thd,
+	kauth_cred_t cred,
+	int slpflag,
+	int slptimeo)
+{
+	struct nfsbuf *bp;
+	struct nfsbuflists blist;
+	int list, error = 0;
+
+	if (flags & V_SAVE) {
+		if ((error = nfs_flush(np, MNT_WAIT, thd, (flags & V_IGNORE_WRITEERR))))
+			return (error);
+	}
+
+	lck_mtx_lock(nfs_buf_mutex);
+	for (;;) {
+		list = NBI_CLEAN;
+		if (nfs_buf_iterprepare(np, &blist, list)) {
+			list = NBI_DIRTY;
+			if (nfs_buf_iterprepare(np, &blist, list))
+				break;
+		}
+		while ((bp = LIST_FIRST(&blist))) {
+			LIST_REMOVE(bp, nb_vnbufs);
+			if (list == NBI_CLEAN)
+				LIST_INSERT_HEAD(&np->n_cleanblkhd, bp, nb_vnbufs);
+			else
+				LIST_INSERT_HEAD(&np->n_dirtyblkhd, bp, nb_vnbufs);
+			nfs_buf_refget(bp);
+			while ((error = nfs_buf_acquire(bp, NBAC_REMOVE, slpflag, slptimeo))) {
+				FSDBG(556, np, bp, NBOFF(bp), bp->nb_flags);
+				if (error != EAGAIN) {
+					FSDBG(554, np, bp, -1, error);
+					nfs_buf_refrele(bp);
+					nfs_buf_itercomplete(np, &blist, list);
+					lck_mtx_unlock(nfs_buf_mutex);
+					return (error);
+				}
 			}
-		} else {
-			if (error) {
-				SET(bp->b_flags, B_ERROR);
-				bp->b_error = np->n_error = error;
-				np->n_flag |= NWRITEERR;
+			nfs_buf_refrele(bp);
+			FSDBG(554, np, bp, NBOFF(bp), bp->nb_flags);
+			lck_mtx_unlock(nfs_buf_mutex);
+			if ((flags & V_SAVE) && UBCINFOEXISTS(NFSTOV(np)) && bp->nb_np &&
+			    (NBOFF(bp) < (off_t)np->n_size)) {
+				/* extra paranoia: make sure we're not */
+				/* somehow leaving any dirty data around */
+				int mustwrite = 0;
+				int end = (NBOFF(bp) + bp->nb_bufsize > (off_t)np->n_size) ?
+				    ((off_t)np->n_size - NBOFF(bp)) : bp->nb_bufsize;
+				if (!ISSET(bp->nb_flags, NB_PAGELIST)) {
+					error = nfs_buf_upl_setup(bp);
+					if (error == EINVAL) {
+						/* vm object must no longer exist */
+						/* hopefully we don't need to do */
+						/* anything for this buffer */
+					} else if (error)
+						printf("nfs_vinvalbuf: upl setup failed %d\n", error);
+					bp->nb_valid = bp->nb_dirty = 0;
+				}
+				nfs_buf_upl_check(bp);
+				/* check for any dirty data before the EOF */
+				if ((bp->nb_dirtyend > 0) && (bp->nb_dirtyoff < end)) {
+					/* clip dirty range to EOF */
+					if (bp->nb_dirtyend > end) {
+						bp->nb_dirtyend = end;
+						if (bp->nb_dirtyoff >= bp->nb_dirtyend)
+							bp->nb_dirtyoff = bp->nb_dirtyend = 0;
+					}
+					if ((bp->nb_dirtyend > 0) && (bp->nb_dirtyoff < end))
+						mustwrite++;
+				}
+				bp->nb_dirty &= (1 << (round_page_32(end)/PAGE_SIZE)) - 1;
+				if (bp->nb_dirty)
+					mustwrite++;
+				/* also make sure we'll have a credential to do the write */
+				if (mustwrite && !IS_VALID_CRED(bp->nb_wcred) && !IS_VALID_CRED(cred)) {
+					printf("nfs_vinvalbuf: found dirty buffer with no write creds\n");
+					mustwrite = 0;
+				}
+				if (mustwrite) {
+					FSDBG(554, np, bp, 0xd00dee, bp->nb_flags);
+					if (!ISSET(bp->nb_flags, NB_PAGELIST))
+						panic("nfs_vinvalbuf: dirty buffer without upl");
+					/* gotta write out dirty data before invalidating */
+					/* (NB_STABLE indicates that data writes should be FILESYNC) */
+					/* (NB_NOCACHE indicates buffer should be discarded) */
+					CLR(bp->nb_flags, (NB_DONE | NB_ERROR | NB_INVAL | NB_ASYNC));
+					SET(bp->nb_flags, NB_STABLE | NB_NOCACHE);
+					if (!IS_VALID_CRED(bp->nb_wcred)) {
+						kauth_cred_ref(cred);
+						bp->nb_wcred = cred;
+					}
+					error = nfs_buf_write(bp);
+					// Note: bp has been released
+					if (error) {
+						FSDBG(554, bp, 0xd00dee, 0xbad, error);
+						nfs_node_lock_force(np);
+						np->n_error = error;
+						np->n_flag |= NWRITEERR;
+						/*
+						 * There was a write error and we need to
+						 * invalidate attrs to sync with server.
+						 * (if this write was extending the file,
+						 * we may no longer know the correct size)
+						 */
+						NATTRINVALIDATE(np);
+						nfs_node_unlock(np);
+						if (error == EINTR) {
+							/*
+							 * Abort on EINTR.  If we don't, we could
+							 * be stuck in this loop forever because
+							 * the buffer will continue to stay dirty.
+							 */
+							lck_mtx_lock(nfs_buf_mutex);
+							nfs_buf_itercomplete(np, &blist, list);
+							lck_mtx_unlock(nfs_buf_mutex);
+							return (error);
+						}
+						error = 0;
+					}
+					lck_mtx_lock(nfs_buf_mutex);
+					continue;
+				}
 			}
-			bp->b_dirtyoff = bp->b_dirtyend = 0;
-#if 1  /* JOE */
+			SET(bp->nb_flags, NB_INVAL);
+			// hold off on FREEUPs until we're done here
+			nfs_buf_release(bp, 0);
+			lck_mtx_lock(nfs_buf_mutex);
+		}
+		nfs_buf_itercomplete(np, &blist, list);
+	}
+	if (!LIST_EMPTY(&(np)->n_dirtyblkhd) || !LIST_EMPTY(&(np)->n_cleanblkhd))
+		panic("nfs_vinvalbuf: flush/inval failed");
+	lck_mtx_unlock(nfs_buf_mutex);
+	nfs_node_lock_force(np);
+	if (!(flags & V_SAVE))
+		np->n_flag &= ~NMODIFIED;
+	if (vnode_vtype(NFSTOV(np)) == VREG)
+		np->n_lastrahead = -1;
+	nfs_node_unlock(np);
+	NFS_BUF_FREEUP();
+	return (0);
+}
+
+
+/*
+ * Flush and invalidate all dirty buffers. If another process is already
+ * doing the flush, just wait for completion.
+ */
+int
+nfs_vinvalbuf(vnode_t vp, int flags, vfs_context_t ctx, int intrflg)
+{
+	return nfs_vinvalbuf2(vp, flags, vfs_context_thread(ctx), vfs_context_ucred(ctx), intrflg);
+}
+
+int
+nfs_vinvalbuf2(vnode_t vp, int flags, thread_t thd, kauth_cred_t cred, int intrflg)
+{
+	nfsnode_t np = VTONFS(vp);
+	struct nfsmount *nmp = VTONMP(vp);
+	int error, rv, slpflag, slptimeo, nflags;
+	off_t size;
+
+	FSDBG_TOP(554, np, flags, intrflg, 0);
+
+	if (nmp && !(nmp->nm_flag & NFSMNT_INT))
+		intrflg = 0;
+	if (intrflg) {
+		slpflag = PCATCH;
+		slptimeo = 2 * hz;
+	} else {
+		slpflag = 0;
+		slptimeo = 0;
+	}
+
+	/* First wait for any other process doing a flush to complete.  */
+	lck_mtx_lock(nfs_buf_mutex);
+	while (np->n_bflag & NBINVALINPROG) {
+		np->n_bflag |= NBINVALWANT;
+		msleep(&np->n_bflag, nfs_buf_mutex, slpflag, "nfs_vinvalbuf", NULL);
+		if ((error = nfs_sigintr(VTONMP(vp), NULL, thd, 0))) {
+			lck_mtx_unlock(nfs_buf_mutex);
+			return (error);
+		}
+	}
+	np->n_bflag |= NBINVALINPROG;
+	lck_mtx_unlock(nfs_buf_mutex);
+
+	/* Now, flush as required.  */
+	error = nfs_vinvalbuf_internal(np, flags, thd, cred, slpflag, 0);
+	while (error) {
+		FSDBG(554, np, 0, 0, error);
+		if ((error = nfs_sigintr(VTONMP(vp), NULL, thd, 0)))
+			goto done;
+		error = nfs_vinvalbuf_internal(np, flags, thd, cred, 0, slptimeo);
+	}
+
+	/* get the pages out of vm also */
+	if (UBCINFOEXISTS(vp) && (size = ubc_getsize(vp)))
+		if (!(rv = ubc_sync_range(vp, 0, size, UBC_PUSHALL | UBC_SYNC | UBC_INVALIDATE)))
+			panic("nfs_vinvalbuf(): ubc_sync_range failed!");
+done:
+	lck_mtx_lock(nfs_buf_mutex);
+	nflags = np->n_bflag;
+	np->n_bflag &= ~(NBINVALINPROG|NBINVALWANT);
+	lck_mtx_unlock(nfs_buf_mutex);
+	if (nflags & NBINVALWANT)
+		wakeup(&np->n_bflag);
+
+	FSDBG_BOT(554, np, flags, intrflg, error);
+	return (error);
+}
+
+/*
+ * Add an async I/O request to the mount's async I/O queue and make
+ * sure that an nfsiod will service it.
+ */
+void
+nfs_asyncio_finish(struct nfsreq *req)
+{
+	struct nfsmount *nmp;
+	struct nfsiod *niod;
+	int started = 0;
+
+	FSDBG_TOP(552, nmp, 0, 0, 0);
+again:
+	if (((nmp = req->r_nmp)) == NULL)
+		return;
+	lck_mtx_lock(nfsiod_mutex);
+	niod = nmp->nm_niod;
+
+	/* grab an nfsiod if we don't have one already */
+	if (!niod) {
+		niod = TAILQ_FIRST(&nfsiodfree);
+		if (niod) {
+			TAILQ_REMOVE(&nfsiodfree, niod, niod_link);
+			TAILQ_INSERT_TAIL(&nfsiodwork, niod, niod_link);
+			niod->niod_nmp = nmp;
+		} else if (((nfsiod_thread_count < NFSIOD_MAX) || (nfsiod_thread_count <= 0)) && (started < 4)) {
 			/*
-			 * validoff and validend represent the real data present
-			 * in this buffer if validoff is non-zero, than we have
-			 * to invalidate the buffer and kill the page when
-			 * biodone is called... the same is also true when
-			 * validend doesn't extend all the way to the end of the
-			 * buffer and validend doesn't equate to the current
-			 * EOF... eventually we need to deal with this in a more
-			 * humane way (like keeping the partial buffer without
-			 * making it immediately available to the VM page cache)
+			 * Try starting a new thread.
+			 * We may try a couple times if other callers
+			 * get the new threads before we do.
 			 */
-			if (bp->b_validoff)
-				SET(bp->b_flags, B_INVAL);
-			else
-			if (bp->b_validend < bp->b_bufsize) {
-				if ((off_t)bp->b_blkno * DEV_BSIZE +
-				    bp->b_validend == np->n_size) {
-					bzero((caddr_t)(bp->b_data +
-							bp->b_validend),
-					      bp->b_bufsize - bp->b_validend);
-					FSDBG(259, bp->b_validend,
-					      bp->b_bufsize - bp->b_validend, 0,
-					      0);
-				} else
-					SET(bp->b_flags, B_INVAL);
-			}
-#endif
-		}
-
-	    } else {
-#if 1  /* JOE */
-		if (bp->b_validoff ||
-		    (bp->b_validend < bp->b_bufsize &&
-		     (off_t)bp->b_blkno * DEV_BSIZE + bp->b_validend !=
-		     np->n_size)) {
-			SET(bp->b_flags, B_INVAL);
-		}
-		if (bp->b_flags & B_INVAL) {
-			FSDBG(260, bp->b_validoff, bp->b_validend,
-			      bp->b_bufsize, bp->b_bcount);
-		}
-#endif
-		bp->b_resid = 0;
-		biodone(bp);
-		FSDBG_BOT(256, bp->b_validoff, bp->b_validend, bp->b_bufsize,
-			  np->n_size);
-		return (0);
-	    }
+			lck_mtx_unlock(nfsiod_mutex);
+			started++;
+			if (!nfsiod_start())
+				goto again;
+			lck_mtx_lock(nfsiod_mutex);
+		}
+	}
+
+	if (req->r_achain.tqe_next == NFSREQNOLIST)
+		TAILQ_INSERT_TAIL(&nmp->nm_iodq, req, r_achain);
+
+	/* If this mount doesn't already have an nfsiod working on it... */
+	if (!nmp->nm_niod) {
+		if (niod) { /* give it the nfsiod we just grabbed */
+			nmp->nm_niod = niod;
+			lck_mtx_unlock(nfsiod_mutex);
+			wakeup(niod);
+		} else if (nfsiod_thread_count > 0) {
+			/* just queue it up on nfsiod mounts queue */
+			TAILQ_INSERT_TAIL(&nfsiodmounts, nmp, nm_iodlink);
+			lck_mtx_unlock(nfsiod_mutex);
+		} else {
+			printf("nfs_asyncio(): no nfsiods? %d %d (%d)\n", nfsiod_thread_count, NFSIOD_MAX, started);
+			lck_mtx_unlock(nfsiod_mutex);
+			/* we have no other option but to be persistent */
+			started = 0;
+			goto again;
+		}
+	} else {
+		lck_mtx_unlock(nfsiod_mutex);
 	}
-	bp->b_resid = uiop->uio_resid;
-	if (must_commit)
-		nfs_clearcommit(vp->v_mount);
 
-	if (bp->b_flags & B_INVAL) {
-		FSDBG(260, bp->b_validoff, bp->b_validend, bp->b_bufsize,
-		      bp->b_bcount);
+	FSDBG_BOT(552, nmp, 0, 0, 0);
+}
+
+/*
+ * queue up async I/O request for resend
+ */
+void
+nfs_asyncio_resend(struct nfsreq *req)
+{
+	struct nfsmount *nmp = req->r_nmp;
+
+	if (!nmp)
+		return;
+	nfs_gss_clnt_rpcdone(req);
+	lck_mtx_lock(&nmp->nm_lock);
+	if (!(req->r_flags & R_RESENDQ)) {
+		TAILQ_INSERT_TAIL(&nmp->nm_resendq, req, r_rchain);
+		req->r_flags |= R_RESENDQ;
 	}
-	FSDBG_BOT(256, bp->b_validoff, bp->b_validend, bp->b_bcount, error);
+	nfs_mount_sock_thread_wake(nmp);
+	lck_mtx_unlock(&nmp->nm_lock);
+}
+
+/*
+ * Read directory data into a buffer.
+ *
+ * Buffer will be filled (unless EOF is hit).
+ * Buffers after this one may also be completely/partially filled.
+ */
+int
+nfs_buf_readdir(struct nfsbuf *bp, vfs_context_t ctx)
+{
+	nfsnode_t np = bp->nb_np;
+	struct nfsmount *nmp = NFSTONMP(np);
+	int error = 0;
+
+	if (!nmp)
+		return (ENXIO);
 
-	biodone(bp);
+	if (nmp->nm_vers < NFS_VER4)
+		error = nfs3_readdir_rpc(np, bp, ctx);
+	else
+		error = nfs4_readdir_rpc(np, bp, ctx);
+
+	if (error && (error != NFSERR_DIRBUFDROPPED)) {
+		SET(bp->nb_flags, NB_ERROR);
+		bp->nb_error = error;
+	}
 	return (error);
 }