path: root/sys/nfs/nfs_bio.c

/*	$OpenBSD: nfs_bio.c,v 1.59 2009/06/23 08:08:50 jasper Exp $	*/
/*	$NetBSD: nfs_bio.c,v 1.25.4.2 1996/07/08 20:47:04 jtc Exp $	*/

/*
 * 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. 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
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/resourcevar.h>
#include <sys/signalvar.h>
#include <sys/proc.h>
#include <sys/buf.h>
#include <sys/vnode.h>
#include <sys/mount.h>
#include <sys/kernel.h>
#include <sys/namei.h>
#include <sys/queue.h>
#include <sys/time.h>

#include <uvm/uvm_extern.h>

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

extern int nfs_numasync;
extern struct nfsstats nfsstats;
struct nfs_bufqhead nfs_bufq;
uint32_t nfs_bufqmax, nfs_bufqlen;

/*
 * Vnode op for read using bio
 * Any similarity to readip() is purely coincidental
 */
int
nfs_bioread(vp, uio, ioflag, cred)
	struct vnode *vp;
	struct uio *uio;
	int ioflag;
	struct ucred *cred;
{
	struct nfsnode *np = VTONFS(vp);
	int biosize, diff;
	struct buf *bp = NULL, *rabp;
	struct vattr vattr;
	struct proc *p;
	struct nfsmount *nmp = VFSTONFS(vp->v_mount);
	daddr64_t lbn, bn, rabn;
	caddr_t baddr;
	int got_buf = 0, nra, error = 0, n = 0, on = 0, not_readin;
	off_t offdiff;

#ifdef 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);
	biosize = nmp->nm_rsize;
	/*
	 * 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 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.
	 */
	if (np->n_flag & NMODIFIED) {
		NFS_INVALIDATE_ATTRCACHE(np);
		error = VOP_GETATTR(vp, &vattr, cred, p);
		if (error)
			return (error);
		np->n_mtime = vattr.va_mtime;
	} else {
		error = VOP_GETATTR(vp, &vattr, cred, p);
		if (error)
			return (error);
		if (timespeccmp(&np->n_mtime, &vattr.va_mtime, !=)) {
			error = nfs_vinvalbuf(vp, V_SAVE, cred, p);
			if (error)
				return (error);
			np->n_mtime = vattr.va_mtime;
		}
	}

	/*
	 * update the cache read creds for this vnode
	 */
	if (np->n_rcred)
		crfree(np->n_rcred);
	np->n_rcred = cred;
	crhold(cred);

	do {
	    if ((vp->v_flag & VROOT) && vp->v_type == VLNK) {
		    return (nfs_readlinkrpc(vp, uio, cred));
	    }
	    baddr = (caddr_t)0;
	    switch (vp->v_type) {
	    case VREG:
		nfsstats.biocache_reads++;
		lbn = uio->uio_offset / biosize;
		on = uio->uio_offset & (biosize - 1);
		bn = lbn * (biosize / DEV_BSIZE);
		not_readin = 1;

		/*
		 * Start the read ahead(s), as required.
		 */
		if (nfs_numasync > 0 && nmp->nm_readahead > 0) {
		    for (nra = 0; nra < nmp->nm_readahead &&
			(lbn + 1 + nra) * biosize < np->n_size; nra++) {
			rabn = (lbn + 1 + nra) * (biosize / DEV_BSIZE);
			if (!incore(vp, rabn)) {
			    rabp = nfs_getcacheblk(vp, rabn, biosize, p);
			    if (!rabp)
				return (EINTR);
			    if ((rabp->b_flags & (B_DELWRI | B_DONE)) == 0) {
				rabp->b_flags |= (B_READ | B_ASYNC);
				if (nfs_asyncio(rabp)) {
				    rabp->b_flags |= B_INVAL;
				    brelse(rabp);
				}
			    } else
				brelse(rabp);
			}
		    }
		}

		/*
		 * 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.
		 */
		if ((bp = incore(vp, bn)) &&
		    (bp->b_flags & (B_BUSY | B_WRITEINPROG)) ==
		    (B_BUSY | B_WRITEINPROG))
			got_buf = 0;
		else {
again:
			bp = nfs_getcacheblk(vp, bn, biosize, p);
			if (!bp)
				return (EINTR);
			got_buf = 1;
			if ((bp->b_flags & (B_DONE | B_DELWRI)) == 0) {
				bp->b_flags |= B_READ;
				not_readin = 0;
				error = nfs_doio(bp, p);
				if (error) {
				    brelse(bp);
				    return (error);
				}
			}
		}
		n = min((unsigned)(biosize - on), uio->uio_resid);
		offdiff = np->n_size - uio->uio_offset;
		if (offdiff < (off_t)n)
			n = (int)offdiff;
		if (not_readin && n > 0) {
			if (on < bp->b_validoff || (on + n) > bp->b_validend) {
				if (!got_buf) {
				    bp = nfs_getcacheblk(vp, bn, biosize, p);
				    if (!bp)
					return (EINTR);
				    got_buf = 1;
				}
				bp->b_flags |= B_INVAFTERWRITE;
				if (bp->b_dirtyend > 0) {
				    if ((bp->b_flags & B_DELWRI) == 0)
					panic("nfsbioread");
				    if (VOP_BWRITE(bp) == EINTR)
					return (EINTR);
				} else
				    brelse(bp);
				goto again;
			}
		}
		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, 0, NFS_MAXPATHLEN, p);
		if (!bp)
			return (EINTR);
		if ((bp->b_flags & B_DONE) == 0) {
			bp->b_flags |= B_READ;
			error = nfs_doio(bp, p);
			if (error) {
				brelse(bp);
				return (error);
			}
		}
		n = min(uio->uio_resid, NFS_MAXPATHLEN - bp->b_resid);
		got_buf = 1;
		on = 0;
		break;
	    default:
		printf(" nfsbioread: type %x unexpected\n",vp->v_type);
		break;
	    }

	    if (n > 0) {
		if (!baddr)
			baddr = bp->b_data;
		error = uiomove(baddr + on, (int)n, uio);
	    }
	    switch (vp->v_type) {
	    case VREG:
		break;
	    case VLNK:
		n = 0;
		break;
	    default:
		printf(" nfsbioread: type %x unexpected\n",vp->v_type);
	    }
	    if (got_buf)
		brelse(bp);
	} while (error == 0 && uio->uio_resid > 0 && n > 0);
	return (error);
}

/*
 * Vnode op for write using bio
 */
int
nfs_write(v)
	void *v;
{
	struct vop_write_args *ap = v;
	int biosize;
	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 buf *bp;
	struct vattr vattr;
	struct nfsmount *nmp = VFSTONFS(vp->v_mount);
	daddr64_t lbn, bn;
	int n, on, error = 0, extended = 0, wrotedta = 0, truncated = 0;

#ifdef DIAGNOSTIC
	if (uio->uio_rw != UIO_WRITE)
		panic("nfs_write mode");
	if (uio->uio_segflg == UIO_USERSPACE && uio->uio_procp != curproc)
		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) {
			NFS_INVALIDATE_ATTRCACHE(np);
			error = nfs_vinvalbuf(vp, V_SAVE, cred, p);
			if (error)
				return (error);
		}
		if (ioflag & IO_APPEND) {
			NFS_INVALIDATE_ATTRCACHE(np);
			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);
	}

	/*
	 * update the cache write creds for this node.
	 */
	if (np->n_wcred)
		crfree(np->n_wcred);
	np->n_wcred = cred;
	crhold(cred);

	/*
	 * 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.
	 */
	biosize = nmp->nm_rsize;
	do {

		/*
		 * XXX make sure we aren't cached in the VM page cache
		 */
		uvm_vnp_uncache(vp);

		nfsstats.biocache_writes++;
		lbn = uio->uio_offset / biosize;
		on = uio->uio_offset & (biosize-1);
		n = min((unsigned)(biosize - on), uio->uio_resid);
		bn = lbn * (biosize / DEV_BSIZE);
again:
		bp = nfs_getcacheblk(vp, bn, biosize, p);
		if (!bp)
			return (EINTR);
		np->n_flag |= NMODIFIED;
		if (uio->uio_offset + n > np->n_size) {
			np->n_size = uio->uio_offset + n;
			uvm_vnp_setsize(vp, (u_long)np->n_size);
			extended = 1;
		} else if (uio->uio_offset + n < np->n_size)
			truncated = 1;

		/*
		 * If the new write will leave a contiguous dirty
		 * area, just update the b_dirtyoff and b_dirtyend,
		 * otherwise force a write rpc of the old dirty area.
		 */
		if (bp->b_dirtyend > 0 &&
		    (on > bp->b_dirtyend || (on + n) < bp->b_dirtyoff)) {
			bp->b_proc = p;
			if (VOP_BWRITE(bp) == EINTR)
				return (EINTR);
			goto again;
		}

		error = uiomove((char *)bp->b_data + on, n, uio);
		if (error) {
			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);
		}

		wrotedta = 1;

		/*
		 * Since this block is being modified, it must be written
		 * again and not just committed.
		 */

		if (NFS_ISV3(vp)) {
			rw_enter_write(&np->n_commitlock);
			if (bp->b_flags & B_NEEDCOMMIT) {
				bp->b_flags &= ~B_NEEDCOMMIT;
				nfs_del_tobecommitted_range(vp, bp);
			}
			nfs_del_committed_range(vp, bp);
			rw_exit_write(&np->n_commitlock);
		} else 
			bp->b_flags &= ~B_NEEDCOMMIT;

		/*
		 * If the lease is non-cachable or IO_SYNC do bwrite().
		 */
		if (ioflag & IO_SYNC) {
			bp->b_proc = p;
			error = VOP_BWRITE(bp);
			if (error)
				return (error);
		} else if ((n + on) == biosize) {
			bp->b_proc = (struct proc *)0;
			bp->b_flags |= B_ASYNC;
			(void)nfs_writebp(bp, 0);
		} else {
			bdwrite(bp);
		}
	} while (uio->uio_resid > 0 && n > 0);

	if (wrotedta)
		VN_KNOTE(vp, NOTE_WRITE | (extended ? NOTE_EXTEND : 0) |
		    (truncated ? NOTE_TRUNCATE : 0));

	return (0);
}

/*
 * 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 buf *
nfs_getcacheblk(vp, bn, size, p)
	struct vnode *vp;
	daddr64_t bn;
	int size;
	struct proc *p;
{
	struct buf *bp;
	struct nfsmount *nmp = VFSTONFS(vp->v_mount);

	if (nmp->nm_flag & NFSMNT_INT) {
		bp = getblk(vp, bn, size, PCATCH, 0);
		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);
		}
	} else
		bp = getblk(vp, bn, size, 0, 0);
	return (bp);
}

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

	error = sintr = stimeo = 0;

	if (ISSET(nmp->nm_flag, NFSMNT_INT)) {
		sintr = PCATCH;
		stimeo = 2 * hz;
	}

	/* First wait for any other process doing a flush to complete. */
	while (np->n_flag & NFLUSHINPROG) {
		np->n_flag |= NFLUSHWANT;
		error = tsleep(&np->n_flag, PRIBIO|sintr, "nfsvinval", stimeo);
		if (error && sintr && nfs_sigintr(nmp, NULL, p))
			return (EINTR);
	}

	/* Now, flush as required. */
	np->n_flag |= NFLUSHINPROG;
	error = vinvalbuf(vp, flags, cred, p, sintr, 0);
	while (error) {
		if (sintr && nfs_sigintr(nmp, NULL, p)) {
			np->n_flag &= ~NFLUSHINPROG;
			if (np->n_flag & NFLUSHWANT) {
				np->n_flag &= ~NFLUSHWANT;
				wakeup(&np->n_flag);
			}
			return (EINTR);
		}
		error = vinvalbuf(vp, flags, cred, p, 0, stimeo);
	}
	np->n_flag &= ~(NMODIFIED | NFLUSHINPROG);
	if (np->n_flag & NFLUSHWANT) {
		np->n_flag &= ~NFLUSHWANT;
		wakeup(&np->n_flag);
	}
	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)
	struct buf *bp;
{
	if (nfs_numasync == 0)
		goto out;

	if (nfs_bufqlen > nfs_bufqmax)
		goto out; /* too many bufs in use, force sync */

	if ((bp->b_flags & B_READ) == 0) {
		bp->b_flags |= B_WRITEINPROG;
	}

	TAILQ_INSERT_TAIL(&nfs_bufq, bp, b_freelist);
	nfs_bufqlen++;

	wakeup_one(&nfs_bufq);
	return (0);

out:
	nfsstats.forcedsync++;
	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, p)
	struct buf *bp;
	struct proc *p;
{
	struct uio *uiop;
	struct vnode *vp;
	struct nfsnode *np;
	struct nfsmount *nmp;
	int s, 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;

	/*
	 * Historically, paging was done with physio, but no more.
	 */
	if (bp->b_flags & B_PHYS) {
	    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_BSHIFT;
	    if (bp->b_flags & B_READ) {
		uiop->uio_rw = UIO_READ;
		nfsstats.read_physios++;
		error = nfs_readrpc(vp, uiop);
	    } else {
		iomode = NFSV3WRITE_DATASYNC;
		uiop->uio_rw = UIO_WRITE;
		nfsstats.write_physios++;
		error = nfs_writerpc(vp, uiop, &iomode, &must_commit);
	    }
	    if (error) {
		bp->b_flags |= B_ERROR;
		bp->b_error = error;
	    }
	} else if (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_BSHIFT;
		nfsstats.read_bios++;
		bcstats.pendingreads++;
		bcstats.numreads++;
		error = nfs_readrpc(vp, uiop);
		if (!error) {
		    bp->b_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->b_bcount - uiop->uio_resid;
			len = np->n_size - ((((off_t)bp->b_blkno) << DEV_BSHIFT)
				+ diff);
			if (len > 0) {
			    len = min(len, uiop->uio_resid);
			    bzero((char *)bp->b_data + diff, len);
			    bp->b_validend = diff + len;
			} else
			    bp->b_validend = diff;
		    } else
			bp->b_validend = bp->b_bcount;
		}
		if (p && (vp->v_flag & VTEXT) &&
		    (timespeccmp(&np->n_mtime, &np->n_vattr.va_mtime, !=))) {
			uprintf("Process killed due to text file modification\n");
			psignal(p, SIGKILL);
		}
		break;
	    case VLNK:
		uiop->uio_offset = (off_t)0;
		nfsstats.readlink_bios++;
		bcstats.pendingreads++;
		bcstats.numreads++;
		error = nfs_readlinkrpc(vp, uiop, curproc->p_ucred);
		break;
	    default:
		printf("nfs_doio:  type %x unexpected\n", vp->v_type);
		break;
	    };
	    if (error) {
		bp->b_flags |= B_ERROR;
		bp->b_error = error;
	    }
	} else {
	    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++;
	    bcstats.pendingwrites++;
	    bcstats.numwrites++;
	    if ((bp->b_flags & (B_ASYNC | B_NEEDCOMMIT | B_NOCACHE)) == B_ASYNC)
		iomode = NFSV3WRITE_UNSTABLE;
	    else
		iomode = NFSV3WRITE_FILESYNC;
	    bp->b_flags |= B_WRITEINPROG;
	    error = nfs_writerpc(vp, uiop, &iomode, &must_commit);

	    rw_enter_write(&np->n_commitlock);
	    if (!error && iomode == NFSV3WRITE_UNSTABLE) {
		bp->b_flags |= B_NEEDCOMMIT;
		nfs_add_tobecommitted_range(vp, bp);
	    } else {
		bp->b_flags &= ~B_NEEDCOMMIT;
		nfs_del_committed_range(vp, bp);
	    }
	    rw_exit_write(&np->n_commitlock);

	    bp->b_flags &= ~B_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
	     * 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.
	     */
	    if (error == EINTR || (!error && (bp->b_flags & B_NEEDCOMMIT))) {
		    s = splbio();
		    buf_dirty(bp);
		    splx(s);

		    if (!(bp->b_flags & B_ASYNC) && error)
			    bp->b_flags |= B_EINTR;
	    } else {
		if (error) {
		    bp->b_flags |= B_ERROR;
		    bp->b_error = np->n_error = error;
		    np->n_flag |= NWRITEERR;
		}
		bp->b_dirtyoff = bp->b_dirtyend = 0;
	    }
	}
	bp->b_resid = uiop->uio_resid;
	if (must_commit)
		nfs_clearcommit(vp->v_mount);
	s = splbio();
	biodone(bp);
	splx(s);
	return (error);
}