xnu-517.3.7.tar.gz

[apple/xnu.git] / bsd / nfs / nfs_bio.c

/*
 * Copyright (c) 2000-2003 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 * 
 * Copyright (c) 1999-2003 Apple Computer, Inc.  All Rights Reserved.
 * 
 * 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. 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, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 * 
 * @APPLE_LICENSE_HEADER_END@
 */
/* Copyright (c) 1995 NeXT Computer, Inc. All Rights Reserved */
/*
 * Copyright (c) 1989, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Rick Macklem at The University of Guelph.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *	@(#)nfs_bio.c	8.9 (Berkeley) 3/30/95
 * FreeBSD-Id: nfs_bio.c,v 1.44 1997/09/10 19:52:25 phk Exp $
 */
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/resourcevar.h>
#include <sys/signalvar.h>
#include <sys/proc.h>
#include <sys/malloc.h>
#include <sys/vnode.h>
#include <sys/dirent.h>
#include <sys/mount.h>
#include <sys/kernel.h>
#include <sys/sysctl.h>
#include <sys/ubc.h>

#include <sys/vm.h>
#include <sys/vmparam.h>

#include <sys/time.h>
#include <kern/clock.h>

#include <nfs/rpcv2.h>
#include <nfs/nfsproto.h>
#include <nfs/nfs.h>
#include <nfs/nfsmount.h>
#include <nfs/nqnfs.h>
#include <nfs/nfsnode.h>

#include <sys/kdebug.h>

#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)

extern int nfs_numasync;
extern int nfs_ioddelwri;
extern struct nfsstats nfsstats;

#define	NFSBUFHASH(dvp, lbn)	\
	(&nfsbufhashtbl[((long)(dvp) / sizeof(*(dvp)) + (int)(lbn)) & nfsbufhash])
LIST_HEAD(nfsbufhashhead, nfsbuf) *nfsbufhashtbl;
struct nfsbuffreehead nfsbuffree, nfsbufdelwri;
u_long nfsbufhash;
int nfsbufhashlock, nfsbufcnt, nfsbufmin, nfsbufmax;
int nfsbuffreecnt, nfsbufdelwricnt, nfsneedbuffer;
int nfs_nbdwrite;

#define NFSBUFWRITE_THROTTLE 9

/*
 * Initialize nfsbuf lists
 */
void
nfs_nbinit(void)
{
	nfsbufhashlock = 0;
	nfsbufhashtbl = hashinit(nbuf, M_TEMP, &nfsbufhash);
	TAILQ_INIT(&nfsbuffree);
	TAILQ_INIT(&nfsbufdelwri);
	nfsbufcnt = nfsbuffreecnt = nfsbufdelwricnt = 0;
	nfsbufmin = 128; // XXX tune me!
	nfsbufmax = 8192; // XXX tune me!
	nfsneedbuffer = 0;
	nfs_nbdwrite = 0;
}

/*
 * try to free up some excess, unused nfsbufs
 */
static void
nfs_buf_freeup(void)
{
	struct nfsbuf *fbp;
	int cnt;

#define NFS_BUF_FREEUP() \
    	do { \
		/* only call nfs_buf_freeup() if it has work to do */ \
		if ((nfsbuffreecnt > nfsbufcnt/4) && \
		    (nfsbufcnt-nfsbuffreecnt/8 > nfsbufmin)) \
			nfs_buf_freeup(); \
	} while (0)

	if (nfsbuffreecnt < nfsbufcnt/4)
		return;
	cnt = nfsbuffreecnt/8;
	if (nfsbufcnt-cnt < nfsbufmin)
		return;

	FSDBG(320, -1, nfsbufcnt, nfsbuffreecnt, cnt);
	while (cnt-- > 0) {
		fbp = TAILQ_FIRST(&nfsbuffree);
		if (!fbp)
			break;
		nfs_buf_remfree(fbp);
		/* disassociate buffer from any vnode */
		if (fbp->nb_vp) {
			struct vnode *oldvp;
			if (fbp->nb_vnbufs.le_next != NFSNOLIST) {
				LIST_REMOVE(fbp, nb_vnbufs);
				fbp->nb_vnbufs.le_next = NFSNOLIST;
			}
			oldvp = fbp->nb_vp;
			fbp->nb_vp = NULL;
			HOLDRELE(oldvp);
		}
		LIST_REMOVE(fbp, nb_hash);
		/* nuke any creds */
		if (fbp->nb_rcred != NOCRED)
			crfree(fbp->nb_rcred);
		if (fbp->nb_wcred != NOCRED)
			crfree(fbp->nb_wcred);
		/* if buf was NB_META, dump buffer */
		if (ISSET(fbp->nb_flags, NB_META) && fbp->nb_data) {
			FREE(fbp->nb_data, M_TEMP);
		}
		FREE(fbp, M_TEMP);
		nfsbufcnt--;
	}
	FSDBG(320, -1, nfsbufcnt, nfsbuffreecnt, cnt);
}

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 {
		nfsbuffreecnt--;
		TAILQ_REMOVE(&nfsbuffree, bp, nb_free);
	}
	bp->nb_free.tqe_next = NFSNOLIST;
	NFSBUFCNTCHK();
}

/*
 * check for existence of nfsbuf in cache
 */
struct nfsbuf *
nfs_buf_incore(struct vnode *vp, daddr_t blkno)
{
	/* Search hash chain */
	struct nfsbuf * bp = NFSBUFHASH(vp, blkno)->lh_first;
	for (; bp != NULL; bp = bp->nb_hash.le_next)
		if (bp->nb_lblkno == blkno && bp->nb_vp == vp &&
		    !ISSET(bp->nb_flags, NB_INVAL)) {
			FSDBG(547, bp, blkno, bp->nb_flags, bp->nb_vp);
			return (bp);
		    }
	return (NULL);
}

/*
 * 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_buf_page_inval(struct vnode *vp, off_t offset)
{
	struct nfsbuf *bp;
	bp = nfs_buf_incore(vp, ubc_offtoblk(vp, offset));
	if (!bp)
		return (0);
	FSDBG(325, bp, bp->nb_flags, bp->nb_dirtyoff, bp->nb_dirtyend);
	if (ISSET(bp->nb_flags, NB_BUSY))
		return (EBUSY);
	/*
	 * 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.
	 */
	if (bp->nb_dirtyend > 0) {
		int start = offset - NBOFF(bp);
		if (bp->nb_dirtyend <= start ||
		    bp->nb_dirtyoff >= (start + PAGE_SIZE))
			return (0);
		return (EBUSY);
	}
	return (0);
}

int
nfs_buf_upl_setup(struct nfsbuf *bp)
{
	kern_return_t kret;
	upl_t upl;
	int s;

	if (ISSET(bp->nb_flags, NB_PAGELIST))
		return (0);

	kret = ubc_create_upl(bp->nb_vp, NBOFF(bp), bp->nb_bufsize,
				&upl, NULL, UPL_PRECIOUS);
	if (kret == KERN_INVALID_ARGUMENT) {
		/* vm object probably doesn't exist any more */
		bp->nb_pagelist = NULL;
		return (EINVAL);
	}
	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_vp);

	s = splbio();
	bp->nb_pagelist = upl;
	SET(bp->nb_flags, NB_PAGELIST);
	splx(s);
	return (0);
}

void
nfs_buf_upl_check(struct nfsbuf *bp)
{
	upl_page_info_t *pl;
	off_t filesize, fileoffset;
	int i, npages;

	if (!ISSET(bp->nb_flags, NB_PAGELIST))
		return;

	npages = round_page_32(bp->nb_bufsize) / PAGE_SIZE;
	filesize = ubc_getsize(bp->nb_vp);
	fileoffset = NBOFF(bp);
	if (fileoffset < filesize)
		SET(bp->nb_flags, NB_CACHE);
	else
		CLR(bp->nb_flags, NB_CACHE);

	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);
			if (!ISSET(bp->nb_flags, NB_WASDIRTY))
				SET(bp->nb_flags, NB_WASDIRTY);
		}
	}
	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);
}

static 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_address_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);
}

/*
 * check range of pages in nfsbuf's UPL for validity
 */
static int
nfs_buf_upl_valid_range(struct nfsbuf *bp, int off, int size)
{
	off_t fileoffset, filesize;
	int pg, lastpg;
	upl_page_info_t *pl;

	if (!ISSET(bp->nb_flags, NB_PAGELIST))
		return (0);
	pl = ubc_upl_pageinfo(bp->nb_pagelist);

	size += off & PAGE_MASK;
	off &= ~PAGE_MASK;
	fileoffset = NBOFF(bp);
	filesize = VTONFS(bp->nb_vp)->n_size;
	if ((fileoffset + off + size) > filesize)
		size = filesize - (fileoffset + off);

	pg = off/PAGE_SIZE;
	lastpg = (off + size - 1)/PAGE_SIZE;
	while (pg <= lastpg) {
		if (!upl_valid_page(pl, pg))
			return (0);
		pg++;
	}
	return (1);
}

/*
 * 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.
 */
static void
nfs_buf_normalize_valid_range(struct nfsnode *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 > np->n_size)
		bp->nb_validend = np->n_size % bp->nb_bufsize;
}

/*
 * try to push out some delayed/uncommitted writes
 */
static void
nfs_buf_delwri_push(void)
{
	struct nfsbuf *bp;
	int i;

	if (TAILQ_EMPTY(&nfsbufdelwri))
		return;

	/* first try to tell the nfsiods to do it */
	if (nfs_asyncio(NULL, NULL) == 0)
		return;

	/* otherwise, try to do some of the work ourselves */
	i = 0;
	while (i < 8 && (bp = TAILQ_FIRST(&nfsbufdelwri)) != NULL) {
		struct nfsnode *np = VTONFS(bp->nb_vp);
		nfs_buf_remfree(bp);
		if (ISSET(bp->nb_flags, NB_NEEDCOMMIT)) {
			/* put buffer at end of delwri list */
			TAILQ_INSERT_TAIL(&nfsbufdelwri, bp, nb_free);
			nfsbufdelwricnt++;
			nfs_flushcommits(np->n_vnode, (struct proc *)0);
		} else {
			SET(bp->nb_flags, (NB_BUSY | NB_ASYNC));
			nfs_buf_write(bp);
		}
		i++;
	}
}

/*
 * 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.
 */
struct nfsbuf *
nfs_buf_get(
	struct vnode *vp,
	daddr_t blkno,
	int size,
	struct proc *p,
	int operation)
{
	struct nfsnode *np = VTONFS(vp);
	struct nfsbuf *bp;
	int i, biosize, bufsize, rv;
	struct ucred *cred;
	int slpflag = PCATCH;

	FSDBG_TOP(541, vp, blkno, size, operation);

	bufsize = size;
	if (bufsize > MAXBSIZE)
		panic("nfs_buf_get: buffer larger than MAXBSIZE requested");

	biosize = vp->v_mount->mnt_stat.f_iosize;

	if (UBCINVALID(vp) || !UBCINFOEXISTS(vp))
		operation = BLK_META;
	else if (bufsize < biosize)
		/* reg files should always have biosize blocks */
		bufsize = biosize;

	/* if BLK_WRITE, check for too many delayed/uncommitted writes */
	if ((operation == BLK_WRITE) && (nfs_nbdwrite > ((nfsbufcnt*3)/4))) {
		FSDBG_TOP(542, vp, blkno, nfs_nbdwrite, ((nfsbufcnt*3)/4));

		/* poke the delwri list */
		nfs_buf_delwri_push();

		/* sleep to let other threads run... */
		tsleep(&nfs_nbdwrite, PCATCH, "nfs_nbdwrite", 1);
		FSDBG_BOT(542, vp, blkno, nfs_nbdwrite, ((nfsbufcnt*3)/4));
	}

loop:
	/*
	 * Obtain a lock to prevent a race condition if the
	 * MALLOC() below happens to block.
	 */
	if (nfsbufhashlock) {
		while (nfsbufhashlock) {
			nfsbufhashlock = -1;
			tsleep(&nfsbufhashlock, PCATCH, "nfsbufget", 0);
			if (nfs_sigintr(VFSTONFS(vp->v_mount), NULL, p))
				return (NULL);
		}
		goto loop;
	}
	nfsbufhashlock = 1;

	/* check for existence of nfsbuf in cache */
	if (bp = nfs_buf_incore(vp, blkno)) {
		/* if busy, set wanted and wait */
		if (ISSET(bp->nb_flags, NB_BUSY)) {
			FSDBG_TOP(543, vp, blkno, bp, bp->nb_flags);
			SET(bp->nb_flags, NB_WANTED);
			/* unlock hash */
			if (nfsbufhashlock < 0) {
				nfsbufhashlock = 0;
				wakeup(&nfsbufhashlock);
			} else
				nfsbufhashlock = 0;
			tsleep(bp, slpflag|(PRIBIO+1), "nfsbufget", (slpflag == PCATCH) ? 0 : 2*hz);
			slpflag = 0;
			FSDBG_BOT(543, vp, blkno, bp, bp->nb_flags);
			if (nfs_sigintr(VFSTONFS(vp->v_mount), NULL, p)) {
				FSDBG_BOT(541, vp, blkno, 0, EINTR);
				return (NULL);
			}
			goto loop;
		}
		if (bp->nb_bufsize != bufsize)
			panic("nfsbuf size mismatch");
		SET(bp->nb_flags, (NB_BUSY | NB_CACHE));
		nfs_buf_remfree(bp);
		/* additional paranoia: */
		if (ISSET(bp->nb_flags, NB_PAGELIST))
			panic("pagelist buffer was not busy");
		goto buffer_setup;
	}

	/*
	 * where to get a free buffer:
	 * - alloc new if we haven't reached min bufs
	 * - free list
	 * - alloc new if we haven't reached max allowed
	 * - start clearing out delwri list and try again
	 */

	if ((nfsbufcnt > nfsbufmin) && !TAILQ_EMPTY(&nfsbuffree)) {
		/* pull an nfsbuf off the free list */
		bp = TAILQ_FIRST(&nfsbuffree);
		FSDBG(544, vp, blkno, bp, bp->nb_flags);
		nfs_buf_remfree(bp);
		if (ISSET(bp->nb_flags, NB_DELWRI))
			panic("nfs_buf_get: delwri");
		SET(bp->nb_flags, NB_BUSY);
		/* disassociate buffer from previous vnode */
		if (bp->nb_vp) {
			struct vnode *oldvp;
			if (bp->nb_vnbufs.le_next != NFSNOLIST) {
				LIST_REMOVE(bp, nb_vnbufs);
				bp->nb_vnbufs.le_next = NFSNOLIST;
			}
			oldvp = bp->nb_vp;
			bp->nb_vp = NULL;
			HOLDRELE(oldvp);
		}
		LIST_REMOVE(bp, nb_hash);
		/* nuke any creds we're holding */
		cred = bp->nb_rcred;
		if (cred != NOCRED) {
			bp->nb_rcred = NOCRED; 
			crfree(cred);
		}
		cred = bp->nb_wcred;
		if (cred != NOCRED) {
			bp->nb_wcred = NOCRED; 
			crfree(cred);
		}
		/* if buf will no longer be NB_META, dump old buffer */
		if ((operation != BLK_META) &&
		    ISSET(bp->nb_flags, NB_META) && bp->nb_data) {
			FREE(bp->nb_data, M_TEMP);
			bp->nb_data = NULL;
		}
		/* 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;
	} else if (nfsbufcnt < nfsbufmax) {
		/* just alloc a new one */
		MALLOC(bp, struct nfsbuf *, sizeof(struct nfsbuf), M_TEMP, M_WAITOK);
		nfsbufcnt++;
		NFSBUFCNTCHK();
		/* init nfsbuf */
		bzero(bp, sizeof(*bp));
		bp->nb_free.tqe_next = NFSNOLIST;
		bp->nb_validoff = bp->nb_validend = -1;
		FSDBG(545, vp, blkno, bp, 0);
	} else {
		/* too many bufs... wait for buffers to free up */
		FSDBG_TOP(546, vp, blkno, nfsbufcnt, nfsbufmax);
		/* unlock hash */
		if (nfsbufhashlock < 0) {
			nfsbufhashlock = 0;
			wakeup(&nfsbufhashlock);
		} else
			nfsbufhashlock = 0;

		/* poke the delwri list */
		nfs_buf_delwri_push();

		nfsneedbuffer = 1;
		tsleep(&nfsneedbuffer, PCATCH, "nfsbufget", 0);
		FSDBG_BOT(546, vp, blkno, nfsbufcnt, nfsbufmax);
		if (nfs_sigintr(VFSTONFS(vp->v_mount), NULL, p)) {
			FSDBG_BOT(541, vp, blkno, 0, EINTR);
			return (NULL);
		}
		goto loop;
	}

setup_nfsbuf:

	/* setup nfsbuf */
	bp->nb_flags = NB_BUSY;
	bp->nb_lblkno = blkno;
	/* insert buf in hash */
	LIST_INSERT_HEAD(NFSBUFHASH(vp, blkno), bp, nb_hash);
	/* associate buffer with new vnode */
	VHOLD(vp);
	bp->nb_vp = vp;
	LIST_INSERT_HEAD(&np->n_cleanblkhd, bp, nb_vnbufs);

buffer_setup:

	switch (operation) {
	case BLK_META:
		SET(bp->nb_flags, NB_META);
		if ((bp->nb_bufsize != bufsize) && bp->nb_data) {
			FREE(bp->nb_data, M_TEMP);
			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)
			MALLOC(bp->nb_data, caddr_t, bufsize, M_TEMP, M_WAITOK);
		if (!bp->nb_data)
			panic("nfs_buf_get: null nb_data");
		bp->nb_bufsize = bufsize;
		break;

	case BLK_READ:
	case BLK_WRITE:
		if (bufsize < PAGE_SIZE)
			bufsize = PAGE_SIZE;
		bp->nb_bufsize = bufsize;
		bp->nb_validoff = bp->nb_validend = -1;

		if (UBCISVALID(vp)) {
			/* setup upl */
			if (nfs_buf_upl_setup(bp)) {
				/* unable to create upl */
				/* vm object must no longer exist */
				/* cleanup buffer and return NULL */
				LIST_REMOVE(bp, nb_vnbufs);
				bp->nb_vnbufs.le_next = NFSNOLIST;
				bp->nb_vp = NULL;
				HOLDRELE(vp);
				if (bp->nb_free.tqe_next != NFSNOLIST)
					panic("nfsbuf on freelist");
				TAILQ_INSERT_HEAD(&nfsbuffree, bp, nb_free);
				nfsbuffreecnt++;
				FSDBG_BOT(541, vp, blkno, 0x2bc, EIO);
				return (NULL);
			}
			nfs_buf_upl_check(bp);
		}
		break;

	default:
		panic("nfs_buf_get: %d unknown operation", operation);
	}

	/* unlock hash */
	if (nfsbufhashlock < 0) {
		nfsbufhashlock = 0;
		wakeup(&nfsbufhashlock);
	} else
		nfsbufhashlock = 0;

	FSDBG_BOT(541, vp, blkno, bp, bp->nb_flags);

	return (bp);
}

void
nfs_buf_release(struct nfsbuf *bp)
{
	struct vnode *vp = bp->nb_vp;

	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);

	if (UBCINFOEXISTS(vp) && bp->nb_bufsize) {
		int upl_flags;
		upl_t upl;
		int i, rv;

		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;
		}
		if (bp->nb_flags & (NB_ERROR | NB_INVAL)) {
			if (bp->nb_flags & (NB_READ | NB_INVAL))
				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;
				ubc_upl_commit_range(upl,
					i*PAGE_SIZE, PAGE_SIZE,
					upl_flags |
					UPL_COMMIT_INACTIVATE |
					UPL_COMMIT_FREE_ON_EMPTY);
			}
		}
pagelist_cleanup_done:
		/* was this the last buffer in the file? */
		if (NBOFF(bp) + bp->nb_bufsize > VTONFS(vp)->n_size) {
			/* if so, invalidate all pages of last buffer past EOF */
			int biosize = vp->v_mount->mnt_stat.f_iosize;
			off_t off, size;
			off = trunc_page_64(VTONFS(vp)->n_size) + PAGE_SIZE_64;
			size = trunc_page_64(NBOFF(bp) + biosize) - off;
			if (size)
				ubc_invalidate(vp, off, size);
		}
		CLR(bp->nb_flags, NB_PAGELIST);
		bp->nb_pagelist = NULL;
	}

	/* Wake up any processes waiting for any buffer to become free. */
	if (nfsneedbuffer) {
		nfsneedbuffer = 0;
		wakeup(&nfsneedbuffer);
	}
	/* Wake up any processes waiting for _this_ buffer to become free. */
	if (ISSET(bp->nb_flags, NB_WANTED)) {
		CLR(bp->nb_flags, NB_WANTED);
		wakeup(bp);
	}

	/* If it's not cacheable, or an error, mark it invalid. */
	if (ISSET(bp->nb_flags, (NB_NOCACHE|NB_ERROR)))
		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 vnode */
		if (bp->nb_vnbufs.le_next != NFSNOLIST) {
			LIST_REMOVE(bp, nb_vnbufs);
			bp->nb_vnbufs.le_next = NFSNOLIST;
		}
		bp->nb_vp = NULL;
		HOLDRELE(vp);
		/* 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((caddr_t)&nfs_nbdwrite);
		}
		/* put buffer at head of free list */
		if (bp->nb_free.tqe_next != NFSNOLIST)
			panic("nfsbuf on freelist");
		TAILQ_INSERT_HEAD(&nfsbuffree, bp, nb_free);
		nfsbuffreecnt++;
		NFS_BUF_FREEUP();
	} 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++;
	} else {
		/* put buffer at end of free list */
		if (bp->nb_free.tqe_next != NFSNOLIST)
			panic("nfsbuf on freelist");
		TAILQ_INSERT_TAIL(&nfsbuffree, bp, nb_free);
		nfsbuffreecnt++;
		NFS_BUF_FREEUP();
	}

	NFSBUFCNTCHK();

	/* Unlock the buffer. */
	CLR(bp->nb_flags, (NB_ASYNC | NB_BUSY | NB_NOCACHE | NB_STABLE | NB_IOD));

	FSDBG_BOT(548, bp, NBOFF(bp), bp->nb_flags, bp->nb_data);
}

/*
 * 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);

	while (!ISSET(bp->nb_flags, NB_DONE))
		tsleep(bp, PRIBIO + 1, "nfs_buf_iowait", 0);

	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)
{
	struct vnode *vp;

	FSDBG_TOP(550, bp, NBOFF(bp), bp->nb_flags, bp->nb_error);

	if (ISSET(bp->nb_flags, NB_DONE))
		panic("nfs_buf_iodone already");
	SET(bp->nb_flags, NB_DONE);		/* note that it's done */
	/*
	 * I/O was done, so don't believe
	 * the DIRTY state from VM anymore
	 */
	CLR(bp->nb_flags, NB_WASDIRTY);

	if (!ISSET(bp->nb_flags, NB_READ)) {
		CLR(bp->nb_flags, NB_WRITEINPROG);
		vpwakeup(bp->nb_vp);
	}

	/* Wakeup the throttled write operations as needed */
	vp = bp->nb_vp;
	if (vp && (vp->v_flag & VTHROTTLED)
		&& (vp->v_numoutput <= (NFSBUFWRITE_THROTTLE / 3))) {
		vp->v_flag &= ~VTHROTTLED;
		wakeup((caddr_t)&vp->v_numoutput);
	}

	if (ISSET(bp->nb_flags, NB_ASYNC))	/* if async, release it */
		nfs_buf_release(bp);
	else {		                        /* or just wakeup the buffer */	
		CLR(bp->nb_flags, NB_WANTED);
		wakeup(bp);
	}

	FSDBG_BOT(550, bp, NBOFF(bp), bp->nb_flags, bp->nb_error);
}

void
nfs_buf_write_delayed(struct nfsbuf *bp)
{
	struct proc *p = current_proc();
	struct vnode *vp = bp->nb_vp;

	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) Charge for the write.
	 *	(3) Make sure it's on its vnode's correct block list,
	 */
	if (!ISSET(bp->nb_flags, NB_DELWRI)) {
		SET(bp->nb_flags, NB_DELWRI);
		if (p && p->p_stats) 
			p->p_stats->p_ru.ru_oublock++;		/* XXX */
		nfs_nbdwrite++;
		NFSBUFCNTCHK();
		/* move to dirty list */
		if (bp->nb_vnbufs.le_next != NFSNOLIST)
			LIST_REMOVE(bp, nb_vnbufs);
		LIST_INSERT_HEAD(&VTONFS(vp)->n_dirtyblkhd, bp, nb_vnbufs);
	}

	/*
	 * If the vnode has "too many" write operations in progress
	 * wait for them to finish the IO
	 */
	while (vp->v_numoutput >= NFSBUFWRITE_THROTTLE) {
		vp->v_flag |= VTHROTTLED;
		tsleep((caddr_t)&vp->v_numoutput, PRIBIO + 1, "nfs_buf_write_delayed", 0);
	}

	/*
	 * If we have too many delayed write buffers, 
	 * more than we can "safely" handle, just fall back to
	 * doing the async write
	 */
	if (nfs_nbdwrite < 0)
		panic("nfs_buf_write_delayed: Negative nfs_nbdwrite");

	if (nfs_nbdwrite > ((nfsbufcnt/4)*3)) {
		/* 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);
	FSDBG_BOT(551, bp, NBOFF(bp), bp->nb_flags, 0);
	return;
}


/*
 * Vnode op for read using bio
 * Any similarity to readip() is purely coincidental
 */
int
nfs_bioread(vp, uio, ioflag, cred, getpages)
	register struct vnode *vp;
	register struct uio *uio;
	int ioflag;
	struct ucred *cred;
	int getpages; // XXX unused!
{
	struct nfsnode *np = VTONFS(vp);
	int biosize, i;
	off_t diff;
	struct nfsbuf *bp = 0, *rabp;
	struct vattr vattr;
	struct proc *p;
	struct nfsmount *nmp = VFSTONFS(vp->v_mount);
	daddr_t lbn, rabn, lastrabn = -1;
	int bufsize;
	int nra, error = 0, n = 0, on = 0;
	int operation = (getpages? BLK_PAGEIN : BLK_READ);
	caddr_t dp;
	struct dirent *direntp;

	FSDBG_TOP(514, vp, uio->uio_offset, uio->uio_resid, ioflag);

#if DIAGNOSTIC
	if (uio->uio_rw != UIO_READ)
		panic("nfs_read mode");
#endif
	if (uio->uio_resid == 0) {
		FSDBG_BOT(514, vp, 0xd1e0001, 0, 0);
		return (0);
	}
	if (uio->uio_offset < 0) {
		FSDBG_BOT(514, vp, 0xd1e0002, 0, EINVAL);
		return (EINVAL);
	}
	p = uio->uio_procp;
	if ((nmp->nm_flag & NFSMNT_NFSV3) &&
	    !(nmp->nm_state & NFSSTA_GOTFSINFO))
		(void)nfs_fsinfo(nmp, vp, cred, p);
	biosize = vp->v_mount->mnt_stat.f_iosize;
	/*
	 * 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_MAXATTRTIMEO seconds out of date. If you find that you need
	 * current attributes this could be forced by setting n_xid 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) {
					FSDBG_BOT(514, vp, 0xd1e0003, 0, error);
					return (error);
				}
			}
			np->n_xid = 0;
			error = VOP_GETATTR(vp, &vattr, cred, p);
			if (error) {
				FSDBG_BOT(514, vp, 0xd1e0004, 0, error);
				return (error);
			}
			np->n_mtime = vattr.va_mtime.tv_sec;
		} else {
			error = VOP_GETATTR(vp, &vattr, cred, p);
			if (error) {
				FSDBG_BOT(514, vp, 0xd1e0005, 0, error);
				return (error);
			}
			if (np->n_mtime != vattr.va_mtime.tv_sec) {
				if (vp->v_type == VDIR) {
					nfs_invaldir(vp);
					/* purge name cache entries */
					cache_purge(vp);
				}
				error = nfs_vinvalbuf(vp, V_SAVE, cred, p, 1);
				if (error) {
					FSDBG_BOT(514, vp, 0xd1e0006, 0, error);
					return (error);
				}
				np->n_mtime = vattr.va_mtime.tv_sec;
			}
		}
	}
	do {

	    /*
	     * 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) {
			FSDBG_BOT(514, vp, 0xd1e0007, 0, 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) {
			    FSDBG_BOT(514, vp, 0xd1e0008, 0, 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) {
			FSDBG_BOT(514, vp, 0xd1e0009, 0, error);
			return (error);
		    }
		}
	    }
	    if ((np->n_flag & NQNFSNONCACHE) || (vp->v_flag & VNOCACHE_DATA)) {
		if ((vp->v_flag & VNOCACHE_DATA) &&
		    (np->n_dirtyblkhd.lh_first || np->n_cleanblkhd.lh_first)) {
			error = nfs_vinvalbuf(vp, V_SAVE, cred, p, 1);
			if (error) {
				FSDBG_BOT(514, vp, 0xd1e000a, 0, error);
				return (error);
			}
		}
		switch (vp->v_type) {
		case VREG:
			error = nfs_readrpc(vp, uio, cred);
			FSDBG_BOT(514, vp, uio->uio_offset, uio->uio_resid, error);
			return (error);
		case VLNK:
			error = nfs_readlinkrpc(vp, uio, cred);
			FSDBG_BOT(514, vp, uio->uio_offset, uio->uio_resid, error);
			return (error);
		case VDIR:
			break;
		default:
			printf(" NQNFSNONCACHE: type %x unexpected\n", vp->v_type);
		};
	    }
	    switch (vp->v_type) {
	    case VREG:
		lbn = uio->uio_offset / biosize;

		/*
		 * Copy directly from any cached pages without grabbing the bufs.
		 */
		if (uio->uio_segflg == UIO_USERSPACE) {
			int io_resid = uio->uio_resid;
			diff = np->n_size - uio->uio_offset;
			if (diff < io_resid)
				io_resid = diff;
			if (io_resid > 0) {
				error = cluster_copy_ubc_data(vp, uio, &io_resid, 0);
				if (error) {
					FSDBG_BOT(514, vp, uio->uio_offset, 0xcacefeed, error);
					return (error);
				}
			}
			/* count any biocache reads that we just copied directly */
			if (lbn != uio->uio_offset / biosize) {
				nfsstats.biocache_reads += (uio->uio_offset / biosize) - lbn;
				FSDBG(514, vp, 0xcacefeed, uio->uio_offset, error);
			}
		}

		lbn = uio->uio_offset / biosize;
		on = uio->uio_offset % biosize;

		/*
		 * Start the read ahead(s), as required.
		 */
		if (nfs_numasync > 0 && nmp->nm_readahead > 0) {
			for (nra = 0; nra < nmp->nm_readahead; nra++) {
				rabn = lbn + 1 + nra;
				if (rabn <= lastrabn) {
					/* we've already (tried to) read this block */
					/* no need to try it again... */
					continue;
				}
				lastrabn = rabn;
				if ((off_t)rabn * biosize >= np->n_size)
					break;
				/* check if block exists and is valid. */
				rabp = nfs_buf_incore(vp, rabn);
				if (rabp && nfs_buf_upl_valid_range(rabp, 0, rabp->nb_bufsize))
					continue;
				rabp = nfs_buf_get(vp, rabn, biosize, p, operation);
				if (!rabp) {
					FSDBG_BOT(514, vp, 0xd1e000b, 0, EINTR);
					return (EINTR);
				}
				if (!ISSET(rabp->nb_flags, (NB_CACHE|NB_DELWRI))) {
					SET(rabp->nb_flags, (NB_READ|NB_ASYNC));
					if (nfs_asyncio(rabp, cred)) {
						SET(rabp->nb_flags, (NB_INVAL|NB_ERROR));
						rabp->nb_error = EIO;
						nfs_buf_release(rabp);
					}
				} else
					nfs_buf_release(rabp);
			}
		}

		if ((uio->uio_resid <= 0) || (uio->uio_offset >= np->n_size)) {
			FSDBG_BOT(514, vp, uio->uio_offset, uio->uio_resid, 0xaaaaaaaa);
			return (0);
		}

		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:
		bufsize = biosize;
		n = min((unsigned)(bufsize - on), uio->uio_resid);
		diff = np->n_size - uio->uio_offset;
		if (diff < n)
			n = diff;

		bp = nfs_buf_get(vp, lbn, bufsize, p, operation);
		if (!bp) {
			FSDBG_BOT(514, vp, 0xd1e000c, 0, EINTR);
			return (EINTR);
		}

		/* 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_32(on);
					bp->nb_validend = round_page_32(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)) {
				/* there are also dirty page(s) in the range, */
				/* so write the buffer out and try again */
				CLR(bp->nb_flags, (NB_DONE | NB_ERROR | NB_INVAL));
				SET(bp->nb_flags, NB_ASYNC);
				/*
				 * NFS has embedded ucred so crhold() risks zone corruption
				 */
				if (bp->nb_wcred == NOCRED)
					bp->nb_wcred = crdup(cred);
				error = nfs_buf_write(bp);
				if (error) {
					FSDBG_BOT(514, vp, 0xd1e000d, 0, error);
					return (error);
				}
				goto again;
			}
			if (!bp->nb_dirty && bp->nb_dirtyend <= 0 &&
			    (lastpg - firstpg + 1) > (bufsize/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 */
				struct iovec iov;
				struct uio auio;
				auio.uio_iov = &iov;
				auio.uio_iovcnt = 1;
				auio.uio_offset = NBOFF(bp) + firstpg * PAGE_SIZE_64;
				auio.uio_resid = (lastpg - firstpg + 1) * PAGE_SIZE;
				auio.uio_segflg = UIO_SYSSPACE;
				auio.uio_rw = UIO_READ;
				auio.uio_procp = p;
				NFS_BUF_MAP(bp);
				iov.iov_base = bp->nb_data + firstpg * PAGE_SIZE;
				iov.iov_len = auio.uio_resid;
				error = nfs_readrpc(vp, &auio, cred);
				if (error) {
					nfs_buf_release(bp);
					FSDBG_BOT(514, vp, 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 (auio.uio_resid > 0) {
					/* if short read, must have hit EOF, */
					/* so zero the rest of the range */
					bzero(iov.iov_base, auio.uio_resid);
				}
				/* 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) {
			SET(bp->nb_flags, NB_READ);
			CLR(bp->nb_flags, (NB_DONE | NB_ERROR | NB_INVAL));
			error = nfs_doio(bp, cred, p);
			if (error) {
				nfs_buf_release(bp);
				FSDBG_BOT(514, vp, 0xd1e000f, 0, error);
				return (error);
			}
		}
buffer_ready:
		vp->v_lastr = lbn;
		/* 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);
		break;
	    case VLNK:
		nfsstats.biocache_readlinks++;
		bp = nfs_buf_get(vp, (daddr_t)0, NFS_MAXPATHLEN, p, operation);
		if (!bp) {
			FSDBG_BOT(514, vp, 0xd1e0010, 0, EINTR);
			return (EINTR);
		}
		if (!ISSET(bp->nb_flags, NB_CACHE)) {
			SET(bp->nb_flags, NB_READ);
			error = nfs_doio(bp, cred, p);
			if (error) {
				SET(bp->nb_flags, NB_ERROR);
				nfs_buf_release(bp);
				FSDBG_BOT(514, vp, 0xd1e0011, 0, error);
				return (error);
			}
		}
		n = min(uio->uio_resid, bp->nb_validend);
		on = 0;
		break;
	    case VDIR:
		nfsstats.biocache_readdirs++;
		if (np->n_direofoffset && uio->uio_offset >= np->n_direofoffset) {
			FSDBG_BOT(514, vp, 0xde0f0001, 0, 0);
			return (0);
		}
		lbn = uio->uio_offset / NFS_DIRBLKSIZ;
		on = uio->uio_offset & (NFS_DIRBLKSIZ - 1);
		bp = nfs_buf_get(vp, lbn, NFS_DIRBLKSIZ, p, operation);
		if (!bp) {
			FSDBG_BOT(514, vp, 0xd1e0012, 0, EINTR);
			return (EINTR);
		}
		if (!ISSET(bp->nb_flags, NB_CACHE)) {
		    SET(bp->nb_flags, NB_READ);
		    error = nfs_doio(bp, cred, p);
		    if (error) {
			nfs_buf_release(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) {
				    FSDBG_BOT(514, vp, 0xde0f0002, 0, 0);
				    return (0);
			    }
			    bp = nfs_buf_get(vp, i, NFS_DIRBLKSIZ, p, operation);
			    if (!bp) {
				    FSDBG_BOT(514, vp, 0xd1e0013, 0, EINTR);
				    return (EINTR);
			    }
			    if (!ISSET(bp->nb_flags, NB_CACHE)) {
				    SET(bp->nb_flags, NB_READ);
				    error = nfs_doio(bp, cred, p);
				    /*
				     * no error + NB_INVAL == directory EOF,
				     * use the block.
				     */
				    if (error == 0 && (bp->nb_flags & NB_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)
				    nfs_buf_release(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) {
		        FSDBG_BOT(514, vp, 0xd1e0014, 0, error);
			return (error);
		    }
		}

		/*
		 * 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) &&
		    !nfs_buf_incore(vp, lbn + 1)) {
			rabp = nfs_buf_get(vp, lbn + 1, NFS_DIRBLKSIZ, p,
					       operation);
			if (rabp) {
			    if (!ISSET(rabp->nb_flags, (NB_CACHE))) {
				SET(rabp->nb_flags, (NB_READ | NB_ASYNC));
				if (nfs_asyncio(rabp, cred)) {
				    SET(rabp->nb_flags, (NB_INVAL|NB_ERROR));
				    rabp->nb_error = EIO;
				    nfs_buf_release(rabp);
				}
			    } else {
				nfs_buf_release(rabp);
			    }
			}
		}
		/*
		 * Make sure we use a signed variant of min() since
		 * the second term may be negative.
		 */
		n = lmin(uio->uio_resid, bp->nb_validend - on);
		/*
		 * 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;
		/*
		 * Make sure that we return an integral number of entries so
		 * that any subsequent calls will start copying from the start
		 * of the next entry.
		 *
		 * If the current value of n has the last entry cut short,
		 * set n to copy everything up to the last entry instead.
		 */
		if (n > 0) {
			dp = bp->nb_data + on;
			while (dp < (bp->nb_data + on + n)) {
				direntp = (struct dirent *)dp;
				dp += direntp->d_reclen;
			}
			if (dp > (bp->nb_data + on + n))
				n = (dp - direntp->d_reclen) - (bp->nb_data + on);
		}
		break;
	    default:
		printf("nfs_bioread: type %x unexpected\n",vp->v_type);
		FSDBG_BOT(514, vp, 0xd1e0015, 0, EINVAL);
		return (EINVAL);
	    };

	    if (n > 0) {
		error = uiomove(bp->nb_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->nb_flags, NB_INVAL);
		break;
	    }
 	    nfs_buf_release(bp);
	} while (error == 0 && uio->uio_resid > 0 && n > 0);
	FSDBG_BOT(514, vp, uio->uio_offset, uio->uio_resid, error);
	return (error);
}


/*
 * Vnode op for write using bio
 */
int
nfs_write(ap)
	struct vop_write_args /* {
		struct vnode *a_vp;
		struct uio *a_uio;
		int  a_ioflag;
		struct ucred *a_cred;
	} */ *ap;
{
	struct uio *uio = ap->a_uio;
	struct proc *p = uio->uio_procp;
	struct vnode *vp = ap->a_vp;
	struct nfsnode *np = VTONFS(vp);
	struct ucred *cred = ap->a_cred;
	int ioflag = ap->a_ioflag;
	struct nfsbuf *bp;
	struct vattr vattr;
	struct nfsmount *nmp = VFSTONFS(vp->v_mount);
	daddr_t lbn;
	int biosize, bufsize, writeop;
	int n, on, error = 0, iomode, must_commit;
	off_t boff, start, end;
	struct iovec iov;
	struct uio auio;

	FSDBG_TOP(515, vp, uio->uio_offset, uio->uio_resid, ioflag);

#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;
		FSDBG_BOT(515, vp, uio->uio_offset, uio->uio_resid, np->n_error);
		return (np->n_error);
	}
	if ((nmp->nm_flag & NFSMNT_NFSV3) &&
	    !(nmp->nm_state & NFSSTA_GOTFSINFO))
		(void)nfs_fsinfo(nmp, vp, cred, p);
	if (ioflag & (IO_APPEND | IO_SYNC)) {
		if (np->n_flag & NMODIFIED) {
			np->n_xid = 0;
			error = nfs_vinvalbuf(vp, V_SAVE, cred, p, 1);
			if (error) {
				FSDBG_BOT(515, vp, uio->uio_offset, 0x10bad01, error);
				return (error);
			}
		}
		if (ioflag & IO_APPEND) {
			np->n_xid = 0;
			error = VOP_GETATTR(vp, &vattr, cred, p);
			if (error) {
				FSDBG_BOT(515, vp, uio->uio_offset, 0x10bad02, error);
				return (error);
			}
			uio->uio_offset = np->n_size;
		}
	}
	if (uio->uio_offset < 0) {
		FSDBG_BOT(515, vp, uio->uio_offset, 0xbad0ff, EINVAL);
		return (EINVAL);
	}
	if (uio->uio_resid == 0) {
		FSDBG_BOT(515, vp, uio->uio_offset, 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);
		FSDBG_BOT(515, vp, uio->uio_offset, 0x2b1f, EFBIG);
		return (EFBIG);
	}

	biosize = vp->v_mount->mnt_stat.f_iosize;

	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) {
				FSDBG_BOT(515, vp, uio->uio_offset, 0x11110001, 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) {
					FSDBG_BOT(515, vp, uio->uio_offset, 0x11110002, error);
					return (error);
				}
				np->n_brev = np->n_lrev;
			}
		}
		if (ISSET(vp->v_flag, VNOCACHE_DATA) &&
		    (np->n_dirtyblkhd.lh_first || np->n_cleanblkhd.lh_first)) {
			error = nfs_vinvalbuf(vp, V_SAVE, cred, p, 1);
			if (error) {
				FSDBG_BOT(515, vp, 0, 0, error);
				return (error);
			}
		}
		if (((np->n_flag & NQNFSNONCACHE) ||
		     ISSET(vp->v_flag, VNOCACHE_DATA)) &&
		    uio->uio_iovcnt == 1) {
		    iomode = NFSV3WRITE_FILESYNC;
		    error = nfs_writerpc(vp, uio, cred, &iomode, &must_commit);
		    if (must_commit)
			nfs_clearcommit(vp->v_mount);
		    FSDBG_BOT(515, vp, uio->uio_offset, uio->uio_resid, error);
		    return (error);
		}
		nfsstats.biocache_writes++;
		lbn = uio->uio_offset / biosize;
		on = uio->uio_offset % biosize;
		n = min((unsigned)(biosize - on), uio->uio_resid);
again:
		bufsize = biosize;
		/*
		 * Get a cache block for writing.  The range to be written is
		 * (off..off+n) 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_buf_get(vp, lbn, bufsize, p, BLK_WRITE);
		if (!bp) {
			FSDBG_BOT(515, vp, uio->uio_offset, uio->uio_resid, EINTR);
			return (EINTR);
		}
		/* map the block because we know we're going to write to it */
		NFS_BUF_MAP(bp);

		if (ISSET(vp->v_flag, VNOCACHE_DATA))
			SET(bp->nb_flags, (NB_NOCACHE|NB_INVAL));

		/*
		 * NFS has embedded ucred so crhold() risks zone corruption
		 */
		if (bp->nb_wcred == NOCRED)
			bp->nb_wcred = crdup(cred);

		/*
		 * If there's already a dirty range AND dirty pages in this block we
		 * need to send a commit AND write the dirty pages before continuing.
		 *
		 * If there's already a dirty range OR dirty pages in this block
		 * and the new write range is not contiguous with the existing range,
		 * then force the buffer to be written out now.
		 * (We used to just extend the dirty range to cover the valid,
		 * but unwritten, data in between also.  But writing ranges
		 * of data that weren't actually written by an application
		 * risks overwriting some other client's data with stale data
		 * that's just masquerading as new written data.)
		 */
		if (bp->nb_dirtyend > 0) {
		    if (on > bp->nb_dirtyend || (on + n) < bp->nb_dirtyoff || bp->nb_dirty) {
			FSDBG(515, vp, uio->uio_offset, bp, 0xd15c001);
			/* write/commit buffer "synchronously" */
			/* (NB_STABLE indicates that data writes should be FILESYNC) */
			CLR(bp->nb_flags, (NB_DONE | NB_ERROR | NB_INVAL));
			SET(bp->nb_flags, (NB_ASYNC | NB_STABLE));
			error = nfs_buf_write(bp);
			if (error) {
			    FSDBG_BOT(515, vp, uio->uio_offset, uio->uio_resid, error);
			    return (error);
			}
			goto again;
		    }
		} else if (bp->nb_dirty) {
		    int firstpg, lastpg;
		    u_int32_t pagemask;
		    /* calculate write range pagemask */
		    firstpg = on/PAGE_SIZE;
		    lastpg = (on+n-1)/PAGE_SIZE;
		    pagemask = ((1 << (lastpg+1)) - 1) & ~((1 << firstpg) - 1);
		    /* check if there are dirty pages outside the write range */
		    if (bp->nb_dirty & ~pagemask) {
			FSDBG(515, vp, uio->uio_offset, bp, 0xd15c002);
			/* write/commit buffer "synchronously" */
			/* (NB_STABLE indicates that data writes should be FILESYNC) */
			CLR(bp->nb_flags, (NB_DONE | NB_ERROR | NB_INVAL));
			SET(bp->nb_flags, (NB_ASYNC | NB_STABLE));
			error = nfs_buf_write(bp);
			if (error) {
			    FSDBG_BOT(515, vp, uio->uio_offset, uio->uio_resid, error);
			    return (error);
			}
			goto again;
		    }
		    /* if the first or last pages are already dirty */
		    /* make sure that the dirty range encompasses those pages */
		    if (NBPGDIRTY(bp,firstpg) || NBPGDIRTY(bp,lastpg)) {
			FSDBG(515, vp, uio->uio_offset, bp, 0xd15c003);
		    	bp->nb_dirtyoff = min(on, firstpg * PAGE_SIZE);
			if (NBPGDIRTY(bp,lastpg)) {
			    bp->nb_dirtyend = (lastpg+1) * PAGE_SIZE;
			    /* clip to EOF */
			    if (NBOFF(bp) + bp->nb_dirtyend > np->n_size)
				    bp->nb_dirtyend = np->n_size - NBOFF(bp);
			} else
			    bp->nb_dirtyend = on+n;
		    }
		}

		/*
		 * Are we extending the size of the file with this write?
		 * If so, update file size now that we have the block.
		 * 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 nfsbuf *eofbp = NULL;
			daddr_t eofbn = np->n_size / biosize;
			int eofoff = np->n_size % biosize;
			int neweofoff = (uio->uio_offset + n) % biosize;

			FSDBG(515, 0xb1ffa000, uio->uio_offset + n, eofoff, neweofoff);

			if (eofoff && eofbn < lbn && nfs_buf_incore(vp, eofbn))
				eofbp = nfs_buf_get(vp, eofbn, biosize, p, BLK_WRITE);

			/* if we're extending within the same last block */
			/* and the block is flagged as being cached... */
			if ((lbn == eofbn) && ISSET(bp->nb_flags, NB_CACHE)) {
				/* ...check that all pages in buffer are valid */
				int endpg = ((neweofoff ? neweofoff : biosize) - 1)/PAGE_SIZE;
				u_int32_t pagemask;
				/* pagemask only has to extend to last page being written to */
				pagemask = (1 << (endpg+1)) - 1;
				FSDBG(515, 0xb1ffa001, bp->nb_valid, pagemask, 0);
				if ((bp->nb_valid & pagemask) != pagemask) {
					/* zerofill any hole */
					if (on > bp->nb_validend) {
						int i;
						for (i=bp->nb_validend/PAGE_SIZE; i <= (on - 1)/PAGE_SIZE; i++)
							NBPGVALID_SET(bp, i);
						NFS_BUF_MAP(bp);
						FSDBG(516, bp, bp->nb_validend, on - bp->nb_validend, 0xf01e);
						bzero((char *)bp->nb_data + bp->nb_validend,
							on - bp->nb_validend);
					}
					/* zerofill any trailing data in the last page */
					if (neweofoff) {
						NFS_BUF_MAP(bp);
						FSDBG(516, bp, neweofoff, PAGE_SIZE - (neweofoff & PAGE_MASK), 0xe0f);
						bzero((char *)bp->nb_data + neweofoff,
							PAGE_SIZE - (neweofoff & PAGE_MASK));
					}
				}
			}
			np->n_flag |= NMODIFIED;
			np->n_size = uio->uio_offset + n;
			ubc_setsize(vp, (off_t)np->n_size); /* XXX errors */
			if (eofbp) {
				/*
				 * We may need to zero any previously invalid data
				 * after the old EOF in the previous EOF buffer.
				 *
				 * For the old last page, don't zero bytes if there
				 * are invalid bytes in that page (i.e. the page isn't
				 * currently valid).
				 * For pages after the old last page, zero them and
				 * mark them as valid.
				 */
				char *d;
				int i;
				if (ISSET(vp->v_flag, VNOCACHE_DATA))
					SET(eofbp->nb_flags, (NB_NOCACHE|NB_INVAL));
				NFS_BUF_MAP(eofbp);
				FSDBG(516, eofbp, eofoff, biosize - eofoff, 0xe0fff01e);
				d = eofbp->nb_data;
				i = eofoff/PAGE_SIZE;
				while (eofoff < biosize) {
					int poff = eofoff & PAGE_MASK;
					if (!poff || NBPGVALID(eofbp,i)) {
						bzero(d + eofoff, PAGE_SIZE - poff);
						NBPGVALID_SET(eofbp, i);
					}
					if (bp->nb_validend == eofoff)
						bp->nb_validend += PAGE_SIZE - poff;
					eofoff += PAGE_SIZE - poff;
					i++;
				}
				nfs_buf_release(eofbp);
			}
		}
		/*
		 * If dirtyend exceeds file size, chop it down.  This should
		 * not occur unless there is a race.
		 */
		if (NBOFF(bp) + bp->nb_dirtyend > np->n_size)
			bp->nb_dirtyend = np->n_size - NBOFF(bp);
		/*
		 * UBC doesn't handle partial pages, so we need to make sure
		 * that any pages left in the page cache are completely valid.
		 *
		 * Writes that are smaller than a block are delayed if they
		 * don't extend to the end of the block.
		 *
		 * If the block isn't (completely) cached, we may need to read
		 * in some parts of pages that aren't covered by the write.
		 * If the write offset (on) isn't page aligned, we'll need to
		 * read the start of the first page being written to.  Likewise,
		 * if the offset of the end of the write (on+n) isn't page aligned,
		 * we'll need to read the end of the last page being written to.
		 *
		 * Notes:
		 * We don't want to read anything we're just going to write over.
		 * We don't want to issue multiple I/Os if we don't have to
		 *   (because they're synchronous rpcs).
		 * We don't want to read anything we already have modified in the
		 *   page cache.
		 */
		if (!ISSET(bp->nb_flags, NB_CACHE) && n < biosize) {
			int firstpg, lastpg, dirtypg;
			int firstpgoff, lastpgoff;
			start = end = -1;
			firstpg = on/PAGE_SIZE;
			firstpgoff = on & PAGE_MASK;
			lastpg = (on+n-1)/PAGE_SIZE;
			lastpgoff = (on+n) & PAGE_MASK;
			if (firstpgoff && !NBPGVALID(bp,firstpg)) {
				/* need to read start of first page */
				start = firstpg * PAGE_SIZE;
				end = start + firstpgoff;
			}
			if (lastpgoff && !NBPGVALID(bp,lastpg)) {
				/* need to read end of last page */
				if (start < 0)
					start = (lastpg * PAGE_SIZE) + lastpgoff;
				end = (lastpg + 1) * PAGE_SIZE;
			}
			if (end > start) {
				/* need to read the data in range: start...end-1 */

				/*
				 * XXX: If we know any of these reads are beyond the
				 * current EOF (what np->n_size was before we possibly
				 * just modified it above), we could short-circuit the
				 * reads and just zero buffer.  No need to make a trip
				 * across the network to read nothing.
				 */

				/* first, check for dirty pages in between */
				/* if there are, we'll have to do two reads because */
				/* we don't want to overwrite the dirty pages. */
				for (dirtypg=start/PAGE_SIZE; dirtypg <= (end-1)/PAGE_SIZE; dirtypg++)
					if (NBPGDIRTY(bp,dirtypg))
						break;

				/* if start is at beginning of page, try */
				/* to get any preceeding pages as well. */
				if (!(start & PAGE_MASK)) {
					/* stop at next dirty/valid page or start of block */
					for (; start > 0; start-=PAGE_SIZE)
						if (NBPGVALID(bp,((start-1)/PAGE_SIZE)))
							break;
				}

				NFS_BUF_MAP(bp);
				/* setup uio for read(s) */
				boff = NBOFF(bp);
				auio.uio_iov = &iov;
				auio.uio_iovcnt = 1;
				auio.uio_segflg = UIO_SYSSPACE;
				auio.uio_rw = UIO_READ;
				auio.uio_procp = p;

				if (dirtypg <= (end-1)/PAGE_SIZE) {
					/* there's a dirty page in the way, so just do two reads */
					/* we'll read the preceding data here */
					auio.uio_offset = boff + start;
					auio.uio_resid = iov.iov_len = on - start;
					iov.iov_base = bp->nb_data + start;
					error = nfs_readrpc(vp, &auio, cred);
					if (error) {
						bp->nb_error = error;
						SET(bp->nb_flags, NB_ERROR);
						printf("nfs_write: readrpc %d", error);
					}
					if (auio.uio_resid > 0) {
						FSDBG(516, bp, iov.iov_base - bp->nb_data, auio.uio_resid, 0xd00dee01);
						bzero(iov.iov_base, auio.uio_resid);
					}
					/* update validoff/validend if necessary */
					if ((bp->nb_validoff < 0) || (bp->nb_validoff > start))
						bp->nb_validoff = start;
					if ((bp->nb_validend < 0) || (bp->nb_validend < on))
						bp->nb_validend = on;
					if (np->n_size > boff + bp->nb_validend)
						bp->nb_validend = min(np->n_size - (boff + start), biosize);
					/* validate any pages before the write offset */
					for (; start < on/PAGE_SIZE; start+=PAGE_SIZE)
						NBPGVALID_SET(bp, start/PAGE_SIZE);
					/* adjust start to read any trailing data */
					start = on+n;
				}

				/* if end is at end of page, try to */
				/* get any following pages as well. */
				if (!(end & PAGE_MASK)) {
					/* stop at next valid page or end of block */
					for (; end < bufsize; end+=PAGE_SIZE)
						if (NBPGVALID(bp,end/PAGE_SIZE))
							break;
				}

				/* now we'll read the (rest of the) data */
				auio.uio_offset = boff + start;
				auio.uio_resid = iov.iov_len = end - start;
				iov.iov_base = bp->nb_data + start;
				error = nfs_readrpc(vp, &auio, cred);
				if (error) {
					bp->nb_error = error;
					SET(bp->nb_flags, NB_ERROR);
					printf("nfs_write: readrpc %d", error);
				}
				if (auio.uio_resid > 0) {
					FSDBG(516, bp, iov.iov_base - bp->nb_data, auio.uio_resid, 0xd00dee02);
					bzero(iov.iov_base, auio.uio_resid);
				}
				/* update validoff/validend if necessary */
				if ((bp->nb_validoff < 0) || (bp->nb_validoff > start))
					bp->nb_validoff = start;
				if ((bp->nb_validend < 0) || (bp->nb_validend < end))
					bp->nb_validend = end;
				if (np->n_size > boff + bp->nb_validend)
					bp->nb_validend = min(np->n_size - (boff + start), biosize);
				/* validate any pages before the write offset's page */
				for (; start < trunc_page_32(on); start+=PAGE_SIZE)
					NBPGVALID_SET(bp, start/PAGE_SIZE);
				/* validate any pages after the range of pages being written to */
				for (; (end - 1) > round_page_32(on+n-1); end-=PAGE_SIZE)
					NBPGVALID_SET(bp, (end-1)/PAGE_SIZE);
				/* Note: pages being written to will be validated when written */
			}
		}

		if (ISSET(bp->nb_flags, NB_ERROR)) {
			error = bp->nb_error;
			nfs_buf_release(bp);
			FSDBG_BOT(515, vp, uio->uio_offset, uio->uio_resid, error);
			return (error);
		}

		np->n_flag |= NMODIFIED;

		/*
		 * Check for valid write lease and get one as required.
		 * In case nfs_buf_get() and/or nfs_buf_write() 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) {
				nfs_buf_release(bp);
				FSDBG_BOT(515, vp, uio->uio_offset, 0x11220001, error);
				return (error);
			}
			if (np->n_lrev != np->n_brev ||
			    (np->n_flag & NQNFSNONCACHE)) {
				nfs_buf_release(bp);
				error = nfs_vinvalbuf(vp, V_SAVE, cred, p, 1);
				if (error) {
					FSDBG_BOT(515, vp, uio->uio_offset, 0x11220002, error);
					return (error);
				}
				np->n_brev = np->n_lrev;
				goto again;
			}
		}
		NFS_BUF_MAP(bp);
		error = uiomove((char *)bp->nb_data + on, n, uio);
		if (error) {
			SET(bp->nb_flags, NB_ERROR);
			nfs_buf_release(bp);
			FSDBG_BOT(515, vp, uio->uio_offset, uio->uio_resid, error);
			return (error);
		}

		/* validate any pages written to */
		start = on & ~PAGE_MASK;
		for (; start < on+n; start += PAGE_SIZE) {
			NBPGVALID_SET(bp, start/PAGE_SIZE);
			/*
			 * This may seem a little weird, but we don't actually set the
			 * dirty bits for writes.  This is because we keep the dirty range
			 * in the nb_dirtyoff/nb_dirtyend fields.  Also, particularly for
			 * delayed writes, when we give the pages back to the VM we don't
			 * want to keep them marked dirty, because when we later write the
			 * buffer we won't be able to tell which pages were written dirty
			 * and which pages were mmapped and dirtied.
			 */
		}
		if (bp->nb_dirtyend > 0) {
			bp->nb_dirtyoff = min(on, bp->nb_dirtyoff);
			bp->nb_dirtyend = max((on + n), bp->nb_dirtyend);
		} else {
			bp->nb_dirtyoff = on;
			bp->nb_dirtyend = on + n;
		}
		if (bp->nb_validend <= 0 || bp->nb_validend < bp->nb_dirtyoff ||
		    bp->nb_validoff > bp->nb_dirtyend) {
			bp->nb_validoff = bp->nb_dirtyoff;
			bp->nb_validend = bp->nb_dirtyend;
		} else {
			bp->nb_validoff = min(bp->nb_validoff, bp->nb_dirtyoff);
			bp->nb_validend = max(bp->nb_validend, bp->nb_dirtyend);
		}
		if (!ISSET(bp->nb_flags, NB_CACHE))
			nfs_buf_normalize_valid_range(np, bp);

		/*
		 * Since this block is being modified, it must be written
		 * again and not just committed.
		 */
		if (ISSET(bp->nb_flags, NB_NEEDCOMMIT)) {
			np->n_needcommitcnt--;
			CHECK_NEEDCOMMITCNT(np);
		}
		CLR(bp->nb_flags, NB_NEEDCOMMIT);

		if ((np->n_flag & NQNFSNONCACHE) ||
		    (ioflag & IO_SYNC) || (vp->v_flag & VNOCACHE_DATA)) {
			bp->nb_proc = p;
			error = nfs_buf_write(bp);
			if (error) {
				FSDBG_BOT(515, vp, uio->uio_offset,
					uio->uio_resid, error);
				return (error);
			}
			if (np->n_flag & NQNFSNONCACHE) {
				error = nfs_vinvalbuf(vp, V_SAVE, cred, p, 1);
				if (error) {
					FSDBG_BOT(515, vp, uio->uio_offset,
						uio->uio_resid, error);
					return (error);
				}
			}
		} else if ((n + on) == biosize && (nmp->nm_flag & NFSMNT_NQNFS) == 0) {
			bp->nb_proc = (struct proc *)0;
			SET(bp->nb_flags, NB_ASYNC);
			nfs_buf_write(bp);
		} else
			nfs_buf_write_delayed(bp);

		if (np->n_needcommitcnt > (nbuf/16))
		        nfs_flushcommits(vp, p);

	} while (uio->uio_resid > 0 && n > 0);

	FSDBG_BOT(515, vp, uio->uio_offset, uio->uio_resid, 0);
	return (0);
}

/*
 * Flush out and invalidate all buffers associated with a vnode.
 * Called with the underlying object locked.
 */
static int
nfs_vinvalbuf_internal(vp, flags, cred, p, slpflag, slptimeo)
	register struct vnode *vp;
	int flags;
	struct ucred *cred;
	struct proc *p;
	int slpflag, slptimeo;
{
	struct nfsbuf *bp;
	struct nfsbuf *nbp, *blist;
	int s, error = 0;
	struct nfsnode *np = VTONFS(vp);

	if (flags & V_SAVE) {
		if (error = VOP_FSYNC(vp, cred, MNT_WAIT, p))
			return (error);
		if (np->n_dirtyblkhd.lh_first)
			panic("nfs_vinvalbuf: dirty bufs (vp 0x%x, bp 0x%x)",
				vp, np->n_dirtyblkhd.lh_first);
	}

	for (;;) {
		blist = np->n_cleanblkhd.lh_first;
		if (!blist)
			blist = np->n_dirtyblkhd.lh_first;
		if (!blist)
			break;

		for (bp = blist; bp; bp = nbp) {
			nbp = bp->nb_vnbufs.le_next;
			s = splbio();
			if (ISSET(bp->nb_flags, NB_BUSY)) {
				SET(bp->nb_flags, NB_WANTED);
				FSDBG_TOP(556, vp, bp, NBOFF(bp), bp->nb_flags);
				error = tsleep((caddr_t)bp,
					slpflag | (PRIBIO + 1), "nfs_vinvalbuf",
					slptimeo);
				FSDBG_BOT(556, vp, bp, NBOFF(bp), bp->nb_flags);
				splx(s);
				if (error) {
					FSDBG(554, vp, bp, -1, error);
					return (error);
				}
				break;
			}
			FSDBG(554, vp, bp, NBOFF(bp), bp->nb_flags);
			nfs_buf_remfree(bp);
			SET(bp->nb_flags, NB_BUSY);
			splx(s);
			if ((flags & V_SAVE) && UBCINFOEXISTS(vp) && (NBOFF(bp) < np->n_size)) {
				/* XXX extra paranoia: make sure we're not */
				/* somehow leaving any dirty data around */
				int mustwrite = 0;
				int end = (NBOFF(bp) + bp->nb_bufsize >= np->n_size) ?
				    bp->nb_bufsize : (np->n_size - NBOFF(bp));
				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 && bp->nb_dirtyoff < end) {
					/* clip dirty range to EOF */
					if (bp->nb_dirtyend > end)
						bp->nb_dirtyend = end;
					mustwrite++;
				}
				bp->nb_dirty &= (1 << (round_page_32(end)/PAGE_SIZE)) - 1;
				if (bp->nb_dirty)
					mustwrite++;
				if (mustwrite) {
					FSDBG(554, vp, 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);
					/*
					 * NFS has embedded ucred so crhold() risks zone corruption
					 */
					if (bp->nb_wcred == NOCRED)
						bp->nb_wcred = crdup(cred);
					error = nfs_buf_write(bp);
					// Note: bp has been released
					if (error) {
						FSDBG(554, bp, 0xd00dee, 0xbad, error);
						np->n_error = error;
						np->n_flag |= NWRITEERR;
						error = 0;
					}
					break;
				}
			}
			SET(bp->nb_flags, NB_INVAL);
			nfs_buf_release(bp);
		}
	}
	if (np->n_dirtyblkhd.lh_first || np->n_cleanblkhd.lh_first)
		panic("nfs_vinvalbuf: flush failed");
	return (0);
}


/*
 * Flush and invalidate all dirty buffers. If another process is already
 * doing the flush, just wait for completion.
 */
int
nfs_vinvalbuf(vp, flags, cred, p, intrflg)
	struct vnode *vp;
	int flags;
	struct ucred *cred;
	struct proc *p;
	int intrflg;
{
	register struct nfsnode *np = VTONFS(vp);
	struct nfsmount *nmp = VFSTONFS(vp->v_mount);
	int error = 0, slpflag, slptimeo;
	int didhold = 0;

	FSDBG_TOP(554, vp, flags, intrflg, 0);

	if (nmp && ((nmp->nm_flag & NFSMNT_INT) == 0))
		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.
	 */
	while (np->n_flag & NFLUSHINPROG) {
		np->n_flag |= NFLUSHWANT;
		FSDBG_TOP(555, vp, flags, intrflg, np->n_flag);
		error = tsleep((caddr_t)&np->n_flag, PRIBIO + 2, "nfsvinval", slptimeo);
		FSDBG_BOT(555, vp, flags, intrflg, np->n_flag);
		if (error && (error = nfs_sigintr(VFSTONFS(vp->v_mount), NULL, p))) {
			FSDBG_BOT(554, vp, flags, intrflg, error);
			return (error);
		}
	}

	/*
	 * Now, flush as required.
	 */
	np->n_flag |= NFLUSHINPROG;
	error = nfs_vinvalbuf_internal(vp, flags, cred, p, slpflag, 0);
	while (error) {
		FSDBG(554, vp, 0, 0, error);
		error = nfs_sigintr(VFSTONFS(vp->v_mount), NULL, p);
		if (error) {
			np->n_flag &= ~NFLUSHINPROG;
			if (np->n_flag & NFLUSHWANT) {
				np->n_flag &= ~NFLUSHWANT;
				wakeup((caddr_t)&np->n_flag);
			}
			FSDBG_BOT(554, vp, flags, intrflg, error);
			return (error);
		}
		error = nfs_vinvalbuf_internal(vp, flags, cred, p, 0, slptimeo);
	}
	np->n_flag &= ~(NMODIFIED | NFLUSHINPROG);
	if (np->n_flag & NFLUSHWANT) {
		np->n_flag &= ~NFLUSHWANT;
		wakeup((caddr_t)&np->n_flag);
	}
	didhold = ubc_hold(vp);
	if (didhold) {
		int rv = ubc_clean(vp, 1); /* get the pages out of vm also */
		if (!rv)
			panic("nfs_vinvalbuf(): ubc_clean failed!");
		ubc_rele(vp);
	}
	FSDBG_BOT(554, vp, flags, intrflg, 0);
	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.
 */
int
nfs_asyncio(bp, cred)
	struct nfsbuf *bp;
	struct ucred *cred;
{
	struct nfsmount *nmp;
	int i;
	int gotiod;
	int slpflag = 0;
	int slptimeo = 0;
	int error, error2;

	if (nfs_numasync == 0)
		return (EIO);

	FSDBG_TOP(552, bp, bp ? NBOFF(bp) : 0, bp ? bp->nb_flags : 0, 0);

	nmp = ((bp != NULL) ? VFSTONFS(bp->nb_vp->v_mount) : NULL);
again:
	if (nmp && nmp->nm_flag & NFSMNT_INT)
		slpflag = PCATCH;
	gotiod = FALSE;

	/* no nfsbuf means tell nfsiod to process delwri list */
	if (!bp)
		nfs_ioddelwri = 1;

	/*
	 * 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;
			if (nmp)
				nmp->nm_bufqiods++;
			wakeup((caddr_t)&nfs_iodwant[i]);
			gotiod = TRUE;
			break;
		}

	/* if we're just poking the delwri list, we're done */
	if (!bp)
		return (0);

	/*
	 * 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;
		}
	}

	/*
	 * If we have an iod which can process the request, then queue
	 * the buffer.
	 */
	FSDBG(552, bp, gotiod, i, nmp->nm_bufqiods);
	if (gotiod) {
		/*
		 * Ensure that the queue never grows too large.
		 */
		while (nmp->nm_bufqlen >= 2*nfs_numasync) {
			if (ISSET(bp->nb_flags, NB_IOD)) {
				/* An nfsiod is attempting this async operation so */
				/* we must not fall asleep on the bufq because we */
				/* could be waiting on ourself.  Just return error */
				/* and we'll do this operation syncrhonously. */
				goto out;
			}
			FSDBG(552, bp, nmp->nm_bufqlen, 2*nfs_numasync, -1);
			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) {
				error2 = nfs_sigintr(nmp, NULL, bp->nb_proc);
				if (error2) {
					FSDBG_BOT(552, bp, NBOFF(bp), bp->nb_flags, error2);
					return (error2);
				}
				if (slpflag == PCATCH) {
					slpflag = 0;
					slptimeo = 2 * hz;
				}
			}
			/*
			 * We might have lost our iod while sleeping,
			 * so check and loop if nescessary.
			 */
			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->nb_flags, NB_READ)) {
			if (bp->nb_rcred == NOCRED && cred != NOCRED) {
				/*
				 * NFS has embedded ucred.
				 * Can not crhold() here as that causes zone corruption
				 */
				bp->nb_rcred = crdup(cred);
			}
		} else {
			SET(bp->nb_flags, NB_WRITEINPROG);
			if (bp->nb_wcred == NOCRED && cred != NOCRED) {
				/*
				 * NFS has embedded ucred.
				 * Can not crhold() here as that causes zone corruption
				 */
				bp->nb_wcred = crdup(cred);
			}
		}

		TAILQ_INSERT_TAIL(&nmp->nm_bufq, bp, nb_free);
		nmp->nm_bufqlen++;
		FSDBG_BOT(552, bp, NBOFF(bp), bp->nb_flags, 0);
		return (0);
	}

out:
	/*
	 * All the iods are busy on other mounts, so return EIO to
	 * force the caller to process the i/o synchronously.
	 */
	NFS_DPF(ASYNCIO, ("nfs_asyncio: no iods available, i/o is synchronous\n"));
	FSDBG_BOT(552, bp, NBOFF(bp), bp->nb_flags, EIO);
	return (EIO);
}

/*
 * Do an I/O operation to/from a cache block. This may be called
 * synchronously or from an nfsiod.
 */
int
nfs_doio(bp, cr, p)
	struct nfsbuf *bp;
	struct ucred *cr;
	struct proc *p;
{
	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->nb_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;

	/*
	 * we've decided to perform I/O for this block,
	 * so we couldn't possibly NB_DONE.  So, clear it.
	 */
	if (ISSET(bp->nb_flags, NB_DONE)) {
		if (!ISSET(bp->nb_flags, NB_ASYNC))
			panic("nfs_doio: done and not async");
		CLR(bp->nb_flags, NB_DONE);
	}
	FSDBG_TOP(256, np->n_size, NBOFF(bp), bp->nb_bufsize, bp->nb_flags);
	FSDBG(257, bp->nb_validoff, bp->nb_validend, bp->nb_dirtyoff,
	      bp->nb_dirtyend);

	if (ISSET(bp->nb_flags, NB_READ)) {
	    if (vp->v_type == VREG)
		    NFS_BUF_MAP(bp);
	    io.iov_len = uiop->uio_resid = bp->nb_bufsize;
	    io.iov_base = bp->nb_data;
	    uiop->uio_rw = UIO_READ;
	    switch (vp->v_type) {
	    case VREG:
		uiop->uio_offset = NBOFF(bp);
		nfsstats.read_bios++;
		error = nfs_readrpc(vp, uiop, cr);
		FSDBG(262, np->n_size, NBOFF(bp), uiop->uio_resid, error);
		if (!error) {
		    /* update valid range */
		    bp->nb_validoff = 0;
		    if (uiop->uio_resid) {
			/*
			 * 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.
			 */
			diff = bp->nb_bufsize - uiop->uio_resid;
			len = np->n_size - (NBOFF(bp) + diff);
			if (len > 0) {
				len = min(len, uiop->uio_resid);
				bzero((char *)bp->nb_data + diff, len);
				bp->nb_validend = diff + len;
				FSDBG(258, diff, len, 0, 1);
			} else
				bp->nb_validend = diff;
		    } else
				bp->nb_validend = bp->nb_bufsize;
		    bp->nb_valid = (1 << (round_page_32(bp->nb_validend)/PAGE_SIZE)) - 1;
		    if (bp->nb_validend & PAGE_MASK) {
			    /* valid range ends in the middle of a page so we */
			    /* need to zero-fill any invalid data at the end */
			    /* of the last page */
			    bzero((caddr_t)(bp->nb_data + bp->nb_validend),
			          bp->nb_bufsize - bp->nb_validend);
			    FSDBG(258, bp->nb_validend,
			          bp->nb_bufsize - bp->nb_validend, 0, 2);
		    }
		}
		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;
		}
		break;
	    case VLNK:
		uiop->uio_offset = (off_t)0;
		nfsstats.readlink_bios++;
		error = nfs_readlinkrpc(vp, uiop, cr);
		if (!error) {
			bp->nb_validoff = 0;
			bp->nb_validend = uiop->uio_offset;
		}
		break;
	    case VDIR:
		nfsstats.readdir_bios++;
		uiop->uio_offset = NBOFF(bp);
		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);
		if (!error) {
			bp->nb_validoff = 0;
			bp->nb_validend = uiop->uio_offset - NBOFF(bp);
			bp->nb_valid = (1 << (round_page_32(bp->nb_validend)/PAGE_SIZE)) - 1;
		}
		break;
	    default:
		printf("nfs_doio: type %x unexpected\n", vp->v_type);
		break;
	    };
	    if (error) {
		SET(bp->nb_flags, NB_ERROR);
		bp->nb_error = error;
	    }

	} else {
	    /* we're doing a write */
	    int doff, dend = 0;

	    /* We need to make sure the pages are locked before doing I/O.  */
	    if (!ISSET(bp->nb_flags, NB_META) && UBCISVALID(vp)) {
		if (!ISSET(bp->nb_flags, NB_PAGELIST)) {
		    error = nfs_buf_upl_setup(bp);
		    if (error) {
			printf("nfs_doio: upl create failed %d\n", error);
			SET(bp->nb_flags, NB_ERROR);
			bp->nb_error = EIO;
			return (EIO);
		    }
		    nfs_buf_upl_check(bp);
		}
	    }

	    if (ISSET(bp->nb_flags, NB_WASDIRTY)) {
		FSDBG(256, bp, NBOFF(bp), bp->nb_dirty, 0xd00dee);
		/*
		 * There are pages marked dirty that need to be written out.
		 *
		 * We don't want to just combine the write range with the
		 * range of pages that are dirty because that could cause us
		 * to write data that wasn't actually written to.
		 * We also don't want to write data more than once.
		 *
		 * If the dirty range just needs to be committed, we do that.
		 * Otherwise, we write the dirty range and clear the dirty bits
		 * for any COMPLETE pages covered by that range.
		 * If there are dirty pages left after that, we write out the
		 * parts that we haven't written yet.
		 */
	    }

	    /*
	     * If NB_NEEDCOMMIT is set, a commit rpc may do the trick. If not
	     * an actual write will have to be done.
	     * If NB_WRITEINPROG is already set, then push it with a write anyhow.
	     */
	    if ((bp->nb_flags & (NB_NEEDCOMMIT | NB_WRITEINPROG)) == NB_NEEDCOMMIT) {
		doff = NBOFF(bp) + bp->nb_dirtyoff;
		SET(bp->nb_flags, NB_WRITEINPROG);
		error = nfs_commit(vp, doff, bp->nb_dirtyend - bp->nb_dirtyoff,
				bp->nb_wcred, bp->nb_proc);
		CLR(bp->nb_flags, NB_WRITEINPROG);
		if (!error) {
		    bp->nb_dirtyoff = bp->nb_dirtyend = 0;
		    CLR(bp->nb_flags, NB_NEEDCOMMIT);
		    np->n_needcommitcnt--;
		    CHECK_NEEDCOMMITCNT(np);
		} else if (error == NFSERR_STALEWRITEVERF)
		    nfs_clearcommit(vp->v_mount);
	    }

	    if (!error && bp->nb_dirtyend > 0) {
		/* there's a dirty range that needs to be written out */
		u_int32_t pagemask;
		int firstpg, lastpg;

		if (NBOFF(bp) + bp->nb_dirtyend > np->n_size)
		    bp->nb_dirtyend = np->n_size - NBOFF(bp);

		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 < bp->nb_bufsize && NBPGDIRTY(bp,dend/PAGE_SIZE))
		    	dend += PAGE_SIZE;
		/* make sure to keep dend clipped to EOF */
		if (NBOFF(bp) + dend > 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/nocache/call; otherwise write FILESYNC */
		if (bp->nb_dirty & ~pagemask)
		    iomode = NFSV3WRITE_FILESYNC;
		else if ((bp->nb_flags & (NB_ASYNC | NB_NEEDCOMMIT | NB_NOCACHE | NB_STABLE)) == NB_ASYNC)
		    iomode = NFSV3WRITE_UNSTABLE;
		else
		    iomode = NFSV3WRITE_FILESYNC;

		/* write the dirty range */
		io.iov_len = uiop->uio_resid = dend - doff;
		uiop->uio_offset = NBOFF(bp) + doff;
		io.iov_base = (char *)bp->nb_data + doff;
		uiop->uio_rw = UIO_WRITE;

		nfsstats.write_bios++;

		SET(bp->nb_flags, NB_WRITEINPROG);
		error = nfs_writerpc(vp, uiop, cr, &iomode, &must_commit);
		if (must_commit)
		    nfs_clearcommit(vp->v_mount);
		/* clear dirty bits for pages we've written */
		if (!error)
		    bp->nb_dirty &= ~pagemask;
		/* set/clear needcommit flag */
		if (!error && iomode == NFSV3WRITE_UNSTABLE) {
		    if (!ISSET(bp->nb_flags, NB_NEEDCOMMIT))
			np->n_needcommitcnt++;
		    SET(bp->nb_flags, NB_NEEDCOMMIT);
		    /* make sure nb_dirtyoff/nb_dirtyend reflect actual range written */
		    bp->nb_dirtyoff = doff;
		    bp->nb_dirtyend = dend;
		} else {
		    if (ISSET(bp->nb_flags, NB_NEEDCOMMIT)) {
			np->n_needcommitcnt--;
			CHECK_NEEDCOMMITCNT(np);
		    }
		    CLR(bp->nb_flags, NB_NEEDCOMMIT);
		}
		CLR(bp->nb_flags, NB_WRITEINPROG);
		/*
		 * 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 NB_ERROR and
		 * report the interruption by setting NB_EINTR.  For the NB_ASYNC case,
		 * NB_EINTR is not relevant.
		 *
		 * 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 NB_DELWRI and
		 * NB_NEEDCOMMIT flags.
		 */
		if (error == EINTR || (!error && bp->nb_flags & NB_NEEDCOMMIT)) {
		    CLR(bp->nb_flags, NB_INVAL | NB_NOCACHE);
		    if (!ISSET(bp->nb_flags, NB_DELWRI)) {
			SET(bp->nb_flags, NB_DELWRI);
			nfs_nbdwrite++;
			NFSBUFCNTCHK();
		    }
		    FSDBG(261, bp->nb_validoff, bp->nb_validend,
			  bp->nb_bufsize, 0);
		    /*
		     * Since for the NB_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->nb_flags, NB_ASYNC)) {
			/* move to dirty list */
			int s = splbio();
			if (bp->nb_vnbufs.le_next != NFSNOLIST)
			    LIST_REMOVE(bp, nb_vnbufs);
			LIST_INSERT_HEAD(&np->n_dirtyblkhd, bp, nb_vnbufs);
			splx(s);
		    } else {
			SET(bp->nb_flags, NB_EINTR);
		    }
		} else {
			/* either there's an error or we don't need to commit */
			if (error) {
			    SET(bp->nb_flags, NB_ERROR);
			    bp->nb_error = np->n_error = error;
			    np->n_flag |= NWRITEERR;
			}
			/* clear the dirty range */
			bp->nb_dirtyoff = bp->nb_dirtyend = 0;
		}
	    }

	    if (!error && bp->nb_dirty) {
		/* there are pages marked dirty that need to be written out */
		int pg, cnt, npages, off, len;

		nfsstats.write_bios++;

		NFS_BUF_MAP(bp);

		/*
		 * we do these writes synchronously because we can't really
		 * support the unstable/needommit method.  We could write
		 * them unstable, clear the dirty bits, and then commit the
		 * whole block later, but if we need to rewrite the data, we
		 * won't have any idea which pages were written because that
		 * info can't be stored in the nb_dirtyoff/nb_dirtyend.  We
		 * also can't leave the dirty bits set because then we wouldn't
		 * be able to tell if the pages were re-dirtied between the end
		 * of the write and the commit.
		 */
		iomode = NFSV3WRITE_FILESYNC;
		uiop->uio_rw = UIO_WRITE;

		SET(bp->nb_flags, NB_WRITEINPROG);
		npages = bp->nb_bufsize/PAGE_SIZE;
		for (pg=0; pg < npages; pg++) {
		    if (!NBPGDIRTY(bp,pg))
		    	continue;
		    cnt = 1;
		    while (((pg+cnt) < npages) && NBPGDIRTY(bp,pg+cnt))
			    cnt++;
		    /* write cnt pages starting with page pg */
		    off = pg * PAGE_SIZE;
		    len = cnt * PAGE_SIZE;

		    /* clip writes to EOF */
		    if (NBOFF(bp) + off + len > np->n_size)
		    	len -= (NBOFF(bp) + off + len) - np->n_size;
		    if (len > 0) {
			io.iov_len = uiop->uio_resid = len;
			uiop->uio_offset = NBOFF(bp) + off;
			io.iov_base = (char *)bp->nb_data + off;
			error = nfs_writerpc(vp, uiop, cr, &iomode, &must_commit);
			if (must_commit)
			    nfs_clearcommit(vp->v_mount);
			if (error)
			    break;
		    }
		    /* clear dirty bits */
		    while (cnt--) {
			   bp->nb_dirty &= ~(1 << pg);
			   /* leave pg on last page */
			   if (cnt) pg++;
		    }
		}
		if (!error) {
		    if (ISSET(bp->nb_flags, NB_NEEDCOMMIT)) {
			np->n_needcommitcnt--;
			CHECK_NEEDCOMMITCNT(np);
		    }
		    CLR(bp->nb_flags, NB_NEEDCOMMIT);
		}
		CLR(bp->nb_flags, NB_WRITEINPROG);
		FSDBG_BOT(256, bp->nb_validoff, bp->nb_validend, bp->nb_bufsize,
			  np->n_size);
	    }

	    if (error) {
		SET(bp->nb_flags, NB_ERROR);
		bp->nb_error = error;
	    }
	}

	FSDBG_BOT(256, bp->nb_validoff, bp->nb_validend, bp->nb_bufsize, error);

	nfs_buf_iodone(bp);
	return (error);
}