sys/ufs/ffs/ffs_vnops.c

root/sys/ufs/ffs/ffs_vnops.c
/*-
 * SPDX-License-Identifier: (BSD-2-Clause AND BSD-3-Clause)
 *
 * Copyright (c) 2002, 2003 Networks Associates Technology, Inc.
 * All rights reserved.
 *
 * This software was developed for the FreeBSD Project by Marshall
 * Kirk McKusick and Network Associates Laboratories, the Security
 * Research Division of Network Associates, Inc. under DARPA/SPAWAR
 * contract N66001-01-C-8035 ("CBOSS"), as part of the DARPA CHATS
 * research program
 *
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
 *
 * Copyright (c) 1982, 1986, 1989, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * 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.
 * from: $FreeBSD: .../ufs/ufs_readwrite.c,v 1.96 2002/08/12 09:22:11 phk ...
 */

#include <sys/cdefs.h>
#include "opt_directio.h"
#include "opt_ffs.h"
#include "opt_ufs.h"

#include <sys/param.h>
#include <sys/bio.h>
#include <sys/systm.h>
#include <sys/buf.h>
#include <sys/conf.h>
#include <sys/extattr.h>
#include <sys/kernel.h>
#include <sys/limits.h>
#include <sys/malloc.h>
#include <sys/mount.h>
#include <sys/priv.h>
#include <sys/rwlock.h>
#include <sys/stat.h>
#include <sys/sysctl.h>
#include <sys/vmmeter.h>
#include <sys/vnode.h>

#include <vm/vm.h>
#include <vm/vm_param.h>
#include <vm/vm_extern.h>
#include <vm/vm_object.h>
#include <vm/vm_page.h>
#include <vm/vm_pager.h>
#include <vm/vnode_pager.h>

#include <ufs/ufs/extattr.h>
#include <ufs/ufs/quota.h>
#include <ufs/ufs/inode.h>
#include <ufs/ufs/ufs_extern.h>
#include <ufs/ufs/ufsmount.h>
#include <ufs/ufs/dir.h>
#ifdef UFS_DIRHASH
#include <ufs/ufs/dirhash.h>
#endif

#include <ufs/ffs/fs.h>
#include <ufs/ffs/ffs_extern.h>

#define ALIGNED_TO(ptr, s)      \
        (((uintptr_t)(ptr) & (_Alignof(s) - 1)) == 0)

#ifdef DIRECTIO
extern int      ffs_rawread(struct vnode *vp, struct uio *uio, int *workdone);
#endif
static vop_fdatasync_t  ffs_fdatasync;
static vop_fsync_t      ffs_fsync;
static vop_getpages_t   ffs_getpages;
static vop_getpages_async_t     ffs_getpages_async;
static vop_lock1_t      ffs_lock;
#ifdef INVARIANTS
static vop_unlock_t     ffs_unlock_debug;
#endif
static vop_read_t       ffs_read;
static vop_write_t      ffs_write;
static int      ffs_extread(struct vnode *vp, struct uio *uio, int ioflag);
static int      ffs_extwrite(struct vnode *vp, struct uio *uio, int ioflag,
                    struct ucred *cred);
static vop_strategy_t   ffsext_strategy;
static vop_closeextattr_t       ffs_closeextattr;
static vop_deleteextattr_t      ffs_deleteextattr;
static vop_getextattr_t ffs_getextattr;
static vop_listextattr_t        ffs_listextattr;
static vop_openextattr_t        ffs_openextattr;
static vop_setextattr_t ffs_setextattr;
static vop_vptofh_t     ffs_vptofh;
static vop_vput_pair_t  ffs_vput_pair;

vop_fplookup_vexec_t ufs_fplookup_vexec;

/* Global vfs data structures for ufs. */
struct vop_vector ffs_vnodeops1 = {
        .vop_default =          &ufs_vnodeops,
        .vop_fsync =            ffs_fsync,
        .vop_fdatasync =        ffs_fdatasync,
        .vop_getpages =         ffs_getpages,
        .vop_getpages_async =   ffs_getpages_async,
        .vop_lock1 =            ffs_lock,
#ifdef INVARIANTS
        .vop_unlock =           ffs_unlock_debug,
#endif
        .vop_read =             ffs_read,
        .vop_reallocblks =      ffs_reallocblks,
        .vop_write =            ffs_write,
        .vop_vptofh =           ffs_vptofh,
        .vop_vput_pair =        ffs_vput_pair,
        .vop_fplookup_vexec =   ufs_fplookup_vexec,
        .vop_fplookup_symlink = VOP_EAGAIN,
};
VFS_VOP_VECTOR_REGISTER(ffs_vnodeops1);

struct vop_vector ffs_fifoops1 = {
        .vop_default =          &ufs_fifoops,
        .vop_fsync =            ffs_fsync,
        .vop_fdatasync =        ffs_fdatasync,
        .vop_lock1 =            ffs_lock,
#ifdef INVARIANTS
        .vop_unlock =           ffs_unlock_debug,
#endif
        .vop_vptofh =           ffs_vptofh,
        .vop_fplookup_vexec =   VOP_EAGAIN,
        .vop_fplookup_symlink = VOP_EAGAIN,
};
VFS_VOP_VECTOR_REGISTER(ffs_fifoops1);

/* Global vfs data structures for ufs. */
struct vop_vector ffs_vnodeops2 = {
        .vop_default =          &ufs_vnodeops,
        .vop_fsync =            ffs_fsync,
        .vop_fdatasync =        ffs_fdatasync,
        .vop_getpages =         ffs_getpages,
        .vop_getpages_async =   ffs_getpages_async,
        .vop_lock1 =            ffs_lock,
#ifdef INVARIANTS
        .vop_unlock =           ffs_unlock_debug,
#endif
        .vop_read =             ffs_read,
        .vop_reallocblks =      ffs_reallocblks,
        .vop_write =            ffs_write,
        .vop_closeextattr =     ffs_closeextattr,
        .vop_deleteextattr =    ffs_deleteextattr,
        .vop_getextattr =       ffs_getextattr,
        .vop_listextattr =      ffs_listextattr,
        .vop_openextattr =      ffs_openextattr,
        .vop_setextattr =       ffs_setextattr,
        .vop_vptofh =           ffs_vptofh,
        .vop_vput_pair =        ffs_vput_pair,
        .vop_fplookup_vexec =   ufs_fplookup_vexec,
        .vop_fplookup_symlink = VOP_EAGAIN,
};
VFS_VOP_VECTOR_REGISTER(ffs_vnodeops2);

struct vop_vector ffs_fifoops2 = {
        .vop_default =          &ufs_fifoops,
        .vop_fsync =            ffs_fsync,
        .vop_fdatasync =        ffs_fdatasync,
        .vop_lock1 =            ffs_lock,
#ifdef INVARIANTS
        .vop_unlock =           ffs_unlock_debug,
#endif
        .vop_reallocblks =      ffs_reallocblks,
        .vop_strategy =         ffsext_strategy,
        .vop_closeextattr =     ffs_closeextattr,
        .vop_deleteextattr =    ffs_deleteextattr,
        .vop_getextattr =       ffs_getextattr,
        .vop_listextattr =      ffs_listextattr,
        .vop_openextattr =      ffs_openextattr,
        .vop_setextattr =       ffs_setextattr,
        .vop_vptofh =           ffs_vptofh,
        .vop_fplookup_vexec =   VOP_EAGAIN,
        .vop_fplookup_symlink = VOP_EAGAIN,
};
VFS_VOP_VECTOR_REGISTER(ffs_fifoops2);

/*
 * Synch an open file.
 */
/* ARGSUSED */
static int
ffs_fsync(struct vop_fsync_args *ap)
{
        struct vnode *vp;
        struct bufobj *bo;
        int error;

        vp = ap->a_vp;
        bo = &vp->v_bufobj;
retry:
        error = ffs_syncvnode(vp, ap->a_waitfor, 0);
        if (error)
                return (error);
        if (ap->a_waitfor == MNT_WAIT && DOINGSOFTDEP(vp)) {
                error = softdep_fsync(vp);
                if (error)
                        return (error);

                /*
                 * The softdep_fsync() function may drop vp lock,
                 * allowing for dirty buffers to reappear on the
                 * bo_dirty list. Recheck and resync as needed.
                 */
                BO_LOCK(bo);
                if ((vp->v_type == VREG || vp->v_type == VDIR) &&
                    (bo->bo_numoutput > 0 || bo->bo_dirty.bv_cnt > 0)) {
                        BO_UNLOCK(bo);
                        goto retry;
                }
                BO_UNLOCK(bo);
        }
        if (ffs_fsfail_cleanup(VFSTOUFS(vp->v_mount), 0))
                return (ENXIO);
        return (0);
}

int
ffs_syncvnode(struct vnode *vp, int waitfor, int flags)
{
        struct inode *ip;
        struct bufobj *bo;
        struct ufsmount *ump;
        struct buf *bp, *nbp;
        ufs_lbn_t lbn;
        int error, passes, wflag;
        bool still_dirty, unlocked, wait;

        ip = VTOI(vp);
        bo = &vp->v_bufobj;
        ump = VFSTOUFS(vp->v_mount);
#ifdef WITNESS
        wflag = IS_SNAPSHOT(ip) ? LK_NOWITNESS : 0;
#else
        wflag = 0;
#endif

        /*
         * When doing MNT_WAIT we must first flush all dependencies
         * on the inode.
         */
        if (DOINGSOFTDEP(vp) && waitfor == MNT_WAIT &&
            (error = softdep_sync_metadata(vp)) != 0) {
                if (ffs_fsfail_cleanup(ump, error))
                        error = 0;
                return (error);
        }

        /*
         * Flush all dirty buffers associated with a vnode.
         */
        error = 0;
        passes = 0;
        wait = false;   /* Always do an async pass first. */
        unlocked = false;
        lbn = lblkno(ITOFS(ip), (ip->i_size + ITOFS(ip)->fs_bsize - 1));
        BO_LOCK(bo);
loop:
        TAILQ_FOREACH(bp, &bo->bo_dirty.bv_hd, b_bobufs)
                bp->b_vflags &= ~BV_SCANNED;
        TAILQ_FOREACH_SAFE(bp, &bo->bo_dirty.bv_hd, b_bobufs, nbp) {
                /*
                 * Reasons to skip this buffer: it has already been considered
                 * on this pass, the buffer has dependencies that will cause
                 * it to be redirtied and it has not already been deferred,
                 * or it is already being written.
                 */
                if ((bp->b_vflags & BV_SCANNED) != 0)
                        continue;
                bp->b_vflags |= BV_SCANNED;
                /*
                 * Flush indirects in order, if requested.
                 *
                 * Note that if only datasync is requested, we can
                 * skip indirect blocks when softupdates are not
                 * active.  Otherwise we must flush them with data,
                 * since dependencies prevent data block writes.
                 */
                if (waitfor == MNT_WAIT && bp->b_lblkno <= -UFS_NDADDR &&
                    (lbn_level(bp->b_lblkno) >= passes ||
                    ((flags & DATA_ONLY) != 0 && !DOINGSOFTDEP(vp))))
                        continue;
                if (bp->b_lblkno > lbn)
                        panic("ffs_syncvnode: syncing truncated data.");
                if (BUF_LOCK(bp, LK_EXCLUSIVE | LK_NOWAIT, NULL) == 0) {
                        BO_UNLOCK(bo);
                } else if (wait) {
                        if (BUF_LOCK(bp, LK_EXCLUSIVE | LK_SLEEPFAIL |
                            LK_INTERLOCK | wflag, BO_LOCKPTR(bo)) != 0) {
                                BO_LOCK(bo);
                                bp->b_vflags &= ~BV_SCANNED;
                                goto next_locked;
                        }
                } else
                        continue;
                if ((bp->b_flags & B_DELWRI) == 0)
                        panic("ffs_fsync: not dirty");
                /*
                 * Check for dependencies and potentially complete them.
                 */
                if (!LIST_EMPTY(&bp->b_dep) &&
                    (error = softdep_sync_buf(vp, bp,
                    wait ? MNT_WAIT : MNT_NOWAIT)) != 0) {
                        /*
                         * Lock order conflict, buffer was already unlocked,
                         * and vnode possibly unlocked.
                         */
                        if (error == ERELOOKUP) {
                                if (vp->v_data == NULL)
                                        return (EBADF);
                                unlocked = true;
                                if (DOINGSOFTDEP(vp) && waitfor == MNT_WAIT &&
                                    (error = softdep_sync_metadata(vp)) != 0) {
                                        if (ffs_fsfail_cleanup(ump, error))
                                                error = 0;
                                        return (unlocked && error == 0 ?
                                            ERELOOKUP : error);
                                }
                                /* Re-evaluate inode size */
                                lbn = lblkno(ITOFS(ip), (ip->i_size +
                                    ITOFS(ip)->fs_bsize - 1));
                                goto next;
                        }
                        /* I/O error. */
                        if (error != EBUSY) {
                                BUF_UNLOCK(bp);
                                return (error);
                        }
                        /* If we deferred once, don't defer again. */
                        if ((bp->b_flags & B_DEFERRED) == 0) {
                                bp->b_flags |= B_DEFERRED;
                                BUF_UNLOCK(bp);
                                goto next;
                        }
                }
                if (wait) {
                        bremfree(bp);
                        error = bwrite(bp);
                        if (ffs_fsfail_cleanup(ump, error))
                                error = 0;
                        if (error != 0)
                                return (error);
                } else if ((bp->b_flags & B_CLUSTEROK)) {
                        (void) vfs_bio_awrite(bp);
                } else {
                        bremfree(bp);
                        (void) bawrite(bp);
                }
next:
                /*
                 * Since we may have slept during the I/O, we need
                 * to start from a known point.
                 */
                BO_LOCK(bo);
next_locked:
                nbp = TAILQ_FIRST(&bo->bo_dirty.bv_hd);
        }
        if (waitfor != MNT_WAIT) {
                BO_UNLOCK(bo);
                if ((flags & NO_INO_UPDT) != 0)
                        return (unlocked ? ERELOOKUP : 0);
                error = ffs_update(vp, 0);
                if (error == 0 && unlocked)
                        error = ERELOOKUP;
                return (error);
        }
        /* Drain IO to see if we're done. */
        bufobj_wwait(bo, 0, 0);
        /*
         * Block devices associated with filesystems may have new I/O
         * requests posted for them even if the vnode is locked, so no
         * amount of trying will get them clean.  We make several passes
         * as a best effort.
         *
         * Regular files may need multiple passes to flush all dependency
         * work as it is possible that we must write once per indirect
         * level, once for the leaf, and once for the inode and each of
         * these will be done with one sync and one async pass.
         */
        if (bo->bo_dirty.bv_cnt > 0) {
                if ((flags & DATA_ONLY) == 0) {
                        still_dirty = true;
                } else {
                        /*
                         * For data-only sync, dirty indirect buffers
                         * are ignored.
                         */
                        still_dirty = false;
                        TAILQ_FOREACH(bp, &bo->bo_dirty.bv_hd, b_bobufs) {
                                if (bp->b_lblkno > -UFS_NDADDR) {
                                        still_dirty = true;
                                        break;
                                }
                        }
                }

                if (still_dirty) {
                        /* Write the inode after sync passes to flush deps. */
                        if (wait && DOINGSOFTDEP(vp) &&
                            (flags & NO_INO_UPDT) == 0) {
                                BO_UNLOCK(bo);
                                ffs_update(vp, 1);
                                BO_LOCK(bo);
                        }
                        /* switch between sync/async. */
                        wait = !wait;
                        if (wait || ++passes < UFS_NIADDR + 2)
                                goto loop;
                }
        }
        BO_UNLOCK(bo);
        error = 0;
        if ((flags & DATA_ONLY) == 0) {
                if ((flags & NO_INO_UPDT) == 0)
                        error = ffs_update(vp, 1);
                if (DOINGSUJ(vp))
                        softdep_journal_fsync(VTOI(vp));
        } else if ((ip->i_flags & (IN_SIZEMOD | IN_IBLKDATA)) != 0) {
                error = ffs_update(vp, 1);
        }
        if (error == 0 && unlocked)
                error = ERELOOKUP;
        if (error == 0)
                ip->i_flag &= ~IN_NEEDSYNC;
        return (error);
}

static int
ffs_fdatasync(struct vop_fdatasync_args *ap)
{

        return (ffs_syncvnode(ap->a_vp, MNT_WAIT, DATA_ONLY));
}

static int
ffs_lock(
        struct vop_lock1_args /* {
                struct vnode *a_vp;
                int a_flags;
                char *file;
                int line;
        } */ *ap)
{
#if !defined(NO_FFS_SNAPSHOT) || defined(DIAGNOSTIC)
        struct vnode *vp = ap->a_vp;
#endif  /* !NO_FFS_SNAPSHOT || DIAGNOSTIC */
#ifdef DIAGNOSTIC
        struct inode *ip;
#endif  /* DIAGNOSTIC */
        int result;
#ifndef NO_FFS_SNAPSHOT
        int flags;
        struct lock *lkp;

        /*
         * Adaptive spinning mixed with SU leads to trouble. use a giant hammer
         * and only use it when LK_NODDLKTREAT is set. Currently this means it
         * is only used during path lookup.
         */
        if ((ap->a_flags & LK_NODDLKTREAT) != 0)
                ap->a_flags |= LK_ADAPTIVE;
        switch (ap->a_flags & LK_TYPE_MASK) {
        case LK_SHARED:
        case LK_UPGRADE:
        case LK_EXCLUSIVE:
                flags = ap->a_flags;
                for (;;) {
                        VNPASS(vp->v_holdcnt != 0, vp);
                        lkp = vp->v_vnlock;
                        result = lockmgr_lock_flags(lkp, flags,
                            &VI_MTX(vp)->lock_object, ap->a_file, ap->a_line);
                        if (lkp == vp->v_vnlock || result != 0)
                                break;
                        /*
                         * Apparent success, except that the vnode
                         * mutated between snapshot file vnode and
                         * regular file vnode while this process
                         * slept.  The lock currently held is not the
                         * right lock.  Release it, and try to get the
                         * new lock.
                         */
                        lockmgr_unlock(lkp);
                        if ((flags & (LK_INTERLOCK | LK_NOWAIT)) ==
                            (LK_INTERLOCK | LK_NOWAIT))
                                return (EBUSY);
                        if ((flags & LK_TYPE_MASK) == LK_UPGRADE)
                                flags = (flags & ~LK_TYPE_MASK) | LK_EXCLUSIVE;
                        flags &= ~LK_INTERLOCK;
                }
#ifdef DIAGNOSTIC
                switch (ap->a_flags & LK_TYPE_MASK) {
                case LK_UPGRADE:
                case LK_EXCLUSIVE:
                        if (result == 0 && vp->v_vnlock->lk_recurse == 0) {
                                ip = VTOI(vp);
                                if (ip != NULL)
                                        ip->i_lock_gen++;
                        }
                }
#endif  /* DIAGNOSTIC */
                break;
        default:
#ifdef DIAGNOSTIC
                if ((ap->a_flags & LK_TYPE_MASK) == LK_DOWNGRADE) {
                        ip = VTOI(vp);
                        if (ip != NULL)
                                ufs_unlock_tracker(ip);
                }
#endif  /* DIAGNOSTIC */
                result = VOP_LOCK1_APV(&ufs_vnodeops, ap);
                break;
        }
#else   /* NO_FFS_SNAPSHOT */
        /*
         * See above for an explanation.
         */
        if ((ap->a_flags & LK_NODDLKTREAT) != 0)
                ap->a_flags |= LK_ADAPTIVE;
#ifdef DIAGNOSTIC
        if ((ap->a_flags & LK_TYPE_MASK) == LK_DOWNGRADE) {
                ip = VTOI(vp);
                if (ip != NULL)
                        ufs_unlock_tracker(ip);
        }
#endif  /* DIAGNOSTIC */
        result =  VOP_LOCK1_APV(&ufs_vnodeops, ap);
#endif  /* NO_FFS_SNAPSHOT */
#ifdef DIAGNOSTIC
        switch (ap->a_flags & LK_TYPE_MASK) {
        case LK_UPGRADE:
        case LK_EXCLUSIVE:
                if (result == 0 && vp->v_vnlock->lk_recurse == 0) {
                        ip = VTOI(vp);
                        if (ip != NULL)
                                ip->i_lock_gen++;
                }
        }
#endif  /* DIAGNOSTIC */
        return (result);
}

#ifdef INVARIANTS
static int
ffs_unlock_debug(struct vop_unlock_args *ap)
{
        struct vnode *vp;
        struct inode *ip;

        vp = ap->a_vp;
        ip = VTOI(vp);
        if (ip->i_flag & UFS_INODE_FLAG_LAZY_MASK_ASSERTABLE) {
                if ((vp->v_mflag & VMP_LAZYLIST) == 0) {
                        VI_LOCK(vp);
                        VNASSERT((vp->v_mflag & VMP_LAZYLIST), vp,
                            ("%s: modified vnode (%x) not on lazy list",
                            __func__, ip->i_flag));
                        VI_UNLOCK(vp);
                }
        }
        KASSERT(vp->v_type != VDIR || vp->v_vnlock->lk_recurse != 0 ||
            (ip->i_flag & IN_ENDOFF) == 0,
            ("ufs dir vp %p ip %p flags %#x", vp, ip, ip->i_flag));
#ifdef DIAGNOSTIC
        if (VOP_ISLOCKED(vp) == LK_EXCLUSIVE && ip != NULL &&
            vp->v_vnlock->lk_recurse == 0)
                ufs_unlock_tracker(ip);
#endif
        return (VOP_UNLOCK_APV(&ufs_vnodeops, ap));
}
#endif

static int
ffs_read_hole(struct uio *uio, long xfersize, long *size)
{
        ssize_t saved_resid, tlen;
        int error;

        while (xfersize > 0) {
                tlen = min(xfersize, ZERO_REGION_SIZE);
                saved_resid = uio->uio_resid;
                error = vn_io_fault_uiomove(__DECONST(void *, zero_region),
                    tlen, uio);
                if (error != 0)
                        return (error);
                tlen = saved_resid - uio->uio_resid;
                xfersize -= tlen;
                *size -= tlen;
        }
        return (0);
}

/*
 * Vnode op for reading.
 */
static int
ffs_read(
        struct vop_read_args /* {
                struct vnode *a_vp;
                struct uio *a_uio;
                int a_ioflag;
                struct ucred *a_cred;
        } */ *ap)
{
        struct vnode *vp;
        struct inode *ip;
        struct uio *uio;
        struct fs *fs;
        struct buf *bp;
        ufs_lbn_t lbn, nextlbn;
        off_t bytesinfile;
        long size, xfersize, blkoffset;
        ssize_t orig_resid;
        int bflag, error, ioflag, seqcount;

        vp = ap->a_vp;
        uio = ap->a_uio;
        ioflag = ap->a_ioflag;
        if (ap->a_ioflag & IO_EXT)
#ifdef notyet
                return (ffs_extread(vp, uio, ioflag));
#else
                panic("ffs_read+IO_EXT");
#endif
#ifdef DIRECTIO
        if ((ioflag & IO_DIRECT) != 0) {
                int workdone;

                error = ffs_rawread(vp, uio, &workdone);
                if (error != 0 || workdone != 0)
                        return error;
        }
#endif

        seqcount = ap->a_ioflag >> IO_SEQSHIFT;
        ip = VTOI(vp);

#ifdef INVARIANTS
        if (uio->uio_rw != UIO_READ)
                panic("ffs_read: mode");

        if (vp->v_type == VLNK) {
                if ((int)ip->i_size < VFSTOUFS(vp->v_mount)->um_maxsymlinklen)
                        panic("ffs_read: short symlink");
        } else if (vp->v_type != VREG && vp->v_type != VDIR)
                panic("ffs_read: type %d",  vp->v_type);
#endif
        orig_resid = uio->uio_resid;
        KASSERT(orig_resid >= 0, ("ffs_read: uio->uio_resid < 0"));
        if (orig_resid == 0)
                return (0);
        KASSERT(uio->uio_offset >= 0, ("ffs_read: uio->uio_offset < 0"));
        fs = ITOFS(ip);
        if (uio->uio_offset < ip->i_size &&
            uio->uio_offset >= fs->fs_maxfilesize)
                return (EOVERFLOW);

        bflag = GB_UNMAPPED | (uio->uio_segflg == UIO_NOCOPY ? 0 : GB_NOSPARSE);
#ifdef WITNESS
        bflag |= IS_SNAPSHOT(ip) ? GB_NOWITNESS : 0;
#endif
        for (error = 0, bp = NULL; uio->uio_resid > 0; bp = NULL) {
                if ((bytesinfile = ip->i_size - uio->uio_offset) <= 0)
                        break;
                lbn = lblkno(fs, uio->uio_offset);
                nextlbn = lbn + 1;

                /*
                 * size of buffer.  The buffer representing the
                 * end of the file is rounded up to the size of
                 * the block type ( fragment or full block,
                 * depending ).
                 */
                size = blksize(fs, ip, lbn);
                blkoffset = blkoff(fs, uio->uio_offset);

                /*
                 * The amount we want to transfer in this iteration is
                 * one FS block less the amount of the data before
                 * our startpoint (duh!)
                 */
                xfersize = fs->fs_bsize - blkoffset;

                /*
                 * But if we actually want less than the block,
                 * or the file doesn't have a whole block more of data,
                 * then use the lesser number.
                 */
                if (uio->uio_resid < xfersize)
                        xfersize = uio->uio_resid;
                if (bytesinfile < xfersize)
                        xfersize = bytesinfile;

                if (lblktosize(fs, nextlbn) >= ip->i_size) {
                        /*
                         * Don't do readahead if this is the end of the file.
                         */
                        error = bread_gb(vp, lbn, size, NOCRED, bflag, &bp);
                } else if ((vp->v_mount->mnt_flag & MNT_NOCLUSTERR) == 0) {
                        /*
                         * Otherwise if we are allowed to cluster,
                         * grab as much as we can.
                         *
                         * XXX  This may not be a win if we are not
                         * doing sequential access.
                         */
                        error = cluster_read(vp, ip->i_size, lbn,
                            size, NOCRED, blkoffset + uio->uio_resid,
                            seqcount, bflag, &bp);
                } else if (seqcount > 1) {
                        /*
                         * If we are NOT allowed to cluster, then
                         * if we appear to be acting sequentially,
                         * fire off a request for a readahead
                         * as well as a read. Note that the 4th and 5th
                         * arguments point to arrays of the size specified in
                         * the 6th argument.
                         */
                        int nextsize = blksize(fs, ip, nextlbn);
                        error = breadn_flags(vp, lbn, lbn, size, &nextlbn,
                            &nextsize, 1, NOCRED, bflag, NULL, &bp);
                } else {
                        /*
                         * Failing all of the above, just read what the
                         * user asked for. Interestingly, the same as
                         * the first option above.
                         */
                        error = bread_gb(vp, lbn, size, NOCRED, bflag, &bp);
                }
                if (error == EJUSTRETURN) {
                        error = ffs_read_hole(uio, xfersize, &size);
                        if (error == 0)
                                continue;
                }
                if (error != 0) {
                        brelse(bp);
                        bp = NULL;
                        break;
                }

                /*
                 * We should only get non-zero b_resid when an I/O error
                 * has occurred, which should cause us to break above.
                 * However, if the short read did not cause an error,
                 * then we want to ensure that we do not uiomove bad
                 * or uninitialized data.
                 */
                size -= bp->b_resid;
                if (size < xfersize) {
                        if (size == 0)
                                break;
                        xfersize = size;
                }

                if (buf_mapped(bp)) {
                        error = vn_io_fault_uiomove((char *)bp->b_data +
                            blkoffset, (int)xfersize, uio);
                } else {
                        error = vn_io_fault_pgmove(bp->b_pages,
                            blkoffset + (bp->b_offset & PAGE_MASK),
                            (int)xfersize, uio);
                }
                if (error)
                        break;

                vfs_bio_brelse(bp, ioflag);
        }

        /*
         * This can only happen in the case of an error
         * because the loop above resets bp to NULL on each iteration
         * and on normal completion has not set a new value into it.
         * so it must have come from a 'break' statement
         */
        if (bp != NULL)
                vfs_bio_brelse(bp, ioflag);

        if ((error == 0 || uio->uio_resid != orig_resid) &&
            (vp->v_mount->mnt_flag & (MNT_NOATIME | MNT_RDONLY)) == 0)
                UFS_INODE_SET_FLAG_SHARED(ip, IN_ACCESS);
        return (error);
}

/*
 * Vnode op for writing.
 */
static int
ffs_write(
        struct vop_write_args /* {
                struct vnode *a_vp;
                struct uio *a_uio;
                int a_ioflag;
                struct ucred *a_cred;
        } */ *ap)
{
        struct vnode *vp;
        struct uio *uio;
        struct inode *ip;
        struct fs *fs;
        struct buf *bp;
        ufs_lbn_t lbn;
        off_t osize;
        ssize_t resid, r;
        int seqcount;
        int blkoffset, error, flags, ioflag, size, xfersize;

        vp = ap->a_vp;
        if (DOINGSUJ(vp))
                softdep_prealloc(vp, MNT_WAIT);
        if (vp->v_data == NULL)
                return (EBADF);

        uio = ap->a_uio;
        ioflag = ap->a_ioflag;
        if (ap->a_ioflag & IO_EXT)
#ifdef notyet
                return (ffs_extwrite(vp, uio, ioflag, ap->a_cred));
#else
                panic("ffs_write+IO_EXT");
#endif

        seqcount = ap->a_ioflag >> IO_SEQSHIFT;
        ip = VTOI(vp);

#ifdef INVARIANTS
        if (uio->uio_rw != UIO_WRITE)
                panic("ffs_write: mode");
#endif

        switch (vp->v_type) {
        case VREG:
                if (ioflag & IO_APPEND)
                        uio->uio_offset = ip->i_size;
                if ((ip->i_flags & APPEND) && uio->uio_offset != ip->i_size)
                        return (EPERM);
                /* FALLTHROUGH */
        case VLNK:
                break;
        case VDIR:
                panic("ffs_write: dir write");
                break;
        default:
                panic("ffs_write: type %p %d (%d,%d)", vp, (int)vp->v_type,
                        (int)uio->uio_offset,
                        (int)uio->uio_resid
                );
        }

        KASSERT(uio->uio_resid >= 0, ("ffs_write: uio->uio_resid < 0"));
        KASSERT(uio->uio_offset >= 0, ("ffs_write: uio->uio_offset < 0"));
        fs = ITOFS(ip);

        /*
         * Maybe this should be above the vnode op call, but so long as
         * file servers have no limits, I don't think it matters.
         */
        error = vn_rlimit_fsizex(vp, uio, fs->fs_maxfilesize, &r,
            uio->uio_td);
        if (error != 0) {
                vn_rlimit_fsizex_res(uio, r);
                return (error);
        }

        resid = uio->uio_resid;
        osize = ip->i_size;
        if (seqcount > BA_SEQMAX)
                flags = BA_SEQMAX << BA_SEQSHIFT;
        else
                flags = seqcount << BA_SEQSHIFT;
        if (ioflag & IO_SYNC)
                flags |= IO_SYNC;
        flags |= BA_UNMAPPED;

        for (error = 0; uio->uio_resid > 0;) {
                lbn = lblkno(fs, uio->uio_offset);
                blkoffset = blkoff(fs, uio->uio_offset);
                xfersize = fs->fs_bsize - blkoffset;
                if (uio->uio_resid < xfersize)
                        xfersize = uio->uio_resid;
                if (uio->uio_offset + xfersize > ip->i_size)
                        vnode_pager_setsize(vp, uio->uio_offset + xfersize);

                /*
                 * We must perform a read-before-write if the transfer size
                 * does not cover the entire buffer.
                 */
                if (fs->fs_bsize > xfersize)
                        flags |= BA_CLRBUF;
                else
                        flags &= ~BA_CLRBUF;
/* XXX is uio->uio_offset the right thing here? */
                error = UFS_BALLOC(vp, uio->uio_offset, xfersize,
                    ap->a_cred, flags, &bp);
                if (error != 0) {
                        vnode_pager_setsize(vp, ip->i_size);
                        break;
                }
                if ((ioflag & (IO_SYNC|IO_INVAL)) == (IO_SYNC|IO_INVAL))
                        bp->b_flags |= B_NOCACHE;

                if (uio->uio_offset + xfersize > ip->i_size) {
                        ip->i_size = uio->uio_offset + xfersize;
                        DIP_SET(ip, i_size, ip->i_size);
                        UFS_INODE_SET_FLAG(ip, IN_SIZEMOD | IN_CHANGE);
                }

                size = blksize(fs, ip, lbn) - bp->b_resid;
                if (size < xfersize)
                        xfersize = size;

                if (buf_mapped(bp)) {
                        error = vn_io_fault_uiomove((char *)bp->b_data +
                            blkoffset, (int)xfersize, uio);
                } else {
                        error = vn_io_fault_pgmove(bp->b_pages,
                            blkoffset + (bp->b_offset & PAGE_MASK),
                            (int)xfersize, uio);
                }
                /*
                 * If the buffer is not already filled and we encounter an
                 * error while trying to fill it, we have to clear out any
                 * garbage data from the pages instantiated for the buffer.
                 * If we do not, a failed uiomove() during a write can leave
                 * the prior contents of the pages exposed to a userland mmap.
                 *
                 * Note that we need only clear buffers with a transfer size
                 * equal to the block size because buffers with a shorter
                 * transfer size were cleared above by the call to UFS_BALLOC()
                 * with the BA_CLRBUF flag set.
                 *
                 * If the source region for uiomove identically mmaps the
                 * buffer, uiomove() performed the NOP copy, and the buffer
                 * content remains valid because the page fault handler
                 * validated the pages.
                 */
                if (error != 0 && (bp->b_flags & B_CACHE) == 0 &&
                    fs->fs_bsize == xfersize) {
                        if (error == EFAULT && LIST_EMPTY(&bp->b_dep)) {
                                bp->b_flags |= B_INVAL | B_RELBUF | B_NOCACHE;
                                brelse(bp);
                                break;
                        } else {
                                vfs_bio_clrbuf(bp);
                        }
                }

                vfs_bio_set_flags(bp, ioflag);

                /*
                 * If IO_SYNC each buffer is written synchronously.  Otherwise
                 * if we have a severe page deficiency write the buffer
                 * asynchronously.  Otherwise try to cluster, and if that
                 * doesn't do it then either do an async write (if O_DIRECT),
                 * or a delayed write (if not).
                 */
                if (ioflag & IO_SYNC) {
                        (void)bwrite(bp);
                } else if (vm_page_count_severe() ||
                            buf_dirty_count_severe() ||
                            (ioflag & IO_ASYNC)) {
                        bp->b_flags |= B_CLUSTEROK;
                        bawrite(bp);
                } else if (xfersize + blkoffset == fs->fs_bsize) {
                        if ((vp->v_mount->mnt_flag & MNT_NOCLUSTERW) == 0) {
                                bp->b_flags |= B_CLUSTEROK;
                                cluster_write(vp, &ip->i_clusterw, bp,
                                    ip->i_size, seqcount, GB_UNMAPPED);
                        } else {
                                bawrite(bp);
                        }
                } else if (ioflag & IO_DIRECT) {
                        bp->b_flags |= B_CLUSTEROK;
                        bawrite(bp);
                } else {
                        bp->b_flags |= B_CLUSTEROK;
                        bdwrite(bp);
                }
                if (error || xfersize == 0)
                        break;
                UFS_INODE_SET_FLAG(ip, IN_CHANGE | IN_UPDATE);
        }
        /*
         * If we successfully wrote any data, and we are not the superuser
         * we clear the setuid and setgid bits as a precaution against
         * tampering.
         */
        if ((ip->i_mode & (ISUID | ISGID)) && resid > uio->uio_resid &&
            ap->a_cred) {
                if (priv_check_cred(ap->a_cred, PRIV_VFS_RETAINSUGID)) {
                        vn_seqc_write_begin(vp);
                        UFS_INODE_SET_MODE(ip, ip->i_mode & ~(ISUID | ISGID));
                        DIP_SET(ip, i_mode, ip->i_mode);
                        vn_seqc_write_end(vp);
                }
        }
        if (error) {
                if (ioflag & IO_UNIT) {
                        (void)ffs_truncate(vp, osize,
                            IO_NORMAL | (ioflag & IO_SYNC), ap->a_cred);
                        uio->uio_offset -= resid - uio->uio_resid;
                        uio->uio_resid = resid;
                }
        } else if (resid > uio->uio_resid && (ioflag & IO_SYNC)) {
                if (!(ioflag & IO_DATASYNC) ||
                    (ip->i_flags & (IN_SIZEMOD | IN_IBLKDATA)))
                        error = ffs_update(vp, 1);
                if (ffs_fsfail_cleanup(VFSTOUFS(vp->v_mount), error))
                        error = ENXIO;
        }
        vn_rlimit_fsizex_res(uio, r);
        return (error);
}

/*
 * Extended attribute area reading.
 */
static int
ffs_extread(struct vnode *vp, struct uio *uio, int ioflag)
{
        struct inode *ip;
        struct ufs2_dinode *dp;
        struct fs *fs;
        struct buf *bp;
        ufs_lbn_t lbn, nextlbn;
        off_t bytesinfile;
        long size, xfersize, blkoffset;
        ssize_t orig_resid;
        int error;

        ip = VTOI(vp);
        fs = ITOFS(ip);
        dp = ip->i_din2;

#ifdef INVARIANTS
        if (uio->uio_rw != UIO_READ || fs->fs_magic != FS_UFS2_MAGIC)
                panic("ffs_extread: mode");

#endif
        orig_resid = uio->uio_resid;
        KASSERT(orig_resid >= 0, ("ffs_extread: uio->uio_resid < 0"));
        if (orig_resid == 0)
                return (0);
        KASSERT(uio->uio_offset >= 0, ("ffs_extread: uio->uio_offset < 0"));

        for (error = 0, bp = NULL; uio->uio_resid > 0; bp = NULL) {
                if ((bytesinfile = dp->di_extsize - uio->uio_offset) <= 0)
                        break;
                lbn = lblkno(fs, uio->uio_offset);
                nextlbn = lbn + 1;

                /*
                 * size of buffer.  The buffer representing the
                 * end of the file is rounded up to the size of
                 * the block type ( fragment or full block,
                 * depending ).
                 */
                size = sblksize(fs, dp->di_extsize, lbn);
                blkoffset = blkoff(fs, uio->uio_offset);

                /*
                 * The amount we want to transfer in this iteration is
                 * one FS block less the amount of the data before
                 * our startpoint (duh!)
                 */
                xfersize = fs->fs_bsize - blkoffset;

                /*
                 * But if we actually want less than the block,
                 * or the file doesn't have a whole block more of data,
                 * then use the lesser number.
                 */
                if (uio->uio_resid < xfersize)
                        xfersize = uio->uio_resid;
                if (bytesinfile < xfersize)
                        xfersize = bytesinfile;

                if (lblktosize(fs, nextlbn) >= dp->di_extsize) {
                        /*
                         * Don't do readahead if this is the end of the info.
                         */
                        error = bread(vp, -1 - lbn, size, NOCRED, &bp);
                } else {
                        /*
                         * If we have a second block, then
                         * fire off a request for a readahead
                         * as well as a read. Note that the 4th and 5th
                         * arguments point to arrays of the size specified in
                         * the 6th argument.
                         */
                        int nextsize = sblksize(fs, dp->di_extsize, nextlbn);
                        nextlbn = -1 - nextlbn;
                        error = breadn(vp, -1 - lbn,
                            size, &nextlbn, &nextsize, 1, NOCRED, &bp);
                }
                if (error) {
                        brelse(bp);
                        bp = NULL;
                        break;
                }

                /*
                 * We should only get non-zero b_resid when an I/O error
                 * has occurred, which should cause us to break above.
                 * However, if the short read did not cause an error,
                 * then we want to ensure that we do not uiomove bad
                 * or uninitialized data.
                 */
                size -= bp->b_resid;
                if (size < xfersize) {
                        if (size == 0)
                                break;
                        xfersize = size;
                }

                error = uiomove((char *)bp->b_data + blkoffset,
                                        (int)xfersize, uio);
                if (error)
                        break;
                vfs_bio_brelse(bp, ioflag);
        }

        /*
         * This can only happen in the case of an error
         * because the loop above resets bp to NULL on each iteration
         * and on normal completion has not set a new value into it.
         * so it must have come from a 'break' statement
         */
        if (bp != NULL)
                vfs_bio_brelse(bp, ioflag);
        return (error);
}

/*
 * Extended attribute area writing.
 */
static int
ffs_extwrite(struct vnode *vp, struct uio *uio, int ioflag, struct ucred *ucred)
{
        struct inode *ip;
        struct ufs2_dinode *dp;
        struct fs *fs;
        struct buf *bp;
        ufs_lbn_t lbn;
        off_t osize;
        ssize_t resid;
        int blkoffset, error, flags, size, xfersize;

        ip = VTOI(vp);
        fs = ITOFS(ip);
        dp = ip->i_din2;

#ifdef INVARIANTS
        if (uio->uio_rw != UIO_WRITE || fs->fs_magic != FS_UFS2_MAGIC)
                panic("ffs_extwrite: mode");
#endif

        if (ioflag & IO_APPEND)
                uio->uio_offset = dp->di_extsize;
        KASSERT(uio->uio_offset >= 0, ("ffs_extwrite: uio->uio_offset < 0"));
        KASSERT(uio->uio_resid >= 0, ("ffs_extwrite: uio->uio_resid < 0"));
        if ((uoff_t)uio->uio_offset + uio->uio_resid >
            UFS_NXADDR * fs->fs_bsize)
                return (EFBIG);

        resid = uio->uio_resid;
        osize = dp->di_extsize;
        flags = IO_EXT;
        if (ioflag & IO_SYNC)
                flags |= IO_SYNC;

        for (error = 0; uio->uio_resid > 0;) {
                lbn = lblkno(fs, uio->uio_offset);
                blkoffset = blkoff(fs, uio->uio_offset);
                xfersize = fs->fs_bsize - blkoffset;
                if (uio->uio_resid < xfersize)
                        xfersize = uio->uio_resid;

                /*
                 * We must perform a read-before-write if the transfer size
                 * does not cover the entire buffer.
                 */
                if (fs->fs_bsize > xfersize)
                        flags |= BA_CLRBUF;
                else
                        flags &= ~BA_CLRBUF;
                error = UFS_BALLOC(vp, uio->uio_offset, xfersize,
                    ucred, flags, &bp);
                if (error != 0)
                        break;
                /*
                 * If the buffer is not valid we have to clear out any
                 * garbage data from the pages instantiated for the buffer.
                 * If we do not, a failed uiomove() during a write can leave
                 * the prior contents of the pages exposed to a userland
                 * mmap().  XXX deal with uiomove() errors a better way.
                 */
                if ((bp->b_flags & B_CACHE) == 0 && fs->fs_bsize <= xfersize)
                        vfs_bio_clrbuf(bp);

                if (uio->uio_offset + xfersize > dp->di_extsize) {
                        dp->di_extsize = uio->uio_offset + xfersize;
                        UFS_INODE_SET_FLAG(ip, IN_SIZEMOD | IN_CHANGE);
                }

                size = sblksize(fs, dp->di_extsize, lbn) - bp->b_resid;
                if (size < xfersize)
                        xfersize = size;

                error =
                    uiomove((char *)bp->b_data + blkoffset, (int)xfersize, uio);

                vfs_bio_set_flags(bp, ioflag);

                /*
                 * If IO_SYNC each buffer is written synchronously.  Otherwise
                 * if we have a severe page deficiency write the buffer
                 * asynchronously.  Otherwise try to cluster, and if that
                 * doesn't do it then either do an async write (if O_DIRECT),
                 * or a delayed write (if not).
                 */
                if (ioflag & IO_SYNC) {
                        (void)bwrite(bp);
                } else if (vm_page_count_severe() ||
                            buf_dirty_count_severe() ||
                            xfersize + blkoffset == fs->fs_bsize ||
                            (ioflag & (IO_ASYNC | IO_DIRECT)))
                        bawrite(bp);
                else
                        bdwrite(bp);
                if (error || xfersize == 0)
                        break;
                UFS_INODE_SET_FLAG(ip, IN_CHANGE);
        }
        /*
         * If we successfully wrote any data, and we are not the superuser
         * we clear the setuid and setgid bits as a precaution against
         * tampering.
         */
        if ((ip->i_mode & (ISUID | ISGID)) && resid > uio->uio_resid && ucred) {
                if (priv_check_cred(ucred, PRIV_VFS_RETAINSUGID)) {
                        vn_seqc_write_begin(vp);
                        UFS_INODE_SET_MODE(ip, ip->i_mode & ~(ISUID | ISGID));
                        dp->di_mode = ip->i_mode;
                        vn_seqc_write_end(vp);
                }
        }
        if (error) {
                if (ioflag & IO_UNIT) {
                        (void)ffs_truncate(vp, osize,
                            IO_EXT | (ioflag&IO_SYNC), ucred);
                        uio->uio_offset -= resid - uio->uio_resid;
                        uio->uio_resid = resid;
                }
        } else if (resid > uio->uio_resid && (ioflag & IO_SYNC))
                error = ffs_update(vp, 1);
        return (error);
}

/*
 * Vnode operating to retrieve a named extended attribute.
 *
 * Locate a particular EA (nspace:name) in the area (ptr:length), and return
 * the length of the EA, and possibly the pointer to the entry and to the data.
 */
static int
ffs_findextattr(uint8_t *ptr, uint64_t length, int nspace, const char *name,
    struct extattr **eapp, uint8_t **eac)
{
        struct extattr *eap, *eaend;
        size_t nlen;

        nlen = strlen(name);
        KASSERT(ALIGNED_TO(ptr, struct extattr), ("unaligned"));
        eap = (struct extattr *)ptr;
        eaend = (struct extattr *)(ptr + length);
        for (; eap < eaend; eap = EXTATTR_NEXT(eap)) {
                KASSERT(EXTATTR_NEXT(eap) <= eaend,
                    ("extattr next %p beyond %p", EXTATTR_NEXT(eap), eaend));
                if (eap->ea_namespace != nspace || eap->ea_namelength != nlen
                    || memcmp(eap->ea_name, name, nlen) != 0)
                        continue;
                if (eapp != NULL)
                        *eapp = eap;
                if (eac != NULL)
                        *eac = EXTATTR_CONTENT(eap);
                return (EXTATTR_CONTENT_SIZE(eap));
        }
        return (-1);
}

static int
ffs_rdextattr(uint8_t **p, struct vnode *vp, struct thread *td)
{
        const struct extattr *eap, *eaend, *eapnext;
        struct inode *ip;
        struct ufs2_dinode *dp;
        struct fs *fs;
        struct uio luio;
        struct iovec liovec;
        uint64_t easize;
        int error;
        uint8_t *eae;

        ip = VTOI(vp);
        fs = ITOFS(ip);
        dp = ip->i_din2;
        easize = dp->di_extsize;
        if ((uoff_t)easize > UFS_NXADDR * fs->fs_bsize)
                return (EFBIG);

        eae = malloc(easize, M_TEMP, M_WAITOK);

        liovec.iov_base = eae;
        liovec.iov_len = easize;
        luio.uio_iov = &liovec;
        luio.uio_iovcnt = 1;
        luio.uio_offset = 0;
        luio.uio_resid = easize;
        luio.uio_segflg = UIO_SYSSPACE;
        luio.uio_rw = UIO_READ;
        luio.uio_td = td;

        error = ffs_extread(vp, &luio, IO_EXT | IO_SYNC);
        if (error) {
                free(eae, M_TEMP);
                return (error);
        }
        /* Validate disk xattrfile contents. */
        for (eap = (void *)eae, eaend = (void *)(eae + easize); eap < eaend;
            eap = eapnext) {
                /* Detect zeroed out tail */
                if (eap->ea_length < sizeof(*eap) || eap->ea_length == 0) {
                        easize = (const uint8_t *)eap - eae;
                        break;
                }
                        
                eapnext = EXTATTR_NEXT(eap);
                /* Bogusly long entry. */
                if (eapnext > eaend) {
                        free(eae, M_TEMP);
                        return (EINTEGRITY);
                }
        }
        ip->i_ea_len = easize;
        *p = eae;
        return (0);
}

static void
ffs_lock_ea(struct vnode *vp)
{
        struct inode *ip;

        ip = VTOI(vp);
        VI_LOCK(vp);
        while (ip->i_flag & IN_EA_LOCKED) {
                UFS_INODE_SET_FLAG(ip, IN_EA_LOCKWAIT);
                msleep(&ip->i_ea_refs, &vp->v_interlock, PINOD, "ufs_ea", 0);
        }
        UFS_INODE_SET_FLAG(ip, IN_EA_LOCKED);
        VI_UNLOCK(vp);
}

static void
ffs_unlock_ea(struct vnode *vp)
{
        struct inode *ip;

        ip = VTOI(vp);
        VI_LOCK(vp);
        if (ip->i_flag & IN_EA_LOCKWAIT)
                wakeup(&ip->i_ea_refs);
        ip->i_flag &= ~(IN_EA_LOCKED | IN_EA_LOCKWAIT);
        VI_UNLOCK(vp);
}

static int
ffs_open_ea(struct vnode *vp, struct ucred *cred, struct thread *td)
{
        struct inode *ip;
        int error;

        ip = VTOI(vp);

        ffs_lock_ea(vp);
        if (ip->i_ea_area != NULL) {
                ip->i_ea_refs++;
                ffs_unlock_ea(vp);
                return (0);
        }
        error = ffs_rdextattr(&ip->i_ea_area, vp, td);
        if (error) {
                ffs_unlock_ea(vp);
                return (error);
        }
        ip->i_ea_error = 0;
        ip->i_ea_refs++;
        ffs_unlock_ea(vp);
        return (0);
}

/*
 * Vnode extattr transaction commit/abort
 */
static int
ffs_close_ea(struct vnode *vp, int commit, struct ucred *cred, struct thread *td)
{
        struct inode *ip;
        struct uio luio;
        struct iovec *liovec;
        struct ufs2_dinode *dp;
        size_t ea_len, tlen;
        int error, i, lcnt;
        bool truncate;

        ip = VTOI(vp);

        ffs_lock_ea(vp);
        if (ip->i_ea_area == NULL) {
                ffs_unlock_ea(vp);
                return (EINVAL);
        }
        dp = ip->i_din2;
        error = ip->i_ea_error;
        truncate = false;
        if (commit && error == 0) {
                ASSERT_VOP_ELOCKED(vp, "ffs_close_ea commit");
                if (cred == NOCRED)
                        cred =  vp->v_mount->mnt_cred;

                ea_len = MAX(ip->i_ea_len, dp->di_extsize);
                for (lcnt = 1, tlen = ea_len - ip->i_ea_len; tlen > 0;) {
                        tlen -= MIN(ZERO_REGION_SIZE, tlen);
                        lcnt++;
                }

                liovec = __builtin_alloca(lcnt * sizeof(struct iovec));
                luio.uio_iovcnt = lcnt;

                liovec[0].iov_base = ip->i_ea_area;
                liovec[0].iov_len = ip->i_ea_len;
                for (i = 1, tlen = ea_len - ip->i_ea_len; i < lcnt; i++) {
                        liovec[i].iov_base = __DECONST(void *, zero_region);
                        liovec[i].iov_len = MIN(ZERO_REGION_SIZE, tlen);
                        tlen -= liovec[i].iov_len;
                }
                MPASS(tlen == 0);

                luio.uio_iov = liovec;
                luio.uio_offset = 0;
                luio.uio_resid = ea_len;
                luio.uio_segflg = UIO_SYSSPACE;
                luio.uio_rw = UIO_WRITE;
                luio.uio_td = td;
                error = ffs_extwrite(vp, &luio, IO_EXT | IO_SYNC, cred);
                if (error == 0 && ip->i_ea_len == 0)
                        truncate = true;
        }
        if (--ip->i_ea_refs == 0) {
                free(ip->i_ea_area, M_TEMP);
                ip->i_ea_area = NULL;
                ip->i_ea_len = 0;
                ip->i_ea_error = 0;
        }
        ffs_unlock_ea(vp);

        if (truncate)
                ffs_truncate(vp, 0, IO_EXT, cred);
        return (error);
}

/*
 * Vnode extattr strategy routine for fifos.
 *
 * We need to check for a read or write of the external attributes.
 * Otherwise we just fall through and do the usual thing.
 */
static int
ffsext_strategy(
        struct vop_strategy_args /* {
                struct vnodeop_desc *a_desc;
                struct vnode *a_vp;
                struct buf *a_bp;
        } */ *ap)
{
        struct vnode *vp;
        daddr_t lbn;

        vp = ap->a_vp;
        lbn = ap->a_bp->b_lblkno;
        if (I_IS_UFS2(VTOI(vp)) && lbn < 0 && lbn >= -UFS_NXADDR)
                return (VOP_STRATEGY_APV(&ufs_vnodeops, ap));
        if (vp->v_type == VFIFO)
                return (VOP_STRATEGY_APV(&ufs_fifoops, ap));
        panic("spec nodes went here");
}

/*
 * Vnode extattr transaction commit/abort
 */
static int
ffs_openextattr(
        struct vop_openextattr_args /* {
                struct vnodeop_desc *a_desc;
                struct vnode *a_vp;
                IN struct ucred *a_cred;
                IN struct thread *a_td;
        } */ *ap)
{

        if (VN_ISDEV(ap->a_vp))
                return (EOPNOTSUPP);

        return (ffs_open_ea(ap->a_vp, ap->a_cred, ap->a_td));
}

/*
 * Vnode extattr transaction commit/abort
 */
static int
ffs_closeextattr(
        struct vop_closeextattr_args /* {
                struct vnodeop_desc *a_desc;
                struct vnode *a_vp;
                int a_commit;
                IN struct ucred *a_cred;
                IN struct thread *a_td;
        } */ *ap)
{
        struct vnode *vp;

        vp = ap->a_vp;
        if (VN_ISDEV(vp))
                return (EOPNOTSUPP);
        if (ap->a_commit && (vp->v_mount->mnt_flag & MNT_RDONLY) != 0)
                return (EROFS);

        if (ap->a_commit && DOINGSUJ(vp)) {
                ASSERT_VOP_ELOCKED(vp, "ffs_closeextattr commit");
                softdep_prealloc(vp, MNT_WAIT);
                if (vp->v_data == NULL)
                        return (EBADF);
        }
        return (ffs_close_ea(vp, ap->a_commit, ap->a_cred, ap->a_td));
}

/*
 * Vnode operation to remove a named attribute.
 */
static int
ffs_deleteextattr(
        struct vop_deleteextattr_args /* {
                IN struct vnode *a_vp;
                IN int a_attrnamespace;
                IN const char *a_name;
                IN struct ucred *a_cred;
                IN struct thread *a_td;
        } */ *ap)
{
        struct vnode *vp;
        struct inode *ip;
        struct extattr *eap;
        uint32_t ul;
        int olen, error, i, easize;
        uint8_t *eae;
        void *tmp;

        vp = ap->a_vp;
        ip = VTOI(vp);

        if (VN_ISDEV(vp))
                return (EOPNOTSUPP);
        if (strlen(ap->a_name) == 0)
                return (EINVAL);
        if (vp->v_mount->mnt_flag & MNT_RDONLY)
                return (EROFS);

        error = extattr_check_cred(vp, ap->a_attrnamespace,
            ap->a_cred, ap->a_td, VWRITE);
        if (error) {
                /*
                 * ffs_lock_ea is not needed there, because the vnode
                 * must be exclusively locked.
                 */
                if (ip->i_ea_area != NULL && ip->i_ea_error == 0)
                        ip->i_ea_error = error;
                return (error);
        }

        if (DOINGSUJ(vp)) {
                ASSERT_VOP_ELOCKED(vp, "ffs_deleteextattr");
                softdep_prealloc(vp, MNT_WAIT);
                if (vp->v_data == NULL)
                        return (EBADF);
        }

        error = ffs_open_ea(vp, ap->a_cred, ap->a_td);
        if (error)
                return (error);

        /* CEM: delete could be done in-place instead */
        eae = malloc(ip->i_ea_len, M_TEMP, M_WAITOK);
        bcopy(ip->i_ea_area, eae, ip->i_ea_len);
        easize = ip->i_ea_len;

        olen = ffs_findextattr(eae, easize, ap->a_attrnamespace, ap->a_name,
            &eap, NULL);
        if (olen == -1) {
                /* delete but nonexistent */
                free(eae, M_TEMP);
                ffs_close_ea(vp, 0, ap->a_cred, ap->a_td);
                return (ENOATTR);
        }
        ul = eap->ea_length;
        i = (uint8_t *)EXTATTR_NEXT(eap) - eae;
        bcopy(EXTATTR_NEXT(eap), eap, easize - i);
        easize -= ul;

        tmp = ip->i_ea_area;
        ip->i_ea_area = eae;
        ip->i_ea_len = easize;
        free(tmp, M_TEMP);
        error = ffs_close_ea(vp, 1, ap->a_cred, ap->a_td);
        return (error);
}

/*
 * Vnode operation to retrieve a named extended attribute.
 */
static int
ffs_getextattr(
        struct vop_getextattr_args /* {
                IN struct vnode *a_vp;
                IN int a_attrnamespace;
                IN const char *a_name;
                INOUT struct uio *a_uio;
                OUT size_t *a_size;
                IN struct ucred *a_cred;
                IN struct thread *a_td;
        } */ *ap)
{
        struct inode *ip;
        uint8_t *eae, *p;
        unsigned easize;
        int error, ealen;

        ip = VTOI(ap->a_vp);

        if (VN_ISDEV(ap->a_vp))
                return (EOPNOTSUPP);

        error = extattr_check_cred(ap->a_vp, ap->a_attrnamespace,
            ap->a_cred, ap->a_td, VREAD);
        if (error)
                return (error);

        error = ffs_open_ea(ap->a_vp, ap->a_cred, ap->a_td);
        if (error)
                return (error);

        eae = ip->i_ea_area;
        easize = ip->i_ea_len;

        ealen = ffs_findextattr(eae, easize, ap->a_attrnamespace, ap->a_name,
            NULL, &p);
        if (ealen >= 0) {
                error = 0;
                if (ap->a_size != NULL)
                        *ap->a_size = ealen;
                else if (ap->a_uio != NULL)
                        error = uiomove(p, ealen, ap->a_uio);
        } else
                error = ENOATTR;

        ffs_close_ea(ap->a_vp, 0, ap->a_cred, ap->a_td);
        return (error);
}

/*
 * Vnode operation to retrieve extended attributes on a vnode.
 */
static int
ffs_listextattr(
        struct vop_listextattr_args /* {
                IN struct vnode *a_vp;
                IN int a_attrnamespace;
                INOUT struct uio *a_uio;
                OUT size_t *a_size;
                IN struct ucred *a_cred;
                IN struct thread *a_td;
        } */ *ap)
{
        struct inode *ip;
        struct extattr *eap, *eaend;
        int error, ealen;

        ip = VTOI(ap->a_vp);

        if (VN_ISDEV(ap->a_vp))
                return (EOPNOTSUPP);

        error = extattr_check_cred(ap->a_vp, ap->a_attrnamespace,
            ap->a_cred, ap->a_td, VREAD);
        if (error)
                return (error);

        error = ffs_open_ea(ap->a_vp, ap->a_cred, ap->a_td);
        if (error)
                return (error);

        error = 0;
        if (ap->a_size != NULL)
                *ap->a_size = 0;

        KASSERT(ALIGNED_TO(ip->i_ea_area, struct extattr), ("unaligned"));
        eap = (struct extattr *)ip->i_ea_area;
        eaend = (struct extattr *)(ip->i_ea_area + ip->i_ea_len);
        for (; error == 0 && eap < eaend; eap = EXTATTR_NEXT(eap)) {
                KASSERT(EXTATTR_NEXT(eap) <= eaend,
                    ("extattr next %p beyond %p", EXTATTR_NEXT(eap), eaend));
                if (eap->ea_namespace != ap->a_attrnamespace)
                        continue;

                ealen = eap->ea_namelength;
                if (ap->a_size != NULL)
                        *ap->a_size += ealen + 1;
                else if (ap->a_uio != NULL)
                        error = uiomove(&eap->ea_namelength, ealen + 1,
                            ap->a_uio);
        }

        ffs_close_ea(ap->a_vp, 0, ap->a_cred, ap->a_td);
        return (error);
}

/*
 * Vnode operation to set a named attribute.
 */
static int
ffs_setextattr(
        struct vop_setextattr_args /* {
                IN struct vnode *a_vp;
                IN int a_attrnamespace;
                IN const char *a_name;
                INOUT struct uio *a_uio;
                IN struct ucred *a_cred;
                IN struct thread *a_td;
        } */ *ap)
{
        struct vnode *vp;
        struct inode *ip;
        struct fs *fs;
        struct extattr *eap;
        uint32_t ealength, ul;
        ssize_t ealen;
        int olen, eapad1, eapad2, error, i, easize;
        uint8_t *eae;
        void *tmp;

        vp = ap->a_vp;
        ip = VTOI(vp);
        fs = ITOFS(ip);

        if (VN_ISDEV(vp))
                return (EOPNOTSUPP);
        if (strlen(ap->a_name) == 0)
                return (EINVAL);

        /* XXX Now unsupported API to delete EAs using NULL uio. */
        if (ap->a_uio == NULL)
                return (EOPNOTSUPP);

        if (vp->v_mount->mnt_flag & MNT_RDONLY)
                return (EROFS);

        ealen = ap->a_uio->uio_resid;
        if (ealen < 0 || ealen > lblktosize(fs, UFS_NXADDR))
                return (EINVAL);

        error = extattr_check_cred(vp, ap->a_attrnamespace,
            ap->a_cred, ap->a_td, VWRITE);
        if (error) {
                /*
                 * ffs_lock_ea is not needed there, because the vnode
                 * must be exclusively locked.
                 */
                if (ip->i_ea_area != NULL && ip->i_ea_error == 0)
                        ip->i_ea_error = error;
                return (error);
        }

        if (DOINGSUJ(vp)) {
                ASSERT_VOP_ELOCKED(vp, "ffs_deleteextattr");
                softdep_prealloc(vp, MNT_WAIT);
                if (vp->v_data == NULL)
                        return (EBADF);
        }

        error = ffs_open_ea(vp, ap->a_cred, ap->a_td);
        if (error)
                return (error);

        ealength = sizeof(uint32_t) + 3 + strlen(ap->a_name);
        eapad1 = roundup2(ealength, 8) - ealength;
        eapad2 = roundup2(ealen, 8) - ealen;
        ealength += eapad1 + ealen + eapad2;

        /*
         * CEM: rewrites of the same size or smaller could be done in-place
         * instead.  (We don't acquire any fine-grained locks in here either,
         * so we could also do bigger writes in-place.)
         */
        eae = malloc(ip->i_ea_len + ealength, M_TEMP, M_WAITOK);
        bcopy(ip->i_ea_area, eae, ip->i_ea_len);
        easize = ip->i_ea_len;

        olen = ffs_findextattr(eae, easize, ap->a_attrnamespace, ap->a_name,
            &eap, NULL);
        if (olen == -1) {
                /* new, append at end */
                KASSERT(ALIGNED_TO(eae + easize, struct extattr),
                    ("unaligned"));
                eap = (struct extattr *)(eae + easize);
                easize += ealength;
        } else {
                ul = eap->ea_length;
                i = (uint8_t *)EXTATTR_NEXT(eap) - eae;
                if (ul != ealength) {
                        bcopy(EXTATTR_NEXT(eap), (uint8_t *)eap + ealength,
                            easize - i);
                        easize += (ealength - ul);
                }
        }
        if (easize > lblktosize(fs, UFS_NXADDR)) {
                free(eae, M_TEMP);
                ffs_close_ea(vp, 0, ap->a_cred, ap->a_td);
                if (ip->i_ea_area != NULL && ip->i_ea_error == 0)
                        ip->i_ea_error = ENOSPC;
                return (ENOSPC);
        }
        eap->ea_length = ealength;
        eap->ea_namespace = ap->a_attrnamespace;
        eap->ea_contentpadlen = eapad2;
        eap->ea_namelength = strlen(ap->a_name);
        memcpy(eap->ea_name, ap->a_name, strlen(ap->a_name));
        bzero(&eap->ea_name[strlen(ap->a_name)], eapad1);
        error = uiomove(EXTATTR_CONTENT(eap), ealen, ap->a_uio);
        if (error) {
                free(eae, M_TEMP);
                ffs_close_ea(vp, 0, ap->a_cred, ap->a_td);
                if (ip->i_ea_area != NULL && ip->i_ea_error == 0)
                        ip->i_ea_error = error;
                return (error);
        }
        bzero((uint8_t *)EXTATTR_CONTENT(eap) + ealen, eapad2);

        tmp = ip->i_ea_area;
        ip->i_ea_area = eae;
        ip->i_ea_len = easize;
        free(tmp, M_TEMP);
        error = ffs_close_ea(vp, 1, ap->a_cred, ap->a_td);
        return (error);
}

/*
 * Vnode pointer to File handle
 */
static int
ffs_vptofh(
        struct vop_vptofh_args /* {
                IN struct vnode *a_vp;
                IN struct fid *a_fhp;
        } */ *ap)
{
        struct inode *ip;
        struct ufid *ufhp;
        _Static_assert(sizeof(struct ufid) <= sizeof(struct fid),
            "struct ufid cannot be larger than struct fid");

        ip = VTOI(ap->a_vp);
        ufhp = (struct ufid *)ap->a_fhp;
        ufhp->ufid_len = sizeof(struct ufid);
        ufhp->ufid_ino = ip->i_number;
        ufhp->ufid_gen = ip->i_gen;
        return (0);
}

SYSCTL_DECL(_vfs_ffs);
static int use_buf_pager = 1;
SYSCTL_INT(_vfs_ffs, OID_AUTO, use_buf_pager, CTLFLAG_RWTUN, &use_buf_pager, 0,
    "Always use buffer pager instead of bmap");

static daddr_t
ffs_gbp_getblkno(struct vnode *vp, vm_ooffset_t off)
{

        return (lblkno(VFSTOUFS(vp->v_mount)->um_fs, off));
}

static int
ffs_gbp_getblksz(struct vnode *vp, daddr_t lbn, long *sz)
{

        *sz = blksize(VFSTOUFS(vp->v_mount)->um_fs, VTOI(vp), lbn);
        return (0);
}

static int
ffs_getpages(struct vop_getpages_args *ap)
{
        struct vnode *vp;
        struct ufsmount *um;

        vp = ap->a_vp;
        um = VFSTOUFS(vp->v_mount);

        if (!use_buf_pager && um->um_devvp->v_bufobj.bo_bsize <= PAGE_SIZE)
                return (vnode_pager_generic_getpages(vp, ap->a_m, ap->a_count,
                    ap->a_rbehind, ap->a_rahead, NULL, NULL));
        return (vfs_bio_getpages(vp, ap->a_m, ap->a_count, ap->a_rbehind,
            ap->a_rahead, ffs_gbp_getblkno, ffs_gbp_getblksz));
}

static int
ffs_getpages_async(struct vop_getpages_async_args *ap)
{
        struct vnode *vp;
        struct ufsmount *um;
        bool do_iodone;
        int error;

        vp = ap->a_vp;
        um = VFSTOUFS(vp->v_mount);
        do_iodone = true;

        if (um->um_devvp->v_bufobj.bo_bsize <= PAGE_SIZE) {
                error = vnode_pager_generic_getpages(vp, ap->a_m, ap->a_count,
                    ap->a_rbehind, ap->a_rahead, ap->a_iodone, ap->a_arg);
                if (error == 0)
                        do_iodone = false;
        } else {
                error = vfs_bio_getpages(vp, ap->a_m, ap->a_count,
                    ap->a_rbehind, ap->a_rahead, ffs_gbp_getblkno,
                    ffs_gbp_getblksz);
        }
        if (do_iodone && ap->a_iodone != NULL)
                ap->a_iodone(ap->a_arg, ap->a_m, ap->a_count, error);

        return (error);
}

static int
ffs_vput_pair(struct vop_vput_pair_args *ap)
{
        struct mount *mp;
        struct vnode *dvp, *vp, *vp1, **vpp;
        struct inode *dp, *ip;
        ino_t ip_ino;
        uint64_t ip_gen;
        int error, vp_locked;

        dvp = ap->a_dvp;
        dp = VTOI(dvp);
        vpp = ap->a_vpp;
        vp = vpp != NULL ? *vpp : NULL;

        if ((dp->i_flag & (IN_NEEDSYNC | IN_ENDOFF)) == 0)
                return (vop_stdvput_pair(ap));

        mp = dvp->v_mount;
        if (vp != NULL) {
                if (dvp == vp) {
                        vunref(vp);
                } else if (ap->a_unlock_vp) {
                        vput(vp);
                } else {
                        MPASS(vp->v_type != VNON);
                        vp_locked = VOP_ISLOCKED(vp);
                        ip = VTOI(vp);
                        ip_ino = ip->i_number;
                        ip_gen = ip->i_gen;
                        VOP_UNLOCK(vp);
                }
        }

        /*
         * If compaction or fsync was requested do it in ffs_vput_pair()
         * now that other locks are no longer held.
         */
        if ((dp->i_flag & IN_ENDOFF) != 0) {
                VNASSERT(I_ENDOFF(dp) != 0 && I_ENDOFF(dp) < dp->i_size, dvp,
                    ("IN_ENDOFF set but I_ENDOFF() is not"));
                dp->i_flag &= ~IN_ENDOFF;
                error = UFS_TRUNCATE(dvp, (off_t)I_ENDOFF(dp), IO_NORMAL |
                    (DOINGASYNC(dvp) ? 0 : IO_SYNC), curthread->td_ucred);
                if (error != 0 && error != ERELOOKUP) {
                        if (!ffs_fsfail_cleanup(VFSTOUFS(mp), error)) {
                                vn_printf(dvp,
                                    "IN_ENDOFF: failed to truncate, "
                                    "error %d\n", error);
                        }
#ifdef UFS_DIRHASH
                        ufsdirhash_free(dp);
#endif
                }
                SET_I_ENDOFF(dp, 0);
        }
        if ((dp->i_flag & IN_NEEDSYNC) != 0) {
                do {
                        error = ffs_syncvnode(dvp, MNT_WAIT, 0);
                } while (error == ERELOOKUP);
        }

        if (vp == dvp) {
                if (ap->a_unlock_vp)
                        vput(dvp);
                return (0);
        }

        vput(dvp);

        if (vp == NULL || ap->a_unlock_vp)
                return (0);
        MPASS(mp != NULL);

        /*
         * It is possible that vp is reclaimed at this point. Only
         * routines that call us with a_unlock_vp == false can find
         * that their vp has been reclaimed. There are three areas
         * that are affected:
         * 1) vn_open_cred() - later VOPs could fail, but
         *    dead_open() returns 0 to simulate successful open.
         * 2) ffs_snapshot() - creation of snapshot fails with EBADF.
         * 3) NFS server (several places) - code is prepared to detect
         *    and respond to dead vnodes by returning ESTALE.
         */
        VOP_LOCK(vp, vp_locked | LK_RETRY);
        if (IS_UFS(vp))
                return (0);

        /*
         * Try harder to recover from reclaimed vp if reclaim was not
         * because underlying inode was cleared.  We saved inode
         * number and inode generation, so we can try to reinstantiate
         * exactly same version of inode.  If this fails, return
         * original doomed vnode and let caller to handle
         * consequences.
         *
         * Note that callers must keep write started around
         * VOP_VPUT_PAIR() calls, so it is safe to use mp without
         * busying it.
         */
        VOP_UNLOCK(vp);
        error = ffs_inotovp(mp, ip_ino, ip_gen, LK_EXCLUSIVE, &vp1,
            FFSV_REPLACE_DOOMED);
        if (error != 0) {
                VOP_LOCK(vp, vp_locked | LK_RETRY);
        } else {
                vrele(vp);
                *vpp = vp1;
        }
        return (error);
}