initial import of NetBSD tree

1 files changed, 826 insertions, 0 deletions

diff --git a/sys/nfs/nfs_bio.c b/sys/nfs/nfs_bio.c
new file mode 100644
index 00000000000..fd4d2b7fad9
--- /dev/null
+++ b/sys/nfs/nfs_bio.c
@@ -0,0 +1,826 @@
+/*	$NetBSD: nfs_bio.c,v 1.21 1995/07/24 21:20:46 cgd 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. 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	8.5 (Berkeley) 1/4/94
+ */
+
+#include <sys/param.h>
+#include <sys/systm.h>
+#include <sys/resourcevar.h>
+#include <sys/proc.h>
+#include <sys/buf.h>
+#include <sys/vnode.h>
+#include <sys/trace.h>
+#include <sys/mount.h>
+#include <sys/kernel.h>
+
+#include <vm/vm.h>
+
+#include <nfs/nfsnode.h>
+#include <nfs/rpcv2.h>
+#include <nfs/nfsv2.h>
+#include <nfs/nfs.h>
+#include <nfs/nfsmount.h>
+#include <nfs/nqnfs.h>
+
+struct buf *incore(), *nfs_getcacheblk();
+extern struct proc *nfs_iodwant[NFS_MAXASYNCDAEMON];
+extern int nfs_numasync;
+
+/*
+ * Vnode op for read using bio
+ * Any similarity to readip() is purely coincidental
+ */
+nfs_bioread(vp, uio, ioflag, cred)
+	register struct vnode *vp;
+	register struct uio *uio;
+	int ioflag;
+	struct ucred *cred;
+{
+	register struct nfsnode *np = VTONFS(vp);
+	register int biosize, diff;
+	struct buf *bp, *rabp;
+	struct vattr vattr;
+	struct proc *p;
+	struct nfsmount *nmp;
+	daddr_t lbn, bn, rabn;
+	caddr_t baddr;
+	int got_buf, nra, error = 0, n, on, not_readin;
+
+#ifdef lint
+	ioflag = ioflag;
+#endif /* lint */
+#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 && vp->v_type != VDIR)
+		return (EINVAL);
+	nmp = VFSTONFS(vp->v_mount);
+	biosize = nmp->nm_rsize;
+	p = uio->uio_procp;
+	/*
+	 * 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.
+	 * The mount flag NFSMNT_MYWRITE says "Assume that my writes are
+	 * the ones changing the modify time.
+	 * NB: This implies that cache data can be read when up to
+	 * NFS_ATTRTIMEO seconds out of date. If you find that you need current
+	 * attributes this could be forced by setting n_attrstamp to 0 before
+	 * the VOP_GETATTR() call.
+	 */
+	if ((nmp->nm_flag & NFSMNT_NQNFS) == 0 && vp->v_type != VLNK) {
+		if (np->n_flag & NMODIFIED) {
+			if ((nmp->nm_flag & NFSMNT_MYWRITE) == 0 ||
+			     vp->v_type != VREG) {
+				if (error = nfs_vinvalbuf(vp, V_SAVE, cred, p, 1))
+					return (error);
+			}
+			np->n_attrstamp = 0;
+			np->n_direofoffset = 0;
+			if (error = VOP_GETATTR(vp, &vattr, cred, p))
+				return (error);
+			np->n_mtime = vattr.va_mtime.ts_sec;
+		} else {
+			if (error = VOP_GETATTR(vp, &vattr, cred, p))
+				return (error);
+			if (np->n_mtime != vattr.va_mtime.ts_sec) {
+				np->n_direofoffset = 0;
+				if (error = nfs_vinvalbuf(vp, V_SAVE, cred, p, 1))
+					return (error);
+				np->n_mtime = vattr.va_mtime.ts_sec;
+			}
+		}
+	}
+	do {
+
+	    /*
+	     * Get a valid lease. If cached data is stale, flush it.
+	     */
+	    if (nmp->nm_flag & NFSMNT_NQNFS) {
+		if (NQNFS_CKINVALID(vp, np, NQL_READ)) {
+		    do {
+			error = nqnfs_getlease(vp, NQL_READ, cred, p);
+		    } while (error == NQNFS_EXPIRED);
+		    if (error)
+			return (error);
+		    if (np->n_lrev != np->n_brev ||
+			(np->n_flag & NQNFSNONCACHE) ||
+			((np->n_flag & NMODIFIED) && vp->v_type == VDIR)) {
+			if (vp->v_type == VDIR) {
+			    np->n_direofoffset = 0;
+			    cache_purge(vp);
+			}
+			if (error = nfs_vinvalbuf(vp, V_SAVE, cred, p, 1))
+			    return (error);
+			np->n_brev = np->n_lrev;
+		    }
+		} else if (vp->v_type == VDIR && (np->n_flag & NMODIFIED)) {
+		    np->n_direofoffset = 0;
+		    cache_purge(vp);
+		    if (error = nfs_vinvalbuf(vp, V_SAVE, cred, p, 1))
+			return (error);
+		}
+	    }
+	    if (np->n_flag & NQNFSNONCACHE) {
+		switch (vp->v_type) {
+		case VREG:
+			error = nfs_readrpc(vp, uio, cred);
+			break;
+		case VLNK:
+			error = nfs_readlinkrpc(vp, uio, cred);
+			break;
+		case VDIR:
+			error = nfs_readdirrpc(vp, uio, cred);
+			break;
+		};
+		return (error);
+	    }
+	    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 &&
+		    lbn == vp->v_lastr + 1) {
+		    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, cred)) {
+				    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;
+				if (error = nfs_doio(bp, cred, p)) {
+				    brelse(bp);
+				    return (error);
+				}
+			}
+		}
+		n = min((unsigned)(biosize - on), uio->uio_resid);
+		diff = np->n_size - uio->uio_offset;
+		if (diff < n)
+			n = diff;
+		if (not_readin && n > 0) {
+			if (on < bp->b_validoff || (on + n) > bp->b_validend) {
+				if (!got_buf) {
+				    bp = nfs_getcacheblk(vp, bn, biosize, p);
+				    if (!bp)
+					return (EINTR);
+				    got_buf = 1;
+				}
+				bp->b_flags |= B_INVAL;
+				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;
+			}
+		}
+		vp->v_lastr = lbn;
+		diff = (on >= bp->b_validend) ? 0 : (bp->b_validend - on);
+		if (diff < n)
+			n = diff;
+		break;
+	    case VLNK:
+		nfsstats.biocache_readlinks++;
+		bp = nfs_getcacheblk(vp, (daddr_t)0, NFS_MAXPATHLEN, p);
+		if (!bp)
+			return (EINTR);
+		if ((bp->b_flags & B_DONE) == 0) {
+			bp->b_flags |= B_READ;
+			if (error = nfs_doio(bp, cred, p)) {
+				brelse(bp);
+				return (error);
+			}
+		}
+		n = min(uio->uio_resid, NFS_MAXPATHLEN - bp->b_resid);
+		got_buf = 1;
+		on = 0;
+		break;
+	    case VDIR:
+		if (uio->uio_resid < NFS_DIRBLKSIZ)
+			return (0);
+		nfsstats.biocache_readdirs++;
+		bn = (daddr_t)uio->uio_offset;
+		bp = nfs_getcacheblk(vp, bn, NFS_DIRBLKSIZ, p);
+		if (!bp)
+			return (EINTR);
+		if ((bp->b_flags & B_DONE) == 0) {
+			bp->b_flags |= B_READ;
+			if (error = nfs_doio(bp, cred, p)) {
+				brelse(bp);
+				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.
+		 */
+		rabn = bp->b_blkno;
+		if (nfs_numasync > 0 && nmp->nm_readahead > 0 &&
+		    rabn != 0 && rabn != np->n_direofoffset &&
+		    !incore(vp, rabn)) {
+			rabp = nfs_getcacheblk(vp, rabn, NFS_DIRBLKSIZ, p);
+			if (rabp) {
+			    if ((rabp->b_flags & (B_DONE | B_DELWRI)) == 0) {
+				rabp->b_flags |= (B_READ | B_ASYNC);
+				if (nfs_asyncio(rabp, cred)) {
+				    rabp->b_flags |= B_INVAL;
+				    brelse(rabp);
+				}
+			    } else
+				brelse(rabp);
+			}
+		}
+		on = 0;
+		n = min(uio->uio_resid, NFS_DIRBLKSIZ - bp->b_resid);
+		got_buf = 1;
+		break;
+	    };
+
+	    if (n > 0) {
+		if (!baddr)
+			baddr = bp->b_data;
+		error = uiomove(baddr + on, (int)n, uio);
+	    }
+	    switch (vp->v_type) {
+	    case VLNK:
+		n = 0;
+		break;
+	    case VDIR:
+		uio->uio_offset = bp->b_blkno;
+		break;
+	    };
+	    if (got_buf)
+		brelse(bp);
+	} while (error == 0 && uio->uio_resid > 0 && n > 0);
+	return (error);
+}
+
+/*
+ * Vnode op for write using bio
+ */
+nfs_write(ap)
+	struct vop_write_args /* {
+		struct vnode *a_vp;
+		struct uio *a_uio;
+		int  a_ioflag;
+		struct ucred *a_cred;
+	} */ *ap;
+{
+	register int biosize;
+	register struct uio *uio = ap->a_uio;
+	struct proc *p = uio->uio_procp;
+	register struct vnode *vp = ap->a_vp;
+	struct nfsnode *np = VTONFS(vp);
+	register struct ucred *cred = ap->a_cred;
+	int ioflag = ap->a_ioflag;
+	struct buf *bp;
+	struct vattr vattr;
+	struct nfsmount *nmp;
+	daddr_t lbn, bn;
+	int n, on, error = 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 (ioflag & (IO_APPEND | IO_SYNC)) {
+		if (np->n_flag & NMODIFIED) {
+			np->n_attrstamp = 0;
+			if (error = nfs_vinvalbuf(vp, V_SAVE, cred, p, 1))
+				return (error);
+		}
+		if (ioflag & IO_APPEND) {
+			np->n_attrstamp = 0;
+			if (error = VOP_GETATTR(vp, &vattr, cred, p))
+				return (error);
+			uio->uio_offset = np->n_size;
+		}
+	}
+	nmp = VFSTONFS(vp->v_mount);
+	if (uio->uio_offset < 0)
+		return (EINVAL);
+	if (uio->uio_resid == 0)
+		return (0);
+	/*
+	 * Maybe this should be above the vnode op call, but so long as
+	 * file servers have no limits, i don't think it matters
+	 */
+	if (p && uio->uio_offset + uio->uio_resid >
+	      p->p_rlimit[RLIMIT_FSIZE].rlim_cur) {
+		psignal(p, SIGXFSZ);
+		return (EFBIG);
+	}
+	/*
+	 * I use nm_rsize, not nm_wsize so that all buffer cache blocks
+	 * will be the same size within a filesystem. nfs_writerpc will
+	 * still use nm_wsize when sizing the rpc's.
+	 */
+	biosize = nmp->nm_rsize;
+	do {
+
+		/*
+		 * XXX make sure we aren't cached in the VM page cache
+		 */
+		(void)vnode_pager_uncache(vp);
+
+		/*
+		 * Check for a valid write lease.
+		 * If non-cachable, just do the rpc
+		 */
+		if ((nmp->nm_flag & NFSMNT_NQNFS) &&
+		    NQNFS_CKINVALID(vp, np, NQL_WRITE)) {
+			do {
+				error = nqnfs_getlease(vp, NQL_WRITE, cred, p);
+			} while (error == NQNFS_EXPIRED);
+			if (error)
+				return (error);
+			if (np->n_lrev != np->n_brev ||
+			    (np->n_flag & NQNFSNONCACHE)) {
+				if (error = nfs_vinvalbuf(vp, V_SAVE, cred, p, 1))
+					return (error);
+				np->n_brev = np->n_lrev;
+			}
+		}
+		if (np->n_flag & NQNFSNONCACHE)
+			return (nfs_writerpc(vp, uio, cred, ioflag));
+		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);
+		if (bp->b_wcred == NOCRED) {
+			crhold(cred);
+			bp->b_wcred = cred;
+		}
+		np->n_flag |= NMODIFIED;
+		if (uio->uio_offset + n > np->n_size) {
+			np->n_size = uio->uio_offset + n;
+			vnode_pager_setsize(vp, (u_long)np->n_size);
+		}
+
+		/*
+		 * 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;
+		}
+
+		/*
+		 * Check for valid write lease and get one as required.
+		 * In case getblk() and/or bwrite() delayed us.
+		 */
+		if ((nmp->nm_flag & NFSMNT_NQNFS) &&
+		    NQNFS_CKINVALID(vp, np, NQL_WRITE)) {
+			do {
+				error = nqnfs_getlease(vp, NQL_WRITE, cred, p);
+			} while (error == NQNFS_EXPIRED);
+			if (error) {
+				brelse(bp);
+				return (error);
+			}
+			if (np->n_lrev != np->n_brev ||
+			    (np->n_flag & NQNFSNONCACHE)) {
+				brelse(bp);
+				if (error = nfs_vinvalbuf(vp, V_SAVE, cred, p, 1))
+					return (error);
+				np->n_brev = np->n_lrev;
+				goto again;
+			}
+		}
+		if (error = uiomove((char *)bp->b_data + on, n, uio)) {
+			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;
+		}
+#ifndef notdef
+		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);
+		}
+#else
+		bp->b_validoff = bp->b_dirtyoff;
+		bp->b_validend = bp->b_dirtyend;
+#endif
+		if (ioflag & IO_APPEND)
+			bp->b_flags |= B_APPENDWRITE;
+
+		/*
+		 * If the lease is non-cachable or IO_SYNC do bwrite().
+		 */
+		if ((np->n_flag & NQNFSNONCACHE) || (ioflag & IO_SYNC)) {
+			bp->b_proc = p;
+			if (error = VOP_BWRITE(bp))
+				return (error);
+		} else if ((n + on) == biosize &&
+			(nmp->nm_flag & NFSMNT_NQNFS) == 0) {
+			bp->b_proc = (struct proc *)0;
+			bawrite(bp);
+		} else
+			bdwrite(bp);
+	} while (uio->uio_resid > 0 && n > 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;
+	daddr_t bn;
+	int size;
+	struct proc *p;
+{
+	register 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.
+ */
+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;
+
+	if ((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;
+		error = tsleep((caddr_t)&np->n_flag, PRIBIO + 2, "nfsvinval",
+			slptimeo);
+		if (error && intrflg && nfs_sigintr(nmp, (struct nfsreq *)0, p))
+			return (EINTR);
+	}
+
+	/*
+	 * Now, flush as required.
+	 */
+	np->n_flag |= NFLUSHINPROG;
+	error = vinvalbuf(vp, flags, cred, p, slpflag, 0);
+	while (error) {
+		if (intrflg && nfs_sigintr(nmp, (struct nfsreq *)0, p)) {
+			np->n_flag &= ~NFLUSHINPROG;
+			if (np->n_flag & NFLUSHWANT) {
+				np->n_flag &= ~NFLUSHWANT;
+				wakeup((caddr_t)&np->n_flag);
+			}
+			return (EINTR);
+		}
+		error = vinvalbuf(vp, flags, cred, p, 0, slptimeo);
+	}
+	np->n_flag &= ~(NMODIFIED | NFLUSHINPROG);
+	if (np->n_flag & NFLUSHWANT) {
+		np->n_flag &= ~NFLUSHWANT;
+		wakeup((caddr_t)&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.
+ */
+nfs_asyncio(bp, cred)
+	register struct buf *bp;
+	struct ucred *cred;
+{
+	register int i;
+
+	if (nfs_numasync == 0)
+		return (EIO);
+	for (i = 0; i < NFS_MAXASYNCDAEMON; i++)
+	    if (nfs_iodwant[i]) {
+		if (bp->b_flags & B_READ) {
+			if (bp->b_rcred == NOCRED && cred != NOCRED) {
+				crhold(cred);
+				bp->b_rcred = cred;
+			}
+		} else {
+			if (bp->b_wcred == NOCRED && cred != NOCRED) {
+				crhold(cred);
+				bp->b_wcred = cred;
+			}
+		}
+	
+		TAILQ_INSERT_TAIL(&nfs_bufq, bp, b_freelist);
+		nfs_iodwant[i] = (struct proc *)0;
+		wakeup((caddr_t)&nfs_iodwant[i]);
+		return (0);
+	    }
+	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)
+	register struct buf *bp;
+	struct cred *cr;
+	struct proc *p;
+{
+	register struct uio *uiop;
+	register struct vnode *vp;
+	struct nfsnode *np;
+	struct nfsmount *nmp;
+	int error, diff, len;
+	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) {
+	    /*
+	     * ...though reading /dev/drum still gets us here.
+	     */
+	    io.iov_len = uiop->uio_resid = bp->b_bcount;
+	    /* mapping was done by vmapbuf() */
+	    io.iov_base = bp->b_data;
+	    uiop->uio_offset = bp->b_blkno * DEV_BSIZE;
+	    if (bp->b_flags & B_READ) {
+		uiop->uio_rw = UIO_READ;
+		nfsstats.read_physios++;
+		error = nfs_readrpc(vp, uiop, cr);
+	    } else {
+		uiop->uio_rw = UIO_WRITE;
+		nfsstats.write_physios++;
+		error = nfs_writerpc(vp, uiop, cr, 0);
+	    }
+	    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 = bp->b_blkno * DEV_BSIZE;
+		nfsstats.read_bios++;
+		error = nfs_readrpc(vp, uiop, cr);
+		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 - (bp->b_blkno * DEV_BSIZE
+				+ diff);
+			if (len > 0) {
+			    len = min(len, uiop->uio_resid);
+			    bzero((char *)bp->b_data + diff, len);
+			    bp->b_validend = diff + len;
+			} else
+			    bp->b_validend = diff;
+		    } else
+			bp->b_validend = bp->b_bcount;
+		}
+		if (p && (vp->v_flag & VTEXT) &&
+			(((nmp->nm_flag & NFSMNT_NQNFS) &&
+			  NQNFS_CKINVALID(vp, np, NQL_READ) &&
+			  np->n_lrev != np->n_brev) ||
+			 (!(nmp->nm_flag & NFSMNT_NQNFS) &&
+			  np->n_mtime != np->n_vattr.va_mtime.ts_sec))) {
+			uprintf("Process killed due to text file modification\n");
+			psignal(p, SIGKILL);
+			p->p_holdcnt++;
+		}
+		break;
+	    case VLNK:
+		uiop->uio_offset = 0;
+		nfsstats.readlink_bios++;
+		error = nfs_readlinkrpc(vp, uiop, cr);
+		break;
+	    case VDIR:
+		uiop->uio_offset = bp->b_lblkno;
+		nfsstats.readdir_bios++;
+		if (VFSTONFS(vp->v_mount)->nm_flag & NFSMNT_NQNFS)
+		    error = nfs_readdirlookrpc(vp, uiop, cr);
+		else
+		    error = nfs_readdirrpc(vp, uiop, cr);
+		/*
+		 * Save offset cookie in b_blkno.
+		 */
+		bp->b_blkno = uiop->uio_offset;
+		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 = (bp->b_blkno * DEV_BSIZE)
+		+ bp->b_dirtyoff;
+	    io.iov_base = (char *)bp->b_data + bp->b_dirtyoff;
+	    uiop->uio_rw = UIO_WRITE;
+	    nfsstats.write_bios++;
+	    if (bp->b_flags & B_APPENDWRITE)
+		error = nfs_writerpc(vp, uiop, cr, IO_APPEND);
+	    else
+		error = nfs_writerpc(vp, uiop, cr, 0);
+	    bp->b_flags &= ~(B_WRITEINPROG | B_APPENDWRITE);
+
+	    /*
+	     * 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.
+	     */
+	    if (error == EINTR) {
+		bp->b_flags &= ~B_INVAL;
+		bp->b_flags |= B_DELWRI;
+
+		/*
+		 * Since for the B_ASYNC case, nfs_bwrite() has reassigned the
+		 * buffer to the clean list, we have to reassign it back to the
+		 * dirty one. Ugh.
+		 */
+		if (bp->b_flags & B_ASYNC)
+		    reassignbuf(bp, vp);
+		else
+		    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;
+	biodone(bp);
+	return (error);
+}