sys/nfs/nfs_bio.c

root/sys/nfs/nfs_bio.c
/*      $NetBSD: nfs_bio.c,v 1.203 2026/05/03 16:02:36 thorpej 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/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: nfs_bio.c,v 1.203 2026/05/03 16:02:36 thorpej Exp $");

#ifdef _KERNEL_OPT
#include "opt_nfs.h"
#include "opt_ddb.h"
#endif

#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/dirent.h>
#include <sys/kauth.h>

#include <uvm/uvm.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 int nfs_commitsize;
extern struct nfsstats nfsstats;

static int nfs_doio_read(struct buf *, struct uio *);
static int nfs_doio_write(struct buf *, struct uio *);
static int nfs_doio_phys(struct buf *, struct uio *);

/*
 * Vnode op for read using bio
 * Any similarity to readip() is purely coincidental
 */
int
nfs_bioread(struct vnode *vp, struct uio *uio, int ioflag,
            kauth_cred_t cred, int cflag)
{
        struct nfsnode *np = VTONFS(vp);
        struct buf *bp = NULL, *rabp;
        struct nfsmount *nmp = VFSTONFS(vp->v_mount);
        struct nfsdircache *ndp = NULL, *nndp = NULL;
        void *baddr;
        int got_buf = 0, error = 0, n = 0, on = 0, en, enn;
        int enough = 0;
        struct dirent *dp, *pdp, *edp, *ep;
        off_t curoff = 0;
        int advice;
        struct lwp *l = curlwp;

#ifdef DIAGNOSTIC
        if (uio->uio_rw != UIO_READ)
                panic("nfs_read mode");
#endif
        if (uio->uio_resid == 0)
                return (0);
        if (vp->v_type != VDIR && uio->uio_offset < 0)
                return (EINVAL);
#ifndef NFS_V2_ONLY
        if ((nmp->nm_flag & NFSMNT_NFSV3) &&
            !(nmp->nm_iflag & NFSMNT_GOTFSINFO))
                (void)nfs_fsinfo(nmp, vp, cred, l);
#endif
        if (vp->v_type != VDIR &&
            (uio->uio_offset + uio->uio_resid) > nmp->nm_maxfilesize)
                return (EFBIG);

        /*
         * For nfs, cache consistency can only be maintained approximately.
         * Although RFC1094 does not specify the criteria, the following is
         * believed to be compatible with the reference port.
         *
         * If the file's modify time on the server has changed since the
         * last read rpc or you have written to the file,
         * you may have lost data cache consistency with the
         * server, so flush all of the file's data out of the cache.
         * Then force a getattr rpc to ensure that you have up to date
         * attributes.
         * NB: This implies that cache data can be read when up to
         * nfs_attrtimeo seconds out of date. If you find that you need current
         * attributes this could be forced by setting n_attrstamp to 0 before
         * the VOP_GETATTR() call.
         */

        if (vp->v_type != VLNK) {
                error = nfs_flushstalebuf(vp, cred, l,
                    NFS_FLUSHSTALEBUF_MYWRITE);
                if (error)
                        return error;
        }

        do {
            /*
             * Don't cache symlinks.
             */
            if ((vp->v_vflag & VV_ROOT) && vp->v_type == VLNK) {
                return (nfs_readlinkrpc(vp, uio, cred));
            }
            baddr = (void *)0;
            switch (vp->v_type) {
            case VREG:
                nfsstats.biocache_reads++;

                advice = IO_ADV_DECODE(ioflag);
                error = 0;
                while (uio->uio_resid > 0) {
                        vsize_t bytelen;

                        nfs_delayedtruncate(vp);
                        if (np->n_size <= uio->uio_offset) {
                                break;
                        }
                        bytelen =
                            MIN(np->n_size - uio->uio_offset, uio->uio_resid);
                        error = ubc_uiomove(&vp->v_uobj, uio, bytelen, advice,
                            UBC_READ | UBC_PARTIALOK | UBC_VNODE_FLAGS(vp));
                        if (error) {
                                /*
                                 * XXXkludge
                                 * the file has been truncated on the server.
                                 * there isn't much we can do.
                                 */
                                if (uio->uio_offset >= np->n_size) {
                                        /* end of file */
                                        error = 0;
                                } else {
                                        break;
                                }
                        }
                }
                break;

            case VLNK:
                nfsstats.biocache_readlinks++;
                bp = nfs_getcacheblk(vp, (daddr_t)0, MAXPATHLEN, l);
                if (!bp)
                        return (EINTR);
                if ((bp->b_oflags & BO_DONE) == 0) {
                        bp->b_flags |= B_READ;
                        error = nfs_doio(bp);
                        if (error) {
                                brelse(bp, 0);
                                return (error);
                        }
                }
                n = MIN(uio->uio_resid, MAXPATHLEN - bp->b_resid);
                got_buf = 1;
                on = 0;
                break;
            case VDIR:
diragain:
                nfsstats.biocache_readdirs++;
                ndp = nfs_searchdircache(vp, uio->uio_offset,
                        (nmp->nm_flag & NFSMNT_XLATECOOKIE), 0);
                if (!ndp) {
                        /*
                         * We've been handed a cookie that is not
                         * in the cache. If we're not translating
                         * 32 <-> 64, it may be a value that was
                         * flushed out of the cache because it grew
                         * too big. Let the server judge if it's
                         * valid or not. In the translation case,
                         * we have no way of validating this value,
                         * so punt.
                         */
                        if (nmp->nm_flag & NFSMNT_XLATECOOKIE)
                                return (EINVAL);
                        ndp = nfs_enterdircache(vp, uio->uio_offset,
                                uio->uio_offset, 0, 0);
                }

                if (NFS_EOFVALID(np) &&
                    ndp->dc_cookie == np->n_direofoffset) {
                        nfs_putdircache(np, ndp);
                        nfsstats.direofcache_hits++;
                        return (0);
                }

                bp = nfs_getcacheblk(vp, NFSDC_BLKNO(ndp), NFS_DIRBLKSIZ, l);
                if (!bp)
                    return (EINTR);
                if ((bp->b_oflags & BO_DONE) == 0) {
                    bp->b_flags |= B_READ;
                    bp->b_dcookie = ndp->dc_blkcookie;
                    error = nfs_doio(bp);
                    if (error) {
                        /*
                         * Yuck! The directory has been modified on the
                         * server. Punt and let the userland code
                         * deal with it.
                         */
                        nfs_putdircache(np, ndp);
                        brelse(bp, 0);
                        /*
                         * nfs_request maps NFSERR_BAD_COOKIE to EINVAL.
                         */
                        if (error == EINVAL) { /* NFSERR_BAD_COOKIE */
                            nfs_invaldircache(vp, 0);
                            nfs_vinvalbuf(vp, 0, cred, l, 1);
                        }
                        return (error);
                    }
                }

                /*
                 * Just return if we hit EOF right away with this
                 * block. Always check here, because direofoffset
                 * may have been set by an nfsiod since the last
                 * check.
                 *
                 * also, empty block implies EOF.
                 */

                if (bp->b_bcount == bp->b_resid ||
                    (NFS_EOFVALID(np) &&
                    ndp->dc_blkcookie == np->n_direofoffset)) {
                        KASSERT(bp->b_bcount != bp->b_resid ||
                            ndp->dc_blkcookie == bp->b_dcookie);
                        nfs_putdircache(np, ndp);
                        brelse(bp, BC_NOCACHE);
                        return 0;
                }

                /*
                 * Find the entry we were looking for in the block.
                 */

                en = ndp->dc_entry;

                pdp = dp = (struct dirent *)bp->b_data;
                edp = (struct dirent *)(void *)((char *)bp->b_data + bp->b_bcount -
                    bp->b_resid);
                enn = 0;
                while (enn < en && dp < edp) {
                        pdp = dp;
                        dp = _DIRENT_NEXT(dp);
                        enn++;
                }

                /*
                 * If the entry number was bigger than the number of
                 * entries in the block, or the cookie of the previous
                 * entry doesn't match, the directory cache is
                 * stale. Flush it and try again (i.e. go to
                 * the server).
                 */
                if (dp >= edp || (struct dirent *)_DIRENT_NEXT(dp) > edp ||
                    (en > 0 && NFS_GETCOOKIE(pdp) != ndp->dc_cookie)) {
#ifdef DEBUG
                        printf("invalid cache: %p %p %p off %jx %jx\n",
                                pdp, dp, edp,
                                (uintmax_t)uio->uio_offset,
                                (uintmax_t)NFS_GETCOOKIE(pdp));
#endif
                        nfs_putdircache(np, ndp);
                        brelse(bp, 0);
                        nfs_invaldircache(vp, 0);
                        nfs_vinvalbuf(vp, 0, cred, l, 0);
                        goto diragain;
                }

                on = (char *)dp - (char *)bp->b_data;

                /*
                 * Cache all entries that may be exported to the
                 * user, as they may be thrown back at us. The
                 * NFSBIO_CACHECOOKIES flag indicates that all
                 * entries are being 'exported', so cache them all.
                 */

                if (en == 0 && pdp == dp) {
                        dp = _DIRENT_NEXT(dp);
                        enn++;
                }

                if (uio->uio_resid < (bp->b_bcount - bp->b_resid - on)) {
                        n = uio->uio_resid;
                        enough = 1;
                } else
                        n = bp->b_bcount - bp->b_resid - on;

                ep = (struct dirent *)(void *)((char *)bp->b_data + on + n);

                /*
                 * Find last complete entry to copy, caching entries
                 * (if requested) as we go.
                 */

                while (dp < ep && (struct dirent *)_DIRENT_NEXT(dp) <= ep) {
                        if (cflag & NFSBIO_CACHECOOKIES) {
                                nndp = nfs_enterdircache(vp, NFS_GETCOOKIE(pdp),
                                    ndp->dc_blkcookie, enn, bp->b_lblkno);
                                if (nmp->nm_flag & NFSMNT_XLATECOOKIE) {
                                        NFS_STASHCOOKIE32(pdp,
                                            nndp->dc_cookie32);
                                }
                                nfs_putdircache(np, nndp);
                        }
                        pdp = dp;
                        dp = _DIRENT_NEXT(dp);
                        enn++;
                }
                nfs_putdircache(np, ndp);

                /*
                 * If the last requested entry was not the last in the
                 * buffer (happens if NFS_DIRFRAGSIZ < NFS_DIRBLKSIZ),
                 * cache the cookie of the last requested one, and
                 * set of the offset to it.
                 */

                if ((on + n) < bp->b_bcount - bp->b_resid) {
                        curoff = NFS_GETCOOKIE(pdp);
                        nndp = nfs_enterdircache(vp, curoff, ndp->dc_blkcookie,
                            enn, bp->b_lblkno);
                        if (nmp->nm_flag & NFSMNT_XLATECOOKIE) {
                                NFS_STASHCOOKIE32(pdp, nndp->dc_cookie32);
                                curoff = nndp->dc_cookie32;
                        }
                        nfs_putdircache(np, nndp);
                } else
                        curoff = bp->b_dcookie;

                /*
                 * Always cache the entry for the next block,
                 * so that readaheads can use it.
                 */
                nndp = nfs_enterdircache(vp, bp->b_dcookie, bp->b_dcookie, 0,0);
                if (nmp->nm_flag & NFSMNT_XLATECOOKIE) {
                        if (curoff == bp->b_dcookie) {
                                NFS_STASHCOOKIE32(pdp, nndp->dc_cookie32);
                                curoff = nndp->dc_cookie32;
                        }
                }

                n = (char *)_DIRENT_NEXT(pdp) - ((char *)bp->b_data + on);

                /*
                 * 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 &&
                    !NFS_EOFVALID(np)) {
                        rabp = nfs_getcacheblk(vp, NFSDC_BLKNO(nndp),
                                                NFS_DIRBLKSIZ, l);
                        if (rabp) {
                            if ((rabp->b_oflags & (BO_DONE | BO_DELWRI)) == 0) {
                                rabp->b_dcookie = nndp->dc_cookie;
                                rabp->b_flags |= (B_READ | B_ASYNC);
                                if (nfs_asyncio(rabp)) {
                                    brelse(rabp, BC_INVAL);
                                }
                            } else
                                brelse(rabp, 0);
                        }
                }
                nfs_putdircache(np, nndp);
                got_buf = 1;
                break;
            default:
                printf(" nfsbioread: type %x unexpected\n",vp->v_type);
                break;
            }

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

/*
 * Vnode op for write using bio
 */
int
nfs_write(void *v)
{
        struct vop_write_args /* {
                struct vnode *a_vp;
                struct uio *a_uio;
                int  a_ioflag;
                kauth_cred_t a_cred;
        } */ *ap = v;
        struct uio *uio = ap->a_uio;
        struct lwp *l = curlwp;
        struct vnode *vp = ap->a_vp;
        struct nfsnode *np = VTONFS(vp);
        kauth_cred_t cred = ap->a_cred;
        struct nfsmount *nmp = VFSTONFS(vp->v_mount);
        voff_t oldoff, origoff;
        vsize_t bytelen;
        int error = 0;
        int ioflag = ap->a_ioflag;

#ifdef DIAGNOSTIC
        if (uio->uio_rw != UIO_WRITE)
                panic("nfs_write mode");
#endif
        if (vp->v_type != VREG)
                return (EIO);
        if (np->n_flag & NWRITEERR) {
                np->n_flag &= ~NWRITEERR;
                return (np->n_error);
        }
#ifndef NFS_V2_ONLY
        if ((nmp->nm_flag & NFSMNT_NFSV3) &&
            !(nmp->nm_iflag & NFSMNT_GOTFSINFO))
                (void)nfs_fsinfo(nmp, vp, cred, l);
#endif
        if (ioflag & IO_APPEND) {
                NFS_INVALIDATE_ATTRCACHE(np);
                error = nfs_flushstalebuf(vp, cred, l,
                    NFS_FLUSHSTALEBUF_MYWRITE);
                if (error)
                        return (error);
                uio->uio_offset = np->n_size;

                /*
                 * This is already checked above VOP_WRITE, but recheck
                 * the append case here to make sure our idea of the
                 * file size is as fresh as possible.
                 */
                if (uio->uio_offset + uio->uio_resid >
                      l->l_proc->p_rlimit[RLIMIT_FSIZE].rlim_cur) {
                        mutex_enter(&proc_lock);
                        psignal(l->l_proc, SIGXFSZ);
                        mutex_exit(&proc_lock);
                        return (EFBIG);
                }
        }
        if (uio->uio_offset < 0)
                return (EINVAL);
        if ((uio->uio_offset + uio->uio_resid) > nmp->nm_maxfilesize)
                return (EFBIG);
        if (uio->uio_resid == 0)
                return (0);

        origoff = uio->uio_offset;
        do {
                bool overwrite; /* if we are overwriting whole pages */
                u_quad_t oldsize;
                oldoff = uio->uio_offset;
                bytelen = uio->uio_resid;

                nfsstats.biocache_writes++;

                oldsize = np->n_size;
                np->n_flag |= NMODIFIED;
                if (np->n_size < uio->uio_offset + bytelen) {
                        np->n_size = uio->uio_offset + bytelen;
                }
                overwrite = false;
                if ((uio->uio_offset & PAGE_MASK) == 0) {
                        if ((vp->v_vflag & VV_MAPPED) == 0 &&
                            bytelen > PAGE_SIZE) {
                                bytelen = trunc_page(bytelen);
                                overwrite = true;
                        } else if ((bytelen & PAGE_MASK) == 0 &&
                            uio->uio_offset >= vp->v_size) {
                                overwrite = true;
                        }
                }
                if (vp->v_size < uio->uio_offset + bytelen) {
                        uvm_vnp_setwritesize(vp, uio->uio_offset + bytelen);
                }
                error = ubc_uiomove(&vp->v_uobj, uio, bytelen,
                    UVM_ADV_RANDOM, UBC_WRITE | UBC_PARTIALOK |
                    (overwrite ? UBC_FAULTBUSY : 0) |
                    UBC_VNODE_FLAGS(vp));
                if (error) {
                        uvm_vnp_setwritesize(vp, vp->v_size);
                        if (overwrite && np->n_size != oldsize) {
                                /*
                                 * backout size and free pages past eof.
                                 */
                                np->n_size = oldsize;
                                rw_enter(vp->v_uobj.vmobjlock, RW_WRITER);
                                (void)VOP_PUTPAGES(vp, round_page(vp->v_size),
                                    0, PGO_SYNCIO | PGO_FREE);
                        }
                        break;
                }

                /*
                 * update UVM's notion of the size now that we've
                 * copied the data into the vnode's pages.
                 */

                if (vp->v_size < uio->uio_offset) {
                        uvm_vnp_setsize(vp, uio->uio_offset);
                }

                if ((oldoff & ~(nmp->nm_wsize - 1)) !=
                    (uio->uio_offset & ~(nmp->nm_wsize - 1))) {
                        rw_enter(vp->v_uobj.vmobjlock, RW_WRITER);
                        error = VOP_PUTPAGES(vp,
                            trunc_page(oldoff & ~(nmp->nm_wsize - 1)),
                            round_page((uio->uio_offset + nmp->nm_wsize - 1) &
                                       ~(nmp->nm_wsize - 1)), PGO_CLEANIT);
                }
        } while (uio->uio_resid > 0);
        if (error == 0 && (ioflag & IO_SYNC) != 0) {
                rw_enter(vp->v_uobj.vmobjlock, RW_WRITER);
                error = VOP_PUTPAGES(vp,
                    trunc_page(origoff & ~(nmp->nm_wsize - 1)),
                    round_page((uio->uio_offset + nmp->nm_wsize - 1) &
                               ~(nmp->nm_wsize - 1)),
                    PGO_CLEANIT | PGO_SYNCIO);
        }
        return error;
}

/*
 * 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(struct vnode *vp, daddr_t bn, int size, struct lwp *l)
{
        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 == NULL) {
                        if (nfs_sigintr(nmp, NULL, l))
                                return (NULL);
                        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, kauth_cred_t cred,
                struct lwp *l, int intrflg)
{
        struct nfsnode *np = VTONFS(vp);
        struct nfsmount *nmp = VFSTONFS(vp->v_mount);
        int error = 0, allerror = 0, slptimeo;
        bool catch_p;

        if ((nmp->nm_flag & NFSMNT_INT) == 0)
                intrflg = 0;
        if (intrflg) {
                catch_p = true;
                slptimeo = 2 * hz;
        } else {
                catch_p = false;
                if (nmp->nm_flag & NFSMNT_SOFT)
                        slptimeo = nmp->nm_retry * nmp->nm_timeo;
                else
                        slptimeo = 0;
        }
        /*
         * First wait for any other process doing a flush to complete.
         */
        mutex_enter(vp->v_interlock);
        while (np->n_flag & NFLUSHINPROG) {
                np->n_flag |= NFLUSHWANT;
                error = mtsleep(&np->n_flag, PRIBIO + 2, "nfsvinval",
                        slptimeo, vp->v_interlock);
                if (error && intrflg && nfs_sigintr(nmp, NULL, l)) {
                        mutex_exit(vp->v_interlock);
                        return EINTR;
                }
        }

        /*
         * Now, flush as required.
         */
        np->n_flag |= NFLUSHINPROG;
        mutex_exit(vp->v_interlock);
        error = vinvalbuf(vp, flags, cred, l, catch_p, 0);
        while (error) {
                if (allerror == 0)
                        allerror = error;
                if (intrflg && nfs_sigintr(nmp, NULL, l)) {
                        error = EINTR;
                        break;
                }
                error = vinvalbuf(vp, flags, cred, l, 0, slptimeo);
        }
        mutex_enter(vp->v_interlock);
        if (allerror != 0) {
                /*
                 * Keep error from vinvalbuf so fsync/close will know.
                 */
                np->n_error = allerror;
                np->n_flag |= NWRITEERR;
        }
        if (error == 0)
                np->n_flag &= ~NMODIFIED;
        np->n_flag &= ~NFLUSHINPROG;
        if (np->n_flag & NFLUSHWANT) {
                np->n_flag &= ~NFLUSHWANT;
                wakeup(&np->n_flag);
        }
        mutex_exit(vp->v_interlock);
        return error;
}

/*
 * nfs_flushstalebuf: flush cache if it's stale.
 *
 * => caller shouldn't own any pages or buffers which belong to the vnode.
 */

int
nfs_flushstalebuf(struct vnode *vp, kauth_cred_t cred, struct lwp *l,
    int flags)
{
        struct nfsnode *np = VTONFS(vp);
        struct vattr vattr;
        int error;

        if (np->n_flag & NMODIFIED) {
                if ((flags & NFS_FLUSHSTALEBUF_MYWRITE) == 0
                    || vp->v_type != VREG) {
                        error = nfs_vinvalbuf(vp, V_SAVE, cred, l, 1);
                        if (error)
                                return error;
                        if (vp->v_type == VDIR) {
                                nfs_invaldircache(vp, 0);
                        }
                } else {
                        /*
                         * XXX assuming writes are ours.
                         */
                }
                NFS_INVALIDATE_ATTRCACHE(np);
                error = VOP_GETATTR(vp, &vattr, cred);
                if (error)
                        return error;
                np->n_mtime = vattr.va_mtime;
        } else {
                error = VOP_GETATTR(vp, &vattr, cred);
                if (error)
                        return error;
                if (timespeccmp(&np->n_mtime, &vattr.va_mtime, !=)) {
                        if (vp->v_type == VDIR) {
                                nfs_invaldircache(vp, 0);
                        }
                        error = nfs_vinvalbuf(vp, V_SAVE, cred, l, 1);
                        if (error)
                                return error;
                        np->n_mtime = vattr.va_mtime;
                }
        }

        return error;
}

/*
 * 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(struct buf *bp)
{
        struct nfs_iod *iod;
        struct nfsmount *nmp;
        int slptimeo = 0, error;
        bool catch_p = false;

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

        nmp = VFSTONFS(bp->b_vp->v_mount);

        if (nmp->nm_flag & NFSMNT_SOFT)
                slptimeo = nmp->nm_retry * nmp->nm_timeo;

        if (nmp->nm_iflag & NFSMNT_DISMNTFORCE)
                slptimeo = hz;

again:
        if (nmp->nm_flag & NFSMNT_INT)
                catch_p = true;

        /*
         * Find a free iod to process this request.
         */

        mutex_enter(&nfs_iodlist_lock);
        iod = LIST_FIRST(&nfs_iodlist_idle);
        if (iod) {
                /*
                 * Found one, so wake it up and tell it which
                 * mount to process.
                 */
                LIST_REMOVE(iod, nid_idle);
                mutex_enter(&iod->nid_lock);
                mutex_exit(&nfs_iodlist_lock);
                KASSERT(iod->nid_mount == NULL);
                iod->nid_mount = nmp;
                cv_signal(&iod->nid_cv);
                mutex_enter(&nmp->nm_lock);
                mutex_exit(&iod->nid_lock);
                nmp->nm_bufqiods++;
                if (nmp->nm_bufqlen < 2 * nmp->nm_bufqiods) {
                        cv_broadcast(&nmp->nm_aiocv);
                }
        } else {
                mutex_exit(&nfs_iodlist_lock);
                mutex_enter(&nmp->nm_lock);
        }

        KASSERT(mutex_owned(&nmp->nm_lock));

        /*
         * If we have an iod which can process the request, then queue
         * the buffer.  However, even if we have an iod, do not initiate
         * queue cleaning if curproc is the pageout daemon. if the NFS mount
         * is via local loopback, we may put curproc (pagedaemon) to sleep
         * waiting for the writes to complete. But the server (ourself)
         * may block the write, waiting for its (ie., our) pagedaemon
         * to produce clean pages to handle the write: deadlock.
         * XXX: start non-loopback mounts straight away?  If "lots free",
         * let pagedaemon start loopback writes anyway?
         */
        if (nmp->nm_bufqiods > 0) {

                /*
                 * Ensure that the queue never grows too large.
                 */
                if (uvm_lwp_is_pagedaemon(curlwp)) {
                        /* Enqueue for later, to avoid free-page deadlock */
                } else while (nmp->nm_bufqlen >= 2 * nmp->nm_bufqiods) {
                        if (catch_p) {
                                error = cv_timedwait_sig(&nmp->nm_aiocv,
                                    &nmp->nm_lock, slptimeo);
                        } else {
                                error = cv_timedwait(&nmp->nm_aiocv,
                                    &nmp->nm_lock, slptimeo);
                        }
                        if (error) {
                                if (error == EWOULDBLOCK &&
                                    nmp->nm_flag & NFSMNT_SOFT) {
                                        mutex_exit(&nmp->nm_lock);
                                        bp->b_error = EIO;
                                        return (EIO);
                                }

                                if (nfs_sigintr(nmp, NULL, curlwp)) {
                                        mutex_exit(&nmp->nm_lock);
                                        return (EINTR);
                                }
                                if (catch_p) {
                                        catch_p = false;
                                        slptimeo = 2 * hz;
                                }
                        }

                        /*
                         * We might have lost our iod while sleeping,
                         * so check and loop if necessary.
                         */

                        if (nmp->nm_bufqiods == 0) {
                                mutex_exit(&nmp->nm_lock);
                                goto again;
                        }
                }
                TAILQ_INSERT_TAIL(&nmp->nm_bufq, bp, b_freelist);
                nmp->nm_bufqlen++;
                mutex_exit(&nmp->nm_lock);
                return (0);
        }
        mutex_exit(&nmp->nm_lock);

        /*
         * All the iods are busy on other mounts, so return EIO to
         * force the caller to process the i/o synchronously.
         */

        return (EIO);
}

/*
 * nfs_doio for read.
 */
static int
nfs_doio_read(struct buf *bp, struct uio *uiop)
{
        struct vnode *vp = bp->b_vp;
        struct nfsnode *np = VTONFS(vp);
        struct nfsmount *nmp = VFSTONFS(vp->v_mount);
        int error = 0;

        uiop->uio_rw = UIO_READ;
        switch (vp->v_type) {
        case VREG:
                nfsstats.read_bios++;
                error = nfs_readrpc(vp, uiop);
                if (!error && uiop->uio_resid) {
                        int diff, len;

                        /*
                         * If uio_resid > 0, there is a hole in the file and
                         * no writes after the hole have been pushed to
                         * the server yet or the file has been truncated
                         * on the server.
                         * Just zero fill the rest of the valid area.
                         */

                        diff = bp->b_bcount - uiop->uio_resid;
                        len = uiop->uio_resid;
                        memset((char *)bp->b_data + diff, 0, len);
                        uiop->uio_resid = 0;
                }
#if 0
                if (uiop->uio_lwp && (vp->v_iflag & VI_TEXT) &&
                    timespeccmp(&np->n_mtime, &np->n_vattr->va_mtime, !=)) {
                        mutex_enter(&proc_lock);
                        killproc(uiop->uio_lwp->l_proc, "process text file was modified");
                        mutex_exit(&proc_lock);
#if 0 /* XXX NJWLWP */
                        uiop->uio_lwp->l_proc->p_holdcnt++;
#endif
                }
#endif
                break;
        case VLNK:
                KASSERT(uiop->uio_offset == (off_t)0);
                nfsstats.readlink_bios++;
                error = nfs_readlinkrpc(vp, uiop, np->n_rcred);
                break;
        case VDIR:
                nfsstats.readdir_bios++;
                uiop->uio_offset = bp->b_dcookie;
#ifndef NFS_V2_ONLY
                if (nmp->nm_flag & NFSMNT_RDIRPLUS) {
                        error = nfs_readdirplusrpc(vp, uiop,
                            curlwp->l_cred);
                        /*
                         * nfs_request maps NFSERR_NOTSUPP to ENOTSUP.
                         */
                        if (error == ENOTSUP)
                                nmp->nm_flag &= ~NFSMNT_RDIRPLUS;
                }
#else
                nmp->nm_flag &= ~NFSMNT_RDIRPLUS;
#endif
                if ((nmp->nm_flag & NFSMNT_RDIRPLUS) == 0)
                        error = nfs_readdirrpc(vp, uiop,
                            curlwp->l_cred);
                if (!error) {
                        bp->b_dcookie = uiop->uio_offset;
                }
                break;
        default:
                printf("nfs_doio:  type %x unexpected\n", vp->v_type);
                break;
        }
        bp->b_error = error;
        return error;
}

/*
 * nfs_doio for write.
 */
static int
nfs_doio_write(struct buf *bp, struct uio *uiop)
{
        struct vnode *vp = bp->b_vp;
        struct nfsnode *np = VTONFS(vp);
        struct nfsmount *nmp = VFSTONFS(vp->v_mount);
        int iomode;
        bool stalewriteverf = false;
        int i, npages = (bp->b_bcount + PAGE_SIZE - 1) >> PAGE_SHIFT;
        struct vm_page **pgs, *spgs[UBC_MAX_PAGES];
#ifndef NFS_V2_ONLY
        bool needcommit = true; /* need only COMMIT RPC */
#else
        bool needcommit = false; /* need only COMMIT RPC */
#endif
        bool pageprotected;
        struct uvm_object *uobj = &vp->v_uobj;
        int error;
        off_t off, cnt;

        if (npages < __arraycount(spgs))
                pgs = spgs;
        else {
                if ((pgs = kmem_alloc(sizeof(*pgs) * npages, KM_NOSLEEP)) ==
                    NULL)
                        return ENOMEM;
        }

        if ((bp->b_flags & B_ASYNC) != 0 && NFS_ISV3(vp)) {
                iomode = NFSV3WRITE_UNSTABLE;
        } else {
                iomode = NFSV3WRITE_FILESYNC;
        }

#ifndef NFS_V2_ONLY
again:
#endif
        rw_enter(&nmp->nm_writeverflock, RW_READER);

        for (i = 0; i < npages; i++) {
                pgs[i] = uvm_pageratop((vaddr_t)bp->b_data + (i << PAGE_SHIFT));
                if (pgs[i]->uobject == uobj &&
                    pgs[i]->offset == uiop->uio_offset + (i << PAGE_SHIFT)) {
                        KASSERT(pgs[i]->flags & PG_BUSY);
                        /*
                         * this page belongs to our object.
                         */
                        rw_enter(uobj->vmobjlock, RW_WRITER);
                        /*
                         * write out the page stably if it's about to
                         * be released because we can't resend it
                         * on the server crash.
                         *
                         * XXX assuming PG_RELEASE|PG_PAGEOUT won't be
                         * changed until unbusy the page.
                         */
                        if (pgs[i]->flags & (PG_RELEASED|PG_PAGEOUT))
                                iomode = NFSV3WRITE_FILESYNC;
                        /*
                         * if we met a page which hasn't been sent yet,
                         * we need do WRITE RPC.
                         */
                        if ((pgs[i]->flags & PG_NEEDCOMMIT) == 0)
                                needcommit = false;
                        rw_exit(uobj->vmobjlock);
                } else {
                        iomode = NFSV3WRITE_FILESYNC;
                        needcommit = false;
                }
        }
        if (!needcommit && iomode == NFSV3WRITE_UNSTABLE) {
                rw_enter(uobj->vmobjlock, RW_WRITER);
                for (i = 0; i < npages; i++) {
                        pgs[i]->flags |= PG_NEEDCOMMIT | PG_RDONLY;
                        pmap_page_protect(pgs[i], VM_PROT_READ);
                }
                rw_exit(uobj->vmobjlock);
                pageprotected = true; /* pages can't be modified during i/o. */
        } else
                pageprotected = false;

        /*
         * Send the data to the server if necessary,
         * otherwise just send a commit rpc.
         */
#ifndef NFS_V2_ONLY
        if (needcommit) {

                /*
                 * If the buffer is in the range that we already committed,
                 * there's nothing to do.
                 *
                 * If it's in the range that we need to commit, push the
                 * whole range at once, otherwise only push the buffer.
                 * In both these cases, acquire the commit lock to avoid
                 * other processes modifying the range.
                 */

                off = uiop->uio_offset;
                cnt = bp->b_bcount;
                mutex_enter(&np->n_commitlock);
                if (!nfs_in_committed_range(vp, off, bp->b_bcount)) {
                        bool pushedrange;
                        if (nfs_in_tobecommitted_range(vp, off, bp->b_bcount)) {
                                pushedrange = true;
                                off = np->n_pushlo;
                                cnt = np->n_pushhi - np->n_pushlo;
                        } else {
                                pushedrange = false;
                        }
                        error = nfs_commit(vp, off, cnt, curlwp);
                        if (error == 0) {
                                if (pushedrange) {
                                        nfs_merge_commit_ranges(vp);
                                } else {
                                        nfs_add_committed_range(vp, off, cnt);
                                }
                        }
                } else {
                        error = 0;
                }
                mutex_exit(&np->n_commitlock);
                rw_exit(&nmp->nm_writeverflock);
                if (!error) {
                        /*
                         * pages are now on stable storage.
                         */
                        uiop->uio_resid = 0;
                        rw_enter(uobj->vmobjlock, RW_WRITER);
                        for (i = 0; i < npages; i++) {
                                pgs[i]->flags &= ~(PG_NEEDCOMMIT | PG_RDONLY);
                        }
                        rw_exit(uobj->vmobjlock);
                        goto out;
                } else if (error == NFSERR_STALEWRITEVERF) {
                        nfs_clearcommit(vp->v_mount);
                        goto again;
                }
                if (error) {
                        bp->b_error = np->n_error = error;
                        np->n_flag |= NWRITEERR;
                }
                goto out;
        }
#endif
        off = uiop->uio_offset;
        cnt = bp->b_bcount;
        uiop->uio_rw = UIO_WRITE;
        nfsstats.write_bios++;
        error = nfs_writerpc(vp, uiop, &iomode, pageprotected, &stalewriteverf);
#ifndef NFS_V2_ONLY
        if (!error && iomode == NFSV3WRITE_UNSTABLE) {
                /*
                 * we need to commit pages later.
                 */
                mutex_enter(&np->n_commitlock);
                nfs_add_tobecommitted_range(vp, off, cnt);
                /*
                 * if there can be too many uncommitted pages, commit them now.
                 */
                if (np->n_pushhi - np->n_pushlo > nfs_commitsize) {
                        off = np->n_pushlo;
                        cnt = nfs_commitsize >> 1;
                        error = nfs_commit(vp, off, cnt, curlwp);
                        if (!error) {
                                nfs_add_committed_range(vp, off, cnt);
                                nfs_del_tobecommitted_range(vp, off, cnt);
                        }
                        if (error == NFSERR_STALEWRITEVERF) {
                                stalewriteverf = true;
                                error = 0; /* it isn't a real error */
                        }
                } else {
                        /*
                         * re-dirty pages so that they will be passed
                         * to us later again.
                         */
                        rw_enter(uobj->vmobjlock, RW_WRITER);
                        for (i = 0; i < npages; i++) {
                                uvm_pagemarkdirty(pgs[i],
                                    UVM_PAGE_STATUS_DIRTY);
                        }
                        rw_exit(uobj->vmobjlock);
                }
                mutex_exit(&np->n_commitlock);
        } else
#endif
        if (!error) {
                /*
                 * pages are now on stable storage.
                 */
                mutex_enter(&np->n_commitlock);
                nfs_del_committed_range(vp, off, cnt);
                mutex_exit(&np->n_commitlock);
                rw_enter(uobj->vmobjlock, RW_WRITER);
                for (i = 0; i < npages; i++) {
                        pgs[i]->flags &= ~(PG_NEEDCOMMIT | PG_RDONLY);
                }
                rw_exit(uobj->vmobjlock);
        } else {
                /*
                 * we got an error.
                 */
                bp->b_error = np->n_error = error;
                np->n_flag |= NWRITEERR;
        }

        rw_exit(&nmp->nm_writeverflock);


        if (stalewriteverf) {
                nfs_clearcommit(vp->v_mount);
        }
#ifndef NFS_V2_ONLY
out:
#endif
        if (pgs != spgs)
                kmem_free(pgs, sizeof(*pgs) * npages);
        return error;
}

/*
 * nfs_doio for B_PHYS.
 */
static int
nfs_doio_phys(struct buf *bp, struct uio *uiop)
{
        struct vnode *vp = bp->b_vp;
        int error;

        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 {
                int iomode = NFSV3WRITE_DATASYNC;
                bool stalewriteverf;
                struct nfsmount *nmp = VFSTONFS(vp->v_mount);

                uiop->uio_rw = UIO_WRITE;
                nfsstats.write_physios++;
                rw_enter(&nmp->nm_writeverflock, RW_READER);
                error = nfs_writerpc(vp, uiop, &iomode, false, &stalewriteverf);
                rw_exit(&nmp->nm_writeverflock);
                if (stalewriteverf) {
                        nfs_clearcommit(bp->b_vp->v_mount);
                }
        }
        bp->b_error = error;
        return error;
}

/*
 * Do an I/O operation to/from a cache block. This may be called
 * synchronously or from an nfsiod.
 */
int
nfs_doio(struct buf *bp)
{
        int error;
        struct uio uio;
        struct uio *uiop = &uio;
        struct iovec io;
        UVMHIST_FUNC("nfs_doio"); UVMHIST_CALLED(ubchist);

        uiop->uio_iov = &io;
        uiop->uio_iovcnt = 1;
        uiop->uio_offset = (((off_t)bp->b_blkno) << DEV_BSHIFT);
        UIO_SETUP_SYSSPACE(uiop);
        io.iov_base = bp->b_data;
        io.iov_len = uiop->uio_resid = bp->b_bcount;

        /*
         * Historically, paging was done with physio, but no more...
         */
        if (bp->b_flags & B_PHYS) {
                /*
                 * ...though reading /dev/drum still gets us here.
                 */
                error = nfs_doio_phys(bp, uiop);
        } else if (bp->b_flags & B_READ) {
                error = nfs_doio_read(bp, uiop);
        } else {
                error = nfs_doio_write(bp, uiop);
        }
        bp->b_resid = uiop->uio_resid;
        biodone(bp);
        return (error);
}

/*
 * Vnode op for VM getpages.
 */

int
nfs_getpages(void *v)
{
        struct vop_getpages_args /* {
                struct vnode *a_vp;
                voff_t a_offset;
                struct vm_page **a_m;
                int *a_count;
                int a_centeridx;
                vm_prot_t a_access_type;
                int a_advice;
                int a_flags;
        } */ *ap = v;

        struct vnode *vp = ap->a_vp;
        struct uvm_object *uobj = &vp->v_uobj;
        struct nfsnode *np = VTONFS(vp);
        const int npages = *ap->a_count;
        struct vm_page *pg, **pgs, **opgs, *spgs[UBC_MAX_PAGES];
        off_t origoffset, len;
        int i, error;
        bool v3 = NFS_ISV3(vp);
        bool write = (ap->a_access_type & VM_PROT_WRITE) != 0;
        bool locked = (ap->a_flags & PGO_LOCKED) != 0;

        /*
         * XXX NFS wants to modify the pages below and that can't be done
         * with a read lock.  We can't upgrade the lock here because it
         * would screw up UVM fault processing.  Have NFS take the I/O
         * path.
         */
        if (locked && rw_lock_op(uobj->vmobjlock) == RW_READER) {
                *ap->a_count = 0;
                ap->a_m[ap->a_centeridx] = NULL;
                return EBUSY;
        }

        /*
         * If we are not locked we are not really using opgs,
         * so just initialize it
         */
        if (!locked || npages < __arraycount(spgs))
                opgs = spgs;
        else {
                if ((opgs = kmem_alloc(npages * sizeof(*opgs), KM_NOSLEEP)) ==
                    NULL)
                        return ENOMEM;
        }

        /*
         * call the genfs code to get the pages.  `pgs' may be NULL
         * when doing read-ahead.
         */
        pgs = ap->a_m;
        if (write && locked && v3) {
                KASSERT(pgs != NULL);
#ifdef DEBUG

                /*
                 * If PGO_LOCKED is set, real pages shouldn't exists
                 * in the array.
                 */

                for (i = 0; i < npages; i++)
                        KDASSERT(pgs[i] == NULL || pgs[i] == PGO_DONTCARE);
#endif
                memcpy(opgs, pgs, npages * sizeof(struct vm_pages *));
        }
        error = genfs_getpages(v);
        if (error)
                goto out;

        /*
         * for read faults where the nfs node is not yet marked NMODIFIED,
         * set PG_RDONLY on the pages so that we come back here if someone
         * tries to modify later via the mapping that will be entered for
         * this fault.
         */

        if (!write && (np->n_flag & NMODIFIED) == 0 && pgs != NULL) {
                if (!locked) {
                        rw_enter(uobj->vmobjlock, RW_WRITER);
                }
                for (i = 0; i < npages; i++) {
                        pg = pgs[i];
                        if (pg == NULL || pg == PGO_DONTCARE) {
                                continue;
                        }
                        pg->flags |= PG_RDONLY;
                }
                if (!locked) {
                        rw_exit(uobj->vmobjlock);
                }
        }
        if (!write)
                goto out;

        /*
         * this is a write fault, update the commit info.
         */

        origoffset = ap->a_offset;
        len = npages << PAGE_SHIFT;

        if (v3) {
                if (!locked) {
                        mutex_enter(&np->n_commitlock);
                } else {
                        if (!mutex_tryenter(&np->n_commitlock)) {

                                /*
                                 * tell the caller that there are no pages
                                 * available and put back original pgs array.
                                 */

                                *ap->a_count = 0;
                                memcpy(pgs, opgs,
                                    npages * sizeof(struct vm_pages *));
                                error = EBUSY;
                                goto out;
                        }
                }
                nfs_del_committed_range(vp, origoffset, len);
                nfs_del_tobecommitted_range(vp, origoffset, len);
        }
        np->n_flag |= NMODIFIED;
        if (!locked) {
                rw_enter(uobj->vmobjlock, RW_WRITER);
        }
        for (i = 0; i < npages; i++) {
                pg = pgs[i];
                if (pg == NULL || pg == PGO_DONTCARE) {
                        continue;
                }
                pg->flags &= ~(PG_NEEDCOMMIT | PG_RDONLY);
        }
        if (!locked) {
                rw_exit(uobj->vmobjlock);
        }
        if (v3) {
                mutex_exit(&np->n_commitlock);
        }
out:
        if (opgs != spgs)
                kmem_free(opgs, sizeof(*opgs) * npages);
        return error;
}