Index: head/sys/kern/vfs_subr.c
===================================================================
--- head/sys/kern/vfs_subr.c	(revision 357070)
+++ head/sys/kern/vfs_subr.c	(revision 357071)
@@ -1,6342 +1,6331 @@
 /*-
  * SPDX-License-Identifier: BSD-3-Clause
  *
  * Copyright (c) 1989, 1993
  *	The Regents of the University of California.  All rights reserved.
  * (c) UNIX System Laboratories, Inc.
  * All or some portions of this file are derived from material licensed
  * to the University of California by American Telephone and Telegraph
  * Co. or Unix System Laboratories, Inc. and are reproduced herein with
  * the permission of UNIX System Laboratories, Inc.
  *
  * 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.
  *
  *	@(#)vfs_subr.c	8.31 (Berkeley) 5/26/95
  */
 
 /*
  * External virtual filesystem routines
  */
 
 #include <sys/cdefs.h>
 __FBSDID("$FreeBSD$");
 
 #include "opt_ddb.h"
 #include "opt_watchdog.h"
 
 #include <sys/param.h>
 #include <sys/systm.h>
 #include <sys/bio.h>
 #include <sys/buf.h>
 #include <sys/capsicum.h>
 #include <sys/condvar.h>
 #include <sys/conf.h>
 #include <sys/counter.h>
 #include <sys/dirent.h>
 #include <sys/event.h>
 #include <sys/eventhandler.h>
 #include <sys/extattr.h>
 #include <sys/file.h>
 #include <sys/fcntl.h>
 #include <sys/jail.h>
 #include <sys/kdb.h>
 #include <sys/kernel.h>
 #include <sys/kthread.h>
 #include <sys/ktr.h>
 #include <sys/lockf.h>
 #include <sys/malloc.h>
 #include <sys/mount.h>
 #include <sys/namei.h>
 #include <sys/pctrie.h>
 #include <sys/priv.h>
 #include <sys/reboot.h>
 #include <sys/refcount.h>
 #include <sys/rwlock.h>
 #include <sys/sched.h>
 #include <sys/sleepqueue.h>
 #include <sys/smp.h>
 #include <sys/stat.h>
 #include <sys/sysctl.h>
 #include <sys/syslog.h>
 #include <sys/vmmeter.h>
 #include <sys/vnode.h>
 #include <sys/watchdog.h>
 
 #include <machine/stdarg.h>
 
 #include <security/mac/mac_framework.h>
 
 #include <vm/vm.h>
 #include <vm/vm_object.h>
 #include <vm/vm_extern.h>
 #include <vm/pmap.h>
 #include <vm/vm_map.h>
 #include <vm/vm_page.h>
 #include <vm/vm_kern.h>
 #include <vm/uma.h>
 
 #ifdef DDB
 #include <ddb/ddb.h>
 #endif
 
 static void	delmntque(struct vnode *vp);
 static int	flushbuflist(struct bufv *bufv, int flags, struct bufobj *bo,
 		    int slpflag, int slptimeo);
 static void	syncer_shutdown(void *arg, int howto);
 static int	vtryrecycle(struct vnode *vp);
 static void	v_init_counters(struct vnode *);
 static void	v_incr_devcount(struct vnode *);
 static void	v_decr_devcount(struct vnode *);
 static void	vgonel(struct vnode *);
 static void	vfs_knllock(void *arg);
 static void	vfs_knlunlock(void *arg);
 static void	vfs_knl_assert_locked(void *arg);
 static void	vfs_knl_assert_unlocked(void *arg);
 static void	destroy_vpollinfo(struct vpollinfo *vi);
 static int	v_inval_buf_range_locked(struct vnode *vp, struct bufobj *bo,
 		    daddr_t startlbn, daddr_t endlbn);
 static void	vnlru_recalc(void);
 
 /*
  * These fences are intended for cases where some synchronization is
  * needed between access of v_iflags and lockless vnode refcount (v_holdcnt
  * and v_usecount) updates.  Access to v_iflags is generally synchronized
  * by the interlock, but we have some internal assertions that check vnode
  * flags without acquiring the lock.  Thus, these fences are INVARIANTS-only
  * for now.
  */
 #ifdef INVARIANTS
 #define	VNODE_REFCOUNT_FENCE_ACQ()	atomic_thread_fence_acq()
 #define	VNODE_REFCOUNT_FENCE_REL()	atomic_thread_fence_rel()
 #else
 #define	VNODE_REFCOUNT_FENCE_ACQ()
 #define	VNODE_REFCOUNT_FENCE_REL()
 #endif
 
 /*
  * Number of vnodes in existence.  Increased whenever getnewvnode()
  * allocates a new vnode, decreased in vdropl() for VIRF_DOOMED vnode.
  */
 static u_long __exclusive_cache_line numvnodes;
 
 SYSCTL_ULONG(_vfs, OID_AUTO, numvnodes, CTLFLAG_RD, &numvnodes, 0,
     "Number of vnodes in existence");
 
 static counter_u64_t vnodes_created;
 SYSCTL_COUNTER_U64(_vfs, OID_AUTO, vnodes_created, CTLFLAG_RD, &vnodes_created,
     "Number of vnodes created by getnewvnode");
 
 /*
  * Conversion tables for conversion from vnode types to inode formats
  * and back.
  */
 enum vtype iftovt_tab[16] = {
 	VNON, VFIFO, VCHR, VNON, VDIR, VNON, VBLK, VNON,
 	VREG, VNON, VLNK, VNON, VSOCK, VNON, VNON, VNON
 };
 int vttoif_tab[10] = {
 	0, S_IFREG, S_IFDIR, S_IFBLK, S_IFCHR, S_IFLNK,
 	S_IFSOCK, S_IFIFO, S_IFMT, S_IFMT
 };
 
 /*
  * List of allocates vnodes in the system.
  */
 static TAILQ_HEAD(freelst, vnode) vnode_list;
 static struct vnode *vnode_list_free_marker;
 static struct vnode *vnode_list_reclaim_marker;
 
 /*
  * "Free" vnode target.  Free vnodes are rarely completely free, but are
  * just ones that are cheap to recycle.  Usually they are for files which
  * have been stat'd but not read; these usually have inode and namecache
  * data attached to them.  This target is the preferred minimum size of a
  * sub-cache consisting mostly of such files. The system balances the size
  * of this sub-cache with its complement to try to prevent either from
  * thrashing while the other is relatively inactive.  The targets express
  * a preference for the best balance.
  *
  * "Above" this target there are 2 further targets (watermarks) related
  * to recyling of free vnodes.  In the best-operating case, the cache is
  * exactly full, the free list has size between vlowat and vhiwat above the
  * free target, and recycling from it and normal use maintains this state.
  * Sometimes the free list is below vlowat or even empty, but this state
  * is even better for immediate use provided the cache is not full.
  * Otherwise, vnlru_proc() runs to reclaim enough vnodes (usually non-free
  * ones) to reach one of these states.  The watermarks are currently hard-
  * coded as 4% and 9% of the available space higher.  These and the default
  * of 25% for wantfreevnodes are too large if the memory size is large.
  * E.g., 9% of 75% of MAXVNODES is more than 566000 vnodes to reclaim
  * whenever vnlru_proc() becomes active.
  */
 static long wantfreevnodes;
 static long __exclusive_cache_line freevnodes;
 SYSCTL_ULONG(_vfs, OID_AUTO, freevnodes, CTLFLAG_RD,
     &freevnodes, 0, "Number of \"free\" vnodes");
 static long freevnodes_old;
 
 static counter_u64_t recycles_count;
 SYSCTL_COUNTER_U64(_vfs, OID_AUTO, recycles, CTLFLAG_RD, &recycles_count,
     "Number of vnodes recycled to meet vnode cache targets");
 
 static counter_u64_t recycles_free_count;
 SYSCTL_COUNTER_U64(_vfs, OID_AUTO, recycles_free, CTLFLAG_RD, &recycles_free_count,
     "Number of free vnodes recycled to meet vnode cache targets");
 
 /*
  * Various variables used for debugging the new implementation of
  * reassignbuf().
  * XXX these are probably of (very) limited utility now.
  */
 static int reassignbufcalls;
 SYSCTL_INT(_vfs, OID_AUTO, reassignbufcalls, CTLFLAG_RW | CTLFLAG_STATS,
     &reassignbufcalls, 0, "Number of calls to reassignbuf");
 
 static counter_u64_t deferred_inact;
 SYSCTL_COUNTER_U64(_vfs, OID_AUTO, deferred_inact, CTLFLAG_RD, &deferred_inact,
     "Number of times inactive processing was deferred");
 
 /* To keep more than one thread at a time from running vfs_getnewfsid */
 static struct mtx mntid_mtx;
 
 /*
  * Lock for any access to the following:
  *	vnode_list
  *	numvnodes
  *	freevnodes
  */
 static struct mtx __exclusive_cache_line vnode_list_mtx;
 
 /* Publicly exported FS */
 struct nfs_public nfs_pub;
 
 static uma_zone_t buf_trie_zone;
 
 /* Zone for allocation of new vnodes - used exclusively by getnewvnode() */
 static uma_zone_t vnode_zone;
 static uma_zone_t vnodepoll_zone;
 
 /*
  * The workitem queue.
  *
  * It is useful to delay writes of file data and filesystem metadata
  * for tens of seconds so that quickly created and deleted files need
  * not waste disk bandwidth being created and removed. To realize this,
  * we append vnodes to a "workitem" queue. When running with a soft
  * updates implementation, most pending metadata dependencies should
  * not wait for more than a few seconds. Thus, mounted on block devices
  * are delayed only about a half the time that file data is delayed.
  * Similarly, directory updates are more critical, so are only delayed
  * about a third the time that file data is delayed. Thus, there are
  * SYNCER_MAXDELAY queues that are processed round-robin at a rate of
  * one each second (driven off the filesystem syncer process). The
  * syncer_delayno variable indicates the next queue that is to be processed.
  * Items that need to be processed soon are placed in this queue:
  *
  *	syncer_workitem_pending[syncer_delayno]
  *
  * A delay of fifteen seconds is done by placing the request fifteen
  * entries later in the queue:
  *
  *	syncer_workitem_pending[(syncer_delayno + 15) & syncer_mask]
  *
  */
 static int syncer_delayno;
 static long syncer_mask;
 LIST_HEAD(synclist, bufobj);
 static struct synclist *syncer_workitem_pending;
 /*
  * The sync_mtx protects:
  *	bo->bo_synclist
  *	sync_vnode_count
  *	syncer_delayno
  *	syncer_state
  *	syncer_workitem_pending
  *	syncer_worklist_len
  *	rushjob
  */
 static struct mtx sync_mtx;
 static struct cv sync_wakeup;
 
 #define SYNCER_MAXDELAY		32
 static int syncer_maxdelay = SYNCER_MAXDELAY;	/* maximum delay time */
 static int syncdelay = 30;		/* max time to delay syncing data */
 static int filedelay = 30;		/* time to delay syncing files */
 SYSCTL_INT(_kern, OID_AUTO, filedelay, CTLFLAG_RW, &filedelay, 0,
     "Time to delay syncing files (in seconds)");
 static int dirdelay = 29;		/* time to delay syncing directories */
 SYSCTL_INT(_kern, OID_AUTO, dirdelay, CTLFLAG_RW, &dirdelay, 0,
     "Time to delay syncing directories (in seconds)");
 static int metadelay = 28;		/* time to delay syncing metadata */
 SYSCTL_INT(_kern, OID_AUTO, metadelay, CTLFLAG_RW, &metadelay, 0,
     "Time to delay syncing metadata (in seconds)");
 static int rushjob;		/* number of slots to run ASAP */
 static int stat_rush_requests;	/* number of times I/O speeded up */
 SYSCTL_INT(_debug, OID_AUTO, rush_requests, CTLFLAG_RW, &stat_rush_requests, 0,
     "Number of times I/O speeded up (rush requests)");
 
 #define	VDBATCH_SIZE 8
 struct vdbatch {
 	u_int index;
 	long freevnodes;
 	struct mtx lock;
 	struct vnode *tab[VDBATCH_SIZE];
 };
 DPCPU_DEFINE_STATIC(struct vdbatch, vd);
 
 static void	vdbatch_dequeue(struct vnode *vp);
 
 /*
  * When shutting down the syncer, run it at four times normal speed.
  */
 #define SYNCER_SHUTDOWN_SPEEDUP		4
 static int sync_vnode_count;
 static int syncer_worklist_len;
 static enum { SYNCER_RUNNING, SYNCER_SHUTTING_DOWN, SYNCER_FINAL_DELAY }
     syncer_state;
 
 /* Target for maximum number of vnodes. */
 u_long desiredvnodes;
 static u_long gapvnodes;		/* gap between wanted and desired */
 static u_long vhiwat;		/* enough extras after expansion */
 static u_long vlowat;		/* minimal extras before expansion */
 static u_long vstir;		/* nonzero to stir non-free vnodes */
 static volatile int vsmalltrigger = 8;	/* pref to keep if > this many pages */
 
 static u_long vnlru_read_freevnodes(void);
 
 /*
  * Note that no attempt is made to sanitize these parameters.
  */
 static int
 sysctl_maxvnodes(SYSCTL_HANDLER_ARGS)
 {
 	u_long val;
 	int error;
 
 	val = desiredvnodes;
 	error = sysctl_handle_long(oidp, &val, 0, req);
 	if (error != 0 || req->newptr == NULL)
 		return (error);
 
 	if (val == desiredvnodes)
 		return (0);
 	mtx_lock(&vnode_list_mtx);
 	desiredvnodes = val;
 	wantfreevnodes = desiredvnodes / 4;
 	vnlru_recalc();
 	mtx_unlock(&vnode_list_mtx);
 	/*
 	 * XXX There is no protection against multiple threads changing
 	 * desiredvnodes at the same time. Locking above only helps vnlru and
 	 * getnewvnode.
 	 */
 	vfs_hash_changesize(desiredvnodes);
 	cache_changesize(desiredvnodes);
 	return (0);
 }
 
 SYSCTL_PROC(_kern, KERN_MAXVNODES, maxvnodes,
     CTLTYPE_ULONG | CTLFLAG_MPSAFE | CTLFLAG_RW, NULL, 0, sysctl_maxvnodes,
     "UL", "Target for maximum number of vnodes");
 
 static int
 sysctl_wantfreevnodes(SYSCTL_HANDLER_ARGS)
 {
 	u_long val;
 	int error;
 
 	val = wantfreevnodes;
 	error = sysctl_handle_long(oidp, &val, 0, req);
 	if (error != 0 || req->newptr == NULL)
 		return (error);
 
 	if (val == wantfreevnodes)
 		return (0);
 	mtx_lock(&vnode_list_mtx);
 	wantfreevnodes = val;
 	vnlru_recalc();
 	mtx_unlock(&vnode_list_mtx);
 	return (0);
 }
 
 SYSCTL_PROC(_vfs, OID_AUTO, wantfreevnodes,
     CTLTYPE_ULONG | CTLFLAG_MPSAFE | CTLFLAG_RW, NULL, 0, sysctl_wantfreevnodes,
     "UL", "Target for minimum number of \"free\" vnodes");
 
 SYSCTL_ULONG(_kern, OID_AUTO, minvnodes, CTLFLAG_RW,
     &wantfreevnodes, 0, "Old name for vfs.wantfreevnodes (legacy)");
 static int vnlru_nowhere;
 SYSCTL_INT(_debug, OID_AUTO, vnlru_nowhere, CTLFLAG_RW,
     &vnlru_nowhere, 0, "Number of times the vnlru process ran without success");
 
 static int
 sysctl_try_reclaim_vnode(SYSCTL_HANDLER_ARGS)
 {
 	struct vnode *vp;
 	struct nameidata nd;
 	char *buf;
 	unsigned long ndflags;
 	int error;
 
 	if (req->newptr == NULL)
 		return (EINVAL);
 	if (req->newlen >= PATH_MAX)
 		return (E2BIG);
 
 	buf = malloc(PATH_MAX, M_TEMP, M_WAITOK);
 	error = SYSCTL_IN(req, buf, req->newlen);
 	if (error != 0)
 		goto out;
 
 	buf[req->newlen] = '\0';
 
 	ndflags = LOCKLEAF | NOFOLLOW | AUDITVNODE1 | NOCACHE | SAVENAME;
 	NDINIT(&nd, LOOKUP, ndflags, UIO_SYSSPACE, buf, curthread);
 	if ((error = namei(&nd)) != 0)
 		goto out;
 	vp = nd.ni_vp;
 
 	if (VN_IS_DOOMED(vp)) {
 		/*
 		 * This vnode is being recycled.  Return != 0 to let the caller
 		 * know that the sysctl had no effect.  Return EAGAIN because a
 		 * subsequent call will likely succeed (since namei will create
 		 * a new vnode if necessary)
 		 */
 		error = EAGAIN;
 		goto putvnode;
 	}
 
 	counter_u64_add(recycles_count, 1);
 	vgone(vp);
 putvnode:
 	NDFREE(&nd, 0);
 out:
 	free(buf, M_TEMP);
 	return (error);
 }
 
 static int
 sysctl_ftry_reclaim_vnode(SYSCTL_HANDLER_ARGS)
 {
 	struct thread *td = curthread;
 	struct vnode *vp;
 	struct file *fp;
 	int error;
 	int fd;
 
 	if (req->newptr == NULL)
 		return (EBADF);
 
         error = sysctl_handle_int(oidp, &fd, 0, req);
         if (error != 0)
                 return (error);
 	error = getvnode(curthread, fd, &cap_fcntl_rights, &fp);
 	if (error != 0)
 		return (error);
 	vp = fp->f_vnode;
 
 	error = vn_lock(vp, LK_EXCLUSIVE);
 	if (error != 0)
 		goto drop;
 
 	counter_u64_add(recycles_count, 1);
 	vgone(vp);
 	VOP_UNLOCK(vp);
 drop:
 	fdrop(fp, td);
 	return (error);
 }
 
 SYSCTL_PROC(_debug, OID_AUTO, try_reclaim_vnode,
     CTLTYPE_STRING | CTLFLAG_MPSAFE | CTLFLAG_WR, NULL, 0,
     sysctl_try_reclaim_vnode, "A", "Try to reclaim a vnode by its pathname");
 SYSCTL_PROC(_debug, OID_AUTO, ftry_reclaim_vnode,
     CTLTYPE_INT | CTLFLAG_MPSAFE | CTLFLAG_WR, NULL, 0,
     sysctl_ftry_reclaim_vnode, "I",
     "Try to reclaim a vnode by its file descriptor");
 
 /* Shift count for (uintptr_t)vp to initialize vp->v_hash. */
 static int vnsz2log;
 
 /*
  * Support for the bufobj clean & dirty pctrie.
  */
 static void *
 buf_trie_alloc(struct pctrie *ptree)
 {
 
 	return uma_zalloc(buf_trie_zone, M_NOWAIT);
 }
 
 static void
 buf_trie_free(struct pctrie *ptree, void *node)
 {
 
 	uma_zfree(buf_trie_zone, node);
 }
 PCTRIE_DEFINE(BUF, buf, b_lblkno, buf_trie_alloc, buf_trie_free);
 
 /*
  * Initialize the vnode management data structures.
  *
  * Reevaluate the following cap on the number of vnodes after the physical
  * memory size exceeds 512GB.  In the limit, as the physical memory size
  * grows, the ratio of the memory size in KB to vnodes approaches 64:1.
  */
 #ifndef	MAXVNODES_MAX
 #define	MAXVNODES_MAX	(512UL * 1024 * 1024 / 64)	/* 8M */
 #endif
 
 static MALLOC_DEFINE(M_VNODE_MARKER, "vnodemarker", "vnode marker");
 
 static struct vnode *
 vn_alloc_marker(struct mount *mp)
 {
 	struct vnode *vp;
 
 	vp = malloc(sizeof(struct vnode), M_VNODE_MARKER, M_WAITOK | M_ZERO);
 	vp->v_type = VMARKER;
 	vp->v_mount = mp;
 
 	return (vp);
 }
 
 static void
 vn_free_marker(struct vnode *vp)
 {
 
 	MPASS(vp->v_type == VMARKER);
 	free(vp, M_VNODE_MARKER);
 }
 
 /*
  * Initialize a vnode as it first enters the zone.
  */
 static int
 vnode_init(void *mem, int size, int flags)
 {
 	struct vnode *vp;
 
 	vp = mem;
 	bzero(vp, size);
 	/*
 	 * Setup locks.
 	 */
 	vp->v_vnlock = &vp->v_lock;
 	mtx_init(&vp->v_interlock, "vnode interlock", NULL, MTX_DEF);
 	/*
 	 * By default, don't allow shared locks unless filesystems opt-in.
 	 */
 	lockinit(vp->v_vnlock, PVFS, "vnode", VLKTIMEOUT,
 	    LK_NOSHARE | LK_IS_VNODE);
 	/*
 	 * Initialize bufobj.
 	 */
 	bufobj_init(&vp->v_bufobj, vp);
 	/*
 	 * Initialize namecache.
 	 */
 	LIST_INIT(&vp->v_cache_src);
 	TAILQ_INIT(&vp->v_cache_dst);
 	/*
 	 * Initialize rangelocks.
 	 */
 	rangelock_init(&vp->v_rl);
 
 	vp->v_dbatchcpu = NOCPU;
 
 	mtx_lock(&vnode_list_mtx);
 	TAILQ_INSERT_BEFORE(vnode_list_free_marker, vp, v_vnodelist);
 	mtx_unlock(&vnode_list_mtx);
 	return (0);
 }
 
 /*
  * Free a vnode when it is cleared from the zone.
  */
 static void
 vnode_fini(void *mem, int size)
 {
 	struct vnode *vp;
 	struct bufobj *bo;
 
 	vp = mem;
 	vdbatch_dequeue(vp);
 	mtx_lock(&vnode_list_mtx);
 	TAILQ_REMOVE(&vnode_list, vp, v_vnodelist);
 	mtx_unlock(&vnode_list_mtx);
 	rangelock_destroy(&vp->v_rl);
 	lockdestroy(vp->v_vnlock);
 	mtx_destroy(&vp->v_interlock);
 	bo = &vp->v_bufobj;
 	rw_destroy(BO_LOCKPTR(bo));
 }
 
 /*
  * Provide the size of NFS nclnode and NFS fh for calculation of the
  * vnode memory consumption.  The size is specified directly to
  * eliminate dependency on NFS-private header.
  *
  * Other filesystems may use bigger or smaller (like UFS and ZFS)
  * private inode data, but the NFS-based estimation is ample enough.
  * Still, we care about differences in the size between 64- and 32-bit
  * platforms.
  *
  * Namecache structure size is heuristically
  * sizeof(struct namecache_ts) + CACHE_PATH_CUTOFF + 1.
  */
 #ifdef _LP64
 #define	NFS_NCLNODE_SZ	(528 + 64)
 #define	NC_SZ		148
 #else
 #define	NFS_NCLNODE_SZ	(360 + 32)
 #define	NC_SZ		92
 #endif
 
 static void
 vntblinit(void *dummy __unused)
 {
 	struct vdbatch *vd;
 	int cpu, physvnodes, virtvnodes;
 	u_int i;
 
 	/*
 	 * Desiredvnodes is a function of the physical memory size and the
 	 * kernel's heap size.  Generally speaking, it scales with the
 	 * physical memory size.  The ratio of desiredvnodes to the physical
 	 * memory size is 1:16 until desiredvnodes exceeds 98,304.
 	 * Thereafter, the
 	 * marginal ratio of desiredvnodes to the physical memory size is
 	 * 1:64.  However, desiredvnodes is limited by the kernel's heap
 	 * size.  The memory required by desiredvnodes vnodes and vm objects
 	 * must not exceed 1/10th of the kernel's heap size.
 	 */
 	physvnodes = maxproc + pgtok(vm_cnt.v_page_count) / 64 +
 	    3 * min(98304 * 16, pgtok(vm_cnt.v_page_count)) / 64;
 	virtvnodes = vm_kmem_size / (10 * (sizeof(struct vm_object) +
 	    sizeof(struct vnode) + NC_SZ * ncsizefactor + NFS_NCLNODE_SZ));
 	desiredvnodes = min(physvnodes, virtvnodes);
 	if (desiredvnodes > MAXVNODES_MAX) {
 		if (bootverbose)
 			printf("Reducing kern.maxvnodes %lu -> %lu\n",
 			    desiredvnodes, MAXVNODES_MAX);
 		desiredvnodes = MAXVNODES_MAX;
 	}
 	wantfreevnodes = desiredvnodes / 4;
 	mtx_init(&mntid_mtx, "mntid", NULL, MTX_DEF);
 	TAILQ_INIT(&vnode_list);
 	mtx_init(&vnode_list_mtx, "vnode_list", NULL, MTX_DEF);
 	/*
 	 * The lock is taken to appease WITNESS.
 	 */
 	mtx_lock(&vnode_list_mtx);
 	vnlru_recalc();
 	mtx_unlock(&vnode_list_mtx);
 	vnode_list_free_marker = vn_alloc_marker(NULL);
 	TAILQ_INSERT_HEAD(&vnode_list, vnode_list_free_marker, v_vnodelist);
 	vnode_list_reclaim_marker = vn_alloc_marker(NULL);
 	TAILQ_INSERT_HEAD(&vnode_list, vnode_list_reclaim_marker, v_vnodelist);
 	vnode_zone = uma_zcreate("VNODE", sizeof (struct vnode), NULL, NULL,
 	    vnode_init, vnode_fini, UMA_ALIGN_PTR, 0);
 	vnodepoll_zone = uma_zcreate("VNODEPOLL", sizeof (struct vpollinfo),
 	    NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
 	/*
 	 * Preallocate enough nodes to support one-per buf so that
 	 * we can not fail an insert.  reassignbuf() callers can not
 	 * tolerate the insertion failure.
 	 */
 	buf_trie_zone = uma_zcreate("BUF TRIE", pctrie_node_size(),
 	    NULL, NULL, pctrie_zone_init, NULL, UMA_ALIGN_PTR, 
 	    UMA_ZONE_NOFREE | UMA_ZONE_VM);
 	uma_prealloc(buf_trie_zone, nbuf);
 
 	vnodes_created = counter_u64_alloc(M_WAITOK);
 	recycles_count = counter_u64_alloc(M_WAITOK);
 	recycles_free_count = counter_u64_alloc(M_WAITOK);
 	deferred_inact = counter_u64_alloc(M_WAITOK);
 
 	/*
 	 * Initialize the filesystem syncer.
 	 */
 	syncer_workitem_pending = hashinit(syncer_maxdelay, M_VNODE,
 	    &syncer_mask);
 	syncer_maxdelay = syncer_mask + 1;
 	mtx_init(&sync_mtx, "Syncer mtx", NULL, MTX_DEF);
 	cv_init(&sync_wakeup, "syncer");
 	for (i = 1; i <= sizeof(struct vnode); i <<= 1)
 		vnsz2log++;
 	vnsz2log--;
 
 	CPU_FOREACH(cpu) {
 		vd = DPCPU_ID_PTR((cpu), vd);
 		bzero(vd, sizeof(*vd));
 		mtx_init(&vd->lock, "vdbatch", NULL, MTX_DEF);
 	}
 }
 SYSINIT(vfs, SI_SUB_VFS, SI_ORDER_FIRST, vntblinit, NULL);
 
 
 /*
  * Mark a mount point as busy. Used to synchronize access and to delay
  * unmounting. Eventually, mountlist_mtx is not released on failure.
  *
  * vfs_busy() is a custom lock, it can block the caller.
  * vfs_busy() only sleeps if the unmount is active on the mount point.
  * For a mountpoint mp, vfs_busy-enforced lock is before lock of any
  * vnode belonging to mp.
  *
  * Lookup uses vfs_busy() to traverse mount points.
  * root fs			var fs
  * / vnode lock		A	/ vnode lock (/var)		D
  * /var vnode lock	B	/log vnode lock(/var/log)	E
  * vfs_busy lock	C	vfs_busy lock			F
  *
  * Within each file system, the lock order is C->A->B and F->D->E.
  *
  * When traversing across mounts, the system follows that lock order:
  *
  *        C->A->B
  *              |
  *              +->F->D->E
  *
  * The lookup() process for namei("/var") illustrates the process:
  *  VOP_LOOKUP() obtains B while A is held
  *  vfs_busy() obtains a shared lock on F while A and B are held
  *  vput() releases lock on B
  *  vput() releases lock on A
  *  VFS_ROOT() obtains lock on D while shared lock on F is held
  *  vfs_unbusy() releases shared lock on F
  *  vn_lock() obtains lock on deadfs vnode vp_crossmp instead of A.
  *    Attempt to lock A (instead of vp_crossmp) while D is held would
  *    violate the global order, causing deadlocks.
  *
  * dounmount() locks B while F is drained.
  */
 int
 vfs_busy(struct mount *mp, int flags)
 {
 
 	MPASS((flags & ~MBF_MASK) == 0);
 	CTR3(KTR_VFS, "%s: mp %p with flags %d", __func__, mp, flags);
 
 	if (vfs_op_thread_enter(mp)) {
 		MPASS((mp->mnt_kern_flag & MNTK_DRAINING) == 0);
 		MPASS((mp->mnt_kern_flag & MNTK_UNMOUNT) == 0);
 		MPASS((mp->mnt_kern_flag & MNTK_REFEXPIRE) == 0);
 		vfs_mp_count_add_pcpu(mp, ref, 1);
 		vfs_mp_count_add_pcpu(mp, lockref, 1);
 		vfs_op_thread_exit(mp);
 		if (flags & MBF_MNTLSTLOCK)
 			mtx_unlock(&mountlist_mtx);
 		return (0);
 	}
 
 	MNT_ILOCK(mp);
 	vfs_assert_mount_counters(mp);
 	MNT_REF(mp);
 	/*
 	 * If mount point is currently being unmounted, sleep until the
 	 * mount point fate is decided.  If thread doing the unmounting fails,
 	 * it will clear MNTK_UNMOUNT flag before waking us up, indicating
 	 * that this mount point has survived the unmount attempt and vfs_busy
 	 * should retry.  Otherwise the unmounter thread will set MNTK_REFEXPIRE
 	 * flag in addition to MNTK_UNMOUNT, indicating that mount point is
 	 * about to be really destroyed.  vfs_busy needs to release its
 	 * reference on the mount point in this case and return with ENOENT,
 	 * telling the caller that mount mount it tried to busy is no longer
 	 * valid.
 	 */
 	while (mp->mnt_kern_flag & MNTK_UNMOUNT) {
 		if (flags & MBF_NOWAIT || mp->mnt_kern_flag & MNTK_REFEXPIRE) {
 			MNT_REL(mp);
 			MNT_IUNLOCK(mp);
 			CTR1(KTR_VFS, "%s: failed busying before sleeping",
 			    __func__);
 			return (ENOENT);
 		}
 		if (flags & MBF_MNTLSTLOCK)
 			mtx_unlock(&mountlist_mtx);
 		mp->mnt_kern_flag |= MNTK_MWAIT;
 		msleep(mp, MNT_MTX(mp), PVFS | PDROP, "vfs_busy", 0);
 		if (flags & MBF_MNTLSTLOCK)
 			mtx_lock(&mountlist_mtx);
 		MNT_ILOCK(mp);
 	}
 	if (flags & MBF_MNTLSTLOCK)
 		mtx_unlock(&mountlist_mtx);
 	mp->mnt_lockref++;
 	MNT_IUNLOCK(mp);
 	return (0);
 }
 
 /*
  * Free a busy filesystem.
  */
 void
 vfs_unbusy(struct mount *mp)
 {
 	int c;
 
 	CTR2(KTR_VFS, "%s: mp %p", __func__, mp);
 
 	if (vfs_op_thread_enter(mp)) {
 		MPASS((mp->mnt_kern_flag & MNTK_DRAINING) == 0);
 		vfs_mp_count_sub_pcpu(mp, lockref, 1);
 		vfs_mp_count_sub_pcpu(mp, ref, 1);
 		vfs_op_thread_exit(mp);
 		return;
 	}
 
 	MNT_ILOCK(mp);
 	vfs_assert_mount_counters(mp);
 	MNT_REL(mp);
 	c = --mp->mnt_lockref;
 	if (mp->mnt_vfs_ops == 0) {
 		MPASS((mp->mnt_kern_flag & MNTK_DRAINING) == 0);
 		MNT_IUNLOCK(mp);
 		return;
 	}
 	if (c < 0)
 		vfs_dump_mount_counters(mp);
 	if (c == 0 && (mp->mnt_kern_flag & MNTK_DRAINING) != 0) {
 		MPASS(mp->mnt_kern_flag & MNTK_UNMOUNT);
 		CTR1(KTR_VFS, "%s: waking up waiters", __func__);
 		mp->mnt_kern_flag &= ~MNTK_DRAINING;
 		wakeup(&mp->mnt_lockref);
 	}
 	MNT_IUNLOCK(mp);
 }
 
 /*
  * Lookup a mount point by filesystem identifier.
  */
 struct mount *
 vfs_getvfs(fsid_t *fsid)
 {
 	struct mount *mp;
 
 	CTR2(KTR_VFS, "%s: fsid %p", __func__, fsid);
 	mtx_lock(&mountlist_mtx);
 	TAILQ_FOREACH(mp, &mountlist, mnt_list) {
 		if (mp->mnt_stat.f_fsid.val[0] == fsid->val[0] &&
 		    mp->mnt_stat.f_fsid.val[1] == fsid->val[1]) {
 			vfs_ref(mp);
 			mtx_unlock(&mountlist_mtx);
 			return (mp);
 		}
 	}
 	mtx_unlock(&mountlist_mtx);
 	CTR2(KTR_VFS, "%s: lookup failed for %p id", __func__, fsid);
 	return ((struct mount *) 0);
 }
 
 /*
  * Lookup a mount point by filesystem identifier, busying it before
  * returning.
  *
  * To avoid congestion on mountlist_mtx, implement simple direct-mapped
  * cache for popular filesystem identifiers.  The cache is lockess, using
  * the fact that struct mount's are never freed.  In worst case we may
  * get pointer to unmounted or even different filesystem, so we have to
  * check what we got, and go slow way if so.
  */
 struct mount *
 vfs_busyfs(fsid_t *fsid)
 {
 #define	FSID_CACHE_SIZE	256
 	typedef struct mount * volatile vmp_t;
 	static vmp_t cache[FSID_CACHE_SIZE];
 	struct mount *mp;
 	int error;
 	uint32_t hash;
 
 	CTR2(KTR_VFS, "%s: fsid %p", __func__, fsid);
 	hash = fsid->val[0] ^ fsid->val[1];
 	hash = (hash >> 16 ^ hash) & (FSID_CACHE_SIZE - 1);
 	mp = cache[hash];
 	if (mp == NULL ||
 	    mp->mnt_stat.f_fsid.val[0] != fsid->val[0] ||
 	    mp->mnt_stat.f_fsid.val[1] != fsid->val[1])
 		goto slow;
 	if (vfs_busy(mp, 0) != 0) {
 		cache[hash] = NULL;
 		goto slow;
 	}
 	if (mp->mnt_stat.f_fsid.val[0] == fsid->val[0] &&
 	    mp->mnt_stat.f_fsid.val[1] == fsid->val[1])
 		return (mp);
 	else
 	    vfs_unbusy(mp);
 
 slow:
 	mtx_lock(&mountlist_mtx);
 	TAILQ_FOREACH(mp, &mountlist, mnt_list) {
 		if (mp->mnt_stat.f_fsid.val[0] == fsid->val[0] &&
 		    mp->mnt_stat.f_fsid.val[1] == fsid->val[1]) {
 			error = vfs_busy(mp, MBF_MNTLSTLOCK);
 			if (error) {
 				cache[hash] = NULL;
 				mtx_unlock(&mountlist_mtx);
 				return (NULL);
 			}
 			cache[hash] = mp;
 			return (mp);
 		}
 	}
 	CTR2(KTR_VFS, "%s: lookup failed for %p id", __func__, fsid);
 	mtx_unlock(&mountlist_mtx);
 	return ((struct mount *) 0);
 }
 
 /*
  * Check if a user can access privileged mount options.
  */
 int
 vfs_suser(struct mount *mp, struct thread *td)
 {
 	int error;
 
 	if (jailed(td->td_ucred)) {
 		/*
 		 * If the jail of the calling thread lacks permission for
 		 * this type of file system, deny immediately.
 		 */
 		if (!prison_allow(td->td_ucred, mp->mnt_vfc->vfc_prison_flag))
 			return (EPERM);
 
 		/*
 		 * If the file system was mounted outside the jail of the
 		 * calling thread, deny immediately.
 		 */
 		if (prison_check(td->td_ucred, mp->mnt_cred) != 0)
 			return (EPERM);
 	}
 
 	/*
 	 * If file system supports delegated administration, we don't check
 	 * for the PRIV_VFS_MOUNT_OWNER privilege - it will be better verified
 	 * by the file system itself.
 	 * If this is not the user that did original mount, we check for
 	 * the PRIV_VFS_MOUNT_OWNER privilege.
 	 */
 	if (!(mp->mnt_vfc->vfc_flags & VFCF_DELEGADMIN) &&
 	    mp->mnt_cred->cr_uid != td->td_ucred->cr_uid) {
 		if ((error = priv_check(td, PRIV_VFS_MOUNT_OWNER)) != 0)
 			return (error);
 	}
 	return (0);
 }
 
 /*
  * Get a new unique fsid.  Try to make its val[0] unique, since this value
  * will be used to create fake device numbers for stat().  Also try (but
  * not so hard) make its val[0] unique mod 2^16, since some emulators only
  * support 16-bit device numbers.  We end up with unique val[0]'s for the
  * first 2^16 calls and unique val[0]'s mod 2^16 for the first 2^8 calls.
  *
  * Keep in mind that several mounts may be running in parallel.  Starting
  * the search one past where the previous search terminated is both a
  * micro-optimization and a defense against returning the same fsid to
  * different mounts.
  */
 void
 vfs_getnewfsid(struct mount *mp)
 {
 	static uint16_t mntid_base;
 	struct mount *nmp;
 	fsid_t tfsid;
 	int mtype;
 
 	CTR2(KTR_VFS, "%s: mp %p", __func__, mp);
 	mtx_lock(&mntid_mtx);
 	mtype = mp->mnt_vfc->vfc_typenum;
 	tfsid.val[1] = mtype;
 	mtype = (mtype & 0xFF) << 24;
 	for (;;) {
 		tfsid.val[0] = makedev(255,
 		    mtype | ((mntid_base & 0xFF00) << 8) | (mntid_base & 0xFF));
 		mntid_base++;
 		if ((nmp = vfs_getvfs(&tfsid)) == NULL)
 			break;
 		vfs_rel(nmp);
 	}
 	mp->mnt_stat.f_fsid.val[0] = tfsid.val[0];
 	mp->mnt_stat.f_fsid.val[1] = tfsid.val[1];
 	mtx_unlock(&mntid_mtx);
 }
 
 /*
  * Knob to control the precision of file timestamps:
  *
  *   0 = seconds only; nanoseconds zeroed.
  *   1 = seconds and nanoseconds, accurate within 1/HZ.
  *   2 = seconds and nanoseconds, truncated to microseconds.
  * >=3 = seconds and nanoseconds, maximum precision.
  */
 enum { TSP_SEC, TSP_HZ, TSP_USEC, TSP_NSEC };
 
 static int timestamp_precision = TSP_USEC;
 SYSCTL_INT(_vfs, OID_AUTO, timestamp_precision, CTLFLAG_RW,
     &timestamp_precision, 0, "File timestamp precision (0: seconds, "
     "1: sec + ns accurate to 1/HZ, 2: sec + ns truncated to us, "
     "3+: sec + ns (max. precision))");
 
 /*
  * Get a current timestamp.
  */
 void
 vfs_timestamp(struct timespec *tsp)
 {
 	struct timeval tv;
 
 	switch (timestamp_precision) {
 	case TSP_SEC:
 		tsp->tv_sec = time_second;
 		tsp->tv_nsec = 0;
 		break;
 	case TSP_HZ:
 		getnanotime(tsp);
 		break;
 	case TSP_USEC:
 		microtime(&tv);
 		TIMEVAL_TO_TIMESPEC(&tv, tsp);
 		break;
 	case TSP_NSEC:
 	default:
 		nanotime(tsp);
 		break;
 	}
 }
 
 /*
  * Set vnode attributes to VNOVAL
  */
 void
 vattr_null(struct vattr *vap)
 {
 
 	vap->va_type = VNON;
 	vap->va_size = VNOVAL;
 	vap->va_bytes = VNOVAL;
 	vap->va_mode = VNOVAL;
 	vap->va_nlink = VNOVAL;
 	vap->va_uid = VNOVAL;
 	vap->va_gid = VNOVAL;
 	vap->va_fsid = VNOVAL;
 	vap->va_fileid = VNOVAL;
 	vap->va_blocksize = VNOVAL;
 	vap->va_rdev = VNOVAL;
 	vap->va_atime.tv_sec = VNOVAL;
 	vap->va_atime.tv_nsec = VNOVAL;
 	vap->va_mtime.tv_sec = VNOVAL;
 	vap->va_mtime.tv_nsec = VNOVAL;
 	vap->va_ctime.tv_sec = VNOVAL;
 	vap->va_ctime.tv_nsec = VNOVAL;
 	vap->va_birthtime.tv_sec = VNOVAL;
 	vap->va_birthtime.tv_nsec = VNOVAL;
 	vap->va_flags = VNOVAL;
 	vap->va_gen = VNOVAL;
 	vap->va_vaflags = 0;
 }
 
 /*
  * Try to reduce the total number of vnodes.
  *
  * This routine (and its user) are buggy in at least the following ways:
  * - all parameters were picked years ago when RAM sizes were significantly
  *   smaller
  * - it can pick vnodes based on pages used by the vm object, but filesystems
  *   like ZFS don't use it making the pick broken
  * - since ZFS has its own aging policy it gets partially combated by this one
  * - a dedicated method should be provided for filesystems to let them decide
  *   whether the vnode should be recycled
  *
  * This routine is called when we have too many vnodes.  It attempts
  * to free <count> vnodes and will potentially free vnodes that still
  * have VM backing store (VM backing store is typically the cause
  * of a vnode blowout so we want to do this).  Therefore, this operation
  * is not considered cheap.
  *
  * A number of conditions may prevent a vnode from being reclaimed.
  * the buffer cache may have references on the vnode, a directory
  * vnode may still have references due to the namei cache representing
  * underlying files, or the vnode may be in active use.   It is not
  * desirable to reuse such vnodes.  These conditions may cause the
  * number of vnodes to reach some minimum value regardless of what
  * you set kern.maxvnodes to.  Do not set kern.maxvnodes too low.
  *
  * @param reclaim_nc_src Only reclaim directories with outgoing namecache
  * 			 entries if this argument is strue
  * @param trigger	 Only reclaim vnodes with fewer than this many resident
  *			 pages.
  * @param target	 How many vnodes to reclaim.
  * @return		 The number of vnodes that were reclaimed.
  */
 static int
 vlrureclaim(bool reclaim_nc_src, int trigger, u_long target)
 {
 	struct vnode *vp, *mvp;
 	struct mount *mp;
 	u_long done;
 	bool retried;
 
 	mtx_assert(&vnode_list_mtx, MA_OWNED);
 
 	retried = false;
 	done = 0;
 
 	mvp = vnode_list_reclaim_marker;
 restart:
 	vp = mvp;
 	while (done < target) {
 		vp = TAILQ_NEXT(vp, v_vnodelist);
 		if (__predict_false(vp == NULL))
 			break;
 
 		if (__predict_false(vp->v_type == VMARKER))
 			continue;
 
 		/*
 		 * If it's been deconstructed already, it's still
 		 * referenced, or it exceeds the trigger, skip it.
 		 * Also skip free vnodes.  We are trying to make space
 		 * to expand the free list, not reduce it.
 		 */
 		if (vp->v_usecount > 0 || vp->v_holdcnt == 0 ||
 		    (!reclaim_nc_src && !LIST_EMPTY(&vp->v_cache_src)))
 			goto next_iter;
 
 		if (vp->v_type == VBAD || vp->v_type == VNON)
 			goto next_iter;
 
 		if (!VI_TRYLOCK(vp))
 			goto next_iter;
 
 		if (vp->v_usecount > 0 || vp->v_holdcnt == 0 ||
 		    (!reclaim_nc_src && !LIST_EMPTY(&vp->v_cache_src)) ||
 		    vp->v_type == VBAD || vp->v_type == VNON ||
 		    (vp->v_object != NULL &&
 		    vp->v_object->resident_page_count > trigger)) {
 			VI_UNLOCK(vp);
 			goto next_iter;
 		}
 		vholdl(vp);
 		VI_UNLOCK(vp);
 		TAILQ_REMOVE(&vnode_list, mvp, v_vnodelist);
 		TAILQ_INSERT_AFTER(&vnode_list, vp, mvp, v_vnodelist);
 		mtx_unlock(&vnode_list_mtx);
 
 		if (vn_start_write(vp, &mp, V_NOWAIT) != 0) {
 			vdrop(vp);
 			goto next_iter_unlocked;
 		}
 		if (VOP_LOCK(vp, LK_EXCLUSIVE|LK_NOWAIT) != 0) {
 			vdrop(vp);
 			vn_finished_write(mp);
 			goto next_iter_unlocked;
 		}
 
 		VI_LOCK(vp);
 		if (vp->v_usecount > 0 ||
 		    (!reclaim_nc_src && !LIST_EMPTY(&vp->v_cache_src)) ||
 		    (vp->v_object != NULL &&
 		    vp->v_object->resident_page_count > trigger)) {
 			VOP_UNLOCK(vp);
 			vdropl(vp);
 			vn_finished_write(mp);
 			goto next_iter_unlocked;
 		}
 		counter_u64_add(recycles_count, 1);
 		vgonel(vp);
 		VOP_UNLOCK(vp);
 		vdropl(vp);
 		vn_finished_write(mp);
 		done++;
 next_iter_unlocked:
 		if (should_yield())
 			kern_yield(PRI_USER);
 		mtx_lock(&vnode_list_mtx);
 		goto restart;
 next_iter:
 		MPASS(vp->v_type != VMARKER);
 		if (!should_yield())
 			continue;
 		TAILQ_REMOVE(&vnode_list, mvp, v_vnodelist);
 		TAILQ_INSERT_AFTER(&vnode_list, vp, mvp, v_vnodelist);
 		mtx_unlock(&vnode_list_mtx);
 		kern_yield(PRI_USER);
 		mtx_lock(&vnode_list_mtx);
 		goto restart;
 	}
 	if (done == 0 && !retried) {
 		TAILQ_REMOVE(&vnode_list, mvp, v_vnodelist);
 		TAILQ_INSERT_HEAD(&vnode_list, mvp, v_vnodelist);
 		retried = true;
 		goto restart;
 	}
 	return (done);
 }
 
 static int max_vnlru_free = 10000; /* limit on vnode free requests per call */
 SYSCTL_INT(_debug, OID_AUTO, max_vnlru_free, CTLFLAG_RW, &max_vnlru_free,
     0,
     "limit on vnode free requests per call to the vnlru_free routine");
 
 /*
  * Attempt to reduce the free list by the requested amount.
  */
 static int
 vnlru_free_locked(int count, struct vfsops *mnt_op)
 {
 	struct vnode *vp, *mvp;
 	struct mount *mp;
 	int ocount;
 
 	mtx_assert(&vnode_list_mtx, MA_OWNED);
 	if (count > max_vnlru_free)
 		count = max_vnlru_free;
 	ocount = count;
 	mvp = vnode_list_free_marker;
 restart:
 	vp = mvp;
 	while (count > 0) {
 		vp = TAILQ_NEXT(vp, v_vnodelist);
 		if (__predict_false(vp == NULL)) {
 			TAILQ_REMOVE(&vnode_list, mvp, v_vnodelist);
 			TAILQ_INSERT_TAIL(&vnode_list, mvp, v_vnodelist);
 			break;
 		}
 		if (__predict_false(vp->v_type == VMARKER))
 			continue;
 
 		/*
 		 * Don't recycle if our vnode is from different type
 		 * of mount point.  Note that mp is type-safe, the
 		 * check does not reach unmapped address even if
 		 * vnode is reclaimed.
 		 * Don't recycle if we can't get the interlock without
 		 * blocking.
 		 */
 		if (vp->v_holdcnt > 0 || (mnt_op != NULL && (mp = vp->v_mount) != NULL &&
 		    mp->mnt_op != mnt_op) || !VI_TRYLOCK(vp)) {
 			continue;
 		}
 		TAILQ_REMOVE(&vnode_list, mvp, v_vnodelist);
 		TAILQ_INSERT_AFTER(&vnode_list, vp, mvp, v_vnodelist);
 		if (__predict_false(vp->v_type == VBAD || vp->v_type == VNON)) {
 			VI_UNLOCK(vp);
 			continue;
 		}
 		vholdl(vp);
 		count--;
 		mtx_unlock(&vnode_list_mtx);
 		VI_UNLOCK(vp);
 		vtryrecycle(vp);
 		vdrop(vp);
 		mtx_lock(&vnode_list_mtx);
 		goto restart;
 	}
 	return (ocount - count);
 }
 
 void
 vnlru_free(int count, struct vfsops *mnt_op)
 {
 
 	mtx_lock(&vnode_list_mtx);
 	vnlru_free_locked(count, mnt_op);
 	mtx_unlock(&vnode_list_mtx);
 }
 
 static void
 vnlru_recalc(void)
 {
 
 	mtx_assert(&vnode_list_mtx, MA_OWNED);
 	gapvnodes = imax(desiredvnodes - wantfreevnodes, 100);
 	vhiwat = gapvnodes / 11; /* 9% -- just under the 10% in vlrureclaim() */
 	vlowat = vhiwat / 2;
 }
 
 /*
  * Attempt to recycle vnodes in a context that is always safe to block.
  * Calling vlrurecycle() from the bowels of filesystem code has some
  * interesting deadlock problems.
  */
 static struct proc *vnlruproc;
 static int vnlruproc_sig;
 
 /*
  * The main freevnodes counter is only updated when threads requeue their vnode
  * batches. CPUs are conditionally walked to compute a more accurate total.
  *
  * Limit how much of a slop are we willing to tolerate. Note: the actual value
  * at any given moment can still exceed slop, but it should not be by significant
  * margin in practice.
  */
 #define VNLRU_FREEVNODES_SLOP 128
 
 static u_long
 vnlru_read_freevnodes(void)
 {
 	struct vdbatch *vd;
 	long slop;
 	int cpu;
 
 	mtx_assert(&vnode_list_mtx, MA_OWNED);
 	if (freevnodes > freevnodes_old)
 		slop = freevnodes - freevnodes_old;
 	else
 		slop = freevnodes_old - freevnodes;
 	if (slop < VNLRU_FREEVNODES_SLOP)
 		return (freevnodes >= 0 ? freevnodes : 0);
 	freevnodes_old = freevnodes;
 	CPU_FOREACH(cpu) {
 		vd = DPCPU_ID_PTR((cpu), vd);
 		freevnodes_old += vd->freevnodes;
 	}
 	return (freevnodes_old >= 0 ? freevnodes_old : 0);
 }
 
 static bool
 vnlru_under(u_long rnumvnodes, u_long limit)
 {
 	u_long rfreevnodes, space;
 
 	if (__predict_false(rnumvnodes > desiredvnodes))
 		return (true);
 
 	space = desiredvnodes - rnumvnodes;
 	if (space < limit) {
 		rfreevnodes = vnlru_read_freevnodes();
 		if (rfreevnodes > wantfreevnodes)
 			space += rfreevnodes - wantfreevnodes;
 	}
 	return (space < limit);
 }
 
 static bool
 vnlru_under_unlocked(u_long rnumvnodes, u_long limit)
 {
 	long rfreevnodes, space;
 
 	if (__predict_false(rnumvnodes > desiredvnodes))
 		return (true);
 
 	space = desiredvnodes - rnumvnodes;
 	if (space < limit) {
 		rfreevnodes = atomic_load_long(&freevnodes);
 		if (rfreevnodes > wantfreevnodes)
 			space += rfreevnodes - wantfreevnodes;
 	}
 	return (space < limit);
 }
 
 static void
 vnlru_kick(void)
 {
 
 	mtx_assert(&vnode_list_mtx, MA_OWNED);
 	if (vnlruproc_sig == 0) {
 		vnlruproc_sig = 1;
 		wakeup(vnlruproc);
 	}
 }
 
 static void
 vnlru_proc(void)
 {
 	u_long rnumvnodes, rfreevnodes, target;
 	unsigned long onumvnodes;
 	int done, force, trigger, usevnodes;
 	bool reclaim_nc_src, want_reread;
 
 	EVENTHANDLER_REGISTER(shutdown_pre_sync, kproc_shutdown, vnlruproc,
 	    SHUTDOWN_PRI_FIRST);
 
 	force = 0;
 	want_reread = false;
 	for (;;) {
 		kproc_suspend_check(vnlruproc);
 		mtx_lock(&vnode_list_mtx);
 		rnumvnodes = atomic_load_long(&numvnodes);
 
 		if (want_reread) {
 			force = vnlru_under(numvnodes, vhiwat) ? 1 : 0;
 			want_reread = false;
 		}
 
 		/*
 		 * If numvnodes is too large (due to desiredvnodes being
 		 * adjusted using its sysctl, or emergency growth), first
 		 * try to reduce it by discarding from the free list.
 		 */
 		if (rnumvnodes > desiredvnodes) {
 			vnlru_free_locked(rnumvnodes - desiredvnodes, NULL);
 			rnumvnodes = atomic_load_long(&numvnodes);
 		}
 		/*
 		 * Sleep if the vnode cache is in a good state.  This is
 		 * when it is not over-full and has space for about a 4%
 		 * or 9% expansion (by growing its size or inexcessively
 		 * reducing its free list).  Otherwise, try to reclaim
 		 * space for a 10% expansion.
 		 */
 		if (vstir && force == 0) {
 			force = 1;
 			vstir = 0;
 		}
 		if (force == 0 && !vnlru_under(rnumvnodes, vlowat)) {
 			vnlruproc_sig = 0;
 			wakeup(&vnlruproc_sig);
 			msleep(vnlruproc, &vnode_list_mtx,
 			    PVFS|PDROP, "vlruwt", hz);
 			continue;
 		}
 		rfreevnodes = vnlru_read_freevnodes();
 
 		onumvnodes = rnumvnodes;
 		/*
 		 * Calculate parameters for recycling.  These are the same
 		 * throughout the loop to give some semblance of fairness.
 		 * The trigger point is to avoid recycling vnodes with lots
 		 * of resident pages.  We aren't trying to free memory; we
 		 * are trying to recycle or at least free vnodes.
 		 */
 		if (rnumvnodes <= desiredvnodes)
 			usevnodes = rnumvnodes - rfreevnodes;
 		else
 			usevnodes = rnumvnodes;
 		if (usevnodes <= 0)
 			usevnodes = 1;
 		/*
 		 * The trigger value is is chosen to give a conservatively
 		 * large value to ensure that it alone doesn't prevent
 		 * making progress.  The value can easily be so large that
 		 * it is effectively infinite in some congested and
 		 * misconfigured cases, and this is necessary.  Normally
 		 * it is about 8 to 100 (pages), which is quite large.
 		 */
 		trigger = vm_cnt.v_page_count * 2 / usevnodes;
 		if (force < 2)
 			trigger = vsmalltrigger;
 		reclaim_nc_src = force >= 3;
 		target = rnumvnodes * (int64_t)gapvnodes / imax(desiredvnodes, 1);
 		target = target / 10 + 1;
 		done = vlrureclaim(reclaim_nc_src, trigger, target);
 		mtx_unlock(&vnode_list_mtx);
 		if (onumvnodes > desiredvnodes && numvnodes <= desiredvnodes)
 			uma_reclaim(UMA_RECLAIM_DRAIN);
 		if (done == 0) {
 			if (force == 0 || force == 1) {
 				force = 2;
 				continue;
 			}
 			if (force == 2) {
 				force = 3;
 				continue;
 			}
 			want_reread = true;
 			force = 0;
 			vnlru_nowhere++;
 			tsleep(vnlruproc, PPAUSE, "vlrup", hz * 3);
 		} else {
 			want_reread = true;
 			kern_yield(PRI_USER);
 		}
 	}
 }
 
 static struct kproc_desc vnlru_kp = {
 	"vnlru",
 	vnlru_proc,
 	&vnlruproc
 };
 SYSINIT(vnlru, SI_SUB_KTHREAD_UPDATE, SI_ORDER_FIRST, kproc_start,
     &vnlru_kp);
  
 /*
  * Routines having to do with the management of the vnode table.
  */
 
 /*
  * Try to recycle a freed vnode.  We abort if anyone picks up a reference
  * before we actually vgone().  This function must be called with the vnode
  * held to prevent the vnode from being returned to the free list midway
  * through vgone().
  */
 static int
 vtryrecycle(struct vnode *vp)
 {
 	struct mount *vnmp;
 
 	CTR2(KTR_VFS, "%s: vp %p", __func__, vp);
 	VNASSERT(vp->v_holdcnt, vp,
 	    ("vtryrecycle: Recycling vp %p without a reference.", vp));
 	/*
 	 * This vnode may found and locked via some other list, if so we
 	 * can't recycle it yet.
 	 */
 	if (VOP_LOCK(vp, LK_EXCLUSIVE | LK_NOWAIT) != 0) {
 		CTR2(KTR_VFS,
 		    "%s: impossible to recycle, vp %p lock is already held",
 		    __func__, vp);
 		return (EWOULDBLOCK);
 	}
 	/*
 	 * Don't recycle if its filesystem is being suspended.
 	 */
 	if (vn_start_write(vp, &vnmp, V_NOWAIT) != 0) {
 		VOP_UNLOCK(vp);
 		CTR2(KTR_VFS,
 		    "%s: impossible to recycle, cannot start the write for %p",
 		    __func__, vp);
 		return (EBUSY);
 	}
 	/*
 	 * If we got this far, we need to acquire the interlock and see if
 	 * anyone picked up this vnode from another list.  If not, we will
 	 * mark it with DOOMED via vgonel() so that anyone who does find it
 	 * will skip over it.
 	 */
 	VI_LOCK(vp);
 	if (vp->v_usecount) {
 		VOP_UNLOCK(vp);
 		VI_UNLOCK(vp);
 		vn_finished_write(vnmp);
 		CTR2(KTR_VFS,
 		    "%s: impossible to recycle, %p is already referenced",
 		    __func__, vp);
 		return (EBUSY);
 	}
 	if (!VN_IS_DOOMED(vp)) {
 		counter_u64_add(recycles_free_count, 1);
 		vgonel(vp);
 	}
 	VOP_UNLOCK(vp);
 	VI_UNLOCK(vp);
 	vn_finished_write(vnmp);
 	return (0);
 }
 
 /*
  * Allocate a new vnode.
  *
  * The operation never returns an error. Returning an error was disabled
  * in r145385 (dated 2005) with the following comment:
  *
  * XXX Not all VFS_VGET/ffs_vget callers check returns.
  *
  * Given the age of this commit (almost 15 years at the time of writing this
  * comment) restoring the ability to fail requires a significant audit of
  * all codepaths.
  *
  * The routine can try to free a vnode or stall for up to 1 second waiting for
  * vnlru to clear things up, but ultimately always performs a M_WAITOK allocation.
  */
 static u_long vn_alloc_cyclecount;
 
 static struct vnode * __noinline
 vn_alloc_hard(struct mount *mp)
 {
 	u_long rnumvnodes, rfreevnodes;
 
 	mtx_lock(&vnode_list_mtx);
 	rnumvnodes = atomic_load_long(&numvnodes);
 	if (rnumvnodes + 1 < desiredvnodes) {
 		vn_alloc_cyclecount = 0;
 		goto alloc;
 	}
 	rfreevnodes = vnlru_read_freevnodes();
 	if (vn_alloc_cyclecount++ >= rfreevnodes) {
 		vn_alloc_cyclecount = 0;
 		vstir = 1;
 	}
 	/*
 	 * Grow the vnode cache if it will not be above its target max
 	 * after growing.  Otherwise, if the free list is nonempty, try
 	 * to reclaim 1 item from it before growing the cache (possibly
 	 * above its target max if the reclamation failed or is delayed).
 	 * Otherwise, wait for some space.  In all cases, schedule
 	 * vnlru_proc() if we are getting short of space.  The watermarks
 	 * should be chosen so that we never wait or even reclaim from
 	 * the free list to below its target minimum.
 	 */
 	if (vnlru_free_locked(1, NULL) > 0)
 		goto alloc;
 	if (mp == NULL || (mp->mnt_kern_flag & MNTK_SUSPEND) == 0) {
 		/*
 		 * Wait for space for a new vnode.
 		 */
 		vnlru_kick();
 		msleep(&vnlruproc_sig, &vnode_list_mtx, PVFS, "vlruwk", hz);
 		if (atomic_load_long(&numvnodes) + 1 > desiredvnodes &&
 		    vnlru_read_freevnodes() > 1)
 			vnlru_free_locked(1, NULL);
 	}
 alloc:
 	rnumvnodes = atomic_fetchadd_long(&numvnodes, 1) + 1;
 	if (vnlru_under(rnumvnodes, vlowat))
 		vnlru_kick();
 	mtx_unlock(&vnode_list_mtx);
 	return (uma_zalloc(vnode_zone, M_WAITOK));
 }
 
 static struct vnode *
 vn_alloc(struct mount *mp)
 {
 	u_long rnumvnodes;
 
 	if (__predict_false(vn_alloc_cyclecount != 0))
 		return (vn_alloc_hard(mp));
 	rnumvnodes = atomic_fetchadd_long(&numvnodes, 1) + 1;
 	if (__predict_false(vnlru_under_unlocked(rnumvnodes, vlowat))) {
 		atomic_subtract_long(&numvnodes, 1);
 		return (vn_alloc_hard(mp));
 	}
 
 	return (uma_zalloc(vnode_zone, M_WAITOK));
 }
 
 static void
 vn_free(struct vnode *vp)
 {
 
 	atomic_subtract_long(&numvnodes, 1);
 	uma_zfree(vnode_zone, vp);
 }
 
 /*
  * Return the next vnode from the free list.
  */
 int
 getnewvnode(const char *tag, struct mount *mp, struct vop_vector *vops,
     struct vnode **vpp)
 {
 	struct vnode *vp;
 	struct thread *td;
 	struct lock_object *lo;
 
 	CTR3(KTR_VFS, "%s: mp %p with tag %s", __func__, mp, tag);
 
 	KASSERT(vops->registered,
 	    ("%s: not registered vector op %p\n", __func__, vops));
 
 	td = curthread;
 	if (td->td_vp_reserved != NULL) {
 		vp = td->td_vp_reserved;
 		td->td_vp_reserved = NULL;
 	} else {
 		vp = vn_alloc(mp);
 	}
 	counter_u64_add(vnodes_created, 1);
 	/*
 	 * Locks are given the generic name "vnode" when created.
 	 * Follow the historic practice of using the filesystem
 	 * name when they allocated, e.g., "zfs", "ufs", "nfs, etc.
 	 *
 	 * Locks live in a witness group keyed on their name. Thus,
 	 * when a lock is renamed, it must also move from the witness
 	 * group of its old name to the witness group of its new name.
 	 *
 	 * The change only needs to be made when the vnode moves
 	 * from one filesystem type to another. We ensure that each
 	 * filesystem use a single static name pointer for its tag so
 	 * that we can compare pointers rather than doing a strcmp().
 	 */
 	lo = &vp->v_vnlock->lock_object;
 #ifdef WITNESS
 	if (lo->lo_name != tag) {
 #endif
 		lo->lo_name = tag;
 #ifdef WITNESS
 		WITNESS_DESTROY(lo);
 		WITNESS_INIT(lo, tag);
 	}
 #endif
 	/*
 	 * By default, don't allow shared locks unless filesystems opt-in.
 	 */
 	vp->v_vnlock->lock_object.lo_flags |= LK_NOSHARE;
 	/*
 	 * Finalize various vnode identity bits.
 	 */
 	KASSERT(vp->v_object == NULL, ("stale v_object %p", vp));
 	KASSERT(vp->v_lockf == NULL, ("stale v_lockf %p", vp));
 	KASSERT(vp->v_pollinfo == NULL, ("stale v_pollinfo %p", vp));
 	vp->v_type = VNON;
 	vp->v_op = vops;
 	v_init_counters(vp);
 	vp->v_bufobj.bo_ops = &buf_ops_bio;
 #ifdef DIAGNOSTIC
 	if (mp == NULL && vops != &dead_vnodeops)
 		printf("NULL mp in getnewvnode(9), tag %s\n", tag);
 #endif
 #ifdef MAC
 	mac_vnode_init(vp);
 	if (mp != NULL && (mp->mnt_flag & MNT_MULTILABEL) == 0)
 		mac_vnode_associate_singlelabel(mp, vp);
 #endif
 	if (mp != NULL) {
 		vp->v_bufobj.bo_bsize = mp->mnt_stat.f_iosize;
 		if ((mp->mnt_kern_flag & MNTK_NOKNOTE) != 0)
 			vp->v_vflag |= VV_NOKNOTE;
 	}
 
 	/*
 	 * For the filesystems which do not use vfs_hash_insert(),
 	 * still initialize v_hash to have vfs_hash_index() useful.
 	 * E.g., nullfs uses vfs_hash_index() on the lower vnode for
 	 * its own hashing.
 	 */
 	vp->v_hash = (uintptr_t)vp >> vnsz2log;
 
 	*vpp = vp;
 	return (0);
 }
 
 void
 getnewvnode_reserve(void)
 {
 	struct thread *td;
 
 	td = curthread;
 	MPASS(td->td_vp_reserved == NULL);
 	td->td_vp_reserved = vn_alloc(NULL);
 }
 
 void
 getnewvnode_drop_reserve(void)
 {
 	struct thread *td;
 
 	td = curthread;
 	if (td->td_vp_reserved != NULL) {
 		vn_free(td->td_vp_reserved);
 		td->td_vp_reserved = NULL;
 	}
 }
 
 static void
 freevnode(struct vnode *vp)
 {
 	struct bufobj *bo;
 
 	/*
 	 * The vnode has been marked for destruction, so free it.
 	 *
 	 * The vnode will be returned to the zone where it will
 	 * normally remain until it is needed for another vnode. We
 	 * need to cleanup (or verify that the cleanup has already
 	 * been done) any residual data left from its current use
 	 * so as not to contaminate the freshly allocated vnode.
 	 */
 	CTR2(KTR_VFS, "%s: destroying the vnode %p", __func__, vp);
 	bo = &vp->v_bufobj;
 	VNASSERT(vp->v_data == NULL, vp, ("cleaned vnode isn't"));
 	VNASSERT(vp->v_holdcnt == 0, vp, ("Non-zero hold count"));
 	VNASSERT(vp->v_usecount == 0, vp, ("Non-zero use count"));
 	VNASSERT(vp->v_writecount == 0, vp, ("Non-zero write count"));
 	VNASSERT(bo->bo_numoutput == 0, vp, ("Clean vnode has pending I/O's"));
 	VNASSERT(bo->bo_clean.bv_cnt == 0, vp, ("cleanbufcnt not 0"));
 	VNASSERT(pctrie_is_empty(&bo->bo_clean.bv_root), vp,
 	    ("clean blk trie not empty"));
 	VNASSERT(bo->bo_dirty.bv_cnt == 0, vp, ("dirtybufcnt not 0"));
 	VNASSERT(pctrie_is_empty(&bo->bo_dirty.bv_root), vp,
 	    ("dirty blk trie not empty"));
 	VNASSERT(TAILQ_EMPTY(&vp->v_cache_dst), vp, ("vp has namecache dst"));
 	VNASSERT(LIST_EMPTY(&vp->v_cache_src), vp, ("vp has namecache src"));
 	VNASSERT(vp->v_cache_dd == NULL, vp, ("vp has namecache for .."));
 	VNASSERT(TAILQ_EMPTY(&vp->v_rl.rl_waiters), vp,
 	    ("Dangling rangelock waiters"));
 	VI_UNLOCK(vp);
 #ifdef MAC
 	mac_vnode_destroy(vp);
 #endif
 	if (vp->v_pollinfo != NULL) {
 		destroy_vpollinfo(vp->v_pollinfo);
 		vp->v_pollinfo = NULL;
 	}
 #ifdef INVARIANTS
 	/* XXX Elsewhere we detect an already freed vnode via NULL v_op. */
 	vp->v_op = NULL;
 #endif
 	vp->v_mountedhere = NULL;
 	vp->v_unpcb = NULL;
 	vp->v_rdev = NULL;
 	vp->v_fifoinfo = NULL;
 	vp->v_lasta = vp->v_clen = vp->v_cstart = vp->v_lastw = 0;
 	vp->v_irflag = 0;
 	vp->v_iflag = 0;
 	vp->v_vflag = 0;
 	bo->bo_flag = 0;
 	vn_free(vp);
 }
 
 /*
  * Delete from old mount point vnode list, if on one.
  */
 static void
 delmntque(struct vnode *vp)
 {
 	struct mount *mp;
 
 	mp = vp->v_mount;
 	if (mp == NULL)
 		return;
 	MNT_ILOCK(mp);
 	VI_LOCK(vp);
 	if (vp->v_mflag & VMP_LAZYLIST) {
 		mtx_lock(&mp->mnt_listmtx);
 		if (vp->v_mflag & VMP_LAZYLIST) {
 			vp->v_mflag &= ~VMP_LAZYLIST;
 			TAILQ_REMOVE(&mp->mnt_lazyvnodelist, vp, v_lazylist);
 			mp->mnt_lazyvnodelistsize--;
 		}
 		mtx_unlock(&mp->mnt_listmtx);
 	}
 	vp->v_mount = NULL;
 	VI_UNLOCK(vp);
 	VNASSERT(mp->mnt_nvnodelistsize > 0, vp,
 		("bad mount point vnode list size"));
 	TAILQ_REMOVE(&mp->mnt_nvnodelist, vp, v_nmntvnodes);
 	mp->mnt_nvnodelistsize--;
 	MNT_REL(mp);
 	MNT_IUNLOCK(mp);
 }
 
 static void
 insmntque_stddtr(struct vnode *vp, void *dtr_arg)
 {
 
 	vp->v_data = NULL;
 	vp->v_op = &dead_vnodeops;
 	vgone(vp);
 	vput(vp);
 }
 
 /*
  * Insert into list of vnodes for the new mount point, if available.
  */
 int
 insmntque1(struct vnode *vp, struct mount *mp,
 	void (*dtr)(struct vnode *, void *), void *dtr_arg)
 {
 
 	KASSERT(vp->v_mount == NULL,
 		("insmntque: vnode already on per mount vnode list"));
 	VNASSERT(mp != NULL, vp, ("Don't call insmntque(foo, NULL)"));
 	ASSERT_VOP_ELOCKED(vp, "insmntque: non-locked vp");
 
 	/*
 	 * We acquire the vnode interlock early to ensure that the
 	 * vnode cannot be recycled by another process releasing a
 	 * holdcnt on it before we get it on both the vnode list
 	 * and the active vnode list. The mount mutex protects only
 	 * manipulation of the vnode list and the vnode freelist
 	 * mutex protects only manipulation of the active vnode list.
 	 * Hence the need to hold the vnode interlock throughout.
 	 */
 	MNT_ILOCK(mp);
 	VI_LOCK(vp);
 	if (((mp->mnt_kern_flag & MNTK_UNMOUNT) != 0 &&
 	    ((mp->mnt_kern_flag & MNTK_UNMOUNTF) != 0 ||
 	    mp->mnt_nvnodelistsize == 0)) &&
 	    (vp->v_vflag & VV_FORCEINSMQ) == 0) {
 		VI_UNLOCK(vp);
 		MNT_IUNLOCK(mp);
 		if (dtr != NULL)
 			dtr(vp, dtr_arg);
 		return (EBUSY);
 	}
 	vp->v_mount = mp;
 	MNT_REF(mp);
 	TAILQ_INSERT_TAIL(&mp->mnt_nvnodelist, vp, v_nmntvnodes);
 	VNASSERT(mp->mnt_nvnodelistsize >= 0, vp,
 		("neg mount point vnode list size"));
 	mp->mnt_nvnodelistsize++;
 	VI_UNLOCK(vp);
 	MNT_IUNLOCK(mp);
 	return (0);
 }
 
 int
 insmntque(struct vnode *vp, struct mount *mp)
 {
 
 	return (insmntque1(vp, mp, insmntque_stddtr, NULL));
 }
 
 /*
  * Flush out and invalidate all buffers associated with a bufobj
  * Called with the underlying object locked.
  */
 int
 bufobj_invalbuf(struct bufobj *bo, int flags, int slpflag, int slptimeo)
 {
 	int error;
 
 	BO_LOCK(bo);
 	if (flags & V_SAVE) {
 		error = bufobj_wwait(bo, slpflag, slptimeo);
 		if (error) {
 			BO_UNLOCK(bo);
 			return (error);
 		}
 		if (bo->bo_dirty.bv_cnt > 0) {
 			BO_UNLOCK(bo);
 			if ((error = BO_SYNC(bo, MNT_WAIT)) != 0)
 				return (error);
 			/*
 			 * XXX We could save a lock/unlock if this was only
 			 * enabled under INVARIANTS
 			 */
 			BO_LOCK(bo);
 			if (bo->bo_numoutput > 0 || bo->bo_dirty.bv_cnt > 0)
 				panic("vinvalbuf: dirty bufs");
 		}
 	}
 	/*
 	 * If you alter this loop please notice that interlock is dropped and
 	 * reacquired in flushbuflist.  Special care is needed to ensure that
 	 * no race conditions occur from this.
 	 */
 	do {
 		error = flushbuflist(&bo->bo_clean,
 		    flags, bo, slpflag, slptimeo);
 		if (error == 0 && !(flags & V_CLEANONLY))
 			error = flushbuflist(&bo->bo_dirty,
 			    flags, bo, slpflag, slptimeo);
 		if (error != 0 && error != EAGAIN) {
 			BO_UNLOCK(bo);
 			return (error);
 		}
 	} while (error != 0);
 
 	/*
 	 * Wait for I/O to complete.  XXX needs cleaning up.  The vnode can
 	 * have write I/O in-progress but if there is a VM object then the
 	 * VM object can also have read-I/O in-progress.
 	 */
 	do {
 		bufobj_wwait(bo, 0, 0);
 		if ((flags & V_VMIO) == 0 && bo->bo_object != NULL) {
 			BO_UNLOCK(bo);
 			vm_object_pip_wait_unlocked(bo->bo_object, "bovlbx");
 			BO_LOCK(bo);
 		}
 	} while (bo->bo_numoutput > 0);
 	BO_UNLOCK(bo);
 
 	/*
 	 * Destroy the copy in the VM cache, too.
 	 */
 	if (bo->bo_object != NULL &&
 	    (flags & (V_ALT | V_NORMAL | V_CLEANONLY | V_VMIO)) == 0) {
 		VM_OBJECT_WLOCK(bo->bo_object);
 		vm_object_page_remove(bo->bo_object, 0, 0, (flags & V_SAVE) ?
 		    OBJPR_CLEANONLY : 0);
 		VM_OBJECT_WUNLOCK(bo->bo_object);
 	}
 
 #ifdef INVARIANTS
 	BO_LOCK(bo);
 	if ((flags & (V_ALT | V_NORMAL | V_CLEANONLY | V_VMIO |
 	    V_ALLOWCLEAN)) == 0 && (bo->bo_dirty.bv_cnt > 0 ||
 	    bo->bo_clean.bv_cnt > 0))
 		panic("vinvalbuf: flush failed");
 	if ((flags & (V_ALT | V_NORMAL | V_CLEANONLY | V_VMIO)) == 0 &&
 	    bo->bo_dirty.bv_cnt > 0)
 		panic("vinvalbuf: flush dirty failed");
 	BO_UNLOCK(bo);
 #endif
 	return (0);
 }
 
 /*
  * Flush out and invalidate all buffers associated with a vnode.
  * Called with the underlying object locked.
  */
 int
 vinvalbuf(struct vnode *vp, int flags, int slpflag, int slptimeo)
 {
 
 	CTR3(KTR_VFS, "%s: vp %p with flags %d", __func__, vp, flags);
 	ASSERT_VOP_LOCKED(vp, "vinvalbuf");
 	if (vp->v_object != NULL && vp->v_object->handle != vp)
 		return (0);
 	return (bufobj_invalbuf(&vp->v_bufobj, flags, slpflag, slptimeo));
 }
 
 /*
  * Flush out buffers on the specified list.
  *
  */
 static int
 flushbuflist(struct bufv *bufv, int flags, struct bufobj *bo, int slpflag,
     int slptimeo)
 {
 	struct buf *bp, *nbp;
 	int retval, error;
 	daddr_t lblkno;
 	b_xflags_t xflags;
 
 	ASSERT_BO_WLOCKED(bo);
 
 	retval = 0;
 	TAILQ_FOREACH_SAFE(bp, &bufv->bv_hd, b_bobufs, nbp) {
 		/*
 		 * If we are flushing both V_NORMAL and V_ALT buffers then
 		 * do not skip any buffers. If we are flushing only V_NORMAL
 		 * buffers then skip buffers marked as BX_ALTDATA. If we are
 		 * flushing only V_ALT buffers then skip buffers not marked
 		 * as BX_ALTDATA.
 		 */
 		if (((flags & (V_NORMAL | V_ALT)) != (V_NORMAL | V_ALT)) &&
 		   (((flags & V_NORMAL) && (bp->b_xflags & BX_ALTDATA) != 0) ||
 		    ((flags & V_ALT) && (bp->b_xflags & BX_ALTDATA) == 0))) {
 			continue;
 		}
 		if (nbp != NULL) {
 			lblkno = nbp->b_lblkno;
 			xflags = nbp->b_xflags & (BX_VNDIRTY | BX_VNCLEAN);
 		}
 		retval = EAGAIN;
 		error = BUF_TIMELOCK(bp,
 		    LK_EXCLUSIVE | LK_SLEEPFAIL | LK_INTERLOCK, BO_LOCKPTR(bo),
 		    "flushbuf", slpflag, slptimeo);
 		if (error) {
 			BO_LOCK(bo);
 			return (error != ENOLCK ? error : EAGAIN);
 		}
 		KASSERT(bp->b_bufobj == bo,
 		    ("bp %p wrong b_bufobj %p should be %p",
 		    bp, bp->b_bufobj, bo));
 		/*
 		 * XXX Since there are no node locks for NFS, I
 		 * believe there is a slight chance that a delayed
 		 * write will occur while sleeping just above, so
 		 * check for it.
 		 */
 		if (((bp->b_flags & (B_DELWRI | B_INVAL)) == B_DELWRI) &&
 		    (flags & V_SAVE)) {
 			bremfree(bp);
 			bp->b_flags |= B_ASYNC;
 			bwrite(bp);
 			BO_LOCK(bo);
 			return (EAGAIN);	/* XXX: why not loop ? */
 		}
 		bremfree(bp);
 		bp->b_flags |= (B_INVAL | B_RELBUF);
 		bp->b_flags &= ~B_ASYNC;
 		brelse(bp);
 		BO_LOCK(bo);
 		if (nbp == NULL)
 			break;
 		nbp = gbincore(bo, lblkno);
 		if (nbp == NULL || (nbp->b_xflags & (BX_VNDIRTY | BX_VNCLEAN))
 		    != xflags)
 			break;			/* nbp invalid */
 	}
 	return (retval);
 }
 
 int
 bnoreuselist(struct bufv *bufv, struct bufobj *bo, daddr_t startn, daddr_t endn)
 {
 	struct buf *bp;
 	int error;
 	daddr_t lblkno;
 
 	ASSERT_BO_LOCKED(bo);
 
 	for (lblkno = startn;;) {
 again:
 		bp = BUF_PCTRIE_LOOKUP_GE(&bufv->bv_root, lblkno);
 		if (bp == NULL || bp->b_lblkno >= endn ||
 		    bp->b_lblkno < startn)
 			break;
 		error = BUF_TIMELOCK(bp, LK_EXCLUSIVE | LK_SLEEPFAIL |
 		    LK_INTERLOCK, BO_LOCKPTR(bo), "brlsfl", 0, 0);
 		if (error != 0) {
 			BO_RLOCK(bo);
 			if (error == ENOLCK)
 				goto again;
 			return (error);
 		}
 		KASSERT(bp->b_bufobj == bo,
 		    ("bp %p wrong b_bufobj %p should be %p",
 		    bp, bp->b_bufobj, bo));
 		lblkno = bp->b_lblkno + 1;
 		if ((bp->b_flags & B_MANAGED) == 0)
 			bremfree(bp);
 		bp->b_flags |= B_RELBUF;
 		/*
 		 * In the VMIO case, use the B_NOREUSE flag to hint that the
 		 * pages backing each buffer in the range are unlikely to be
 		 * reused.  Dirty buffers will have the hint applied once
 		 * they've been written.
 		 */
 		if ((bp->b_flags & B_VMIO) != 0)
 			bp->b_flags |= B_NOREUSE;
 		brelse(bp);
 		BO_RLOCK(bo);
 	}
 	return (0);
 }
 
 /*
  * Truncate a file's buffer and pages to a specified length.  This
  * is in lieu of the old vinvalbuf mechanism, which performed unneeded
  * sync activity.
  */
 int
 vtruncbuf(struct vnode *vp, off_t length, int blksize)
 {
 	struct buf *bp, *nbp;
 	struct bufobj *bo;
 	daddr_t startlbn;
 
 	CTR4(KTR_VFS, "%s: vp %p with block %d:%ju", __func__,
 	    vp, blksize, (uintmax_t)length);
 
 	/*
 	 * Round up to the *next* lbn.
 	 */
 	startlbn = howmany(length, blksize);
 
 	ASSERT_VOP_LOCKED(vp, "vtruncbuf");
 
 	bo = &vp->v_bufobj;
 restart_unlocked:
 	BO_LOCK(bo);
 
 	while (v_inval_buf_range_locked(vp, bo, startlbn, INT64_MAX) == EAGAIN)
 		;
 
 	if (length > 0) {
 restartsync:
 		TAILQ_FOREACH_SAFE(bp, &bo->bo_dirty.bv_hd, b_bobufs, nbp) {
 			if (bp->b_lblkno > 0)
 				continue;
 			/*
 			 * Since we hold the vnode lock this should only
 			 * fail if we're racing with the buf daemon.
 			 */
 			if (BUF_LOCK(bp,
 			    LK_EXCLUSIVE | LK_SLEEPFAIL | LK_INTERLOCK,
 			    BO_LOCKPTR(bo)) == ENOLCK)
 				goto restart_unlocked;
 
 			VNASSERT((bp->b_flags & B_DELWRI), vp,
 			    ("buf(%p) on dirty queue without DELWRI", bp));
 
 			bremfree(bp);
 			bawrite(bp);
 			BO_LOCK(bo);
 			goto restartsync;
 		}
 	}
 
 	bufobj_wwait(bo, 0, 0);
 	BO_UNLOCK(bo);
 	vnode_pager_setsize(vp, length);
 
 	return (0);
 }
 
 /*
  * Invalidate the cached pages of a file's buffer within the range of block
  * numbers [startlbn, endlbn).
  */
 void
 v_inval_buf_range(struct vnode *vp, daddr_t startlbn, daddr_t endlbn,
     int blksize)
 {
 	struct bufobj *bo;
 	off_t start, end;
 
 	ASSERT_VOP_LOCKED(vp, "v_inval_buf_range");
 
 	start = blksize * startlbn;
 	end = blksize * endlbn;
 
 	bo = &vp->v_bufobj;
 	BO_LOCK(bo);
 	MPASS(blksize == bo->bo_bsize);
 
 	while (v_inval_buf_range_locked(vp, bo, startlbn, endlbn) == EAGAIN)
 		;
 
 	BO_UNLOCK(bo);
 	vn_pages_remove(vp, OFF_TO_IDX(start), OFF_TO_IDX(end + PAGE_SIZE - 1));
 }
 
 static int
 v_inval_buf_range_locked(struct vnode *vp, struct bufobj *bo,
     daddr_t startlbn, daddr_t endlbn)
 {
 	struct buf *bp, *nbp;
 	bool anyfreed;
 
 	ASSERT_VOP_LOCKED(vp, "v_inval_buf_range_locked");
 	ASSERT_BO_LOCKED(bo);
 
 	do {
 		anyfreed = false;
 		TAILQ_FOREACH_SAFE(bp, &bo->bo_clean.bv_hd, b_bobufs, nbp) {
 			if (bp->b_lblkno < startlbn || bp->b_lblkno >= endlbn)
 				continue;
 			if (BUF_LOCK(bp,
 			    LK_EXCLUSIVE | LK_SLEEPFAIL | LK_INTERLOCK,
 			    BO_LOCKPTR(bo)) == ENOLCK) {
 				BO_LOCK(bo);
 				return (EAGAIN);
 			}
 
 			bremfree(bp);
 			bp->b_flags |= B_INVAL | B_RELBUF;
 			bp->b_flags &= ~B_ASYNC;
 			brelse(bp);
 			anyfreed = true;
 
 			BO_LOCK(bo);
 			if (nbp != NULL &&
 			    (((nbp->b_xflags & BX_VNCLEAN) == 0) ||
 			    nbp->b_vp != vp ||
 			    (nbp->b_flags & B_DELWRI) != 0))
 				return (EAGAIN);
 		}
 
 		TAILQ_FOREACH_SAFE(bp, &bo->bo_dirty.bv_hd, b_bobufs, nbp) {
 			if (bp->b_lblkno < startlbn || bp->b_lblkno >= endlbn)
 				continue;
 			if (BUF_LOCK(bp,
 			    LK_EXCLUSIVE | LK_SLEEPFAIL | LK_INTERLOCK,
 			    BO_LOCKPTR(bo)) == ENOLCK) {
 				BO_LOCK(bo);
 				return (EAGAIN);
 			}
 			bremfree(bp);
 			bp->b_flags |= B_INVAL | B_RELBUF;
 			bp->b_flags &= ~B_ASYNC;
 			brelse(bp);
 			anyfreed = true;
 
 			BO_LOCK(bo);
 			if (nbp != NULL &&
 			    (((nbp->b_xflags & BX_VNDIRTY) == 0) ||
 			    (nbp->b_vp != vp) ||
 			    (nbp->b_flags & B_DELWRI) == 0))
 				return (EAGAIN);
 		}
 	} while (anyfreed);
 	return (0);
 }
 
 static void
 buf_vlist_remove(struct buf *bp)
 {
 	struct bufv *bv;
 
 	KASSERT(bp->b_bufobj != NULL, ("No b_bufobj %p", bp));
 	ASSERT_BO_WLOCKED(bp->b_bufobj);
 	KASSERT((bp->b_xflags & (BX_VNDIRTY|BX_VNCLEAN)) !=
 	    (BX_VNDIRTY|BX_VNCLEAN),
 	    ("buf_vlist_remove: Buf %p is on two lists", bp));
 	if (bp->b_xflags & BX_VNDIRTY)
 		bv = &bp->b_bufobj->bo_dirty;
 	else
 		bv = &bp->b_bufobj->bo_clean;
 	BUF_PCTRIE_REMOVE(&bv->bv_root, bp->b_lblkno);
 	TAILQ_REMOVE(&bv->bv_hd, bp, b_bobufs);
 	bv->bv_cnt--;
 	bp->b_xflags &= ~(BX_VNDIRTY | BX_VNCLEAN);
 }
 
 /*
  * Add the buffer to the sorted clean or dirty block list.
  *
  * NOTE: xflags is passed as a constant, optimizing this inline function!
  */
 static void
 buf_vlist_add(struct buf *bp, struct bufobj *bo, b_xflags_t xflags)
 {
 	struct bufv *bv;
 	struct buf *n;
 	int error;
 
 	ASSERT_BO_WLOCKED(bo);
 	KASSERT((xflags & BX_VNDIRTY) == 0 || (bo->bo_flag & BO_DEAD) == 0,
 	    ("dead bo %p", bo));
 	KASSERT((bp->b_xflags & (BX_VNDIRTY|BX_VNCLEAN)) == 0,
 	    ("buf_vlist_add: Buf %p has existing xflags %d", bp, bp->b_xflags));
 	bp->b_xflags |= xflags;
 	if (xflags & BX_VNDIRTY)
 		bv = &bo->bo_dirty;
 	else
 		bv = &bo->bo_clean;
 
 	/*
 	 * Keep the list ordered.  Optimize empty list insertion.  Assume
 	 * we tend to grow at the tail so lookup_le should usually be cheaper
 	 * than _ge. 
 	 */
 	if (bv->bv_cnt == 0 ||
 	    bp->b_lblkno > TAILQ_LAST(&bv->bv_hd, buflists)->b_lblkno)
 		TAILQ_INSERT_TAIL(&bv->bv_hd, bp, b_bobufs);
 	else if ((n = BUF_PCTRIE_LOOKUP_LE(&bv->bv_root, bp->b_lblkno)) == NULL)
 		TAILQ_INSERT_HEAD(&bv->bv_hd, bp, b_bobufs);
 	else
 		TAILQ_INSERT_AFTER(&bv->bv_hd, n, bp, b_bobufs);
 	error = BUF_PCTRIE_INSERT(&bv->bv_root, bp);
 	if (error)
 		panic("buf_vlist_add:  Preallocated nodes insufficient.");
 	bv->bv_cnt++;
 }
 
 /*
  * Look up a buffer using the buffer tries.
  */
 struct buf *
 gbincore(struct bufobj *bo, daddr_t lblkno)
 {
 	struct buf *bp;
 
 	ASSERT_BO_LOCKED(bo);
 	bp = BUF_PCTRIE_LOOKUP(&bo->bo_clean.bv_root, lblkno);
 	if (bp != NULL)
 		return (bp);
 	return BUF_PCTRIE_LOOKUP(&bo->bo_dirty.bv_root, lblkno);
 }
 
 /*
  * Associate a buffer with a vnode.
  */
 void
 bgetvp(struct vnode *vp, struct buf *bp)
 {
 	struct bufobj *bo;
 
 	bo = &vp->v_bufobj;
 	ASSERT_BO_WLOCKED(bo);
 	VNASSERT(bp->b_vp == NULL, bp->b_vp, ("bgetvp: not free"));
 
 	CTR3(KTR_BUF, "bgetvp(%p) vp %p flags %X", bp, vp, bp->b_flags);
 	VNASSERT((bp->b_xflags & (BX_VNDIRTY|BX_VNCLEAN)) == 0, vp,
 	    ("bgetvp: bp already attached! %p", bp));
 
 	vhold(vp);
 	bp->b_vp = vp;
 	bp->b_bufobj = bo;
 	/*
 	 * Insert onto list for new vnode.
 	 */
 	buf_vlist_add(bp, bo, BX_VNCLEAN);
 }
 
 /*
  * Disassociate a buffer from a vnode.
  */
 void
 brelvp(struct buf *bp)
 {
 	struct bufobj *bo;
 	struct vnode *vp;
 
 	CTR3(KTR_BUF, "brelvp(%p) vp %p flags %X", bp, bp->b_vp, bp->b_flags);
 	KASSERT(bp->b_vp != NULL, ("brelvp: NULL"));
 
 	/*
 	 * Delete from old vnode list, if on one.
 	 */
 	vp = bp->b_vp;		/* XXX */
 	bo = bp->b_bufobj;
 	BO_LOCK(bo);
 	if (bp->b_xflags & (BX_VNDIRTY | BX_VNCLEAN))
 		buf_vlist_remove(bp);
 	else
 		panic("brelvp: Buffer %p not on queue.", bp);
 	if ((bo->bo_flag & BO_ONWORKLST) && bo->bo_dirty.bv_cnt == 0) {
 		bo->bo_flag &= ~BO_ONWORKLST;
 		mtx_lock(&sync_mtx);
 		LIST_REMOVE(bo, bo_synclist);
 		syncer_worklist_len--;
 		mtx_unlock(&sync_mtx);
 	}
 	bp->b_vp = NULL;
 	bp->b_bufobj = NULL;
 	BO_UNLOCK(bo);
 	vdrop(vp);
 }
 
 /*
  * Add an item to the syncer work queue.
  */
 static void
 vn_syncer_add_to_worklist(struct bufobj *bo, int delay)
 {
 	int slot;
 
 	ASSERT_BO_WLOCKED(bo);
 
 	mtx_lock(&sync_mtx);
 	if (bo->bo_flag & BO_ONWORKLST)
 		LIST_REMOVE(bo, bo_synclist);
 	else {
 		bo->bo_flag |= BO_ONWORKLST;
 		syncer_worklist_len++;
 	}
 
 	if (delay > syncer_maxdelay - 2)
 		delay = syncer_maxdelay - 2;
 	slot = (syncer_delayno + delay) & syncer_mask;
 
 	LIST_INSERT_HEAD(&syncer_workitem_pending[slot], bo, bo_synclist);
 	mtx_unlock(&sync_mtx);
 }
 
 static int
 sysctl_vfs_worklist_len(SYSCTL_HANDLER_ARGS)
 {
 	int error, len;
 
 	mtx_lock(&sync_mtx);
 	len = syncer_worklist_len - sync_vnode_count;
 	mtx_unlock(&sync_mtx);
 	error = SYSCTL_OUT(req, &len, sizeof(len));
 	return (error);
 }
 
 SYSCTL_PROC(_vfs, OID_AUTO, worklist_len,
     CTLTYPE_INT | CTLFLAG_MPSAFE| CTLFLAG_RD, NULL, 0,
     sysctl_vfs_worklist_len, "I", "Syncer thread worklist length");
 
 static struct proc *updateproc;
 static void sched_sync(void);
 static struct kproc_desc up_kp = {
 	"syncer",
 	sched_sync,
 	&updateproc
 };
 SYSINIT(syncer, SI_SUB_KTHREAD_UPDATE, SI_ORDER_FIRST, kproc_start, &up_kp);
 
 static int
 sync_vnode(struct synclist *slp, struct bufobj **bo, struct thread *td)
 {
 	struct vnode *vp;
 	struct mount *mp;
 
 	*bo = LIST_FIRST(slp);
 	if (*bo == NULL)
 		return (0);
 	vp = bo2vnode(*bo);
 	if (VOP_ISLOCKED(vp) != 0 || VI_TRYLOCK(vp) == 0)
 		return (1);
 	/*
 	 * We use vhold in case the vnode does not
 	 * successfully sync.  vhold prevents the vnode from
 	 * going away when we unlock the sync_mtx so that
 	 * we can acquire the vnode interlock.
 	 */
 	vholdl(vp);
 	mtx_unlock(&sync_mtx);
 	VI_UNLOCK(vp);
 	if (vn_start_write(vp, &mp, V_NOWAIT) != 0) {
 		vdrop(vp);
 		mtx_lock(&sync_mtx);
 		return (*bo == LIST_FIRST(slp));
 	}
 	vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
 	(void) VOP_FSYNC(vp, MNT_LAZY, td);
 	VOP_UNLOCK(vp);
 	vn_finished_write(mp);
 	BO_LOCK(*bo);
 	if (((*bo)->bo_flag & BO_ONWORKLST) != 0) {
 		/*
 		 * Put us back on the worklist.  The worklist
 		 * routine will remove us from our current
 		 * position and then add us back in at a later
 		 * position.
 		 */
 		vn_syncer_add_to_worklist(*bo, syncdelay);
 	}
 	BO_UNLOCK(*bo);
 	vdrop(vp);
 	mtx_lock(&sync_mtx);
 	return (0);
 }
 
 static int first_printf = 1;
 
 /*
  * System filesystem synchronizer daemon.
  */
 static void
 sched_sync(void)
 {
 	struct synclist *next, *slp;
 	struct bufobj *bo;
 	long starttime;
 	struct thread *td = curthread;
 	int last_work_seen;
 	int net_worklist_len;
 	int syncer_final_iter;
 	int error;
 
 	last_work_seen = 0;
 	syncer_final_iter = 0;
 	syncer_state = SYNCER_RUNNING;
 	starttime = time_uptime;
 	td->td_pflags |= TDP_NORUNNINGBUF;
 
 	EVENTHANDLER_REGISTER(shutdown_pre_sync, syncer_shutdown, td->td_proc,
 	    SHUTDOWN_PRI_LAST);
 
 	mtx_lock(&sync_mtx);
 	for (;;) {
 		if (syncer_state == SYNCER_FINAL_DELAY &&
 		    syncer_final_iter == 0) {
 			mtx_unlock(&sync_mtx);
 			kproc_suspend_check(td->td_proc);
 			mtx_lock(&sync_mtx);
 		}
 		net_worklist_len = syncer_worklist_len - sync_vnode_count;
 		if (syncer_state != SYNCER_RUNNING &&
 		    starttime != time_uptime) {
 			if (first_printf) {
 				printf("\nSyncing disks, vnodes remaining... ");
 				first_printf = 0;
 			}
 			printf("%d ", net_worklist_len);
 		}
 		starttime = time_uptime;
 
 		/*
 		 * Push files whose dirty time has expired.  Be careful
 		 * of interrupt race on slp queue.
 		 *
 		 * Skip over empty worklist slots when shutting down.
 		 */
 		do {
 			slp = &syncer_workitem_pending[syncer_delayno];
 			syncer_delayno += 1;
 			if (syncer_delayno == syncer_maxdelay)
 				syncer_delayno = 0;
 			next = &syncer_workitem_pending[syncer_delayno];
 			/*
 			 * If the worklist has wrapped since the
 			 * it was emptied of all but syncer vnodes,
 			 * switch to the FINAL_DELAY state and run
 			 * for one more second.
 			 */
 			if (syncer_state == SYNCER_SHUTTING_DOWN &&
 			    net_worklist_len == 0 &&
 			    last_work_seen == syncer_delayno) {
 				syncer_state = SYNCER_FINAL_DELAY;
 				syncer_final_iter = SYNCER_SHUTDOWN_SPEEDUP;
 			}
 		} while (syncer_state != SYNCER_RUNNING && LIST_EMPTY(slp) &&
 		    syncer_worklist_len > 0);
 
 		/*
 		 * Keep track of the last time there was anything
 		 * on the worklist other than syncer vnodes.
 		 * Return to the SHUTTING_DOWN state if any
 		 * new work appears.
 		 */
 		if (net_worklist_len > 0 || syncer_state == SYNCER_RUNNING)
 			last_work_seen = syncer_delayno;
 		if (net_worklist_len > 0 && syncer_state == SYNCER_FINAL_DELAY)
 			syncer_state = SYNCER_SHUTTING_DOWN;
 		while (!LIST_EMPTY(slp)) {
 			error = sync_vnode(slp, &bo, td);
 			if (error == 1) {
 				LIST_REMOVE(bo, bo_synclist);
 				LIST_INSERT_HEAD(next, bo, bo_synclist);
 				continue;
 			}
 
 			if (first_printf == 0) {
 				/*
 				 * Drop the sync mutex, because some watchdog
 				 * drivers need to sleep while patting
 				 */
 				mtx_unlock(&sync_mtx);
 				wdog_kern_pat(WD_LASTVAL);
 				mtx_lock(&sync_mtx);
 			}
 
 		}
 		if (syncer_state == SYNCER_FINAL_DELAY && syncer_final_iter > 0)
 			syncer_final_iter--;
 		/*
 		 * The variable rushjob allows the kernel to speed up the
 		 * processing of the filesystem syncer process. A rushjob
 		 * value of N tells the filesystem syncer to process the next
 		 * N seconds worth of work on its queue ASAP. Currently rushjob
 		 * is used by the soft update code to speed up the filesystem
 		 * syncer process when the incore state is getting so far
 		 * ahead of the disk that the kernel memory pool is being
 		 * threatened with exhaustion.
 		 */
 		if (rushjob > 0) {
 			rushjob -= 1;
 			continue;
 		}
 		/*
 		 * Just sleep for a short period of time between
 		 * iterations when shutting down to allow some I/O
 		 * to happen.
 		 *
 		 * If it has taken us less than a second to process the
 		 * current work, then wait. Otherwise start right over
 		 * again. We can still lose time if any single round
 		 * takes more than two seconds, but it does not really
 		 * matter as we are just trying to generally pace the
 		 * filesystem activity.
 		 */
 		if (syncer_state != SYNCER_RUNNING ||
 		    time_uptime == starttime) {
 			thread_lock(td);
 			sched_prio(td, PPAUSE);
 			thread_unlock(td);
 		}
 		if (syncer_state != SYNCER_RUNNING)
 			cv_timedwait(&sync_wakeup, &sync_mtx,
 			    hz / SYNCER_SHUTDOWN_SPEEDUP);
 		else if (time_uptime == starttime)
 			cv_timedwait(&sync_wakeup, &sync_mtx, hz);
 	}
 }
 
 /*
  * Request the syncer daemon to speed up its work.
  * We never push it to speed up more than half of its
  * normal turn time, otherwise it could take over the cpu.
  */
 int
 speedup_syncer(void)
 {
 	int ret = 0;
 
 	mtx_lock(&sync_mtx);
 	if (rushjob < syncdelay / 2) {
 		rushjob += 1;
 		stat_rush_requests += 1;
 		ret = 1;
 	}
 	mtx_unlock(&sync_mtx);
 	cv_broadcast(&sync_wakeup);
 	return (ret);
 }
 
 /*
  * Tell the syncer to speed up its work and run though its work
  * list several times, then tell it to shut down.
  */
 static void
 syncer_shutdown(void *arg, int howto)
 {
 
 	if (howto & RB_NOSYNC)
 		return;
 	mtx_lock(&sync_mtx);
 	syncer_state = SYNCER_SHUTTING_DOWN;
 	rushjob = 0;
 	mtx_unlock(&sync_mtx);
 	cv_broadcast(&sync_wakeup);
 	kproc_shutdown(arg, howto);
 }
 
 void
 syncer_suspend(void)
 {
 
 	syncer_shutdown(updateproc, 0);
 }
 
 void
 syncer_resume(void)
 {
 
 	mtx_lock(&sync_mtx);
 	first_printf = 1;
 	syncer_state = SYNCER_RUNNING;
 	mtx_unlock(&sync_mtx);
 	cv_broadcast(&sync_wakeup);
 	kproc_resume(updateproc);
 }
 
 /*
  * Reassign a buffer from one vnode to another.
  * Used to assign file specific control information
  * (indirect blocks) to the vnode to which they belong.
  */
 void
 reassignbuf(struct buf *bp)
 {
 	struct vnode *vp;
 	struct bufobj *bo;
 	int delay;
 #ifdef INVARIANTS
 	struct bufv *bv;
 #endif
 
 	vp = bp->b_vp;
 	bo = bp->b_bufobj;
 	++reassignbufcalls;
 
 	CTR3(KTR_BUF, "reassignbuf(%p) vp %p flags %X",
 	    bp, bp->b_vp, bp->b_flags);
 	/*
 	 * B_PAGING flagged buffers cannot be reassigned because their vp
 	 * is not fully linked in.
 	 */
 	if (bp->b_flags & B_PAGING)
 		panic("cannot reassign paging buffer");
 
 	/*
 	 * Delete from old vnode list, if on one.
 	 */
 	BO_LOCK(bo);
 	if (bp->b_xflags & (BX_VNDIRTY | BX_VNCLEAN))
 		buf_vlist_remove(bp);
 	else
 		panic("reassignbuf: Buffer %p not on queue.", bp);
 	/*
 	 * If dirty, put on list of dirty buffers; otherwise insert onto list
 	 * of clean buffers.
 	 */
 	if (bp->b_flags & B_DELWRI) {
 		if ((bo->bo_flag & BO_ONWORKLST) == 0) {
 			switch (vp->v_type) {
 			case VDIR:
 				delay = dirdelay;
 				break;
 			case VCHR:
 				delay = metadelay;
 				break;
 			default:
 				delay = filedelay;
 			}
 			vn_syncer_add_to_worklist(bo, delay);
 		}
 		buf_vlist_add(bp, bo, BX_VNDIRTY);
 	} else {
 		buf_vlist_add(bp, bo, BX_VNCLEAN);
 
 		if ((bo->bo_flag & BO_ONWORKLST) && bo->bo_dirty.bv_cnt == 0) {
 			mtx_lock(&sync_mtx);
 			LIST_REMOVE(bo, bo_synclist);
 			syncer_worklist_len--;
 			mtx_unlock(&sync_mtx);
 			bo->bo_flag &= ~BO_ONWORKLST;
 		}
 	}
 #ifdef INVARIANTS
 	bv = &bo->bo_clean;
 	bp = TAILQ_FIRST(&bv->bv_hd);
 	KASSERT(bp == NULL || bp->b_bufobj == bo,
 	    ("bp %p wrong b_bufobj %p should be %p", bp, bp->b_bufobj, bo));
 	bp = TAILQ_LAST(&bv->bv_hd, buflists);
 	KASSERT(bp == NULL || bp->b_bufobj == bo,
 	    ("bp %p wrong b_bufobj %p should be %p", bp, bp->b_bufobj, bo));
 	bv = &bo->bo_dirty;
 	bp = TAILQ_FIRST(&bv->bv_hd);
 	KASSERT(bp == NULL || bp->b_bufobj == bo,
 	    ("bp %p wrong b_bufobj %p should be %p", bp, bp->b_bufobj, bo));
 	bp = TAILQ_LAST(&bv->bv_hd, buflists);
 	KASSERT(bp == NULL || bp->b_bufobj == bo,
 	    ("bp %p wrong b_bufobj %p should be %p", bp, bp->b_bufobj, bo));
 #endif
 	BO_UNLOCK(bo);
 }
 
 static void
 v_init_counters(struct vnode *vp)
 {
 
 	VNASSERT(vp->v_type == VNON && vp->v_data == NULL && vp->v_iflag == 0,
 	    vp, ("%s called for an initialized vnode", __FUNCTION__));
 	ASSERT_VI_UNLOCKED(vp, __FUNCTION__);
 
 	refcount_init(&vp->v_holdcnt, 1);
 	refcount_init(&vp->v_usecount, 1);
 }
 
 /*
  * Increment si_usecount of the associated device, if any.
  */
 static void
 v_incr_devcount(struct vnode *vp)
 {
 
 	ASSERT_VI_LOCKED(vp, __FUNCTION__);
 	if (vp->v_type == VCHR && vp->v_rdev != NULL) {
 		dev_lock();
 		vp->v_rdev->si_usecount++;
 		dev_unlock();
 	}
 }
 
 /*
  * Decrement si_usecount of the associated device, if any.
  */
 static void
 v_decr_devcount(struct vnode *vp)
 {
 
 	ASSERT_VI_LOCKED(vp, __FUNCTION__);
 	if (vp->v_type == VCHR && vp->v_rdev != NULL) {
 		dev_lock();
 		vp->v_rdev->si_usecount--;
 		dev_unlock();
 	}
 }
 
 /*
  * Grab a particular vnode from the free list, increment its
  * reference count and lock it.  VIRF_DOOMED is set if the vnode
  * is being destroyed.  Only callers who specify LK_RETRY will
  * see doomed vnodes.  If inactive processing was delayed in
  * vput try to do it here.
  *
  * usecount is manipulated using atomics without holding any locks,
  * except when transitioning 0->1 in which case the interlock is held.
 
  * holdcnt is manipulated using atomics without holding any locks,
  * except when transitioning 1->0 in which case the interlock is held.
  */
 enum vgetstate
 vget_prep(struct vnode *vp)
 {
 	enum vgetstate vs;
 
 	if (refcount_acquire_if_not_zero(&vp->v_usecount)) {
 		vs = VGET_USECOUNT;
 	} else {
 		vhold(vp);
 		vs = VGET_HOLDCNT;
 	}
 	return (vs);
 }
 
 int
 vget(struct vnode *vp, int flags, struct thread *td)
 {
 	enum vgetstate vs;
 
 	MPASS(td == curthread);
 
 	vs = vget_prep(vp);
 	return (vget_finish(vp, flags, vs));
 }
 
 int
 vget_finish(struct vnode *vp, int flags, enum vgetstate vs)
 {
-	int error, oweinact;
+	int error;
 
 	VNASSERT((flags & LK_TYPE_MASK) != 0, vp,
 	    ("%s: invalid lock operation", __func__));
 
 	if ((flags & LK_INTERLOCK) != 0)
 		ASSERT_VI_LOCKED(vp, __func__);
 	else
 		ASSERT_VI_UNLOCKED(vp, __func__);
 	VNASSERT(vp->v_holdcnt > 0, vp, ("%s: vnode not held", __func__));
 	if (vs == VGET_USECOUNT) {
 		VNASSERT(vp->v_usecount > 0, vp,
 		    ("%s: vnode without usecount when VGET_USECOUNT was passed",
 		    __func__));
 	}
 
 	if ((error = vn_lock(vp, flags)) != 0) {
 		if (vs == VGET_USECOUNT)
 			vrele(vp);
 		else
 			vdrop(vp);
 		CTR2(KTR_VFS, "%s: impossible to lock vnode %p", __func__,
 		    vp);
 		return (error);
 	}
 
 	if (vs == VGET_USECOUNT) {
-		VNASSERT((vp->v_iflag & VI_OWEINACT) == 0, vp,
-		    ("%s: vnode with usecount and VI_OWEINACT set", __func__));
 		return (0);
 	}
 
 	/*
 	 * We hold the vnode. If the usecount is 0 it will be utilized to keep
 	 * the vnode around. Otherwise someone else lended their hold count and
 	 * we have to drop ours.
 	 */
 	if (refcount_acquire_if_not_zero(&vp->v_usecount)) {
 #ifdef INVARIANTS
 		int old = atomic_fetchadd_int(&vp->v_holdcnt, -1);
 		VNASSERT(old > 1, vp, ("%s: wrong hold count %d", __func__, old));
 #else
 		refcount_release(&vp->v_holdcnt);
 #endif
-		VNODE_REFCOUNT_FENCE_ACQ();
-		VNASSERT((vp->v_iflag & VI_OWEINACT) == 0, vp,
-		    ("%s: vnode with usecount and VI_OWEINACT set", __func__));
 		return (0);
 	}
 
 	/*
 	 * We don't guarantee that any particular close will
 	 * trigger inactive processing so just make a best effort
 	 * here at preventing a reference to a removed file.  If
 	 * we don't succeed no harm is done.
 	 *
 	 * Upgrade our holdcnt to a usecount.
 	 */
 	VI_LOCK(vp);
 	/*
 	 * See the previous section. By the time we get here we may find
 	 * ourselves in the same spot.
 	 */
 	if (refcount_acquire_if_not_zero(&vp->v_usecount)) {
 #ifdef INVARIANTS
 		int old = atomic_fetchadd_int(&vp->v_holdcnt, -1);
 		VNASSERT(old > 1, vp, ("%s: wrong hold count %d", __func__, old));
 #else
 		refcount_release(&vp->v_holdcnt);
 #endif
-		VNODE_REFCOUNT_FENCE_ACQ();
-		VNASSERT((vp->v_iflag & VI_OWEINACT) == 0, vp,
-		    ("%s: vnode with usecount and VI_OWEINACT set",
-		    __func__));
 		VI_UNLOCK(vp);
 		return (0);
 	}
-	if ((vp->v_iflag & VI_OWEINACT) == 0) {
-		oweinact = 0;
-	} else {
-		oweinact = 1;
-		vp->v_iflag &= ~VI_OWEINACT;
-		VNODE_REFCOUNT_FENCE_REL();
-	}
 	v_incr_devcount(vp);
 	refcount_acquire(&vp->v_usecount);
-	if (oweinact && VOP_ISLOCKED(vp) == LK_EXCLUSIVE &&
-	    (flags & LK_NOWAIT) == 0)
-		vinactive(vp);
 	VI_UNLOCK(vp);
 	return (0);
 }
 
 /*
  * Increase the reference (use) and hold count of a vnode.
  * This will also remove the vnode from the free list if it is presently free.
  */
 void
 vref(struct vnode *vp)
 {
 
 	ASSERT_VI_UNLOCKED(vp, __func__);
 	CTR2(KTR_VFS, "%s: vp %p", __func__, vp);
 	if (refcount_acquire_if_not_zero(&vp->v_usecount)) {
 		VNODE_REFCOUNT_FENCE_ACQ();
 		VNASSERT(vp->v_holdcnt > 0, vp,
 		    ("%s: active vnode not held", __func__));
-		VNASSERT((vp->v_iflag & VI_OWEINACT) == 0, vp,
-		    ("%s: vnode with usecount and VI_OWEINACT set", __func__));
 		return;
 	}
 	VI_LOCK(vp);
 	vrefl(vp);
 	VI_UNLOCK(vp);
 }
 
 void
 vrefl(struct vnode *vp)
 {
 
 	ASSERT_VI_LOCKED(vp, __func__);
 	CTR2(KTR_VFS, "%s: vp %p", __func__, vp);
 	if (refcount_acquire_if_not_zero(&vp->v_usecount)) {
 		VNODE_REFCOUNT_FENCE_ACQ();
 		VNASSERT(vp->v_holdcnt > 0, vp,
 		    ("%s: active vnode not held", __func__));
-		VNASSERT((vp->v_iflag & VI_OWEINACT) == 0, vp,
-		    ("%s: vnode with usecount and VI_OWEINACT set", __func__));
 		return;
 	}
 	vholdl(vp);
-	if ((vp->v_iflag & VI_OWEINACT) != 0) {
-		vp->v_iflag &= ~VI_OWEINACT;
-		VNODE_REFCOUNT_FENCE_REL();
-	}
 	v_incr_devcount(vp);
 	refcount_acquire(&vp->v_usecount);
 }
 
 void
 vrefact(struct vnode *vp)
 {
 
 	CTR2(KTR_VFS, "%s: vp %p", __func__, vp);
 #ifdef INVARIANTS
 	int old = atomic_fetchadd_int(&vp->v_usecount, 1);
 	VNASSERT(old > 0, vp, ("%s: wrong use count %d", __func__, old));
 #else
 	refcount_acquire(&vp->v_usecount);
 #endif
 }
 
 /*
  * Return reference count of a vnode.
  *
  * The results of this call are only guaranteed when some mechanism is used to
  * stop other processes from gaining references to the vnode.  This may be the
  * case if the caller holds the only reference.  This is also useful when stale
  * data is acceptable as race conditions may be accounted for by some other
  * means.
  */
 int
 vrefcnt(struct vnode *vp)
 {
 
 	return (vp->v_usecount);
 }
 
 void
 vlazy(struct vnode *vp)
 {
 	struct mount *mp;
 
 	VNASSERT(vp->v_holdcnt > 0, vp, ("%s: vnode not held", __func__));
 
 	if ((vp->v_mflag & VMP_LAZYLIST) != 0)
 		return;
 	mp = vp->v_mount;
 	mtx_lock(&mp->mnt_listmtx);
 	if ((vp->v_mflag & VMP_LAZYLIST) == 0) {
 		vp->v_mflag |= VMP_LAZYLIST;
 		TAILQ_INSERT_TAIL(&mp->mnt_lazyvnodelist, vp, v_lazylist);
 		mp->mnt_lazyvnodelistsize++;
 	}
 	mtx_unlock(&mp->mnt_listmtx);
 }
 
 static void
 vdefer_inactive(struct vnode *vp)
 {
 
 	ASSERT_VI_LOCKED(vp, __func__);
-	VNASSERT(vp->v_iflag & VI_OWEINACT, vp,
-	    ("%s: vnode without VI_OWEINACT", __func__));
+	VNASSERT(vp->v_holdcnt > 0, vp,
+	    ("%s: vnode without hold count", __func__));
 	if (VN_IS_DOOMED(vp)) {
 		vdropl(vp);
 		return;
 	}
 	if (vp->v_iflag & VI_DEFINACT) {
 		VNASSERT(vp->v_holdcnt > 1, vp, ("lost hold count"));
 		vdropl(vp);
 		return;
 	}
+	if (vp->v_usecount > 0) {
+		vp->v_iflag &= ~VI_OWEINACT;
+		vdropl(vp);
+		return;
+	}
 	vlazy(vp);
 	vp->v_iflag |= VI_DEFINACT;
 	VI_UNLOCK(vp);
 	counter_u64_add(deferred_inact, 1);
 }
 
 static void
-vdefer_inactive_cond(struct vnode *vp)
+vdefer_inactive_unlocked(struct vnode *vp)
 {
 
 	VI_LOCK(vp);
-	VNASSERT(vp->v_holdcnt > 0, vp, ("vnode without hold count"));
 	if ((vp->v_iflag & VI_OWEINACT) == 0) {
 		vdropl(vp);
 		return;
 	}
 	vdefer_inactive(vp);
 }
 
 enum vputx_op { VPUTX_VRELE, VPUTX_VPUT, VPUTX_VUNREF };
 
 /*
  * Decrement the use and hold counts for a vnode.
  *
  * See an explanation near vget() as to why atomic operation is safe.
  *
  * XXX Some filesystems pass in an exclusively locked vnode and strongly depend
  * on the lock being held all the way until VOP_INACTIVE. This in particular
  * happens with UFS which adds half-constructed vnodes to the hash, where they
  * can be found by other code.
  */
 static void
 vputx(struct vnode *vp, enum vputx_op func)
 {
 	int error;
 
 	KASSERT(vp != NULL, ("vputx: null vp"));
 	if (func == VPUTX_VUNREF)
 		ASSERT_VOP_LOCKED(vp, "vunref");
 	else if (func == VPUTX_VPUT)
 		ASSERT_VOP_LOCKED(vp, "vput");
 	ASSERT_VI_UNLOCKED(vp, __func__);
 	VNASSERT(vp->v_holdcnt > 0 && vp->v_usecount > 0, vp,
 	    ("%s: wrong ref counts", __func__));
 
 	CTR2(KTR_VFS, "%s: vp %p", __func__, vp);
 
 	/*
 	 * We want to hold the vnode until the inactive finishes to
 	 * prevent vgone() races.  We drop the use count here and the
 	 * hold count below when we're done.
 	 *
 	 * If we release the last usecount we take ownership of the hold
 	 * count which provides liveness of the vnode, in which case we
 	 * have to vdrop.
 	 */
 	if (!refcount_release(&vp->v_usecount)) {
 		if (func == VPUTX_VPUT)
 			VOP_UNLOCK(vp);
 		return;
 	}
 	VI_LOCK(vp);
 	v_decr_devcount(vp);
 	/*
 	 * By the time we got here someone else might have transitioned
 	 * the count back to > 0.
 	 */
 	if (vp->v_usecount > 0 || vp->v_iflag & VI_DOINGINACT)
 		goto out;
 
 	/*
 	 * Check if the fs wants to perform inactive processing. Note we
 	 * may be only holding the interlock, in which case it is possible
 	 * someone else called vgone on the vnode and ->v_data is now NULL.
 	 * Since vgone performs inactive on its own there is nothing to do
 	 * here but to drop our hold count.
 	 */
 	if (__predict_false(VN_IS_DOOMED(vp)) ||
 	    VOP_NEED_INACTIVE(vp) == 0)
 		goto out;
 
 	/*
 	 * We must call VOP_INACTIVE with the node locked. Mark
 	 * as VI_DOINGINACT to avoid recursion.
 	 */
 	vp->v_iflag |= VI_OWEINACT;
 	switch (func) {
 	case VPUTX_VRELE:
 		error = vn_lock(vp, LK_EXCLUSIVE | LK_INTERLOCK);
 		VI_LOCK(vp);
 		break;
 	case VPUTX_VPUT:
 		error = 0;
 		if (VOP_ISLOCKED(vp) != LK_EXCLUSIVE) {
 			error = VOP_LOCK(vp, LK_UPGRADE | LK_INTERLOCK |
 			    LK_NOWAIT);
 			VI_LOCK(vp);
 		}
 		break;
 	case VPUTX_VUNREF:
 		error = 0;
 		if (VOP_ISLOCKED(vp) != LK_EXCLUSIVE) {
 			error = VOP_LOCK(vp, LK_TRYUPGRADE | LK_INTERLOCK);
 			VI_LOCK(vp);
 		}
 		break;
 	}
 	VNASSERT(vp->v_usecount == 0 || (vp->v_iflag & VI_OWEINACT) == 0, vp,
 	    ("vnode with usecount and VI_OWEINACT set"));
 	if (error == 0) {
-		if (vp->v_iflag & VI_OWEINACT)
-			vinactive(vp);
+		vinactive(vp);
 		if (func != VPUTX_VUNREF)
 			VOP_UNLOCK(vp);
 		vdropl(vp);
-	} else if (vp->v_iflag & VI_OWEINACT) {
-		vdefer_inactive(vp);
 	} else {
-		vdropl(vp);
+		vdefer_inactive(vp);
 	}
 	return;
 out:
 	if (func == VPUTX_VPUT)
 		VOP_UNLOCK(vp);
 	vdropl(vp);
 }
 
 /*
  * Vnode put/release.
  * If count drops to zero, call inactive routine and return to freelist.
  */
 void
 vrele(struct vnode *vp)
 {
 
 	vputx(vp, VPUTX_VRELE);
 }
 
 /*
  * Release an already locked vnode.  This give the same effects as
  * unlock+vrele(), but takes less time and avoids releasing and
  * re-aquiring the lock (as vrele() acquires the lock internally.)
  */
 void
 vput(struct vnode *vp)
 {
 
 	vputx(vp, VPUTX_VPUT);
 }
 
 /*
  * Release an exclusively locked vnode. Do not unlock the vnode lock.
  */
 void
 vunref(struct vnode *vp)
 {
 
 	vputx(vp, VPUTX_VUNREF);
 }
 
 void
 vhold(struct vnode *vp)
 {
 	struct vdbatch *vd;
 	int old;
 
 	CTR2(KTR_VFS, "%s: vp %p", __func__, vp);
 	old = atomic_fetchadd_int(&vp->v_holdcnt, 1);
 	VNASSERT(old >= 0, vp, ("%s: wrong hold count %d", __func__, old));
 	if (old != 0)
 		return;
 	critical_enter();
 	vd = DPCPU_PTR(vd);
 	vd->freevnodes--;
 	critical_exit();
 }
 
 void
 vholdl(struct vnode *vp)
 {
 
 	ASSERT_VI_LOCKED(vp, __func__);
 	CTR2(KTR_VFS, "%s: vp %p", __func__, vp);
 	vhold(vp);
 }
 
 void
 vholdnz(struct vnode *vp)
 {
 
 	CTR2(KTR_VFS, "%s: vp %p", __func__, vp);
 #ifdef INVARIANTS
 	int old = atomic_fetchadd_int(&vp->v_holdcnt, 1);
 	VNASSERT(old > 0, vp, ("%s: wrong hold count %d", __func__, old));
 #else
 	atomic_add_int(&vp->v_holdcnt, 1);
 #endif
 }
 
 static void __noinline
 vdbatch_process(struct vdbatch *vd)
 {
 	struct vnode *vp;
 	int i;
 
 	mtx_assert(&vd->lock, MA_OWNED);
 	MPASS(curthread->td_pinned > 0);
 	MPASS(vd->index == VDBATCH_SIZE);
 
 	mtx_lock(&vnode_list_mtx);
 	critical_enter();
 	freevnodes += vd->freevnodes;
 	for (i = 0; i < VDBATCH_SIZE; i++) {
 		vp = vd->tab[i];
 		TAILQ_REMOVE(&vnode_list, vp, v_vnodelist);
 		TAILQ_INSERT_TAIL(&vnode_list, vp, v_vnodelist);
 		MPASS(vp->v_dbatchcpu != NOCPU);
 		vp->v_dbatchcpu = NOCPU;
 	}
 	mtx_unlock(&vnode_list_mtx);
 	critical_exit();
 	vd->freevnodes = 0;
 	bzero(vd->tab, sizeof(vd->tab));
 	vd->index = 0;
 }
 
 static void
 vdbatch_enqueue(struct vnode *vp)
 {
 	struct vdbatch *vd;
 
 	ASSERT_VI_LOCKED(vp, __func__);
 	VNASSERT(!VN_IS_DOOMED(vp), vp,
 	    ("%s: deferring requeue of a doomed vnode", __func__));
 
 	critical_enter();
 	vd = DPCPU_PTR(vd);
 	vd->freevnodes++;
 	if (vp->v_dbatchcpu != NOCPU) {
 		VI_UNLOCK(vp);
 		critical_exit();
 		return;
 	}
 
 	sched_pin();
 	critical_exit();
 	mtx_lock(&vd->lock);
 	MPASS(vd->index < VDBATCH_SIZE);
 	MPASS(vd->tab[vd->index] == NULL);
 	/*
 	 * A hack: we depend on being pinned so that we know what to put in
 	 * ->v_dbatchcpu.
 	 */
 	vp->v_dbatchcpu = curcpu;
 	vd->tab[vd->index] = vp;
 	vd->index++;
 	VI_UNLOCK(vp);
 	if (vd->index == VDBATCH_SIZE)
 		vdbatch_process(vd);
 	mtx_unlock(&vd->lock);
 	sched_unpin();
 }
 
 /*
  * This routine must only be called for vnodes which are about to be
  * deallocated. Supporting dequeue for arbitrary vndoes would require
  * validating that the locked batch matches.
  */
 static void
 vdbatch_dequeue(struct vnode *vp)
 {
 	struct vdbatch *vd;
 	int i;
 	short cpu;
 
 	VNASSERT(vp->v_type == VBAD || vp->v_type == VNON, vp,
 	    ("%s: called for a used vnode\n", __func__));
 
 	cpu = vp->v_dbatchcpu;
 	if (cpu == NOCPU)
 		return;
 
 	vd = DPCPU_ID_PTR(cpu, vd);
 	mtx_lock(&vd->lock);
 	for (i = 0; i < vd->index; i++) {
 		if (vd->tab[i] != vp)
 			continue;
 		vp->v_dbatchcpu = NOCPU;
 		vd->index--;
 		vd->tab[i] = vd->tab[vd->index];
 		vd->tab[vd->index] = NULL;
 		break;
 	}
 	mtx_unlock(&vd->lock);
 	/*
 	 * Either we dequeued the vnode above or the target CPU beat us to it.
 	 */
 	MPASS(vp->v_dbatchcpu == NOCPU);
 }
 
 /*
  * Drop the hold count of the vnode.  If this is the last reference to
  * the vnode we place it on the free list unless it has been vgone'd
  * (marked VIRF_DOOMED) in which case we will free it.
  *
  * Because the vnode vm object keeps a hold reference on the vnode if
  * there is at least one resident non-cached page, the vnode cannot
  * leave the active list without the page cleanup done.
  */
 static void
 vdrop_deactivate(struct vnode *vp)
 {
 	struct mount *mp;
 
 	ASSERT_VI_LOCKED(vp, __func__);
 	/*
 	 * Mark a vnode as free: remove it from its active list
 	 * and put it up for recycling on the freelist.
 	 */
 	VNASSERT(!VN_IS_DOOMED(vp), vp,
 	    ("vdrop: returning doomed vnode"));
 	VNASSERT(vp->v_op != NULL, vp,
 	    ("vdrop: vnode already reclaimed."));
 	VNASSERT((vp->v_iflag & VI_OWEINACT) == 0, vp,
 	    ("vnode with VI_OWEINACT set"));
 	VNASSERT((vp->v_iflag & VI_DEFINACT) == 0, vp,
 	    ("vnode with VI_DEFINACT set"));
 	if (vp->v_mflag & VMP_LAZYLIST) {
 		mp = vp->v_mount;
 		mtx_lock(&mp->mnt_listmtx);
 		VNASSERT(vp->v_mflag & VMP_LAZYLIST, vp, ("lost VMP_LAZYLIST"));
 		/*
 		 * Don't remove the vnode from the lazy list if another thread
 		 * has increased the hold count. It may have re-enqueued the
 		 * vnode to the lazy list and is now responsible for its
 		 * removal.
 		 */
 		if (vp->v_holdcnt == 0) {
 			vp->v_mflag &= ~VMP_LAZYLIST;
 			TAILQ_REMOVE(&mp->mnt_lazyvnodelist, vp, v_lazylist);
 			mp->mnt_lazyvnodelistsize--;
 		}
 		mtx_unlock(&mp->mnt_listmtx);
 	}
 	vdbatch_enqueue(vp);
 }
 
 void
 vdrop(struct vnode *vp)
 {
 
 	ASSERT_VI_UNLOCKED(vp, __func__);
 	CTR2(KTR_VFS, "%s: vp %p", __func__, vp);
 	if (refcount_release_if_not_last(&vp->v_holdcnt))
 		return;
 	VI_LOCK(vp);
 	vdropl(vp);
 }
 
 void
 vdropl(struct vnode *vp)
 {
 
 	ASSERT_VI_LOCKED(vp, __func__);
 	CTR2(KTR_VFS, "%s: vp %p", __func__, vp);
 	if (!refcount_release(&vp->v_holdcnt)) {
 		VI_UNLOCK(vp);
 		return;
 	}
 	if (VN_IS_DOOMED(vp)) {
 		freevnode(vp);
 		return;
 	}
 	vdrop_deactivate(vp);
 }
 
 /*
  * Call VOP_INACTIVE on the vnode and manage the DOINGINACT and OWEINACT
  * flags.  DOINGINACT prevents us from recursing in calls to vinactive.
- * OWEINACT tracks whether a vnode missed a call to inactive due to a
- * failed lock upgrade.
  */
-void
-vinactive(struct vnode *vp)
+static void
+vinactivef(struct vnode *vp)
 {
 	struct vm_object *obj;
 
 	ASSERT_VOP_ELOCKED(vp, "vinactive");
 	ASSERT_VI_LOCKED(vp, "vinactive");
 	VNASSERT((vp->v_iflag & VI_DOINGINACT) == 0, vp,
 	    ("vinactive: recursed on VI_DOINGINACT"));
 	CTR2(KTR_VFS, "%s: vp %p", __func__, vp);
 	vp->v_iflag |= VI_DOINGINACT;
 	vp->v_iflag &= ~VI_OWEINACT;
 	VI_UNLOCK(vp);
 	/*
 	 * Before moving off the active list, we must be sure that any
 	 * modified pages are converted into the vnode's dirty
 	 * buffers, since these will no longer be checked once the
 	 * vnode is on the inactive list.
 	 *
 	 * The write-out of the dirty pages is asynchronous.  At the
 	 * point that VOP_INACTIVE() is called, there could still be
 	 * pending I/O and dirty pages in the object.
 	 */
 	if ((obj = vp->v_object) != NULL && (vp->v_vflag & VV_NOSYNC) == 0 &&
 	    vm_object_mightbedirty(obj)) {
 		VM_OBJECT_WLOCK(obj);
 		vm_object_page_clean(obj, 0, 0, 0);
 		VM_OBJECT_WUNLOCK(obj);
 	}
 	VOP_INACTIVE(vp, curthread);
 	VI_LOCK(vp);
 	VNASSERT(vp->v_iflag & VI_DOINGINACT, vp,
 	    ("vinactive: lost VI_DOINGINACT"));
 	vp->v_iflag &= ~VI_DOINGINACT;
 }
 
+void
+vinactive(struct vnode *vp)
+{
+
+	ASSERT_VOP_ELOCKED(vp, "vinactive");
+	ASSERT_VI_LOCKED(vp, "vinactive");
+	CTR2(KTR_VFS, "%s: vp %p", __func__, vp);
+
+	if ((vp->v_iflag & VI_OWEINACT) == 0)
+		return;
+	if (vp->v_iflag & VI_DOINGINACT)
+		return;
+	if (vp->v_usecount > 0) {
+		vp->v_iflag &= ~VI_OWEINACT;
+		return;
+	}
+	vinactivef(vp);
+}
+
 /*
  * Remove any vnodes in the vnode table belonging to mount point mp.
  *
  * If FORCECLOSE is not specified, there should not be any active ones,
  * return error if any are found (nb: this is a user error, not a
  * system error). If FORCECLOSE is specified, detach any active vnodes
  * that are found.
  *
  * If WRITECLOSE is set, only flush out regular file vnodes open for
  * writing.
  *
  * SKIPSYSTEM causes any vnodes marked VV_SYSTEM to be skipped.
  *
  * `rootrefs' specifies the base reference count for the root vnode
  * of this filesystem. The root vnode is considered busy if its
  * v_usecount exceeds this value. On a successful return, vflush(, td)
  * will call vrele() on the root vnode exactly rootrefs times.
  * If the SKIPSYSTEM or WRITECLOSE flags are specified, rootrefs must
  * be zero.
  */
 #ifdef DIAGNOSTIC
 static int busyprt = 0;		/* print out busy vnodes */
 SYSCTL_INT(_debug, OID_AUTO, busyprt, CTLFLAG_RW, &busyprt, 0, "Print out busy vnodes");
 #endif
 
 int
 vflush(struct mount *mp, int rootrefs, int flags, struct thread *td)
 {
 	struct vnode *vp, *mvp, *rootvp = NULL;
 	struct vattr vattr;
 	int busy = 0, error;
 
 	CTR4(KTR_VFS, "%s: mp %p with rootrefs %d and flags %d", __func__, mp,
 	    rootrefs, flags);
 	if (rootrefs > 0) {
 		KASSERT((flags & (SKIPSYSTEM | WRITECLOSE)) == 0,
 		    ("vflush: bad args"));
 		/*
 		 * Get the filesystem root vnode. We can vput() it
 		 * immediately, since with rootrefs > 0, it won't go away.
 		 */
 		if ((error = VFS_ROOT(mp, LK_EXCLUSIVE, &rootvp)) != 0) {
 			CTR2(KTR_VFS, "%s: vfs_root lookup failed with %d",
 			    __func__, error);
 			return (error);
 		}
 		vput(rootvp);
 	}
 loop:
 	MNT_VNODE_FOREACH_ALL(vp, mp, mvp) {
 		vholdl(vp);
 		error = vn_lock(vp, LK_INTERLOCK | LK_EXCLUSIVE);
 		if (error) {
 			vdrop(vp);
 			MNT_VNODE_FOREACH_ALL_ABORT(mp, mvp);
 			goto loop;
 		}
 		/*
 		 * Skip over a vnodes marked VV_SYSTEM.
 		 */
 		if ((flags & SKIPSYSTEM) && (vp->v_vflag & VV_SYSTEM)) {
 			VOP_UNLOCK(vp);
 			vdrop(vp);
 			continue;
 		}
 		/*
 		 * If WRITECLOSE is set, flush out unlinked but still open
 		 * files (even if open only for reading) and regular file
 		 * vnodes open for writing.
 		 */
 		if (flags & WRITECLOSE) {
 			if (vp->v_object != NULL) {
 				VM_OBJECT_WLOCK(vp->v_object);
 				vm_object_page_clean(vp->v_object, 0, 0, 0);
 				VM_OBJECT_WUNLOCK(vp->v_object);
 			}
 			error = VOP_FSYNC(vp, MNT_WAIT, td);
 			if (error != 0) {
 				VOP_UNLOCK(vp);
 				vdrop(vp);
 				MNT_VNODE_FOREACH_ALL_ABORT(mp, mvp);
 				return (error);
 			}
 			error = VOP_GETATTR(vp, &vattr, td->td_ucred);
 			VI_LOCK(vp);
 
 			if ((vp->v_type == VNON ||
 			    (error == 0 && vattr.va_nlink > 0)) &&
 			    (vp->v_writecount <= 0 || vp->v_type != VREG)) {
 				VOP_UNLOCK(vp);
 				vdropl(vp);
 				continue;
 			}
 		} else
 			VI_LOCK(vp);
 		/*
 		 * With v_usecount == 0, all we need to do is clear out the
 		 * vnode data structures and we are done.
 		 *
 		 * If FORCECLOSE is set, forcibly close the vnode.
 		 */
 		if (vp->v_usecount == 0 || (flags & FORCECLOSE)) {
 			vgonel(vp);
 		} else {
 			busy++;
 #ifdef DIAGNOSTIC
 			if (busyprt)
 				vn_printf(vp, "vflush: busy vnode ");
 #endif
 		}
 		VOP_UNLOCK(vp);
 		vdropl(vp);
 	}
 	if (rootrefs > 0 && (flags & FORCECLOSE) == 0) {
 		/*
 		 * If just the root vnode is busy, and if its refcount
 		 * is equal to `rootrefs', then go ahead and kill it.
 		 */
 		VI_LOCK(rootvp);
 		KASSERT(busy > 0, ("vflush: not busy"));
 		VNASSERT(rootvp->v_usecount >= rootrefs, rootvp,
 		    ("vflush: usecount %d < rootrefs %d",
 		     rootvp->v_usecount, rootrefs));
 		if (busy == 1 && rootvp->v_usecount == rootrefs) {
 			VOP_LOCK(rootvp, LK_EXCLUSIVE|LK_INTERLOCK);
 			vgone(rootvp);
 			VOP_UNLOCK(rootvp);
 			busy = 0;
 		} else
 			VI_UNLOCK(rootvp);
 	}
 	if (busy) {
 		CTR2(KTR_VFS, "%s: failing as %d vnodes are busy", __func__,
 		    busy);
 		return (EBUSY);
 	}
 	for (; rootrefs > 0; rootrefs--)
 		vrele(rootvp);
 	return (0);
 }
 
 /*
  * Recycle an unused vnode to the front of the free list.
  */
 int
 vrecycle(struct vnode *vp)
 {
 	int recycled;
 
 	VI_LOCK(vp);
 	recycled = vrecyclel(vp);
 	VI_UNLOCK(vp);
 	return (recycled);
 }
 
 /*
  * vrecycle, with the vp interlock held.
  */
 int
 vrecyclel(struct vnode *vp)
 {
 	int recycled;
 
 	ASSERT_VOP_ELOCKED(vp, __func__);
 	ASSERT_VI_LOCKED(vp, __func__);
 	CTR2(KTR_VFS, "%s: vp %p", __func__, vp);
 	recycled = 0;
 	if (vp->v_usecount == 0) {
 		recycled = 1;
 		vgonel(vp);
 	}
 	return (recycled);
 }
 
 /*
  * Eliminate all activity associated with a vnode
  * in preparation for reuse.
  */
 void
 vgone(struct vnode *vp)
 {
 	VI_LOCK(vp);
 	vgonel(vp);
 	VI_UNLOCK(vp);
 }
 
 static void
 notify_lowervp_vfs_dummy(struct mount *mp __unused,
     struct vnode *lowervp __unused)
 {
 }
 
 /*
  * Notify upper mounts about reclaimed or unlinked vnode.
  */
 void
 vfs_notify_upper(struct vnode *vp, int event)
 {
 	static struct vfsops vgonel_vfsops = {
 		.vfs_reclaim_lowervp = notify_lowervp_vfs_dummy,
 		.vfs_unlink_lowervp = notify_lowervp_vfs_dummy,
 	};
 	struct mount *mp, *ump, *mmp;
 
 	mp = vp->v_mount;
 	if (mp == NULL)
 		return;
 	if (TAILQ_EMPTY(&mp->mnt_uppers))
 		return;
 
 	mmp = malloc(sizeof(struct mount), M_TEMP, M_WAITOK | M_ZERO);
 	mmp->mnt_op = &vgonel_vfsops;
 	mmp->mnt_kern_flag |= MNTK_MARKER;
 	MNT_ILOCK(mp);
 	mp->mnt_kern_flag |= MNTK_VGONE_UPPER;
 	for (ump = TAILQ_FIRST(&mp->mnt_uppers); ump != NULL;) {
 		if ((ump->mnt_kern_flag & MNTK_MARKER) != 0) {
 			ump = TAILQ_NEXT(ump, mnt_upper_link);
 			continue;
 		}
 		TAILQ_INSERT_AFTER(&mp->mnt_uppers, ump, mmp, mnt_upper_link);
 		MNT_IUNLOCK(mp);
 		switch (event) {
 		case VFS_NOTIFY_UPPER_RECLAIM:
 			VFS_RECLAIM_LOWERVP(ump, vp);
 			break;
 		case VFS_NOTIFY_UPPER_UNLINK:
 			VFS_UNLINK_LOWERVP(ump, vp);
 			break;
 		default:
 			KASSERT(0, ("invalid event %d", event));
 			break;
 		}
 		MNT_ILOCK(mp);
 		ump = TAILQ_NEXT(mmp, mnt_upper_link);
 		TAILQ_REMOVE(&mp->mnt_uppers, mmp, mnt_upper_link);
 	}
 	free(mmp, M_TEMP);
 	mp->mnt_kern_flag &= ~MNTK_VGONE_UPPER;
 	if ((mp->mnt_kern_flag & MNTK_VGONE_WAITER) != 0) {
 		mp->mnt_kern_flag &= ~MNTK_VGONE_WAITER;
 		wakeup(&mp->mnt_uppers);
 	}
 	MNT_IUNLOCK(mp);
 }
 
 /*
  * vgone, with the vp interlock held.
  */
 static void
 vgonel(struct vnode *vp)
 {
 	struct thread *td;
 	struct mount *mp;
 	vm_object_t object;
 	bool active, oweinact;
 
 	ASSERT_VOP_ELOCKED(vp, "vgonel");
 	ASSERT_VI_LOCKED(vp, "vgonel");
 	VNASSERT(vp->v_holdcnt, vp,
 	    ("vgonel: vp %p has no reference.", vp));
 	CTR2(KTR_VFS, "%s: vp %p", __func__, vp);
 	td = curthread;
 
 	/*
 	 * Don't vgonel if we're already doomed.
 	 */
 	if (vp->v_irflag & VIRF_DOOMED)
 		return;
 	vp->v_irflag |= VIRF_DOOMED;
 
 	/*
 	 * Check to see if the vnode is in use.  If so, we have to call
 	 * VOP_CLOSE() and VOP_INACTIVE().
 	 */
 	active = vp->v_usecount > 0;
 	oweinact = (vp->v_iflag & VI_OWEINACT) != 0;
 	/*
 	 * If we need to do inactive VI_OWEINACT will be set.
 	 */
 	if (vp->v_iflag & VI_DEFINACT) {
 		VNASSERT(vp->v_holdcnt > 1, vp, ("lost hold count"));
 		vp->v_iflag &= ~VI_DEFINACT;
 		vdropl(vp);
 	} else {
 		VNASSERT(vp->v_holdcnt > 0, vp, ("vnode without hold count"));
 		VI_UNLOCK(vp);
 	}
 	vfs_notify_upper(vp, VFS_NOTIFY_UPPER_RECLAIM);
 
 	/*
 	 * If purging an active vnode, it must be closed and
 	 * deactivated before being reclaimed.
 	 */
 	if (active)
 		VOP_CLOSE(vp, FNONBLOCK, NOCRED, td);
 	if (oweinact || active) {
 		VI_LOCK(vp);
-		if ((vp->v_iflag & VI_DOINGINACT) == 0)
-			vinactive(vp);
+		vinactivef(vp);
 		VI_UNLOCK(vp);
 	}
 	if (vp->v_type == VSOCK)
 		vfs_unp_reclaim(vp);
 
 	/*
 	 * Clean out any buffers associated with the vnode.
 	 * If the flush fails, just toss the buffers.
 	 */
 	mp = NULL;
 	if (!TAILQ_EMPTY(&vp->v_bufobj.bo_dirty.bv_hd))
 		(void) vn_start_secondary_write(vp, &mp, V_WAIT);
 	if (vinvalbuf(vp, V_SAVE, 0, 0) != 0) {
 		while (vinvalbuf(vp, 0, 0, 0) != 0)
 			;
 	}
 
 	BO_LOCK(&vp->v_bufobj);
 	KASSERT(TAILQ_EMPTY(&vp->v_bufobj.bo_dirty.bv_hd) &&
 	    vp->v_bufobj.bo_dirty.bv_cnt == 0 &&
 	    TAILQ_EMPTY(&vp->v_bufobj.bo_clean.bv_hd) &&
 	    vp->v_bufobj.bo_clean.bv_cnt == 0,
 	    ("vp %p bufobj not invalidated", vp));
 
 	/*
 	 * For VMIO bufobj, BO_DEAD is set later, or in
 	 * vm_object_terminate() after the object's page queue is
 	 * flushed.
 	 */
 	object = vp->v_bufobj.bo_object;
 	if (object == NULL)
 		vp->v_bufobj.bo_flag |= BO_DEAD;
 	BO_UNLOCK(&vp->v_bufobj);
 
 	/*
 	 * Handle the VM part.  Tmpfs handles v_object on its own (the
 	 * OBJT_VNODE check).  Nullfs or other bypassing filesystems
 	 * should not touch the object borrowed from the lower vnode
 	 * (the handle check).
 	 */
 	if (object != NULL && object->type == OBJT_VNODE &&
 	    object->handle == vp)
 		vnode_destroy_vobject(vp);
 
 	/*
 	 * Reclaim the vnode.
 	 */
 	if (VOP_RECLAIM(vp, td))
 		panic("vgone: cannot reclaim");
 	if (mp != NULL)
 		vn_finished_secondary_write(mp);
 	VNASSERT(vp->v_object == NULL, vp,
 	    ("vop_reclaim left v_object vp=%p", vp));
 	/*
 	 * Clear the advisory locks and wake up waiting threads.
 	 */
 	(void)VOP_ADVLOCKPURGE(vp);
 	vp->v_lockf = NULL;
 	/*
 	 * Delete from old mount point vnode list.
 	 */
 	delmntque(vp);
 	cache_purge(vp);
 	/*
 	 * Done with purge, reset to the standard lock and invalidate
 	 * the vnode.
 	 */
 	VI_LOCK(vp);
 	vp->v_vnlock = &vp->v_lock;
 	vp->v_op = &dead_vnodeops;
 	vp->v_type = VBAD;
 }
 
 /*
  * Calculate the total number of references to a special device.
  */
 int
 vcount(struct vnode *vp)
 {
 	int count;
 
 	dev_lock();
 	count = vp->v_rdev->si_usecount;
 	dev_unlock();
 	return (count);
 }
 
 /*
  * Print out a description of a vnode.
  */
 static char *typename[] =
 {"VNON", "VREG", "VDIR", "VBLK", "VCHR", "VLNK", "VSOCK", "VFIFO", "VBAD",
  "VMARKER"};
 
 void
 vn_printf(struct vnode *vp, const char *fmt, ...)
 {
 	va_list ap;
 	char buf[256], buf2[16];
 	u_long flags;
 
 	va_start(ap, fmt);
 	vprintf(fmt, ap);
 	va_end(ap);
 	printf("%p: ", (void *)vp);
 	printf("type %s\n", typename[vp->v_type]);
 	printf("    usecount %d, writecount %d, refcount %d",
 	    vp->v_usecount, vp->v_writecount, vp->v_holdcnt);
 	switch (vp->v_type) {
 	case VDIR:
 		printf(" mountedhere %p\n", vp->v_mountedhere);
 		break;
 	case VCHR:
 		printf(" rdev %p\n", vp->v_rdev);
 		break;
 	case VSOCK:
 		printf(" socket %p\n", vp->v_unpcb);
 		break;
 	case VFIFO:
 		printf(" fifoinfo %p\n", vp->v_fifoinfo);
 		break;
 	default:
 		printf("\n");
 		break;
 	}
 	buf[0] = '\0';
 	buf[1] = '\0';
 	if (vp->v_irflag & VIRF_DOOMED)
 		strlcat(buf, "|VIRF_DOOMED", sizeof(buf));
 	flags = vp->v_irflag & ~(VIRF_DOOMED);
 	if (flags != 0) {
 		snprintf(buf2, sizeof(buf2), "|VIRF(0x%lx)", flags);
 		strlcat(buf, buf2, sizeof(buf));
 	}
 	if (vp->v_vflag & VV_ROOT)
 		strlcat(buf, "|VV_ROOT", sizeof(buf));
 	if (vp->v_vflag & VV_ISTTY)
 		strlcat(buf, "|VV_ISTTY", sizeof(buf));
 	if (vp->v_vflag & VV_NOSYNC)
 		strlcat(buf, "|VV_NOSYNC", sizeof(buf));
 	if (vp->v_vflag & VV_ETERNALDEV)
 		strlcat(buf, "|VV_ETERNALDEV", sizeof(buf));
 	if (vp->v_vflag & VV_CACHEDLABEL)
 		strlcat(buf, "|VV_CACHEDLABEL", sizeof(buf));
 	if (vp->v_vflag & VV_VMSIZEVNLOCK)
 		strlcat(buf, "|VV_VMSIZEVNLOCK", sizeof(buf));
 	if (vp->v_vflag & VV_COPYONWRITE)
 		strlcat(buf, "|VV_COPYONWRITE", sizeof(buf));
 	if (vp->v_vflag & VV_SYSTEM)
 		strlcat(buf, "|VV_SYSTEM", sizeof(buf));
 	if (vp->v_vflag & VV_PROCDEP)
 		strlcat(buf, "|VV_PROCDEP", sizeof(buf));
 	if (vp->v_vflag & VV_NOKNOTE)
 		strlcat(buf, "|VV_NOKNOTE", sizeof(buf));
 	if (vp->v_vflag & VV_DELETED)
 		strlcat(buf, "|VV_DELETED", sizeof(buf));
 	if (vp->v_vflag & VV_MD)
 		strlcat(buf, "|VV_MD", sizeof(buf));
 	if (vp->v_vflag & VV_FORCEINSMQ)
 		strlcat(buf, "|VV_FORCEINSMQ", sizeof(buf));
 	if (vp->v_vflag & VV_READLINK)
 		strlcat(buf, "|VV_READLINK", sizeof(buf));
 	flags = vp->v_vflag & ~(VV_ROOT | VV_ISTTY | VV_NOSYNC | VV_ETERNALDEV |
 	    VV_CACHEDLABEL | VV_COPYONWRITE | VV_SYSTEM | VV_PROCDEP |
 	    VV_NOKNOTE | VV_DELETED | VV_MD | VV_FORCEINSMQ);
 	if (flags != 0) {
 		snprintf(buf2, sizeof(buf2), "|VV(0x%lx)", flags);
 		strlcat(buf, buf2, sizeof(buf));
 	}
 	if (vp->v_iflag & VI_TEXT_REF)
 		strlcat(buf, "|VI_TEXT_REF", sizeof(buf));
 	if (vp->v_iflag & VI_MOUNT)
 		strlcat(buf, "|VI_MOUNT", sizeof(buf));
 	if (vp->v_iflag & VI_DOINGINACT)
 		strlcat(buf, "|VI_DOINGINACT", sizeof(buf));
 	if (vp->v_iflag & VI_OWEINACT)
 		strlcat(buf, "|VI_OWEINACT", sizeof(buf));
 	if (vp->v_iflag & VI_DEFINACT)
 		strlcat(buf, "|VI_DEFINACT", sizeof(buf));
 	flags = vp->v_iflag & ~(VI_TEXT_REF | VI_MOUNT | VI_DOINGINACT |
 	    VI_OWEINACT | VI_DEFINACT);
 	if (flags != 0) {
 		snprintf(buf2, sizeof(buf2), "|VI(0x%lx)", flags);
 		strlcat(buf, buf2, sizeof(buf));
 	}
 	if (vp->v_mflag & VMP_LAZYLIST)
 		strlcat(buf, "|VMP_LAZYLIST", sizeof(buf));
 	flags = vp->v_mflag & ~(VMP_LAZYLIST);
 	if (flags != 0) {
 		snprintf(buf2, sizeof(buf2), "|VMP(0x%lx)", flags);
 		strlcat(buf, buf2, sizeof(buf));
 	}
 	printf("    flags (%s)\n", buf + 1);
 	if (mtx_owned(VI_MTX(vp)))
 		printf(" VI_LOCKed");
 	if (vp->v_object != NULL)
 		printf("    v_object %p ref %d pages %d "
 		    "cleanbuf %d dirtybuf %d\n",
 		    vp->v_object, vp->v_object->ref_count,
 		    vp->v_object->resident_page_count,
 		    vp->v_bufobj.bo_clean.bv_cnt,
 		    vp->v_bufobj.bo_dirty.bv_cnt);
 	printf("    ");
 	lockmgr_printinfo(vp->v_vnlock);
 	if (vp->v_data != NULL)
 		VOP_PRINT(vp);
 }
 
 #ifdef DDB
 /*
  * List all of the locked vnodes in the system.
  * Called when debugging the kernel.
  */
 DB_SHOW_COMMAND(lockedvnods, lockedvnodes)
 {
 	struct mount *mp;
 	struct vnode *vp;
 
 	/*
 	 * Note: because this is DDB, we can't obey the locking semantics
 	 * for these structures, which means we could catch an inconsistent
 	 * state and dereference a nasty pointer.  Not much to be done
 	 * about that.
 	 */
 	db_printf("Locked vnodes\n");
 	TAILQ_FOREACH(mp, &mountlist, mnt_list) {
 		TAILQ_FOREACH(vp, &mp->mnt_nvnodelist, v_nmntvnodes) {
 			if (vp->v_type != VMARKER && VOP_ISLOCKED(vp))
 				vn_printf(vp, "vnode ");
 		}
 	}
 }
 
 /*
  * Show details about the given vnode.
  */
 DB_SHOW_COMMAND(vnode, db_show_vnode)
 {
 	struct vnode *vp;
 
 	if (!have_addr)
 		return;
 	vp = (struct vnode *)addr;
 	vn_printf(vp, "vnode ");
 }
 
 /*
  * Show details about the given mount point.
  */
 DB_SHOW_COMMAND(mount, db_show_mount)
 {
 	struct mount *mp;
 	struct vfsopt *opt;
 	struct statfs *sp;
 	struct vnode *vp;
 	char buf[512];
 	uint64_t mflags;
 	u_int flags;
 
 	if (!have_addr) {
 		/* No address given, print short info about all mount points. */
 		TAILQ_FOREACH(mp, &mountlist, mnt_list) {
 			db_printf("%p %s on %s (%s)\n", mp,
 			    mp->mnt_stat.f_mntfromname,
 			    mp->mnt_stat.f_mntonname,
 			    mp->mnt_stat.f_fstypename);
 			if (db_pager_quit)
 				break;
 		}
 		db_printf("\nMore info: show mount <addr>\n");
 		return;
 	}
 
 	mp = (struct mount *)addr;
 	db_printf("%p %s on %s (%s)\n", mp, mp->mnt_stat.f_mntfromname,
 	    mp->mnt_stat.f_mntonname, mp->mnt_stat.f_fstypename);
 
 	buf[0] = '\0';
 	mflags = mp->mnt_flag;
 #define	MNT_FLAG(flag)	do {						\
 	if (mflags & (flag)) {						\
 		if (buf[0] != '\0')					\
 			strlcat(buf, ", ", sizeof(buf));		\
 		strlcat(buf, (#flag) + 4, sizeof(buf));			\
 		mflags &= ~(flag);					\
 	}								\
 } while (0)
 	MNT_FLAG(MNT_RDONLY);
 	MNT_FLAG(MNT_SYNCHRONOUS);
 	MNT_FLAG(MNT_NOEXEC);
 	MNT_FLAG(MNT_NOSUID);
 	MNT_FLAG(MNT_NFS4ACLS);
 	MNT_FLAG(MNT_UNION);
 	MNT_FLAG(MNT_ASYNC);
 	MNT_FLAG(MNT_SUIDDIR);
 	MNT_FLAG(MNT_SOFTDEP);
 	MNT_FLAG(MNT_NOSYMFOLLOW);
 	MNT_FLAG(MNT_GJOURNAL);
 	MNT_FLAG(MNT_MULTILABEL);
 	MNT_FLAG(MNT_ACLS);
 	MNT_FLAG(MNT_NOATIME);
 	MNT_FLAG(MNT_NOCLUSTERR);
 	MNT_FLAG(MNT_NOCLUSTERW);
 	MNT_FLAG(MNT_SUJ);
 	MNT_FLAG(MNT_EXRDONLY);
 	MNT_FLAG(MNT_EXPORTED);
 	MNT_FLAG(MNT_DEFEXPORTED);
 	MNT_FLAG(MNT_EXPORTANON);
 	MNT_FLAG(MNT_EXKERB);
 	MNT_FLAG(MNT_EXPUBLIC);
 	MNT_FLAG(MNT_LOCAL);
 	MNT_FLAG(MNT_QUOTA);
 	MNT_FLAG(MNT_ROOTFS);
 	MNT_FLAG(MNT_USER);
 	MNT_FLAG(MNT_IGNORE);
 	MNT_FLAG(MNT_UPDATE);
 	MNT_FLAG(MNT_DELEXPORT);
 	MNT_FLAG(MNT_RELOAD);
 	MNT_FLAG(MNT_FORCE);
 	MNT_FLAG(MNT_SNAPSHOT);
 	MNT_FLAG(MNT_BYFSID);
 #undef MNT_FLAG
 	if (mflags != 0) {
 		if (buf[0] != '\0')
 			strlcat(buf, ", ", sizeof(buf));
 		snprintf(buf + strlen(buf), sizeof(buf) - strlen(buf),
 		    "0x%016jx", mflags);
 	}
 	db_printf("    mnt_flag = %s\n", buf);
 
 	buf[0] = '\0';
 	flags = mp->mnt_kern_flag;
 #define	MNT_KERN_FLAG(flag)	do {					\
 	if (flags & (flag)) {						\
 		if (buf[0] != '\0')					\
 			strlcat(buf, ", ", sizeof(buf));		\
 		strlcat(buf, (#flag) + 5, sizeof(buf));			\
 		flags &= ~(flag);					\
 	}								\
 } while (0)
 	MNT_KERN_FLAG(MNTK_UNMOUNTF);
 	MNT_KERN_FLAG(MNTK_ASYNC);
 	MNT_KERN_FLAG(MNTK_SOFTDEP);
 	MNT_KERN_FLAG(MNTK_DRAINING);
 	MNT_KERN_FLAG(MNTK_REFEXPIRE);
 	MNT_KERN_FLAG(MNTK_EXTENDED_SHARED);
 	MNT_KERN_FLAG(MNTK_SHARED_WRITES);
 	MNT_KERN_FLAG(MNTK_NO_IOPF);
 	MNT_KERN_FLAG(MNTK_VGONE_UPPER);
 	MNT_KERN_FLAG(MNTK_VGONE_WAITER);
 	MNT_KERN_FLAG(MNTK_LOOKUP_EXCL_DOTDOT);
 	MNT_KERN_FLAG(MNTK_MARKER);
 	MNT_KERN_FLAG(MNTK_USES_BCACHE);
 	MNT_KERN_FLAG(MNTK_NOASYNC);
 	MNT_KERN_FLAG(MNTK_UNMOUNT);
 	MNT_KERN_FLAG(MNTK_MWAIT);
 	MNT_KERN_FLAG(MNTK_SUSPEND);
 	MNT_KERN_FLAG(MNTK_SUSPEND2);
 	MNT_KERN_FLAG(MNTK_SUSPENDED);
 	MNT_KERN_FLAG(MNTK_LOOKUP_SHARED);
 	MNT_KERN_FLAG(MNTK_NOKNOTE);
 #undef MNT_KERN_FLAG
 	if (flags != 0) {
 		if (buf[0] != '\0')
 			strlcat(buf, ", ", sizeof(buf));
 		snprintf(buf + strlen(buf), sizeof(buf) - strlen(buf),
 		    "0x%08x", flags);
 	}
 	db_printf("    mnt_kern_flag = %s\n", buf);
 
 	db_printf("    mnt_opt = ");
 	opt = TAILQ_FIRST(mp->mnt_opt);
 	if (opt != NULL) {
 		db_printf("%s", opt->name);
 		opt = TAILQ_NEXT(opt, link);
 		while (opt != NULL) {
 			db_printf(", %s", opt->name);
 			opt = TAILQ_NEXT(opt, link);
 		}
 	}
 	db_printf("\n");
 
 	sp = &mp->mnt_stat;
 	db_printf("    mnt_stat = { version=%u type=%u flags=0x%016jx "
 	    "bsize=%ju iosize=%ju blocks=%ju bfree=%ju bavail=%jd files=%ju "
 	    "ffree=%jd syncwrites=%ju asyncwrites=%ju syncreads=%ju "
 	    "asyncreads=%ju namemax=%u owner=%u fsid=[%d, %d] }\n",
 	    (u_int)sp->f_version, (u_int)sp->f_type, (uintmax_t)sp->f_flags,
 	    (uintmax_t)sp->f_bsize, (uintmax_t)sp->f_iosize,
 	    (uintmax_t)sp->f_blocks, (uintmax_t)sp->f_bfree,
 	    (intmax_t)sp->f_bavail, (uintmax_t)sp->f_files,
 	    (intmax_t)sp->f_ffree, (uintmax_t)sp->f_syncwrites,
 	    (uintmax_t)sp->f_asyncwrites, (uintmax_t)sp->f_syncreads,
 	    (uintmax_t)sp->f_asyncreads, (u_int)sp->f_namemax,
 	    (u_int)sp->f_owner, (int)sp->f_fsid.val[0], (int)sp->f_fsid.val[1]);
 
 	db_printf("    mnt_cred = { uid=%u ruid=%u",
 	    (u_int)mp->mnt_cred->cr_uid, (u_int)mp->mnt_cred->cr_ruid);
 	if (jailed(mp->mnt_cred))
 		db_printf(", jail=%d", mp->mnt_cred->cr_prison->pr_id);
 	db_printf(" }\n");
 	db_printf("    mnt_ref = %d (with %d in the struct)\n",
 	    vfs_mount_fetch_counter(mp, MNT_COUNT_REF), mp->mnt_ref);
 	db_printf("    mnt_gen = %d\n", mp->mnt_gen);
 	db_printf("    mnt_nvnodelistsize = %d\n", mp->mnt_nvnodelistsize);
 	db_printf("    mnt_lazyvnodelistsize = %d\n",
 	    mp->mnt_lazyvnodelistsize);
 	db_printf("    mnt_writeopcount = %d (with %d in the struct)\n",
 	    vfs_mount_fetch_counter(mp, MNT_COUNT_WRITEOPCOUNT), mp->mnt_writeopcount);
 	db_printf("    mnt_maxsymlinklen = %d\n", mp->mnt_maxsymlinklen);
 	db_printf("    mnt_iosize_max = %d\n", mp->mnt_iosize_max);
 	db_printf("    mnt_hashseed = %u\n", mp->mnt_hashseed);
 	db_printf("    mnt_lockref = %d (with %d in the struct)\n",
 	    vfs_mount_fetch_counter(mp, MNT_COUNT_LOCKREF), mp->mnt_lockref);
 	db_printf("    mnt_secondary_writes = %d\n", mp->mnt_secondary_writes);
 	db_printf("    mnt_secondary_accwrites = %d\n",
 	    mp->mnt_secondary_accwrites);
 	db_printf("    mnt_gjprovider = %s\n",
 	    mp->mnt_gjprovider != NULL ? mp->mnt_gjprovider : "NULL");
 	db_printf("    mnt_vfs_ops = %d\n", mp->mnt_vfs_ops);
 
 	db_printf("\n\nList of active vnodes\n");
 	TAILQ_FOREACH(vp, &mp->mnt_nvnodelist, v_nmntvnodes) {
 		if (vp->v_type != VMARKER && vp->v_holdcnt > 0) {
 			vn_printf(vp, "vnode ");
 			if (db_pager_quit)
 				break;
 		}
 	}
 	db_printf("\n\nList of inactive vnodes\n");
 	TAILQ_FOREACH(vp, &mp->mnt_nvnodelist, v_nmntvnodes) {
 		if (vp->v_type != VMARKER && vp->v_holdcnt == 0) {
 			vn_printf(vp, "vnode ");
 			if (db_pager_quit)
 				break;
 		}
 	}
 }
 #endif	/* DDB */
 
 /*
  * Fill in a struct xvfsconf based on a struct vfsconf.
  */
 static int
 vfsconf2x(struct sysctl_req *req, struct vfsconf *vfsp)
 {
 	struct xvfsconf xvfsp;
 
 	bzero(&xvfsp, sizeof(xvfsp));
 	strcpy(xvfsp.vfc_name, vfsp->vfc_name);
 	xvfsp.vfc_typenum = vfsp->vfc_typenum;
 	xvfsp.vfc_refcount = vfsp->vfc_refcount;
 	xvfsp.vfc_flags = vfsp->vfc_flags;
 	/*
 	 * These are unused in userland, we keep them
 	 * to not break binary compatibility.
 	 */
 	xvfsp.vfc_vfsops = NULL;
 	xvfsp.vfc_next = NULL;
 	return (SYSCTL_OUT(req, &xvfsp, sizeof(xvfsp)));
 }
 
 #ifdef COMPAT_FREEBSD32
 struct xvfsconf32 {
 	uint32_t	vfc_vfsops;
 	char		vfc_name[MFSNAMELEN];
 	int32_t		vfc_typenum;
 	int32_t		vfc_refcount;
 	int32_t		vfc_flags;
 	uint32_t	vfc_next;
 };
 
 static int
 vfsconf2x32(struct sysctl_req *req, struct vfsconf *vfsp)
 {
 	struct xvfsconf32 xvfsp;
 
 	bzero(&xvfsp, sizeof(xvfsp));
 	strcpy(xvfsp.vfc_name, vfsp->vfc_name);
 	xvfsp.vfc_typenum = vfsp->vfc_typenum;
 	xvfsp.vfc_refcount = vfsp->vfc_refcount;
 	xvfsp.vfc_flags = vfsp->vfc_flags;
 	return (SYSCTL_OUT(req, &xvfsp, sizeof(xvfsp)));
 }
 #endif
 
 /*
  * Top level filesystem related information gathering.
  */
 static int
 sysctl_vfs_conflist(SYSCTL_HANDLER_ARGS)
 {
 	struct vfsconf *vfsp;
 	int error;
 
 	error = 0;
 	vfsconf_slock();
 	TAILQ_FOREACH(vfsp, &vfsconf, vfc_list) {
 #ifdef COMPAT_FREEBSD32
 		if (req->flags & SCTL_MASK32)
 			error = vfsconf2x32(req, vfsp);
 		else
 #endif
 			error = vfsconf2x(req, vfsp);
 		if (error)
 			break;
 	}
 	vfsconf_sunlock();
 	return (error);
 }
 
 SYSCTL_PROC(_vfs, OID_AUTO, conflist, CTLTYPE_OPAQUE | CTLFLAG_RD |
     CTLFLAG_MPSAFE, NULL, 0, sysctl_vfs_conflist,
     "S,xvfsconf", "List of all configured filesystems");
 
 #ifndef BURN_BRIDGES
 static int	sysctl_ovfs_conf(SYSCTL_HANDLER_ARGS);
 
 static int
 vfs_sysctl(SYSCTL_HANDLER_ARGS)
 {
 	int *name = (int *)arg1 - 1;	/* XXX */
 	u_int namelen = arg2 + 1;	/* XXX */
 	struct vfsconf *vfsp;
 
 	log(LOG_WARNING, "userland calling deprecated sysctl, "
 	    "please rebuild world\n");
 
 #if 1 || defined(COMPAT_PRELITE2)
 	/* Resolve ambiguity between VFS_VFSCONF and VFS_GENERIC. */
 	if (namelen == 1)
 		return (sysctl_ovfs_conf(oidp, arg1, arg2, req));
 #endif
 
 	switch (name[1]) {
 	case VFS_MAXTYPENUM:
 		if (namelen != 2)
 			return (ENOTDIR);
 		return (SYSCTL_OUT(req, &maxvfsconf, sizeof(int)));
 	case VFS_CONF:
 		if (namelen != 3)
 			return (ENOTDIR);	/* overloaded */
 		vfsconf_slock();
 		TAILQ_FOREACH(vfsp, &vfsconf, vfc_list) {
 			if (vfsp->vfc_typenum == name[2])
 				break;
 		}
 		vfsconf_sunlock();
 		if (vfsp == NULL)
 			return (EOPNOTSUPP);
 #ifdef COMPAT_FREEBSD32
 		if (req->flags & SCTL_MASK32)
 			return (vfsconf2x32(req, vfsp));
 		else
 #endif
 			return (vfsconf2x(req, vfsp));
 	}
 	return (EOPNOTSUPP);
 }
 
 static SYSCTL_NODE(_vfs, VFS_GENERIC, generic, CTLFLAG_RD | CTLFLAG_SKIP |
     CTLFLAG_MPSAFE, vfs_sysctl,
     "Generic filesystem");
 
 #if 1 || defined(COMPAT_PRELITE2)
 
 static int
 sysctl_ovfs_conf(SYSCTL_HANDLER_ARGS)
 {
 	int error;
 	struct vfsconf *vfsp;
 	struct ovfsconf ovfs;
 
 	vfsconf_slock();
 	TAILQ_FOREACH(vfsp, &vfsconf, vfc_list) {
 		bzero(&ovfs, sizeof(ovfs));
 		ovfs.vfc_vfsops = vfsp->vfc_vfsops;	/* XXX used as flag */
 		strcpy(ovfs.vfc_name, vfsp->vfc_name);
 		ovfs.vfc_index = vfsp->vfc_typenum;
 		ovfs.vfc_refcount = vfsp->vfc_refcount;
 		ovfs.vfc_flags = vfsp->vfc_flags;
 		error = SYSCTL_OUT(req, &ovfs, sizeof ovfs);
 		if (error != 0) {
 			vfsconf_sunlock();
 			return (error);
 		}
 	}
 	vfsconf_sunlock();
 	return (0);
 }
 
 #endif /* 1 || COMPAT_PRELITE2 */
 #endif /* !BURN_BRIDGES */
 
 #define KINFO_VNODESLOP		10
 #ifdef notyet
 /*
  * Dump vnode list (via sysctl).
  */
 /* ARGSUSED */
 static int
 sysctl_vnode(SYSCTL_HANDLER_ARGS)
 {
 	struct xvnode *xvn;
 	struct mount *mp;
 	struct vnode *vp;
 	int error, len, n;
 
 	/*
 	 * Stale numvnodes access is not fatal here.
 	 */
 	req->lock = 0;
 	len = (numvnodes + KINFO_VNODESLOP) * sizeof *xvn;
 	if (!req->oldptr)
 		/* Make an estimate */
 		return (SYSCTL_OUT(req, 0, len));
 
 	error = sysctl_wire_old_buffer(req, 0);
 	if (error != 0)
 		return (error);
 	xvn = malloc(len, M_TEMP, M_ZERO | M_WAITOK);
 	n = 0;
 	mtx_lock(&mountlist_mtx);
 	TAILQ_FOREACH(mp, &mountlist, mnt_list) {
 		if (vfs_busy(mp, MBF_NOWAIT | MBF_MNTLSTLOCK))
 			continue;
 		MNT_ILOCK(mp);
 		TAILQ_FOREACH(vp, &mp->mnt_nvnodelist, v_nmntvnodes) {
 			if (n == len)
 				break;
 			vref(vp);
 			xvn[n].xv_size = sizeof *xvn;
 			xvn[n].xv_vnode = vp;
 			xvn[n].xv_id = 0;	/* XXX compat */
 #define XV_COPY(field) xvn[n].xv_##field = vp->v_##field
 			XV_COPY(usecount);
 			XV_COPY(writecount);
 			XV_COPY(holdcnt);
 			XV_COPY(mount);
 			XV_COPY(numoutput);
 			XV_COPY(type);
 #undef XV_COPY
 			xvn[n].xv_flag = vp->v_vflag;
 
 			switch (vp->v_type) {
 			case VREG:
 			case VDIR:
 			case VLNK:
 				break;
 			case VBLK:
 			case VCHR:
 				if (vp->v_rdev == NULL) {
 					vrele(vp);
 					continue;
 				}
 				xvn[n].xv_dev = dev2udev(vp->v_rdev);
 				break;
 			case VSOCK:
 				xvn[n].xv_socket = vp->v_socket;
 				break;
 			case VFIFO:
 				xvn[n].xv_fifo = vp->v_fifoinfo;
 				break;
 			case VNON:
 			case VBAD:
 			default:
 				/* shouldn't happen? */
 				vrele(vp);
 				continue;
 			}
 			vrele(vp);
 			++n;
 		}
 		MNT_IUNLOCK(mp);
 		mtx_lock(&mountlist_mtx);
 		vfs_unbusy(mp);
 		if (n == len)
 			break;
 	}
 	mtx_unlock(&mountlist_mtx);
 
 	error = SYSCTL_OUT(req, xvn, n * sizeof *xvn);
 	free(xvn, M_TEMP);
 	return (error);
 }
 
 SYSCTL_PROC(_kern, KERN_VNODE, vnode, CTLTYPE_OPAQUE | CTLFLAG_RD |
     CTLFLAG_MPSAFE, 0, 0, sysctl_vnode, "S,xvnode",
     "");
 #endif
 
 static void
 unmount_or_warn(struct mount *mp)
 {
 	int error;
 
 	error = dounmount(mp, MNT_FORCE, curthread);
 	if (error != 0) {
 		printf("unmount of %s failed (", mp->mnt_stat.f_mntonname);
 		if (error == EBUSY)
 			printf("BUSY)\n");
 		else
 			printf("%d)\n", error);
 	}
 }
 
 /*
  * Unmount all filesystems. The list is traversed in reverse order
  * of mounting to avoid dependencies.
  */
 void
 vfs_unmountall(void)
 {
 	struct mount *mp, *tmp;
 
 	CTR1(KTR_VFS, "%s: unmounting all filesystems", __func__);
 
 	/*
 	 * Since this only runs when rebooting, it is not interlocked.
 	 */
 	TAILQ_FOREACH_REVERSE_SAFE(mp, &mountlist, mntlist, mnt_list, tmp) {
 		vfs_ref(mp);
 
 		/*
 		 * Forcibly unmounting "/dev" before "/" would prevent clean
 		 * unmount of the latter.
 		 */
 		if (mp == rootdevmp)
 			continue;
 
 		unmount_or_warn(mp);
 	}
 
 	if (rootdevmp != NULL)
 		unmount_or_warn(rootdevmp);
 }
 
 static void
 vfs_deferred_inactive(struct vnode *vp, int lkflags)
 {
 
 	ASSERT_VI_LOCKED(vp, __func__);
 	VNASSERT((vp->v_iflag & VI_DEFINACT) == 0, vp, ("VI_DEFINACT still set"));
 	if ((vp->v_iflag & VI_OWEINACT) == 0) {
 		vdropl(vp);
 		return;
 	}
 	if (vn_lock(vp, lkflags) == 0) {
 		VI_LOCK(vp);
-		if ((vp->v_iflag & (VI_OWEINACT | VI_DOINGINACT)) == VI_OWEINACT)
-			vinactive(vp);
+		vinactive(vp);
 		VOP_UNLOCK(vp);
 		vdropl(vp);
 		return;
 	}
-	vdefer_inactive_cond(vp);
+	vdefer_inactive_unlocked(vp);
 }
 
 static int
 vfs_periodic_inactive_filter(struct vnode *vp, void *arg)
 {
 
 	return (vp->v_iflag & VI_DEFINACT);
 }
 
 static void __noinline
 vfs_periodic_inactive(struct mount *mp, int flags)
 {
 	struct vnode *vp, *mvp;
 	int lkflags;
 
 	lkflags = LK_EXCLUSIVE | LK_INTERLOCK;
 	if (flags != MNT_WAIT)
 		lkflags |= LK_NOWAIT;
 
 	MNT_VNODE_FOREACH_LAZY(vp, mp, mvp, vfs_periodic_inactive_filter, NULL) {
 		if ((vp->v_iflag & VI_DEFINACT) == 0) {
 			VI_UNLOCK(vp);
 			continue;
 		}
 		vp->v_iflag &= ~VI_DEFINACT;
 		vfs_deferred_inactive(vp, lkflags);
 	}
 }
 
 static inline bool
 vfs_want_msync(struct vnode *vp)
 {
 	struct vm_object *obj;
 
 	/*
 	 * This test may be performed without any locks held.
 	 * We rely on vm_object's type stability.
 	 */
 	if (vp->v_vflag & VV_NOSYNC)
 		return (false);
 	obj = vp->v_object;
 	return (obj != NULL && vm_object_mightbedirty(obj));
 }
 
 static int
 vfs_periodic_msync_inactive_filter(struct vnode *vp, void *arg __unused)
 {
 
 	if (vp->v_vflag & VV_NOSYNC)
 		return (false);
 	if (vp->v_iflag & VI_DEFINACT)
 		return (true);
 	return (vfs_want_msync(vp));
 }
 
 static void __noinline
 vfs_periodic_msync_inactive(struct mount *mp, int flags)
 {
 	struct vnode *vp, *mvp;
 	struct vm_object *obj;
 	struct thread *td;
 	int lkflags, objflags;
 	bool seen_defer;
 
 	td = curthread;
 
 	lkflags = LK_EXCLUSIVE | LK_INTERLOCK;
 	if (flags != MNT_WAIT) {
 		lkflags |= LK_NOWAIT;
 		objflags = OBJPC_NOSYNC;
 	} else {
 		objflags = OBJPC_SYNC;
 	}
 
 	MNT_VNODE_FOREACH_LAZY(vp, mp, mvp, vfs_periodic_msync_inactive_filter, NULL) {
 		seen_defer = false;
 		if (vp->v_iflag & VI_DEFINACT) {
 			vp->v_iflag &= ~VI_DEFINACT;
 			seen_defer = true;
 		}
 		if (!vfs_want_msync(vp)) {
 			if (seen_defer)
 				vfs_deferred_inactive(vp, lkflags);
 			else
 				VI_UNLOCK(vp);
 			continue;
 		}
 		if (vget(vp, lkflags, td) == 0) {
 			obj = vp->v_object;
 			if (obj != NULL && (vp->v_vflag & VV_NOSYNC) == 0) {
 				VM_OBJECT_WLOCK(obj);
 				vm_object_page_clean(obj, 0, 0, objflags);
 				VM_OBJECT_WUNLOCK(obj);
 			}
 			vput(vp);
 			if (seen_defer)
 				vdrop(vp);
 		} else {
 			if (seen_defer)
-				vdefer_inactive_cond(vp);
+				vdefer_inactive_unlocked(vp);
 		}
 	}
 }
 
 void
 vfs_periodic(struct mount *mp, int flags)
 {
 
 	CTR2(KTR_VFS, "%s: mp %p", __func__, mp);
 
 	if ((mp->mnt_kern_flag & MNTK_NOMSYNC) != 0)
 		vfs_periodic_inactive(mp, flags);
 	else
 		vfs_periodic_msync_inactive(mp, flags);
 }
 
 static void
 destroy_vpollinfo_free(struct vpollinfo *vi)
 {
 
 	knlist_destroy(&vi->vpi_selinfo.si_note);
 	mtx_destroy(&vi->vpi_lock);
 	uma_zfree(vnodepoll_zone, vi);
 }
 
 static void
 destroy_vpollinfo(struct vpollinfo *vi)
 {
 
 	knlist_clear(&vi->vpi_selinfo.si_note, 1);
 	seldrain(&vi->vpi_selinfo);
 	destroy_vpollinfo_free(vi);
 }
 
 /*
  * Initialize per-vnode helper structure to hold poll-related state.
  */
 void
 v_addpollinfo(struct vnode *vp)
 {
 	struct vpollinfo *vi;
 
 	if (vp->v_pollinfo != NULL)
 		return;
 	vi = uma_zalloc(vnodepoll_zone, M_WAITOK | M_ZERO);
 	mtx_init(&vi->vpi_lock, "vnode pollinfo", NULL, MTX_DEF);
 	knlist_init(&vi->vpi_selinfo.si_note, vp, vfs_knllock,
 	    vfs_knlunlock, vfs_knl_assert_locked, vfs_knl_assert_unlocked);
 	VI_LOCK(vp);
 	if (vp->v_pollinfo != NULL) {
 		VI_UNLOCK(vp);
 		destroy_vpollinfo_free(vi);
 		return;
 	}
 	vp->v_pollinfo = vi;
 	VI_UNLOCK(vp);
 }
 
 /*
  * Record a process's interest in events which might happen to
  * a vnode.  Because poll uses the historic select-style interface
  * internally, this routine serves as both the ``check for any
  * pending events'' and the ``record my interest in future events''
  * functions.  (These are done together, while the lock is held,
  * to avoid race conditions.)
  */
 int
 vn_pollrecord(struct vnode *vp, struct thread *td, int events)
 {
 
 	v_addpollinfo(vp);
 	mtx_lock(&vp->v_pollinfo->vpi_lock);
 	if (vp->v_pollinfo->vpi_revents & events) {
 		/*
 		 * This leaves events we are not interested
 		 * in available for the other process which
 		 * which presumably had requested them
 		 * (otherwise they would never have been
 		 * recorded).
 		 */
 		events &= vp->v_pollinfo->vpi_revents;
 		vp->v_pollinfo->vpi_revents &= ~events;
 
 		mtx_unlock(&vp->v_pollinfo->vpi_lock);
 		return (events);
 	}
 	vp->v_pollinfo->vpi_events |= events;
 	selrecord(td, &vp->v_pollinfo->vpi_selinfo);
 	mtx_unlock(&vp->v_pollinfo->vpi_lock);
 	return (0);
 }
 
 /*
  * Routine to create and manage a filesystem syncer vnode.
  */
 #define sync_close ((int (*)(struct  vop_close_args *))nullop)
 static int	sync_fsync(struct  vop_fsync_args *);
 static int	sync_inactive(struct  vop_inactive_args *);
 static int	sync_reclaim(struct  vop_reclaim_args *);
 
 static struct vop_vector sync_vnodeops = {
 	.vop_bypass =	VOP_EOPNOTSUPP,
 	.vop_close =	sync_close,		/* close */
 	.vop_fsync =	sync_fsync,		/* fsync */
 	.vop_inactive =	sync_inactive,	/* inactive */
 	.vop_need_inactive = vop_stdneed_inactive, /* need_inactive */
 	.vop_reclaim =	sync_reclaim,	/* reclaim */
 	.vop_lock1 =	vop_stdlock,	/* lock */
 	.vop_unlock =	vop_stdunlock,	/* unlock */
 	.vop_islocked =	vop_stdislocked,	/* islocked */
 };
 VFS_VOP_VECTOR_REGISTER(sync_vnodeops);
 
 /*
  * Create a new filesystem syncer vnode for the specified mount point.
  */
 void
 vfs_allocate_syncvnode(struct mount *mp)
 {
 	struct vnode *vp;
 	struct bufobj *bo;
 	static long start, incr, next;
 	int error;
 
 	/* Allocate a new vnode */
 	error = getnewvnode("syncer", mp, &sync_vnodeops, &vp);
 	if (error != 0)
 		panic("vfs_allocate_syncvnode: getnewvnode() failed");
 	vp->v_type = VNON;
 	vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
 	vp->v_vflag |= VV_FORCEINSMQ;
 	error = insmntque(vp, mp);
 	if (error != 0)
 		panic("vfs_allocate_syncvnode: insmntque() failed");
 	vp->v_vflag &= ~VV_FORCEINSMQ;
 	VOP_UNLOCK(vp);
 	/*
 	 * Place the vnode onto the syncer worklist. We attempt to
 	 * scatter them about on the list so that they will go off
 	 * at evenly distributed times even if all the filesystems
 	 * are mounted at once.
 	 */
 	next += incr;
 	if (next == 0 || next > syncer_maxdelay) {
 		start /= 2;
 		incr /= 2;
 		if (start == 0) {
 			start = syncer_maxdelay / 2;
 			incr = syncer_maxdelay;
 		}
 		next = start;
 	}
 	bo = &vp->v_bufobj;
 	BO_LOCK(bo);
 	vn_syncer_add_to_worklist(bo, syncdelay > 0 ? next % syncdelay : 0);
 	/* XXX - vn_syncer_add_to_worklist() also grabs and drops sync_mtx. */
 	mtx_lock(&sync_mtx);
 	sync_vnode_count++;
 	if (mp->mnt_syncer == NULL) {
 		mp->mnt_syncer = vp;
 		vp = NULL;
 	}
 	mtx_unlock(&sync_mtx);
 	BO_UNLOCK(bo);
 	if (vp != NULL) {
 		vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
 		vgone(vp);
 		vput(vp);
 	}
 }
 
 void
 vfs_deallocate_syncvnode(struct mount *mp)
 {
 	struct vnode *vp;
 
 	mtx_lock(&sync_mtx);
 	vp = mp->mnt_syncer;
 	if (vp != NULL)
 		mp->mnt_syncer = NULL;
 	mtx_unlock(&sync_mtx);
 	if (vp != NULL)
 		vrele(vp);
 }
 
 /*
  * Do a lazy sync of the filesystem.
  */
 static int
 sync_fsync(struct vop_fsync_args *ap)
 {
 	struct vnode *syncvp = ap->a_vp;
 	struct mount *mp = syncvp->v_mount;
 	int error, save;
 	struct bufobj *bo;
 
 	/*
 	 * We only need to do something if this is a lazy evaluation.
 	 */
 	if (ap->a_waitfor != MNT_LAZY)
 		return (0);
 
 	/*
 	 * Move ourselves to the back of the sync list.
 	 */
 	bo = &syncvp->v_bufobj;
 	BO_LOCK(bo);
 	vn_syncer_add_to_worklist(bo, syncdelay);
 	BO_UNLOCK(bo);
 
 	/*
 	 * Walk the list of vnodes pushing all that are dirty and
 	 * not already on the sync list.
 	 */
 	if (vfs_busy(mp, MBF_NOWAIT) != 0)
 		return (0);
 	if (vn_start_write(NULL, &mp, V_NOWAIT) != 0) {
 		vfs_unbusy(mp);
 		return (0);
 	}
 	save = curthread_pflags_set(TDP_SYNCIO);
 	/*
 	 * The filesystem at hand may be idle with free vnodes stored in the
 	 * batch.  Return them instead of letting them stay there indefinitely.
 	 */
 	vfs_periodic(mp, MNT_NOWAIT);
 	error = VFS_SYNC(mp, MNT_LAZY);
 	curthread_pflags_restore(save);
 	vn_finished_write(mp);
 	vfs_unbusy(mp);
 	return (error);
 }
 
 /*
  * The syncer vnode is no referenced.
  */
 static int
 sync_inactive(struct vop_inactive_args *ap)
 {
 
 	vgone(ap->a_vp);
 	return (0);
 }
 
 /*
  * The syncer vnode is no longer needed and is being decommissioned.
  *
  * Modifications to the worklist must be protected by sync_mtx.
  */
 static int
 sync_reclaim(struct vop_reclaim_args *ap)
 {
 	struct vnode *vp = ap->a_vp;
 	struct bufobj *bo;
 
 	bo = &vp->v_bufobj;
 	BO_LOCK(bo);
 	mtx_lock(&sync_mtx);
 	if (vp->v_mount->mnt_syncer == vp)
 		vp->v_mount->mnt_syncer = NULL;
 	if (bo->bo_flag & BO_ONWORKLST) {
 		LIST_REMOVE(bo, bo_synclist);
 		syncer_worklist_len--;
 		sync_vnode_count--;
 		bo->bo_flag &= ~BO_ONWORKLST;
 	}
 	mtx_unlock(&sync_mtx);
 	BO_UNLOCK(bo);
 
 	return (0);
 }
 
 int
 vn_need_pageq_flush(struct vnode *vp)
 {
 	struct vm_object *obj;
 	int need;
 
 	MPASS(mtx_owned(VI_MTX(vp)));
 	need = 0;
 	if ((obj = vp->v_object) != NULL && (vp->v_vflag & VV_NOSYNC) == 0 &&
 	    vm_object_mightbedirty(obj))
 		need = 1;
 	return (need);
 }
 
 /*
  * Check if vnode represents a disk device
  */
 int
 vn_isdisk(struct vnode *vp, int *errp)
 {
 	int error;
 
 	if (vp->v_type != VCHR) {
 		error = ENOTBLK;
 		goto out;
 	}
 	error = 0;
 	dev_lock();
 	if (vp->v_rdev == NULL)
 		error = ENXIO;
 	else if (vp->v_rdev->si_devsw == NULL)
 		error = ENXIO;
 	else if (!(vp->v_rdev->si_devsw->d_flags & D_DISK))
 		error = ENOTBLK;
 	dev_unlock();
 out:
 	if (errp != NULL)
 		*errp = error;
 	return (error == 0);
 }
 
 /*
  * Common filesystem object access control check routine.  Accepts a
  * vnode's type, "mode", uid and gid, requested access mode, credentials,
  * and optional call-by-reference privused argument allowing vaccess()
  * to indicate to the caller whether privilege was used to satisfy the
  * request (obsoleted).  Returns 0 on success, or an errno on failure.
  */
 int
 vaccess(enum vtype type, mode_t file_mode, uid_t file_uid, gid_t file_gid,
     accmode_t accmode, struct ucred *cred, int *privused)
 {
 	accmode_t dac_granted;
 	accmode_t priv_granted;
 
 	KASSERT((accmode & ~(VEXEC | VWRITE | VREAD | VADMIN | VAPPEND)) == 0,
 	    ("invalid bit in accmode"));
 	KASSERT((accmode & VAPPEND) == 0 || (accmode & VWRITE),
 	    ("VAPPEND without VWRITE"));
 
 	/*
 	 * Look for a normal, non-privileged way to access the file/directory
 	 * as requested.  If it exists, go with that.
 	 */
 
 	if (privused != NULL)
 		*privused = 0;
 
 	dac_granted = 0;
 
 	/* Check the owner. */
 	if (cred->cr_uid == file_uid) {
 		dac_granted |= VADMIN;
 		if (file_mode & S_IXUSR)
 			dac_granted |= VEXEC;
 		if (file_mode & S_IRUSR)
 			dac_granted |= VREAD;
 		if (file_mode & S_IWUSR)
 			dac_granted |= (VWRITE | VAPPEND);
 
 		if ((accmode & dac_granted) == accmode)
 			return (0);
 
 		goto privcheck;
 	}
 
 	/* Otherwise, check the groups (first match) */
 	if (groupmember(file_gid, cred)) {
 		if (file_mode & S_IXGRP)
 			dac_granted |= VEXEC;
 		if (file_mode & S_IRGRP)
 			dac_granted |= VREAD;
 		if (file_mode & S_IWGRP)
 			dac_granted |= (VWRITE | VAPPEND);
 
 		if ((accmode & dac_granted) == accmode)
 			return (0);
 
 		goto privcheck;
 	}
 
 	/* Otherwise, check everyone else. */
 	if (file_mode & S_IXOTH)
 		dac_granted |= VEXEC;
 	if (file_mode & S_IROTH)
 		dac_granted |= VREAD;
 	if (file_mode & S_IWOTH)
 		dac_granted |= (VWRITE | VAPPEND);
 	if ((accmode & dac_granted) == accmode)
 		return (0);
 
 privcheck:
 	/*
 	 * Build a privilege mask to determine if the set of privileges
 	 * satisfies the requirements when combined with the granted mask
 	 * from above.  For each privilege, if the privilege is required,
 	 * bitwise or the request type onto the priv_granted mask.
 	 */
 	priv_granted = 0;
 
 	if (type == VDIR) {
 		/*
 		 * For directories, use PRIV_VFS_LOOKUP to satisfy VEXEC
 		 * requests, instead of PRIV_VFS_EXEC.
 		 */
 		if ((accmode & VEXEC) && ((dac_granted & VEXEC) == 0) &&
 		    !priv_check_cred(cred, PRIV_VFS_LOOKUP))
 			priv_granted |= VEXEC;
 	} else {
 		/*
 		 * Ensure that at least one execute bit is on. Otherwise,
 		 * a privileged user will always succeed, and we don't want
 		 * this to happen unless the file really is executable.
 		 */
 		if ((accmode & VEXEC) && ((dac_granted & VEXEC) == 0) &&
 		    (file_mode & (S_IXUSR | S_IXGRP | S_IXOTH)) != 0 &&
 		    !priv_check_cred(cred, PRIV_VFS_EXEC))
 			priv_granted |= VEXEC;
 	}
 
 	if ((accmode & VREAD) && ((dac_granted & VREAD) == 0) &&
 	    !priv_check_cred(cred, PRIV_VFS_READ))
 		priv_granted |= VREAD;
 
 	if ((accmode & VWRITE) && ((dac_granted & VWRITE) == 0) &&
 	    !priv_check_cred(cred, PRIV_VFS_WRITE))
 		priv_granted |= (VWRITE | VAPPEND);
 
 	if ((accmode & VADMIN) && ((dac_granted & VADMIN) == 0) &&
 	    !priv_check_cred(cred, PRIV_VFS_ADMIN))
 		priv_granted |= VADMIN;
 
 	if ((accmode & (priv_granted | dac_granted)) == accmode) {
 		/* XXX audit: privilege used */
 		if (privused != NULL)
 			*privused = 1;
 		return (0);
 	}
 
 	return ((accmode & VADMIN) ? EPERM : EACCES);
 }
 
 /*
  * Credential check based on process requesting service, and per-attribute
  * permissions.
  */
 int
 extattr_check_cred(struct vnode *vp, int attrnamespace, struct ucred *cred,
     struct thread *td, accmode_t accmode)
 {
 
 	/*
 	 * Kernel-invoked always succeeds.
 	 */
 	if (cred == NOCRED)
 		return (0);
 
 	/*
 	 * Do not allow privileged processes in jail to directly manipulate
 	 * system attributes.
 	 */
 	switch (attrnamespace) {
 	case EXTATTR_NAMESPACE_SYSTEM:
 		/* Potentially should be: return (EPERM); */
 		return (priv_check_cred(cred, PRIV_VFS_EXTATTR_SYSTEM));
 	case EXTATTR_NAMESPACE_USER:
 		return (VOP_ACCESS(vp, accmode, cred, td));
 	default:
 		return (EPERM);
 	}
 }
 
 #ifdef DEBUG_VFS_LOCKS
 /*
  * This only exists to suppress warnings from unlocked specfs accesses.  It is
  * no longer ok to have an unlocked VFS.
  */
 #define	IGNORE_LOCK(vp) (KERNEL_PANICKED() || (vp) == NULL ||		\
 	(vp)->v_type == VCHR ||	(vp)->v_type == VBAD)
 
 int vfs_badlock_ddb = 1;	/* Drop into debugger on violation. */
 SYSCTL_INT(_debug, OID_AUTO, vfs_badlock_ddb, CTLFLAG_RW, &vfs_badlock_ddb, 0,
     "Drop into debugger on lock violation");
 
 int vfs_badlock_mutex = 1;	/* Check for interlock across VOPs. */
 SYSCTL_INT(_debug, OID_AUTO, vfs_badlock_mutex, CTLFLAG_RW, &vfs_badlock_mutex,
     0, "Check for interlock across VOPs");
 
 int vfs_badlock_print = 1;	/* Print lock violations. */
 SYSCTL_INT(_debug, OID_AUTO, vfs_badlock_print, CTLFLAG_RW, &vfs_badlock_print,
     0, "Print lock violations");
 
 int vfs_badlock_vnode = 1;	/* Print vnode details on lock violations. */
 SYSCTL_INT(_debug, OID_AUTO, vfs_badlock_vnode, CTLFLAG_RW, &vfs_badlock_vnode,
     0, "Print vnode details on lock violations");
 
 #ifdef KDB
 int vfs_badlock_backtrace = 1;	/* Print backtrace at lock violations. */
 SYSCTL_INT(_debug, OID_AUTO, vfs_badlock_backtrace, CTLFLAG_RW,
     &vfs_badlock_backtrace, 0, "Print backtrace at lock violations");
 #endif
 
 static void
 vfs_badlock(const char *msg, const char *str, struct vnode *vp)
 {
 
 #ifdef KDB
 	if (vfs_badlock_backtrace)
 		kdb_backtrace();
 #endif
 	if (vfs_badlock_vnode)
 		vn_printf(vp, "vnode ");
 	if (vfs_badlock_print)
 		printf("%s: %p %s\n", str, (void *)vp, msg);
 	if (vfs_badlock_ddb)
 		kdb_enter(KDB_WHY_VFSLOCK, "lock violation");
 }
 
 void
 assert_vi_locked(struct vnode *vp, const char *str)
 {
 
 	if (vfs_badlock_mutex && !mtx_owned(VI_MTX(vp)))
 		vfs_badlock("interlock is not locked but should be", str, vp);
 }
 
 void
 assert_vi_unlocked(struct vnode *vp, const char *str)
 {
 
 	if (vfs_badlock_mutex && mtx_owned(VI_MTX(vp)))
 		vfs_badlock("interlock is locked but should not be", str, vp);
 }
 
 void
 assert_vop_locked(struct vnode *vp, const char *str)
 {
 	int locked;
 
 	if (!IGNORE_LOCK(vp)) {
 		locked = VOP_ISLOCKED(vp);
 		if (locked == 0 || locked == LK_EXCLOTHER)
 			vfs_badlock("is not locked but should be", str, vp);
 	}
 }
 
 void
 assert_vop_unlocked(struct vnode *vp, const char *str)
 {
 
 	if (!IGNORE_LOCK(vp) && VOP_ISLOCKED(vp) == LK_EXCLUSIVE)
 		vfs_badlock("is locked but should not be", str, vp);
 }
 
 void
 assert_vop_elocked(struct vnode *vp, const char *str)
 {
 
 	if (!IGNORE_LOCK(vp) && VOP_ISLOCKED(vp) != LK_EXCLUSIVE)
 		vfs_badlock("is not exclusive locked but should be", str, vp);
 }
 #endif /* DEBUG_VFS_LOCKS */
 
 void
 vop_rename_fail(struct vop_rename_args *ap)
 {
 
 	if (ap->a_tvp != NULL)
 		vput(ap->a_tvp);
 	if (ap->a_tdvp == ap->a_tvp)
 		vrele(ap->a_tdvp);
 	else
 		vput(ap->a_tdvp);
 	vrele(ap->a_fdvp);
 	vrele(ap->a_fvp);
 }
 
 void
 vop_rename_pre(void *ap)
 {
 	struct vop_rename_args *a = ap;
 
 #ifdef DEBUG_VFS_LOCKS
 	if (a->a_tvp)
 		ASSERT_VI_UNLOCKED(a->a_tvp, "VOP_RENAME");
 	ASSERT_VI_UNLOCKED(a->a_tdvp, "VOP_RENAME");
 	ASSERT_VI_UNLOCKED(a->a_fvp, "VOP_RENAME");
 	ASSERT_VI_UNLOCKED(a->a_fdvp, "VOP_RENAME");
 
 	/* Check the source (from). */
 	if (a->a_tdvp->v_vnlock != a->a_fdvp->v_vnlock &&
 	    (a->a_tvp == NULL || a->a_tvp->v_vnlock != a->a_fdvp->v_vnlock))
 		ASSERT_VOP_UNLOCKED(a->a_fdvp, "vop_rename: fdvp locked");
 	if (a->a_tvp == NULL || a->a_tvp->v_vnlock != a->a_fvp->v_vnlock)
 		ASSERT_VOP_UNLOCKED(a->a_fvp, "vop_rename: fvp locked");
 
 	/* Check the target. */
 	if (a->a_tvp)
 		ASSERT_VOP_LOCKED(a->a_tvp, "vop_rename: tvp not locked");
 	ASSERT_VOP_LOCKED(a->a_tdvp, "vop_rename: tdvp not locked");
 #endif
 	if (a->a_tdvp != a->a_fdvp)
 		vhold(a->a_fdvp);
 	if (a->a_tvp != a->a_fvp)
 		vhold(a->a_fvp);
 	vhold(a->a_tdvp);
 	if (a->a_tvp)
 		vhold(a->a_tvp);
 }
 
 #ifdef DEBUG_VFS_LOCKS
 void
 vop_strategy_pre(void *ap)
 {
 	struct vop_strategy_args *a;
 	struct buf *bp;
 
 	a = ap;
 	bp = a->a_bp;
 
 	/*
 	 * Cluster ops lock their component buffers but not the IO container.
 	 */
 	if ((bp->b_flags & B_CLUSTER) != 0)
 		return;
 
 	if (!KERNEL_PANICKED() && !BUF_ISLOCKED(bp)) {
 		if (vfs_badlock_print)
 			printf(
 			    "VOP_STRATEGY: bp is not locked but should be\n");
 		if (vfs_badlock_ddb)
 			kdb_enter(KDB_WHY_VFSLOCK, "lock violation");
 	}
 }
 
 void
 vop_lock_pre(void *ap)
 {
 	struct vop_lock1_args *a = ap;
 
 	if ((a->a_flags & LK_INTERLOCK) == 0)
 		ASSERT_VI_UNLOCKED(a->a_vp, "VOP_LOCK");
 	else
 		ASSERT_VI_LOCKED(a->a_vp, "VOP_LOCK");
 }
 
 void
 vop_lock_post(void *ap, int rc)
 {
 	struct vop_lock1_args *a = ap;
 
 	ASSERT_VI_UNLOCKED(a->a_vp, "VOP_LOCK");
 	if (rc == 0 && (a->a_flags & LK_EXCLOTHER) == 0)
 		ASSERT_VOP_LOCKED(a->a_vp, "VOP_LOCK");
 }
 
 void
 vop_unlock_pre(void *ap)
 {
 	struct vop_unlock_args *a = ap;
 
 	ASSERT_VOP_LOCKED(a->a_vp, "VOP_UNLOCK");
 }
 
 void
 vop_unlock_post(void *ap, int rc)
 {
 	return;
 }
 
 void
 vop_need_inactive_pre(void *ap)
 {
 	struct vop_need_inactive_args *a = ap;
 
 	ASSERT_VI_LOCKED(a->a_vp, "VOP_NEED_INACTIVE");
 }
 
 void
 vop_need_inactive_post(void *ap, int rc)
 {
 	struct vop_need_inactive_args *a = ap;
 
 	ASSERT_VI_LOCKED(a->a_vp, "VOP_NEED_INACTIVE");
 }
 #endif
 
 void
 vop_create_post(void *ap, int rc)
 {
 	struct vop_create_args *a = ap;
 
 	if (!rc)
 		VFS_KNOTE_LOCKED(a->a_dvp, NOTE_WRITE);
 }
 
 void
 vop_deleteextattr_post(void *ap, int rc)
 {
 	struct vop_deleteextattr_args *a = ap;
 
 	if (!rc)
 		VFS_KNOTE_LOCKED(a->a_vp, NOTE_ATTRIB);
 }
 
 void
 vop_link_post(void *ap, int rc)
 {
 	struct vop_link_args *a = ap;
 
 	if (!rc) {
 		VFS_KNOTE_LOCKED(a->a_vp, NOTE_LINK);
 		VFS_KNOTE_LOCKED(a->a_tdvp, NOTE_WRITE);
 	}
 }
 
 void
 vop_mkdir_post(void *ap, int rc)
 {
 	struct vop_mkdir_args *a = ap;
 
 	if (!rc)
 		VFS_KNOTE_LOCKED(a->a_dvp, NOTE_WRITE | NOTE_LINK);
 }
 
 void
 vop_mknod_post(void *ap, int rc)
 {
 	struct vop_mknod_args *a = ap;
 
 	if (!rc)
 		VFS_KNOTE_LOCKED(a->a_dvp, NOTE_WRITE);
 }
 
 void
 vop_reclaim_post(void *ap, int rc)
 {
 	struct vop_reclaim_args *a = ap;
 
 	if (!rc)
 		VFS_KNOTE_LOCKED(a->a_vp, NOTE_REVOKE);
 }
 
 void
 vop_remove_post(void *ap, int rc)
 {
 	struct vop_remove_args *a = ap;
 
 	if (!rc) {
 		VFS_KNOTE_LOCKED(a->a_dvp, NOTE_WRITE);
 		VFS_KNOTE_LOCKED(a->a_vp, NOTE_DELETE);
 	}
 }
 
 void
 vop_rename_post(void *ap, int rc)
 {
 	struct vop_rename_args *a = ap;
 	long hint;
 
 	if (!rc) {
 		hint = NOTE_WRITE;
 		if (a->a_fdvp == a->a_tdvp) {
 			if (a->a_tvp != NULL && a->a_tvp->v_type == VDIR)
 				hint |= NOTE_LINK;
 			VFS_KNOTE_UNLOCKED(a->a_fdvp, hint);
 			VFS_KNOTE_UNLOCKED(a->a_tdvp, hint);
 		} else {
 			hint |= NOTE_EXTEND;
 			if (a->a_fvp->v_type == VDIR)
 				hint |= NOTE_LINK;
 			VFS_KNOTE_UNLOCKED(a->a_fdvp, hint);
 
 			if (a->a_fvp->v_type == VDIR && a->a_tvp != NULL &&
 			    a->a_tvp->v_type == VDIR)
 				hint &= ~NOTE_LINK;
 			VFS_KNOTE_UNLOCKED(a->a_tdvp, hint);
 		}
 
 		VFS_KNOTE_UNLOCKED(a->a_fvp, NOTE_RENAME);
 		if (a->a_tvp)
 			VFS_KNOTE_UNLOCKED(a->a_tvp, NOTE_DELETE);
 	}
 	if (a->a_tdvp != a->a_fdvp)
 		vdrop(a->a_fdvp);
 	if (a->a_tvp != a->a_fvp)
 		vdrop(a->a_fvp);
 	vdrop(a->a_tdvp);
 	if (a->a_tvp)
 		vdrop(a->a_tvp);
 }
 
 void
 vop_rmdir_post(void *ap, int rc)
 {
 	struct vop_rmdir_args *a = ap;
 
 	if (!rc) {
 		VFS_KNOTE_LOCKED(a->a_dvp, NOTE_WRITE | NOTE_LINK);
 		VFS_KNOTE_LOCKED(a->a_vp, NOTE_DELETE);
 	}
 }
 
 void
 vop_setattr_post(void *ap, int rc)
 {
 	struct vop_setattr_args *a = ap;
 
 	if (!rc)
 		VFS_KNOTE_LOCKED(a->a_vp, NOTE_ATTRIB);
 }
 
 void
 vop_setextattr_post(void *ap, int rc)
 {
 	struct vop_setextattr_args *a = ap;
 
 	if (!rc)
 		VFS_KNOTE_LOCKED(a->a_vp, NOTE_ATTRIB);
 }
 
 void
 vop_symlink_post(void *ap, int rc)
 {
 	struct vop_symlink_args *a = ap;
 
 	if (!rc)
 		VFS_KNOTE_LOCKED(a->a_dvp, NOTE_WRITE);
 }
 
 void
 vop_open_post(void *ap, int rc)
 {
 	struct vop_open_args *a = ap;
 
 	if (!rc)
 		VFS_KNOTE_LOCKED(a->a_vp, NOTE_OPEN);
 }
 
 void
 vop_close_post(void *ap, int rc)
 {
 	struct vop_close_args *a = ap;
 
 	if (!rc && (a->a_cred != NOCRED || /* filter out revokes */
 	    !VN_IS_DOOMED(a->a_vp))) {
 		VFS_KNOTE_LOCKED(a->a_vp, (a->a_fflag & FWRITE) != 0 ?
 		    NOTE_CLOSE_WRITE : NOTE_CLOSE);
 	}
 }
 
 void
 vop_read_post(void *ap, int rc)
 {
 	struct vop_read_args *a = ap;
 
 	if (!rc)
 		VFS_KNOTE_LOCKED(a->a_vp, NOTE_READ);
 }
 
 void
 vop_readdir_post(void *ap, int rc)
 {
 	struct vop_readdir_args *a = ap;
 
 	if (!rc)
 		VFS_KNOTE_LOCKED(a->a_vp, NOTE_READ);
 }
 
 static struct knlist fs_knlist;
 
 static void
 vfs_event_init(void *arg)
 {
 	knlist_init_mtx(&fs_knlist, NULL);
 }
 /* XXX - correct order? */
 SYSINIT(vfs_knlist, SI_SUB_VFS, SI_ORDER_ANY, vfs_event_init, NULL);
 
 void
 vfs_event_signal(fsid_t *fsid, uint32_t event, intptr_t data __unused)
 {
 
 	KNOTE_UNLOCKED(&fs_knlist, event);
 }
 
 static int	filt_fsattach(struct knote *kn);
 static void	filt_fsdetach(struct knote *kn);
 static int	filt_fsevent(struct knote *kn, long hint);
 
 struct filterops fs_filtops = {
 	.f_isfd = 0,
 	.f_attach = filt_fsattach,
 	.f_detach = filt_fsdetach,
 	.f_event = filt_fsevent
 };
 
 static int
 filt_fsattach(struct knote *kn)
 {
 
 	kn->kn_flags |= EV_CLEAR;
 	knlist_add(&fs_knlist, kn, 0);
 	return (0);
 }
 
 static void
 filt_fsdetach(struct knote *kn)
 {
 
 	knlist_remove(&fs_knlist, kn, 0);
 }
 
 static int
 filt_fsevent(struct knote *kn, long hint)
 {
 
 	kn->kn_fflags |= hint;
 	return (kn->kn_fflags != 0);
 }
 
 static int
 sysctl_vfs_ctl(SYSCTL_HANDLER_ARGS)
 {
 	struct vfsidctl vc;
 	int error;
 	struct mount *mp;
 
 	error = SYSCTL_IN(req, &vc, sizeof(vc));
 	if (error)
 		return (error);
 	if (vc.vc_vers != VFS_CTL_VERS1)
 		return (EINVAL);
 	mp = vfs_getvfs(&vc.vc_fsid);
 	if (mp == NULL)
 		return (ENOENT);
 	/* ensure that a specific sysctl goes to the right filesystem. */
 	if (strcmp(vc.vc_fstypename, "*") != 0 &&
 	    strcmp(vc.vc_fstypename, mp->mnt_vfc->vfc_name) != 0) {
 		vfs_rel(mp);
 		return (EINVAL);
 	}
 	VCTLTOREQ(&vc, req);
 	error = VFS_SYSCTL(mp, vc.vc_op, req);
 	vfs_rel(mp);
 	return (error);
 }
 
 SYSCTL_PROC(_vfs, OID_AUTO, ctl, CTLTYPE_OPAQUE | CTLFLAG_MPSAFE | CTLFLAG_WR,
     NULL, 0, sysctl_vfs_ctl, "",
     "Sysctl by fsid");
 
 /*
  * Function to initialize a va_filerev field sensibly.
  * XXX: Wouldn't a random number make a lot more sense ??
  */
 u_quad_t
 init_va_filerev(void)
 {
 	struct bintime bt;
 
 	getbinuptime(&bt);
 	return (((u_quad_t)bt.sec << 32LL) | (bt.frac >> 32LL));
 }
 
 static int	filt_vfsread(struct knote *kn, long hint);
 static int	filt_vfswrite(struct knote *kn, long hint);
 static int	filt_vfsvnode(struct knote *kn, long hint);
 static void	filt_vfsdetach(struct knote *kn);
 static struct filterops vfsread_filtops = {
 	.f_isfd = 1,
 	.f_detach = filt_vfsdetach,
 	.f_event = filt_vfsread
 };
 static struct filterops vfswrite_filtops = {
 	.f_isfd = 1,
 	.f_detach = filt_vfsdetach,
 	.f_event = filt_vfswrite
 };
 static struct filterops vfsvnode_filtops = {
 	.f_isfd = 1,
 	.f_detach = filt_vfsdetach,
 	.f_event = filt_vfsvnode
 };
 
 static void
 vfs_knllock(void *arg)
 {
 	struct vnode *vp = arg;
 
 	vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
 }
 
 static void
 vfs_knlunlock(void *arg)
 {
 	struct vnode *vp = arg;
 
 	VOP_UNLOCK(vp);
 }
 
 static void
 vfs_knl_assert_locked(void *arg)
 {
 #ifdef DEBUG_VFS_LOCKS
 	struct vnode *vp = arg;
 
 	ASSERT_VOP_LOCKED(vp, "vfs_knl_assert_locked");
 #endif
 }
 
 static void
 vfs_knl_assert_unlocked(void *arg)
 {
 #ifdef DEBUG_VFS_LOCKS
 	struct vnode *vp = arg;
 
 	ASSERT_VOP_UNLOCKED(vp, "vfs_knl_assert_unlocked");
 #endif
 }
 
 int
 vfs_kqfilter(struct vop_kqfilter_args *ap)
 {
 	struct vnode *vp = ap->a_vp;
 	struct knote *kn = ap->a_kn;
 	struct knlist *knl;
 
 	switch (kn->kn_filter) {
 	case EVFILT_READ:
 		kn->kn_fop = &vfsread_filtops;
 		break;
 	case EVFILT_WRITE:
 		kn->kn_fop = &vfswrite_filtops;
 		break;
 	case EVFILT_VNODE:
 		kn->kn_fop = &vfsvnode_filtops;
 		break;
 	default:
 		return (EINVAL);
 	}
 
 	kn->kn_hook = (caddr_t)vp;
 
 	v_addpollinfo(vp);
 	if (vp->v_pollinfo == NULL)
 		return (ENOMEM);
 	knl = &vp->v_pollinfo->vpi_selinfo.si_note;
 	vhold(vp);
 	knlist_add(knl, kn, 0);
 
 	return (0);
 }
 
 /*
  * Detach knote from vnode
  */
 static void
 filt_vfsdetach(struct knote *kn)
 {
 	struct vnode *vp = (struct vnode *)kn->kn_hook;
 
 	KASSERT(vp->v_pollinfo != NULL, ("Missing v_pollinfo"));
 	knlist_remove(&vp->v_pollinfo->vpi_selinfo.si_note, kn, 0);
 	vdrop(vp);
 }
 
 /*ARGSUSED*/
 static int
 filt_vfsread(struct knote *kn, long hint)
 {
 	struct vnode *vp = (struct vnode *)kn->kn_hook;
 	struct vattr va;
 	int res;
 
 	/*
 	 * filesystem is gone, so set the EOF flag and schedule
 	 * the knote for deletion.
 	 */
 	if (hint == NOTE_REVOKE || (hint == 0 && vp->v_type == VBAD)) {
 		VI_LOCK(vp);
 		kn->kn_flags |= (EV_EOF | EV_ONESHOT);
 		VI_UNLOCK(vp);
 		return (1);
 	}
 
 	if (VOP_GETATTR(vp, &va, curthread->td_ucred))
 		return (0);
 
 	VI_LOCK(vp);
 	kn->kn_data = va.va_size - kn->kn_fp->f_offset;
 	res = (kn->kn_sfflags & NOTE_FILE_POLL) != 0 || kn->kn_data != 0;
 	VI_UNLOCK(vp);
 	return (res);
 }
 
 /*ARGSUSED*/
 static int
 filt_vfswrite(struct knote *kn, long hint)
 {
 	struct vnode *vp = (struct vnode *)kn->kn_hook;
 
 	VI_LOCK(vp);
 
 	/*
 	 * filesystem is gone, so set the EOF flag and schedule
 	 * the knote for deletion.
 	 */
 	if (hint == NOTE_REVOKE || (hint == 0 && vp->v_type == VBAD))
 		kn->kn_flags |= (EV_EOF | EV_ONESHOT);
 
 	kn->kn_data = 0;
 	VI_UNLOCK(vp);
 	return (1);
 }
 
 static int
 filt_vfsvnode(struct knote *kn, long hint)
 {
 	struct vnode *vp = (struct vnode *)kn->kn_hook;
 	int res;
 
 	VI_LOCK(vp);
 	if (kn->kn_sfflags & hint)
 		kn->kn_fflags |= hint;
 	if (hint == NOTE_REVOKE || (hint == 0 && vp->v_type == VBAD)) {
 		kn->kn_flags |= EV_EOF;
 		VI_UNLOCK(vp);
 		return (1);
 	}
 	res = (kn->kn_fflags != 0);
 	VI_UNLOCK(vp);
 	return (res);
 }
 
 /*
  * Returns whether the directory is empty or not.
  * If it is empty, the return value is 0; otherwise
  * the return value is an error value (which may
  * be ENOTEMPTY).
  */
 int
 vfs_emptydir(struct vnode *vp)
 {
 	struct uio uio;
 	struct iovec iov;
 	struct dirent *dirent, *dp, *endp;
 	int error, eof;
 
 	error = 0;
 	eof = 0;
 
 	ASSERT_VOP_LOCKED(vp, "vfs_emptydir");
 
 	dirent = malloc(sizeof(struct dirent), M_TEMP, M_WAITOK);
 	iov.iov_base = dirent;
 	iov.iov_len = sizeof(struct dirent);
 
 	uio.uio_iov = &iov;
 	uio.uio_iovcnt = 1;
 	uio.uio_offset = 0;
 	uio.uio_resid = sizeof(struct dirent);
 	uio.uio_segflg = UIO_SYSSPACE;
 	uio.uio_rw = UIO_READ;
 	uio.uio_td = curthread;
 
 	while (eof == 0 && error == 0) {
 		error = VOP_READDIR(vp, &uio, curthread->td_ucred, &eof,
 		    NULL, NULL);
 		if (error != 0)
 			break;
 		endp = (void *)((uint8_t *)dirent +
 		    sizeof(struct dirent) - uio.uio_resid);
 		for (dp = dirent; dp < endp;
 		     dp = (void *)((uint8_t *)dp + GENERIC_DIRSIZ(dp))) {
 			if (dp->d_type == DT_WHT)
 				continue;
 			if (dp->d_namlen == 0)
 				continue;
 			if (dp->d_type != DT_DIR &&
 			    dp->d_type != DT_UNKNOWN) {
 				error = ENOTEMPTY;
 				break;
 			}
 			if (dp->d_namlen > 2) {
 				error = ENOTEMPTY;
 				break;
 			}
 			if (dp->d_namlen == 1 &&
 			    dp->d_name[0] != '.') {
 				error = ENOTEMPTY;
 				break;
 			}
 			if (dp->d_namlen == 2 &&
 			    dp->d_name[1] != '.') {
 				error = ENOTEMPTY;
 				break;
 			}
 			uio.uio_resid = sizeof(struct dirent);
 		}
 	}
 	free(dirent, M_TEMP);
 	return (error);
 }
 
 int
 vfs_read_dirent(struct vop_readdir_args *ap, struct dirent *dp, off_t off)
 {
 	int error;
 
 	if (dp->d_reclen > ap->a_uio->uio_resid)
 		return (ENAMETOOLONG);
 	error = uiomove(dp, dp->d_reclen, ap->a_uio);
 	if (error) {
 		if (ap->a_ncookies != NULL) {
 			if (ap->a_cookies != NULL)
 				free(ap->a_cookies, M_TEMP);
 			ap->a_cookies = NULL;
 			*ap->a_ncookies = 0;
 		}
 		return (error);
 	}
 	if (ap->a_ncookies == NULL)
 		return (0);
 
 	KASSERT(ap->a_cookies,
 	    ("NULL ap->a_cookies value with non-NULL ap->a_ncookies!"));
 
 	*ap->a_cookies = realloc(*ap->a_cookies,
 	    (*ap->a_ncookies + 1) * sizeof(u_long), M_TEMP, M_WAITOK | M_ZERO);
 	(*ap->a_cookies)[*ap->a_ncookies] = off;
 	*ap->a_ncookies += 1;
 	return (0);
 }
 
 /*
  * Mark for update the access time of the file if the filesystem
  * supports VOP_MARKATIME.  This functionality is used by execve and
  * mmap, so we want to avoid the I/O implied by directly setting
  * va_atime for the sake of efficiency.
  */
 void
 vfs_mark_atime(struct vnode *vp, struct ucred *cred)
 {
 	struct mount *mp;
 
 	mp = vp->v_mount;
 	ASSERT_VOP_LOCKED(vp, "vfs_mark_atime");
 	if (mp != NULL && (mp->mnt_flag & (MNT_NOATIME | MNT_RDONLY)) == 0)
 		(void)VOP_MARKATIME(vp);
 }
 
 /*
  * The purpose of this routine is to remove granularity from accmode_t,
  * reducing it into standard unix access bits - VEXEC, VREAD, VWRITE,
  * VADMIN and VAPPEND.
  *
  * If it returns 0, the caller is supposed to continue with the usual
  * access checks using 'accmode' as modified by this routine.  If it
  * returns nonzero value, the caller is supposed to return that value
  * as errno.
  *
  * Note that after this routine runs, accmode may be zero.
  */
 int
 vfs_unixify_accmode(accmode_t *accmode)
 {
 	/*
 	 * There is no way to specify explicit "deny" rule using
 	 * file mode or POSIX.1e ACLs.
 	 */
 	if (*accmode & VEXPLICIT_DENY) {
 		*accmode = 0;
 		return (0);
 	}
 
 	/*
 	 * None of these can be translated into usual access bits.
 	 * Also, the common case for NFSv4 ACLs is to not contain
 	 * either of these bits. Caller should check for VWRITE
 	 * on the containing directory instead.
 	 */
 	if (*accmode & (VDELETE_CHILD | VDELETE))
 		return (EPERM);
 
 	if (*accmode & VADMIN_PERMS) {
 		*accmode &= ~VADMIN_PERMS;
 		*accmode |= VADMIN;
 	}
 
 	/*
 	 * There is no way to deny VREAD_ATTRIBUTES, VREAD_ACL
 	 * or VSYNCHRONIZE using file mode or POSIX.1e ACL.
 	 */
 	*accmode &= ~(VSTAT_PERMS | VSYNCHRONIZE);
 
 	return (0);
 }
 
 /*
  * Clear out a doomed vnode (if any) and replace it with a new one as long
  * as the fs is not being unmounted. Return the root vnode to the caller.
  */
 static int __noinline
 vfs_cache_root_fallback(struct mount *mp, int flags, struct vnode **vpp)
 {
 	struct vnode *vp;
 	int error;
 
 restart:
 	if (mp->mnt_rootvnode != NULL) {
 		MNT_ILOCK(mp);
 		vp = mp->mnt_rootvnode;
 		if (vp != NULL) {
 			if (!VN_IS_DOOMED(vp)) {
 				vrefact(vp);
 				MNT_IUNLOCK(mp);
 				error = vn_lock(vp, flags);
 				if (error == 0) {
 					*vpp = vp;
 					return (0);
 				}
 				vrele(vp);
 				goto restart;
 			}
 			/*
 			 * Clear the old one.
 			 */
 			mp->mnt_rootvnode = NULL;
 		}
 		MNT_IUNLOCK(mp);
 		if (vp != NULL) {
 			/*
 			 * Paired with a fence in vfs_op_thread_exit().
 			 */
 			atomic_thread_fence_acq();
 			vfs_op_barrier_wait(mp);
 			vrele(vp);
 		}
 	}
 	error = VFS_CACHEDROOT(mp, flags, vpp);
 	if (error != 0)
 		return (error);
 	if (mp->mnt_vfs_ops == 0) {
 		MNT_ILOCK(mp);
 		if (mp->mnt_vfs_ops != 0) {
 			MNT_IUNLOCK(mp);
 			return (0);
 		}
 		if (mp->mnt_rootvnode == NULL) {
 			vrefact(*vpp);
 			mp->mnt_rootvnode = *vpp;
 		} else {
 			if (mp->mnt_rootvnode != *vpp) {
 				if (!VN_IS_DOOMED(mp->mnt_rootvnode)) {
 					panic("%s: mismatch between vnode returned "
 					    " by VFS_CACHEDROOT and the one cached "
 					    " (%p != %p)",
 					    __func__, *vpp, mp->mnt_rootvnode);
 				}
 			}
 		}
 		MNT_IUNLOCK(mp);
 	}
 	return (0);
 }
 
 int
 vfs_cache_root(struct mount *mp, int flags, struct vnode **vpp)
 {
 	struct vnode *vp;
 	int error;
 
 	if (!vfs_op_thread_enter(mp))
 		return (vfs_cache_root_fallback(mp, flags, vpp));
 	vp = (struct vnode *)atomic_load_ptr(&mp->mnt_rootvnode);
 	if (vp == NULL || VN_IS_DOOMED(vp)) {
 		vfs_op_thread_exit(mp);
 		return (vfs_cache_root_fallback(mp, flags, vpp));
 	}
 	vrefact(vp);
 	vfs_op_thread_exit(mp);
 	error = vn_lock(vp, flags);
 	if (error != 0) {
 		vrele(vp);
 		return (vfs_cache_root_fallback(mp, flags, vpp));
 	}
 	*vpp = vp;
 	return (0);
 }
 
 struct vnode *
 vfs_cache_root_clear(struct mount *mp)
 {
 	struct vnode *vp;
 
 	/*
 	 * ops > 0 guarantees there is nobody who can see this vnode
 	 */
 	MPASS(mp->mnt_vfs_ops > 0);
 	vp = mp->mnt_rootvnode;
 	mp->mnt_rootvnode = NULL;
 	return (vp);
 }
 
 void
 vfs_cache_root_set(struct mount *mp, struct vnode *vp)
 {
 
 	MPASS(mp->mnt_vfs_ops > 0);
 	vrefact(vp);
 	mp->mnt_rootvnode = vp;
 }
 
 /*
  * These are helper functions for filesystems to traverse all
  * their vnodes.  See MNT_VNODE_FOREACH_ALL() in sys/mount.h.
  *
  * This interface replaces MNT_VNODE_FOREACH.
  */
 
 
 struct vnode *
 __mnt_vnode_next_all(struct vnode **mvp, struct mount *mp)
 {
 	struct vnode *vp;
 
 	if (should_yield())
 		kern_yield(PRI_USER);
 	MNT_ILOCK(mp);
 	KASSERT((*mvp)->v_mount == mp, ("marker vnode mount list mismatch"));
 	for (vp = TAILQ_NEXT(*mvp, v_nmntvnodes); vp != NULL;
 	    vp = TAILQ_NEXT(vp, v_nmntvnodes)) {
 		/* Allow a racy peek at VIRF_DOOMED to save a lock acquisition. */
 		if (vp->v_type == VMARKER || VN_IS_DOOMED(vp))
 			continue;
 		VI_LOCK(vp);
 		if (VN_IS_DOOMED(vp)) {
 			VI_UNLOCK(vp);
 			continue;
 		}
 		break;
 	}
 	if (vp == NULL) {
 		__mnt_vnode_markerfree_all(mvp, mp);
 		/* MNT_IUNLOCK(mp); -- done in above function */
 		mtx_assert(MNT_MTX(mp), MA_NOTOWNED);
 		return (NULL);
 	}
 	TAILQ_REMOVE(&mp->mnt_nvnodelist, *mvp, v_nmntvnodes);
 	TAILQ_INSERT_AFTER(&mp->mnt_nvnodelist, vp, *mvp, v_nmntvnodes);
 	MNT_IUNLOCK(mp);
 	return (vp);
 }
 
 struct vnode *
 __mnt_vnode_first_all(struct vnode **mvp, struct mount *mp)
 {
 	struct vnode *vp;
 
 	*mvp = vn_alloc_marker(mp);
 	MNT_ILOCK(mp);
 	MNT_REF(mp);
 
 	TAILQ_FOREACH(vp, &mp->mnt_nvnodelist, v_nmntvnodes) {
 		/* Allow a racy peek at VIRF_DOOMED to save a lock acquisition. */
 		if (vp->v_type == VMARKER || VN_IS_DOOMED(vp))
 			continue;
 		VI_LOCK(vp);
 		if (VN_IS_DOOMED(vp)) {
 			VI_UNLOCK(vp);
 			continue;
 		}
 		break;
 	}
 	if (vp == NULL) {
 		MNT_REL(mp);
 		MNT_IUNLOCK(mp);
 		vn_free_marker(*mvp);
 		*mvp = NULL;
 		return (NULL);
 	}
 	TAILQ_INSERT_AFTER(&mp->mnt_nvnodelist, vp, *mvp, v_nmntvnodes);
 	MNT_IUNLOCK(mp);
 	return (vp);
 }
 
 void
 __mnt_vnode_markerfree_all(struct vnode **mvp, struct mount *mp)
 {
 
 	if (*mvp == NULL) {
 		MNT_IUNLOCK(mp);
 		return;
 	}
 
 	mtx_assert(MNT_MTX(mp), MA_OWNED);
 
 	KASSERT((*mvp)->v_mount == mp, ("marker vnode mount list mismatch"));
 	TAILQ_REMOVE(&mp->mnt_nvnodelist, *mvp, v_nmntvnodes);
 	MNT_REL(mp);
 	MNT_IUNLOCK(mp);
 	vn_free_marker(*mvp);
 	*mvp = NULL;
 }
 
 /*
  * These are helper functions for filesystems to traverse their
  * lazy vnodes.  See MNT_VNODE_FOREACH_LAZY() in sys/mount.h
  */
 static void
 mnt_vnode_markerfree_lazy(struct vnode **mvp, struct mount *mp)
 {
 
 	KASSERT((*mvp)->v_mount == mp, ("marker vnode mount list mismatch"));
 
 	MNT_ILOCK(mp);
 	MNT_REL(mp);
 	MNT_IUNLOCK(mp);
 	vn_free_marker(*mvp);
 	*mvp = NULL;
 }
 
 /*
  * Relock the mp mount vnode list lock with the vp vnode interlock in the
  * conventional lock order during mnt_vnode_next_lazy iteration.
  *
  * On entry, the mount vnode list lock is held and the vnode interlock is not.
  * The list lock is dropped and reacquired.  On success, both locks are held.
  * On failure, the mount vnode list lock is held but the vnode interlock is
  * not, and the procedure may have yielded.
  */
 static bool
 mnt_vnode_next_lazy_relock(struct vnode *mvp, struct mount *mp,
     struct vnode *vp)
 {
 	const struct vnode *tmp;
 	bool held, ret;
 
 	VNASSERT(mvp->v_mount == mp && mvp->v_type == VMARKER &&
 	    TAILQ_NEXT(mvp, v_lazylist) != NULL, mvp,
 	    ("%s: bad marker", __func__));
 	VNASSERT(vp->v_mount == mp && vp->v_type != VMARKER, vp,
 	    ("%s: inappropriate vnode", __func__));
 	ASSERT_VI_UNLOCKED(vp, __func__);
 	mtx_assert(&mp->mnt_listmtx, MA_OWNED);
 
 	ret = false;
 
 	TAILQ_REMOVE(&mp->mnt_lazyvnodelist, mvp, v_lazylist);
 	TAILQ_INSERT_BEFORE(vp, mvp, v_lazylist);
 
 	/*
 	 * Use a hold to prevent vp from disappearing while the mount vnode
 	 * list lock is dropped and reacquired.  Normally a hold would be
 	 * acquired with vhold(), but that might try to acquire the vnode
 	 * interlock, which would be a LOR with the mount vnode list lock.
 	 */
 	held = refcount_acquire_if_not_zero(&vp->v_holdcnt);
 	mtx_unlock(&mp->mnt_listmtx);
 	if (!held)
 		goto abort;
 	VI_LOCK(vp);
 	if (!refcount_release_if_not_last(&vp->v_holdcnt)) {
 		vdropl(vp);
 		goto abort;
 	}
 	mtx_lock(&mp->mnt_listmtx);
 
 	/*
 	 * Determine whether the vnode is still the next one after the marker,
 	 * excepting any other markers.  If the vnode has not been doomed by
 	 * vgone() then the hold should have ensured that it remained on the
 	 * lazy list.  If it has been doomed but is still on the lazy list,
 	 * don't abort, but rather skip over it (avoid spinning on doomed
 	 * vnodes).
 	 */
 	tmp = mvp;
 	do {
 		tmp = TAILQ_NEXT(tmp, v_lazylist);
 	} while (tmp != NULL && tmp->v_type == VMARKER);
 	if (tmp != vp) {
 		mtx_unlock(&mp->mnt_listmtx);
 		VI_UNLOCK(vp);
 		goto abort;
 	}
 
 	ret = true;
 	goto out;
 abort:
 	maybe_yield();
 	mtx_lock(&mp->mnt_listmtx);
 out:
 	if (ret)
 		ASSERT_VI_LOCKED(vp, __func__);
 	else
 		ASSERT_VI_UNLOCKED(vp, __func__);
 	mtx_assert(&mp->mnt_listmtx, MA_OWNED);
 	return (ret);
 }
 
 static struct vnode *
 mnt_vnode_next_lazy(struct vnode **mvp, struct mount *mp, mnt_lazy_cb_t *cb,
     void *cbarg)
 {
 	struct vnode *vp, *nvp;
 
 	mtx_assert(&mp->mnt_listmtx, MA_OWNED);
 	KASSERT((*mvp)->v_mount == mp, ("marker vnode mount list mismatch"));
 restart:
 	vp = TAILQ_NEXT(*mvp, v_lazylist);
 	while (vp != NULL) {
 		if (vp->v_type == VMARKER) {
 			vp = TAILQ_NEXT(vp, v_lazylist);
 			continue;
 		}
 		/*
 		 * See if we want to process the vnode. Note we may encounter a
 		 * long string of vnodes we don't care about and hog the list
 		 * as a result. Check for it and requeue the marker.
 		 */
 		if (VN_IS_DOOMED(vp) || !cb(vp, cbarg)) {
 			if (!should_yield()) {
 				vp = TAILQ_NEXT(vp, v_lazylist);
 				continue;
 			}
 			TAILQ_REMOVE(&mp->mnt_lazyvnodelist, *mvp,
 			    v_lazylist);
 			TAILQ_INSERT_AFTER(&mp->mnt_lazyvnodelist, vp, *mvp,
 			    v_lazylist);
 			mtx_unlock(&mp->mnt_listmtx);
 			kern_yield(PRI_USER);
 			mtx_lock(&mp->mnt_listmtx);
 			goto restart;
 		}
 		/*
 		 * Try-lock because this is the wrong lock order.  If that does
 		 * not succeed, drop the mount vnode list lock and try to
 		 * reacquire it and the vnode interlock in the right order.
 		 */
 		if (!VI_TRYLOCK(vp) &&
 		    !mnt_vnode_next_lazy_relock(*mvp, mp, vp))
 			goto restart;
 		KASSERT(vp->v_type != VMARKER, ("locked marker %p", vp));
 		KASSERT(vp->v_mount == mp || vp->v_mount == NULL,
 		    ("alien vnode on the lazy list %p %p", vp, mp));
 		if (vp->v_mount == mp && !VN_IS_DOOMED(vp))
 			break;
 		nvp = TAILQ_NEXT(vp, v_lazylist);
 		VI_UNLOCK(vp);
 		vp = nvp;
 	}
 	TAILQ_REMOVE(&mp->mnt_lazyvnodelist, *mvp, v_lazylist);
 
 	/* Check if we are done */
 	if (vp == NULL) {
 		mtx_unlock(&mp->mnt_listmtx);
 		mnt_vnode_markerfree_lazy(mvp, mp);
 		return (NULL);
 	}
 	TAILQ_INSERT_AFTER(&mp->mnt_lazyvnodelist, vp, *mvp, v_lazylist);
 	mtx_unlock(&mp->mnt_listmtx);
 	ASSERT_VI_LOCKED(vp, "lazy iter");
 	return (vp);
 }
 
 struct vnode *
 __mnt_vnode_next_lazy(struct vnode **mvp, struct mount *mp, mnt_lazy_cb_t *cb,
     void *cbarg)
 {
 
 	if (should_yield())
 		kern_yield(PRI_USER);
 	mtx_lock(&mp->mnt_listmtx);
 	return (mnt_vnode_next_lazy(mvp, mp, cb, cbarg));
 }
 
 struct vnode *
 __mnt_vnode_first_lazy(struct vnode **mvp, struct mount *mp, mnt_lazy_cb_t *cb,
     void *cbarg)
 {
 	struct vnode *vp;
 
 	*mvp = vn_alloc_marker(mp);
 	MNT_ILOCK(mp);
 	MNT_REF(mp);
 	MNT_IUNLOCK(mp);
 
 	mtx_lock(&mp->mnt_listmtx);
 	vp = TAILQ_FIRST(&mp->mnt_lazyvnodelist);
 	if (vp == NULL) {
 		mtx_unlock(&mp->mnt_listmtx);
 		mnt_vnode_markerfree_lazy(mvp, mp);
 		return (NULL);
 	}
 	TAILQ_INSERT_BEFORE(vp, *mvp, v_lazylist);
 	return (mnt_vnode_next_lazy(mvp, mp, cb, cbarg));
 }
 
 void
 __mnt_vnode_markerfree_lazy(struct vnode **mvp, struct mount *mp)
 {
 
 	if (*mvp == NULL)
 		return;
 
 	mtx_lock(&mp->mnt_listmtx);
 	TAILQ_REMOVE(&mp->mnt_lazyvnodelist, *mvp, v_lazylist);
 	mtx_unlock(&mp->mnt_listmtx);
 	mnt_vnode_markerfree_lazy(mvp, mp);
 }
Index: head/sys/ufs/ffs/ffs_snapshot.c
===================================================================
--- head/sys/ufs/ffs/ffs_snapshot.c	(revision 357070)
+++ head/sys/ufs/ffs/ffs_snapshot.c	(revision 357071)
@@ -1,2722 +1,2714 @@
 /*-
  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
  *
  * Copyright 2000 Marshall Kirk McKusick. All Rights Reserved.
  *
  * Further information about snapshots can be obtained from:
  *
  *	Marshall Kirk McKusick		http://www.mckusick.com/softdep/
  *	1614 Oxford Street		mckusick@mckusick.com
  *	Berkeley, CA 94709-1608		+1-510-843-9542
  *	USA
  *
  * 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 MARSHALL KIRK MCKUSICK ``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 MARSHALL KIRK MCKUSICK 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.
  *
  *	@(#)ffs_snapshot.c	8.11 (McKusick) 7/23/00
  */
 
 #include <sys/cdefs.h>
 __FBSDID("$FreeBSD$");
 
 #include "opt_quota.h"
 
 #include <sys/param.h>
 #include <sys/kernel.h>
 #include <sys/systm.h>
 #include <sys/conf.h>
 #include <sys/gsb_crc32.h>
 #include <sys/bio.h>
 #include <sys/buf.h>
 #include <sys/fcntl.h>
 #include <sys/proc.h>
 #include <sys/namei.h>
 #include <sys/sched.h>
 #include <sys/stat.h>
 #include <sys/malloc.h>
 #include <sys/mount.h>
 #include <sys/resource.h>
 #include <sys/resourcevar.h>
 #include <sys/rwlock.h>
 #include <sys/vnode.h>
 
 #include <geom/geom.h>
 
 #include <ufs/ufs/extattr.h>
 #include <ufs/ufs/quota.h>
 #include <ufs/ufs/ufsmount.h>
 #include <ufs/ufs/inode.h>
 #include <ufs/ufs/ufs_extern.h>
 
 #include <ufs/ffs/fs.h>
 #include <ufs/ffs/ffs_extern.h>
 
 #define KERNCRED thread0.td_ucred
 
 #include "opt_ffs.h"
 
 #ifdef NO_FFS_SNAPSHOT
 int
 ffs_snapshot(mp, snapfile)
 	struct mount *mp;
 	char *snapfile;
 {
 	return (EINVAL);
 }
 
 int
 ffs_snapblkfree(fs, devvp, bno, size, inum, vtype, wkhd)
 	struct fs *fs;
 	struct vnode *devvp;
 	ufs2_daddr_t bno;
 	long size;
 	ino_t inum;
 	enum vtype vtype;
 	struct workhead *wkhd;
 {
 	return (EINVAL);
 }
 
 void
 ffs_snapremove(vp)
 	struct vnode *vp;
 {
 }
 
 void
 ffs_snapshot_mount(mp)
 	struct mount *mp;
 {
 }
 
 void
 ffs_snapshot_unmount(mp)
 	struct mount *mp;
 {
 }
 
 void
 ffs_snapgone(ip)
 	struct inode *ip;
 {
 }
 
 int
 ffs_copyonwrite(devvp, bp)
 	struct vnode *devvp;
 	struct buf *bp;
 {
 	return (EINVAL);
 }
 
 void
 ffs_sync_snap(mp, waitfor)
 	struct mount *mp;
 	int waitfor;
 {
 }
 
 #else
 FEATURE(ffs_snapshot, "FFS snapshot support");
 
 LIST_HEAD(, snapdata) snapfree;
 static struct mtx snapfree_lock;
 MTX_SYSINIT(ffs_snapfree, &snapfree_lock, "snapdata free list", MTX_DEF);
 
 static int cgaccount(int, struct vnode *, struct buf *, int);
 static int expunge_ufs1(struct vnode *, struct inode *, struct fs *,
     int (*)(struct vnode *, ufs1_daddr_t *, ufs1_daddr_t *, struct fs *,
     ufs_lbn_t, int), int, int);
 static int indiracct_ufs1(struct vnode *, struct vnode *, int,
     ufs1_daddr_t, ufs_lbn_t, ufs_lbn_t, ufs_lbn_t, ufs_lbn_t, struct fs *,
     int (*)(struct vnode *, ufs1_daddr_t *, ufs1_daddr_t *, struct fs *,
     ufs_lbn_t, int), int);
 static int fullacct_ufs1(struct vnode *, ufs1_daddr_t *, ufs1_daddr_t *,
     struct fs *, ufs_lbn_t, int);
 static int snapacct_ufs1(struct vnode *, ufs1_daddr_t *, ufs1_daddr_t *,
     struct fs *, ufs_lbn_t, int);
 static int mapacct_ufs1(struct vnode *, ufs1_daddr_t *, ufs1_daddr_t *,
     struct fs *, ufs_lbn_t, int);
 static int expunge_ufs2(struct vnode *, struct inode *, struct fs *,
     int (*)(struct vnode *, ufs2_daddr_t *, ufs2_daddr_t *, struct fs *,
     ufs_lbn_t, int), int, int);
 static int indiracct_ufs2(struct vnode *, struct vnode *, int,
     ufs2_daddr_t, ufs_lbn_t, ufs_lbn_t, ufs_lbn_t, ufs_lbn_t, struct fs *,
     int (*)(struct vnode *, ufs2_daddr_t *, ufs2_daddr_t *, struct fs *,
     ufs_lbn_t, int), int);
 static int fullacct_ufs2(struct vnode *, ufs2_daddr_t *, ufs2_daddr_t *,
     struct fs *, ufs_lbn_t, int);
 static int snapacct_ufs2(struct vnode *, ufs2_daddr_t *, ufs2_daddr_t *,
     struct fs *, ufs_lbn_t, int);
 static int mapacct_ufs2(struct vnode *, ufs2_daddr_t *, ufs2_daddr_t *,
     struct fs *, ufs_lbn_t, int);
 static int readblock(struct vnode *vp, struct buf *, ufs2_daddr_t);
 static void try_free_snapdata(struct vnode *devvp);
 static struct snapdata *ffs_snapdata_acquire(struct vnode *devvp);
 static int ffs_bp_snapblk(struct vnode *, struct buf *);
 
 /*
  * To ensure the consistency of snapshots across crashes, we must
  * synchronously write out copied blocks before allowing the
  * originals to be modified. Because of the rather severe speed
  * penalty that this imposes, the code normally only ensures
  * persistence for the filesystem metadata contained within a
  * snapshot. Setting the following flag allows this crash
  * persistence to be enabled for file contents.
  */
 int dopersistence = 0;
 
 #ifdef DIAGNOSTIC
 #include <sys/sysctl.h>
 SYSCTL_INT(_debug, OID_AUTO, dopersistence, CTLFLAG_RW, &dopersistence, 0, "");
 static int snapdebug = 0;
 SYSCTL_INT(_debug, OID_AUTO, snapdebug, CTLFLAG_RW, &snapdebug, 0, "");
 int collectsnapstats = 0;
 SYSCTL_INT(_debug, OID_AUTO, collectsnapstats, CTLFLAG_RW, &collectsnapstats,
 	0, "");
 #endif /* DIAGNOSTIC */
 
 /*
  * Create a snapshot file and initialize it for the filesystem.
  */
 int
 ffs_snapshot(mp, snapfile)
 	struct mount *mp;
 	char *snapfile;
 {
 	ufs2_daddr_t numblks, blkno, *blkp, *snapblklist;
 	int error, cg, snaploc;
 	int i, size, len, loc;
 	ufs2_daddr_t blockno;
 	uint64_t flag;
 	char saved_nice = 0;
 	long redo = 0, snaplistsize = 0;
 	int32_t *lp;
 	void *space;
 	struct fs *copy_fs = NULL, *fs;
 	struct thread *td = curthread;
 	struct inode *ip, *xp;
 	struct buf *bp, *nbp, *ibp;
 	struct nameidata nd;
 	struct mount *wrtmp;
 	struct vattr vat;
 	struct vnode *vp, *xvp, *mvp, *devvp;
 	struct uio auio;
 	struct iovec aiov;
 	struct snapdata *sn;
 	struct ufsmount *ump;
 #ifdef DIAGNOSTIC
 	struct timespec starttime = {0, 0}, endtime;
 #endif
 
 	ump = VFSTOUFS(mp);
 	fs = ump->um_fs;
 	sn = NULL;
 	/*
 	 * At the moment, journaled soft updates cannot support
 	 * taking snapshots.
 	 */
 	if (MOUNTEDSUJ(mp)) {
 		vfs_mount_error(mp, "%s: Snapshots are not yet supported when "
 		    "running with journaled soft updates", fs->fs_fsmnt);
 		return (EOPNOTSUPP);
 	}
 	MNT_ILOCK(mp);
 	flag = mp->mnt_flag;
 	MNT_IUNLOCK(mp);
 	/*
 	 * Need to serialize access to snapshot code per filesystem.
 	 */
 	/*
 	 * Assign a snapshot slot in the superblock.
 	 */
 	UFS_LOCK(ump);
 	for (snaploc = 0; snaploc < FSMAXSNAP; snaploc++)
 		if (fs->fs_snapinum[snaploc] == 0)
 			break;
 	UFS_UNLOCK(ump);
 	if (snaploc == FSMAXSNAP)
 		return (ENOSPC);
 	/*
 	 * Create the snapshot file.
 	 */
 restart:
 	NDINIT(&nd, CREATE, LOCKPARENT | LOCKLEAF | NOCACHE, UIO_SYSSPACE,
 	    snapfile, td);
 	if ((error = namei(&nd)) != 0)
 		return (error);
 	if (nd.ni_vp != NULL) {
 		vput(nd.ni_vp);
 		error = EEXIST;
 	}
 	if (nd.ni_dvp->v_mount != mp)
 		error = EXDEV;
 	if (error) {
 		NDFREE(&nd, NDF_ONLY_PNBUF);
 		if (nd.ni_dvp == nd.ni_vp)
 			vrele(nd.ni_dvp);
 		else
 			vput(nd.ni_dvp);
 		return (error);
 	}
 	VATTR_NULL(&vat);
 	vat.va_type = VREG;
 	vat.va_mode = S_IRUSR;
 	vat.va_vaflags |= VA_EXCLUSIVE;
 	if (VOP_GETWRITEMOUNT(nd.ni_dvp, &wrtmp))
 		wrtmp = NULL;
 	if (wrtmp != mp)
 		panic("ffs_snapshot: mount mismatch");
 	vfs_rel(wrtmp);
 	if (vn_start_write(NULL, &wrtmp, V_NOWAIT) != 0) {
 		NDFREE(&nd, NDF_ONLY_PNBUF);
 		vput(nd.ni_dvp);
 		if ((error = vn_start_write(NULL, &wrtmp,
 		    V_XSLEEP | PCATCH)) != 0)
 			return (error);
 		goto restart;
 	}
 	error = VOP_CREATE(nd.ni_dvp, &nd.ni_vp, &nd.ni_cnd, &vat);
 	VOP_UNLOCK(nd.ni_dvp);
 	if (error) {
 		NDFREE(&nd, NDF_ONLY_PNBUF);
 		vn_finished_write(wrtmp);
 		vrele(nd.ni_dvp);
 		return (error);
 	}
 	vp = nd.ni_vp;
 	vnode_create_vobject(nd.ni_vp, fs->fs_size, td);
 	vp->v_vflag |= VV_SYSTEM;
 	ip = VTOI(vp);
 	devvp = ITODEVVP(ip);
 	/*
 	 * Allocate and copy the last block contents so as to be able
 	 * to set size to that of the filesystem.
 	 */
 	numblks = howmany(fs->fs_size, fs->fs_frag);
 	error = UFS_BALLOC(vp, lblktosize(fs, (off_t)(numblks - 1)),
 	    fs->fs_bsize, KERNCRED, BA_CLRBUF, &bp);
 	if (error)
 		goto out;
 	ip->i_size = lblktosize(fs, (off_t)numblks);
 	DIP_SET(ip, i_size, ip->i_size);
 	UFS_INODE_SET_FLAG(ip, IN_CHANGE | IN_UPDATE);
 	error = readblock(vp, bp, numblks - 1);
 	bawrite(bp);
 	if (error != 0)
 		goto out;
 	/*
 	 * Preallocate critical data structures so that we can copy
 	 * them in without further allocation after we suspend all
 	 * operations on the filesystem. We would like to just release
 	 * the allocated buffers without writing them since they will
 	 * be filled in below once we are ready to go, but this upsets
 	 * the soft update code, so we go ahead and write the new buffers.
 	 *
 	 * Allocate all indirect blocks and mark all of them as not
 	 * needing to be copied.
 	 */
 	for (blkno = UFS_NDADDR; blkno < numblks; blkno += NINDIR(fs)) {
 		error = UFS_BALLOC(vp, lblktosize(fs, (off_t)blkno),
 		    fs->fs_bsize, td->td_ucred, BA_METAONLY, &ibp);
 		if (error)
 			goto out;
 		bawrite(ibp);
 	}
 	/*
 	 * Allocate copies for the superblock and its summary information.
 	 */
 	error = UFS_BALLOC(vp, fs->fs_sblockloc, fs->fs_sbsize, KERNCRED,
 	    0, &nbp);
 	if (error)
 		goto out;
 	bawrite(nbp);
 	blkno = fragstoblks(fs, fs->fs_csaddr);
 	len = howmany(fs->fs_cssize, fs->fs_bsize);
 	for (loc = 0; loc < len; loc++) {
 		error = UFS_BALLOC(vp, lblktosize(fs, (off_t)(blkno + loc)),
 		    fs->fs_bsize, KERNCRED, 0, &nbp);
 		if (error)
 			goto out;
 		bawrite(nbp);
 	}
 	/*
 	 * Allocate all cylinder group blocks.
 	 */
 	for (cg = 0; cg < fs->fs_ncg; cg++) {
 		error = UFS_BALLOC(vp, lfragtosize(fs, cgtod(fs, cg)),
 		    fs->fs_bsize, KERNCRED, 0, &nbp);
 		if (error)
 			goto out;
 		bawrite(nbp);
 		if (cg % 10 == 0)
 			ffs_syncvnode(vp, MNT_WAIT, 0);
 	}
 	/*
 	 * Copy all the cylinder group maps. Although the
 	 * filesystem is still active, we hope that only a few
 	 * cylinder groups will change between now and when we
 	 * suspend operations. Thus, we will be able to quickly
 	 * touch up the few cylinder groups that changed during
 	 * the suspension period.
 	 */
 	len = howmany(fs->fs_ncg, NBBY);
 	space = malloc(len, M_DEVBUF, M_WAITOK|M_ZERO);
 	UFS_LOCK(ump);
 	fs->fs_active = space;
 	UFS_UNLOCK(ump);
 	for (cg = 0; cg < fs->fs_ncg; cg++) {
 		error = UFS_BALLOC(vp, lfragtosize(fs, cgtod(fs, cg)),
 		    fs->fs_bsize, KERNCRED, 0, &nbp);
 		if (error)
 			goto out;
 		error = cgaccount(cg, vp, nbp, 1);
 		bawrite(nbp);
 		if (cg % 10 == 0)
 			ffs_syncvnode(vp, MNT_WAIT, 0);
 		if (error)
 			goto out;
 	}
 	/*
 	 * Change inode to snapshot type file.
 	 */
 	ip->i_flags |= SF_SNAPSHOT;
 	DIP_SET(ip, i_flags, ip->i_flags);
 	UFS_INODE_SET_FLAG(ip, IN_CHANGE | IN_UPDATE);
 	/*
 	 * Ensure that the snapshot is completely on disk.
 	 * Since we have marked it as a snapshot it is safe to
 	 * unlock it as no process will be allowed to write to it.
 	 */
 	if ((error = ffs_syncvnode(vp, MNT_WAIT, 0)) != 0)
 		goto out;
 	VOP_UNLOCK(vp);
 	/*
 	 * All allocations are done, so we can now snapshot the system.
 	 *
 	 * Recind nice scheduling while running with the filesystem suspended.
 	 */
 	if (td->td_proc->p_nice > 0) {
 		struct proc *p;
 
 		p = td->td_proc;
 		PROC_LOCK(p);
 		saved_nice = p->p_nice;
 		sched_nice(p, 0);
 		PROC_UNLOCK(p);
 	}
 	/*
 	 * Suspend operation on filesystem.
 	 */
 	for (;;) {
 		vn_finished_write(wrtmp);
 		if ((error = vfs_write_suspend(vp->v_mount, 0)) != 0) {
 			vn_start_write(NULL, &wrtmp, V_WAIT);
 			vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
 			goto out;
 		}
 		if (mp->mnt_kern_flag & MNTK_SUSPENDED)
 			break;
 		vn_start_write(NULL, &wrtmp, V_WAIT);
 	}
 	vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
 	if (ip->i_effnlink == 0) {
 		error = ENOENT;		/* Snapshot file unlinked */
 		goto out1;
 	}
 #ifdef DIAGNOSTIC
 	if (collectsnapstats)
 		nanotime(&starttime);
 #endif
 
 	/* The last block might have changed.  Copy it again to be sure. */
 	error = UFS_BALLOC(vp, lblktosize(fs, (off_t)(numblks - 1)),
 	    fs->fs_bsize, KERNCRED, BA_CLRBUF, &bp);
 	if (error != 0)
 		goto out1;
 	error = readblock(vp, bp, numblks - 1);
 	bp->b_flags |= B_VALIDSUSPWRT;
 	bawrite(bp);
 	if (error != 0)
 		goto out1;
 	/*
 	 * First, copy all the cylinder group maps that have changed.
 	 */
 	for (cg = 0; cg < fs->fs_ncg; cg++) {
 		if ((ACTIVECGNUM(fs, cg) & ACTIVECGOFF(cg)) != 0)
 			continue;
 		redo++;
 		error = UFS_BALLOC(vp, lfragtosize(fs, cgtod(fs, cg)),
 		    fs->fs_bsize, KERNCRED, 0, &nbp);
 		if (error)
 			goto out1;
 		error = cgaccount(cg, vp, nbp, 2);
 		bawrite(nbp);
 		if (error)
 			goto out1;
 	}
 	/*
 	 * Grab a copy of the superblock and its summary information.
 	 * We delay writing it until the suspension is released below.
 	 */
 	copy_fs = malloc((u_long)fs->fs_bsize, M_UFSMNT, M_WAITOK);
 	bcopy(fs, copy_fs, fs->fs_sbsize);
 	if ((fs->fs_flags & (FS_UNCLEAN | FS_NEEDSFSCK)) == 0)
 		copy_fs->fs_clean = 1;
 	size = fs->fs_bsize < SBLOCKSIZE ? fs->fs_bsize : SBLOCKSIZE;
 	if (fs->fs_sbsize < size)
 		bzero(&((char *)copy_fs)[fs->fs_sbsize],
 		    size - fs->fs_sbsize);
 	size = blkroundup(fs, fs->fs_cssize);
 	if (fs->fs_contigsumsize > 0)
 		size += fs->fs_ncg * sizeof(int32_t);
 	space = malloc((u_long)size, M_UFSMNT, M_WAITOK);
 	copy_fs->fs_csp = space;
 	bcopy(fs->fs_csp, copy_fs->fs_csp, fs->fs_cssize);
 	space = (char *)space + fs->fs_cssize;
 	loc = howmany(fs->fs_cssize, fs->fs_fsize);
 	i = fs->fs_frag - loc % fs->fs_frag;
 	len = (i == fs->fs_frag) ? 0 : i * fs->fs_fsize;
 	if (len > 0) {
 		if ((error = bread(devvp, fsbtodb(fs, fs->fs_csaddr + loc),
 		    len, KERNCRED, &bp)) != 0) {
 			brelse(bp);
 			free(copy_fs->fs_csp, M_UFSMNT);
 			free(copy_fs, M_UFSMNT);
 			copy_fs = NULL;
 			goto out1;
 		}
 		bcopy(bp->b_data, space, (u_int)len);
 		space = (char *)space + len;
 		bp->b_flags |= B_INVAL | B_NOCACHE;
 		brelse(bp);
 	}
 	if (fs->fs_contigsumsize > 0) {
 		copy_fs->fs_maxcluster = lp = space;
 		for (i = 0; i < fs->fs_ncg; i++)
 			*lp++ = fs->fs_contigsumsize;
 	}
 	/*
 	 * We must check for active files that have been unlinked
 	 * (e.g., with a zero link count). We have to expunge all
 	 * trace of these files from the snapshot so that they are
 	 * not reclaimed prematurely by fsck or unnecessarily dumped.
 	 * We turn off the MNTK_SUSPENDED flag to avoid a panic from
 	 * spec_strategy about writing on a suspended filesystem.
 	 * Note that we skip unlinked snapshot files as they will
 	 * be handled separately below.
 	 *
 	 * We also calculate the needed size for the snapshot list.
 	 */
 	snaplistsize = fs->fs_ncg + howmany(fs->fs_cssize, fs->fs_bsize) +
 	    FSMAXSNAP + 1 /* superblock */ + 1 /* last block */ + 1 /* size */;
 	MNT_ILOCK(mp);
 	mp->mnt_kern_flag &= ~MNTK_SUSPENDED;
 	MNT_IUNLOCK(mp);
 loop:
 	MNT_VNODE_FOREACH_ALL(xvp, mp, mvp) {
 		if ((xvp->v_usecount == 0 &&
 		     (xvp->v_iflag & (VI_OWEINACT | VI_DOINGINACT)) == 0) ||
 		    xvp->v_type == VNON ||
 		    IS_SNAPSHOT(VTOI(xvp))) {
 			VI_UNLOCK(xvp);
 			continue;
 		}
 		/*
 		 * We can skip parent directory vnode because it must have
 		 * this snapshot file in it.
 		 */
 		if (xvp == nd.ni_dvp) {
 			VI_UNLOCK(xvp);
 			continue;
 		}
 		vholdl(xvp);
 		if (vn_lock(xvp, LK_EXCLUSIVE | LK_INTERLOCK) != 0) {
 			MNT_VNODE_FOREACH_ALL_ABORT(mp, mvp);
 			vdrop(xvp);
 			goto loop;
 		}
 		VI_LOCK(xvp);
 		if (xvp->v_usecount == 0 &&
 		    (xvp->v_iflag & (VI_OWEINACT | VI_DOINGINACT)) == 0) {
 			VI_UNLOCK(xvp);
 			VOP_UNLOCK(xvp);
 			vdrop(xvp);
 			continue;
 		}
 		VI_UNLOCK(xvp);
 #ifdef DIAGNOSTIC
 		if (snapdebug)
 			vn_printf(xvp, "ffs_snapshot: busy vnode ");
 #endif
 		if (VOP_GETATTR(xvp, &vat, td->td_ucred) == 0 &&
 		    vat.va_nlink > 0) {
 			VOP_UNLOCK(xvp);
 			vdrop(xvp);
 			continue;
 		}
 		xp = VTOI(xvp);
 		if (ffs_checkfreefile(copy_fs, vp, xp->i_number)) {
 			VOP_UNLOCK(xvp);
 			vdrop(xvp);
 			continue;
 		}
 		/*
 		 * If there is a fragment, clear it here.
 		 */
 		blkno = 0;
 		loc = howmany(xp->i_size, fs->fs_bsize) - 1;
 		if (loc < UFS_NDADDR) {
 			len = fragroundup(fs, blkoff(fs, xp->i_size));
 			if (len != 0 && len < fs->fs_bsize) {
 				ffs_blkfree(ump, copy_fs, vp,
 				    DIP(xp, i_db[loc]), len, xp->i_number,
 				    xvp->v_type, NULL, SINGLETON_KEY);
 				blkno = DIP(xp, i_db[loc]);
 				DIP_SET(xp, i_db[loc], 0);
 			}
 		}
 		snaplistsize += 1;
 		if (I_IS_UFS1(xp))
 			error = expunge_ufs1(vp, xp, copy_fs, fullacct_ufs1,
 			    BLK_NOCOPY, 1);
 		else
 			error = expunge_ufs2(vp, xp, copy_fs, fullacct_ufs2,
 			    BLK_NOCOPY, 1);
 		if (blkno)
 			DIP_SET(xp, i_db[loc], blkno);
 		if (!error)
 			error = ffs_freefile(ump, copy_fs, vp, xp->i_number,
 			    xp->i_mode, NULL);
 		VOP_UNLOCK(xvp);
 		vdrop(xvp);
 		if (error) {
 			free(copy_fs->fs_csp, M_UFSMNT);
 			free(copy_fs, M_UFSMNT);
 			copy_fs = NULL;
 			MNT_VNODE_FOREACH_ALL_ABORT(mp, mvp);
 			goto out1;
 		}
 	}
 	/*
 	 * Erase the journal file from the snapshot.
 	 */
 	if (fs->fs_flags & FS_SUJ) {
 		error = softdep_journal_lookup(mp, &xvp);
 		if (error) {
 			free(copy_fs->fs_csp, M_UFSMNT);
 			free(copy_fs, M_UFSMNT);
 			copy_fs = NULL;
 			goto out1;
 		}
 		xp = VTOI(xvp);
 		if (I_IS_UFS1(xp))
 			error = expunge_ufs1(vp, xp, copy_fs, fullacct_ufs1,
 			    BLK_NOCOPY, 0);
 		else
 			error = expunge_ufs2(vp, xp, copy_fs, fullacct_ufs2,
 			    BLK_NOCOPY, 0);
 		vput(xvp);
 	}
 	/*
 	 * Acquire a lock on the snapdata structure, creating it if necessary.
 	 */
 	sn = ffs_snapdata_acquire(devvp);
 	/* 
 	 * Change vnode to use shared snapshot lock instead of the original
 	 * private lock.
 	 */
 	vp->v_vnlock = &sn->sn_lock;
 	lockmgr(&vp->v_lock, LK_RELEASE, NULL);
 	xp = TAILQ_FIRST(&sn->sn_head);
 	/*
 	 * If this is the first snapshot on this filesystem, then we need
 	 * to allocate the space for the list of preallocated snapshot blocks.
 	 * This list will be refined below, but this preliminary one will
 	 * keep us out of deadlock until the full one is ready.
 	 */
 	if (xp == NULL) {
 		snapblklist = malloc(snaplistsize * sizeof(daddr_t),
 		    M_UFSMNT, M_WAITOK);
 		blkp = &snapblklist[1];
 		*blkp++ = lblkno(fs, fs->fs_sblockloc);
 		blkno = fragstoblks(fs, fs->fs_csaddr);
 		for (cg = 0; cg < fs->fs_ncg; cg++) {
 			if (fragstoblks(fs, cgtod(fs, cg) > blkno))
 				break;
 			*blkp++ = fragstoblks(fs, cgtod(fs, cg));
 		}
 		len = howmany(fs->fs_cssize, fs->fs_bsize);
 		for (loc = 0; loc < len; loc++)
 			*blkp++ = blkno + loc;
 		for (; cg < fs->fs_ncg; cg++)
 			*blkp++ = fragstoblks(fs, cgtod(fs, cg));
 		snapblklist[0] = blkp - snapblklist;
 		VI_LOCK(devvp);
 		if (sn->sn_blklist != NULL)
 			panic("ffs_snapshot: non-empty list");
 		sn->sn_blklist = snapblklist;
 		sn->sn_listsize = blkp - snapblklist;
 		VI_UNLOCK(devvp);
 	}
 	/*
 	 * Record snapshot inode. Since this is the newest snapshot,
 	 * it must be placed at the end of the list.
 	 */
 	VI_LOCK(devvp);
 	fs->fs_snapinum[snaploc] = ip->i_number;
 	if (ip->i_nextsnap.tqe_prev != 0)
 		panic("ffs_snapshot: %ju already on list",
 		    (uintmax_t)ip->i_number);
 	TAILQ_INSERT_TAIL(&sn->sn_head, ip, i_nextsnap);
 	devvp->v_vflag |= VV_COPYONWRITE;
 	VI_UNLOCK(devvp);
 	ASSERT_VOP_LOCKED(vp, "ffs_snapshot vp");
 out1:
 	KASSERT((sn != NULL && copy_fs != NULL && error == 0) ||
 		(sn == NULL && copy_fs == NULL && error != 0),
 		("email phk@ and mckusick@"));
 	/*
 	 * Resume operation on filesystem.
 	 */
 	vfs_write_resume(vp->v_mount, VR_START_WRITE | VR_NO_SUSPCLR);
 #ifdef DIAGNOSTIC
 	if (collectsnapstats && starttime.tv_sec > 0) {
 		nanotime(&endtime);
 		timespecsub(&endtime, &starttime, &endtime);
 		printf("%s: suspended %ld.%03ld sec, redo %ld of %d\n",
 		    vp->v_mount->mnt_stat.f_mntonname, (long)endtime.tv_sec,
 		    endtime.tv_nsec / 1000000, redo, fs->fs_ncg);
 	}
 #endif
 	if (copy_fs == NULL)
 		goto out;
 	/*
 	 * Copy allocation information from all the snapshots in
 	 * this snapshot and then expunge them from its view.
 	 */
 	TAILQ_FOREACH(xp, &sn->sn_head, i_nextsnap) {
 		if (xp == ip)
 			break;
 		if (I_IS_UFS1(xp))
 			error = expunge_ufs1(vp, xp, fs, snapacct_ufs1,
 			    BLK_SNAP, 0);
 		else
 			error = expunge_ufs2(vp, xp, fs, snapacct_ufs2,
 			    BLK_SNAP, 0);
 		if (error == 0 && xp->i_effnlink == 0) {
 			error = ffs_freefile(ump,
 					     copy_fs,
 					     vp,
 					     xp->i_number,
 					     xp->i_mode, NULL);
 		}
 		if (error) {
 			fs->fs_snapinum[snaploc] = 0;
 			goto done;
 		}
 	}
 	/*
 	 * Allocate space for the full list of preallocated snapshot blocks.
 	 */
 	snapblklist = malloc(snaplistsize * sizeof(daddr_t),
 	    M_UFSMNT, M_WAITOK);
 	ip->i_snapblklist = &snapblklist[1];
 	/*
 	 * Expunge the blocks used by the snapshots from the set of
 	 * blocks marked as used in the snapshot bitmaps. Also, collect
 	 * the list of allocated blocks in i_snapblklist.
 	 */
 	if (I_IS_UFS1(ip))
 		error = expunge_ufs1(vp, ip, copy_fs, mapacct_ufs1,
 		    BLK_SNAP, 0);
 	else
 		error = expunge_ufs2(vp, ip, copy_fs, mapacct_ufs2,
 		    BLK_SNAP, 0);
 	if (error) {
 		fs->fs_snapinum[snaploc] = 0;
 		free(snapblklist, M_UFSMNT);
 		goto done;
 	}
 	if (snaplistsize < ip->i_snapblklist - snapblklist)
 		panic("ffs_snapshot: list too small");
 	snaplistsize = ip->i_snapblklist - snapblklist;
 	snapblklist[0] = snaplistsize;
 	ip->i_snapblklist = 0;
 	/*
 	 * Write out the list of allocated blocks to the end of the snapshot.
 	 */
 	auio.uio_iov = &aiov;
 	auio.uio_iovcnt = 1;
 	aiov.iov_base = (void *)snapblklist;
 	aiov.iov_len = snaplistsize * sizeof(daddr_t);
 	auio.uio_resid = aiov.iov_len;
 	auio.uio_offset = ip->i_size;
 	auio.uio_segflg = UIO_SYSSPACE;
 	auio.uio_rw = UIO_WRITE;
 	auio.uio_td = td;
 	if ((error = VOP_WRITE(vp, &auio, IO_UNIT, td->td_ucred)) != 0) {
 		fs->fs_snapinum[snaploc] = 0;
 		free(snapblklist, M_UFSMNT);
 		goto done;
 	}
 	/*
 	 * Write the superblock and its summary information
 	 * to the snapshot.
 	 */
 	blkno = fragstoblks(fs, fs->fs_csaddr);
 	len = howmany(fs->fs_cssize, fs->fs_bsize);
 	space = copy_fs->fs_csp;
 	for (loc = 0; loc < len; loc++) {
 		error = bread(vp, blkno + loc, fs->fs_bsize, KERNCRED, &nbp);
 		if (error) {
 			fs->fs_snapinum[snaploc] = 0;
 			free(snapblklist, M_UFSMNT);
 			goto done;
 		}
 		bcopy(space, nbp->b_data, fs->fs_bsize);
 		space = (char *)space + fs->fs_bsize;
 		bawrite(nbp);
 	}
 	error = bread(vp, lblkno(fs, fs->fs_sblockloc), fs->fs_bsize,
 	    KERNCRED, &nbp);
 	if (error) {
 		brelse(nbp);
 	} else {
 		loc = blkoff(fs, fs->fs_sblockloc);
 		copy_fs->fs_fmod = 0;
 		copy_fs->fs_ckhash = ffs_calc_sbhash(copy_fs);
 		bcopy((char *)copy_fs, &nbp->b_data[loc], (u_int)fs->fs_sbsize);
 		bawrite(nbp);
 	}
 	/*
 	 * As this is the newest list, it is the most inclusive, so
 	 * should replace the previous list.
 	 */
 	VI_LOCK(devvp);
 	space = sn->sn_blklist;
 	sn->sn_blklist = snapblklist;
 	sn->sn_listsize = snaplistsize;
 	VI_UNLOCK(devvp);
 	if (space != NULL)
 		free(space, M_UFSMNT);
 	/*
 	 * Preallocate all the direct blocks in the snapshot inode so
 	 * that we never have to write the inode itself to commit an
 	 * update to the contents of the snapshot. Note that once
 	 * created, the size of the snapshot will never change, so
 	 * there will never be a need to write the inode except to
 	 * update the non-integrity-critical time fields and
 	 * allocated-block count.
 	 */
 	for (blockno = 0; blockno < UFS_NDADDR; blockno++) {
 		if (DIP(ip, i_db[blockno]) != 0)
 			continue;
 		error = UFS_BALLOC(vp, lblktosize(fs, blockno),
 		    fs->fs_bsize, KERNCRED, BA_CLRBUF, &bp);
 		if (error)
 			break;
 		error = readblock(vp, bp, blockno);
 		bawrite(bp);
 		if (error != 0)
 			break;
 	}
 done:
 	free(copy_fs->fs_csp, M_UFSMNT);
 	free(copy_fs, M_UFSMNT);
 	copy_fs = NULL;
 out:
 	NDFREE(&nd, NDF_ONLY_PNBUF);
 	if (saved_nice > 0) {
 		struct proc *p;
 
 		p = td->td_proc;
 		PROC_LOCK(p);
 		sched_nice(td->td_proc, saved_nice);
 		PROC_UNLOCK(td->td_proc);
 	}
 	UFS_LOCK(ump);
 	if (fs->fs_active != 0) {
 		free(fs->fs_active, M_DEVBUF);
 		fs->fs_active = 0;
 	}
 	UFS_UNLOCK(ump);
 	MNT_ILOCK(mp);
 	mp->mnt_flag = (mp->mnt_flag & MNT_QUOTA) | (flag & ~MNT_QUOTA);
 	MNT_IUNLOCK(mp);
 	if (error)
 		(void) ffs_truncate(vp, (off_t)0, 0, NOCRED);
 	(void) ffs_syncvnode(vp, MNT_WAIT, 0);
 	if (error)
 		vput(vp);
 	else
 		VOP_UNLOCK(vp);
 	vrele(nd.ni_dvp);
 	vn_finished_write(wrtmp);
 	process_deferred_inactive(mp);
 	return (error);
 }
 
 /*
  * Copy a cylinder group map. All the unallocated blocks are marked
  * BLK_NOCOPY so that the snapshot knows that it need not copy them
  * if they are later written. If passno is one, then this is a first
  * pass, so only setting needs to be done. If passno is 2, then this
  * is a revision to a previous pass which must be undone as the
  * replacement pass is done.
  */
 static int
 cgaccount(cg, vp, nbp, passno)
 	int cg;
 	struct vnode *vp;
 	struct buf *nbp;
 	int passno;
 {
 	struct buf *bp, *ibp;
 	struct inode *ip;
 	struct cg *cgp;
 	struct fs *fs;
 	ufs2_daddr_t base, numblks;
 	int error, len, loc, indiroff;
 
 	ip = VTOI(vp);
 	fs = ITOFS(ip);
 	if ((error = ffs_getcg(fs, ITODEVVP(ip), cg, 0, &bp, &cgp)) != 0)
 		return (error);
 	UFS_LOCK(ITOUMP(ip));
 	ACTIVESET(fs, cg);
 	/*
 	 * Recomputation of summary information might not have been performed
 	 * at mount time.  Sync up summary information for current cylinder
 	 * group while data is in memory to ensure that result of background
 	 * fsck is slightly more consistent.
 	 */
 	fs->fs_cs(fs, cg) = cgp->cg_cs;
 	UFS_UNLOCK(ITOUMP(ip));
 	bcopy(bp->b_data, nbp->b_data, fs->fs_cgsize);
 	if (fs->fs_cgsize < fs->fs_bsize)
 		bzero(&nbp->b_data[fs->fs_cgsize],
 		    fs->fs_bsize - fs->fs_cgsize);
 	cgp = (struct cg *)nbp->b_data;
 	bqrelse(bp);
 	if (passno == 2)
 		nbp->b_flags |= B_VALIDSUSPWRT;
 	numblks = howmany(fs->fs_size, fs->fs_frag);
 	len = howmany(fs->fs_fpg, fs->fs_frag);
 	base = cgbase(fs, cg) / fs->fs_frag;
 	if (base + len >= numblks)
 		len = numblks - base - 1;
 	loc = 0;
 	if (base < UFS_NDADDR) {
 		for ( ; loc < UFS_NDADDR; loc++) {
 			if (ffs_isblock(fs, cg_blksfree(cgp), loc))
 				DIP_SET(ip, i_db[loc], BLK_NOCOPY);
 			else if (passno == 2 && DIP(ip, i_db[loc])== BLK_NOCOPY)
 				DIP_SET(ip, i_db[loc], 0);
 			else if (passno == 1 && DIP(ip, i_db[loc])== BLK_NOCOPY)
 				panic("ffs_snapshot: lost direct block");
 		}
 	}
 	error = UFS_BALLOC(vp, lblktosize(fs, (off_t)(base + loc)),
 	    fs->fs_bsize, KERNCRED, BA_METAONLY, &ibp);
 	if (error) {
 		goto out;
 	}
 	indiroff = (base + loc - UFS_NDADDR) % NINDIR(fs);
 	for ( ; loc < len; loc++, indiroff++) {
 		if (indiroff >= NINDIR(fs)) {
 			if (passno == 2)
 				ibp->b_flags |= B_VALIDSUSPWRT;
 			bawrite(ibp);
 			error = UFS_BALLOC(vp,
 			    lblktosize(fs, (off_t)(base + loc)),
 			    fs->fs_bsize, KERNCRED, BA_METAONLY, &ibp);
 			if (error) {
 				goto out;
 			}
 			indiroff = 0;
 		}
 		if (I_IS_UFS1(ip)) {
 			if (ffs_isblock(fs, cg_blksfree(cgp), loc))
 				((ufs1_daddr_t *)(ibp->b_data))[indiroff] =
 				    BLK_NOCOPY;
 			else if (passno == 2 && ((ufs1_daddr_t *)(ibp->b_data))
 			    [indiroff] == BLK_NOCOPY)
 				((ufs1_daddr_t *)(ibp->b_data))[indiroff] = 0;
 			else if (passno == 1 && ((ufs1_daddr_t *)(ibp->b_data))
 			    [indiroff] == BLK_NOCOPY)
 				panic("ffs_snapshot: lost indirect block");
 			continue;
 		}
 		if (ffs_isblock(fs, cg_blksfree(cgp), loc))
 			((ufs2_daddr_t *)(ibp->b_data))[indiroff] = BLK_NOCOPY;
 		else if (passno == 2 &&
 		    ((ufs2_daddr_t *)(ibp->b_data)) [indiroff] == BLK_NOCOPY)
 			((ufs2_daddr_t *)(ibp->b_data))[indiroff] = 0;
 		else if (passno == 1 &&
 		    ((ufs2_daddr_t *)(ibp->b_data)) [indiroff] == BLK_NOCOPY)
 			panic("ffs_snapshot: lost indirect block");
 	}
 	if (passno == 2)
 		ibp->b_flags |= B_VALIDSUSPWRT;
 	bdwrite(ibp);
 out:
 	/*
 	 * We have to calculate the crc32c here rather than just setting the
 	 * BX_CYLGRP b_xflags because the allocation of the block for the
 	 * the cylinder group map will always be a full size block (fs_bsize)
 	 * even though the cylinder group may be smaller (fs_cgsize). The
 	 * crc32c must be computed only over fs_cgsize whereas the BX_CYLGRP
 	 * flag causes it to be computed over the size of the buffer.
 	 */
 	if ((fs->fs_metackhash & CK_CYLGRP) != 0) {
 		((struct cg *)nbp->b_data)->cg_ckhash = 0;
 		((struct cg *)nbp->b_data)->cg_ckhash =
 		    calculate_crc32c(~0L, nbp->b_data, fs->fs_cgsize);
 	}
 	return (error);
 }
 
 /*
  * Before expunging a snapshot inode, note all the
  * blocks that it claims with BLK_SNAP so that fsck will
  * be able to account for those blocks properly and so
  * that this snapshot knows that it need not copy them
  * if the other snapshot holding them is freed. This code
  * is reproduced once each for UFS1 and UFS2.
  */
 static int
 expunge_ufs1(snapvp, cancelip, fs, acctfunc, expungetype, clearmode)
 	struct vnode *snapvp;
 	struct inode *cancelip;
 	struct fs *fs;
 	int (*acctfunc)(struct vnode *, ufs1_daddr_t *, ufs1_daddr_t *,
 	    struct fs *, ufs_lbn_t, int);
 	int expungetype;
 	int clearmode;
 {
 	int i, error, indiroff;
 	ufs_lbn_t lbn, rlbn;
 	ufs2_daddr_t len, blkno, numblks, blksperindir;
 	struct ufs1_dinode *dip;
 	struct thread *td = curthread;
 	struct buf *bp;
 
 	/*
 	 * Prepare to expunge the inode. If its inode block has not
 	 * yet been copied, then allocate and fill the copy.
 	 */
 	lbn = fragstoblks(fs, ino_to_fsba(fs, cancelip->i_number));
 	blkno = 0;
 	if (lbn < UFS_NDADDR) {
 		blkno = VTOI(snapvp)->i_din1->di_db[lbn];
 	} else {
 		if (DOINGSOFTDEP(snapvp))
 			softdep_prealloc(snapvp, MNT_WAIT);
 		td->td_pflags |= TDP_COWINPROGRESS;
 		error = ffs_balloc_ufs1(snapvp, lblktosize(fs, (off_t)lbn),
 		   fs->fs_bsize, KERNCRED, BA_METAONLY, &bp);
 		td->td_pflags &= ~TDP_COWINPROGRESS;
 		if (error)
 			return (error);
 		indiroff = (lbn - UFS_NDADDR) % NINDIR(fs);
 		blkno = ((ufs1_daddr_t *)(bp->b_data))[indiroff];
 		bqrelse(bp);
 	}
 	if (blkno != 0) {
 		if ((error = bread(snapvp, lbn, fs->fs_bsize, KERNCRED, &bp)))
 			return (error);
 	} else {
 		error = ffs_balloc_ufs1(snapvp, lblktosize(fs, (off_t)lbn),
 		    fs->fs_bsize, KERNCRED, 0, &bp);
 		if (error)
 			return (error);
 		if ((error = readblock(snapvp, bp, lbn)) != 0)
 			return (error);
 	}
 	/*
 	 * Set a snapshot inode to be a zero length file, regular files
 	 * or unlinked snapshots to be completely unallocated.
 	 */
 	dip = (struct ufs1_dinode *)bp->b_data +
 	    ino_to_fsbo(fs, cancelip->i_number);
 	if (clearmode || cancelip->i_effnlink == 0)
 		dip->di_mode = 0;
 	dip->di_size = 0;
 	dip->di_blocks = 0;
 	dip->di_flags &= ~SF_SNAPSHOT;
 	bzero(&dip->di_db[0], (UFS_NDADDR + UFS_NIADDR) * sizeof(ufs1_daddr_t));
 	bdwrite(bp);
 	/*
 	 * Now go through and expunge all the blocks in the file
 	 * using the function requested.
 	 */
 	numblks = howmany(cancelip->i_size, fs->fs_bsize);
 	if ((error = (*acctfunc)(snapvp, &cancelip->i_din1->di_db[0],
 	    &cancelip->i_din1->di_db[UFS_NDADDR], fs, 0, expungetype)))
 		return (error);
 	if ((error = (*acctfunc)(snapvp, &cancelip->i_din1->di_ib[0],
 	    &cancelip->i_din1->di_ib[UFS_NIADDR], fs, -1, expungetype)))
 		return (error);
 	blksperindir = 1;
 	lbn = -UFS_NDADDR;
 	len = numblks - UFS_NDADDR;
 	rlbn = UFS_NDADDR;
 	for (i = 0; len > 0 && i < UFS_NIADDR; i++) {
 		error = indiracct_ufs1(snapvp, ITOV(cancelip), i,
 		    cancelip->i_din1->di_ib[i], lbn, rlbn, len,
 		    blksperindir, fs, acctfunc, expungetype);
 		if (error)
 			return (error);
 		blksperindir *= NINDIR(fs);
 		lbn -= blksperindir + 1;
 		len -= blksperindir;
 		rlbn += blksperindir;
 	}
 	return (0);
 }
 
 /*
  * Descend an indirect block chain for vnode cancelvp accounting for all
  * its indirect blocks in snapvp.
  */ 
 static int
 indiracct_ufs1(snapvp, cancelvp, level, blkno, lbn, rlbn, remblks,
 	    blksperindir, fs, acctfunc, expungetype)
 	struct vnode *snapvp;
 	struct vnode *cancelvp;
 	int level;
 	ufs1_daddr_t blkno;
 	ufs_lbn_t lbn;
 	ufs_lbn_t rlbn;
 	ufs_lbn_t remblks;
 	ufs_lbn_t blksperindir;
 	struct fs *fs;
 	int (*acctfunc)(struct vnode *, ufs1_daddr_t *, ufs1_daddr_t *,
 	    struct fs *, ufs_lbn_t, int);
 	int expungetype;
 {
 	int error, num, i;
 	ufs_lbn_t subblksperindir;
 	struct indir indirs[UFS_NIADDR + 2];
 	ufs1_daddr_t last, *bap;
 	struct buf *bp;
 
 	if (blkno == 0) {
 		if (expungetype == BLK_NOCOPY)
 			return (0);
 		panic("indiracct_ufs1: missing indir");
 	}
 	if ((error = ufs_getlbns(cancelvp, rlbn, indirs, &num)) != 0)
 		return (error);
 	if (lbn != indirs[num - 1 - level].in_lbn || num < 2)
 		panic("indiracct_ufs1: botched params");
 	/*
 	 * We have to expand bread here since it will deadlock looking
 	 * up the block number for any blocks that are not in the cache.
 	 */
 	bp = getblk(cancelvp, lbn, fs->fs_bsize, 0, 0, 0);
 	bp->b_blkno = fsbtodb(fs, blkno);
 	if ((bp->b_flags & (B_DONE | B_DELWRI)) == 0 &&
 	    (error = readblock(cancelvp, bp, fragstoblks(fs, blkno)))) {
 		brelse(bp);
 		return (error);
 	}
 	/*
 	 * Account for the block pointers in this indirect block.
 	 */
 	last = howmany(remblks, blksperindir);
 	if (last > NINDIR(fs))
 		last = NINDIR(fs);
 	bap = malloc(fs->fs_bsize, M_DEVBUF, M_WAITOK);
 	bcopy(bp->b_data, (caddr_t)bap, fs->fs_bsize);
 	bqrelse(bp);
 	error = (*acctfunc)(snapvp, &bap[0], &bap[last], fs,
 	    level == 0 ? rlbn : -1, expungetype);
 	if (error || level == 0)
 		goto out;
 	/*
 	 * Account for the block pointers in each of the indirect blocks
 	 * in the levels below us.
 	 */
 	subblksperindir = blksperindir / NINDIR(fs);
 	for (lbn++, level--, i = 0; i < last; i++) {
 		error = indiracct_ufs1(snapvp, cancelvp, level, bap[i], lbn,
 		    rlbn, remblks, subblksperindir, fs, acctfunc, expungetype);
 		if (error)
 			goto out;
 		rlbn += blksperindir;
 		lbn -= blksperindir;
 		remblks -= blksperindir;
 	}
 out:
 	free(bap, M_DEVBUF);
 	return (error);
 }
 
 /*
  * Do both snap accounting and map accounting.
  */
 static int
 fullacct_ufs1(vp, oldblkp, lastblkp, fs, lblkno, exptype)
 	struct vnode *vp;
 	ufs1_daddr_t *oldblkp, *lastblkp;
 	struct fs *fs;
 	ufs_lbn_t lblkno;
 	int exptype;	/* BLK_SNAP or BLK_NOCOPY */
 {
 	int error;
 
 	if ((error = snapacct_ufs1(vp, oldblkp, lastblkp, fs, lblkno, exptype)))
 		return (error);
 	return (mapacct_ufs1(vp, oldblkp, lastblkp, fs, lblkno, exptype));
 }
 
 /*
  * Identify a set of blocks allocated in a snapshot inode.
  */
 static int
 snapacct_ufs1(vp, oldblkp, lastblkp, fs, lblkno, expungetype)
 	struct vnode *vp;
 	ufs1_daddr_t *oldblkp, *lastblkp;
 	struct fs *fs;
 	ufs_lbn_t lblkno;
 	int expungetype;	/* BLK_SNAP or BLK_NOCOPY */
 {
 	struct inode *ip = VTOI(vp);
 	ufs1_daddr_t blkno, *blkp;
 	ufs_lbn_t lbn;
 	struct buf *ibp;
 	int error;
 
 	for ( ; oldblkp < lastblkp; oldblkp++) {
 		blkno = *oldblkp;
 		if (blkno == 0 || blkno == BLK_NOCOPY || blkno == BLK_SNAP)
 			continue;
 		lbn = fragstoblks(fs, blkno);
 		if (lbn < UFS_NDADDR) {
 			blkp = &ip->i_din1->di_db[lbn];
 			UFS_INODE_SET_FLAG(ip, IN_CHANGE | IN_UPDATE);
 		} else {
 			error = ffs_balloc_ufs1(vp, lblktosize(fs, (off_t)lbn),
 			    fs->fs_bsize, KERNCRED, BA_METAONLY, &ibp);
 			if (error)
 				return (error);
 			blkp = &((ufs1_daddr_t *)(ibp->b_data))
 			    [(lbn - UFS_NDADDR) % NINDIR(fs)];
 		}
 		/*
 		 * If we are expunging a snapshot vnode and we
 		 * find a block marked BLK_NOCOPY, then it is
 		 * one that has been allocated to this snapshot after
 		 * we took our current snapshot and can be ignored.
 		 */
 		if (expungetype == BLK_SNAP && *blkp == BLK_NOCOPY) {
 			if (lbn >= UFS_NDADDR)
 				brelse(ibp);
 		} else {
 			if (*blkp != 0)
 				panic("snapacct_ufs1: bad block");
 			*blkp = expungetype;
 			if (lbn >= UFS_NDADDR)
 				bdwrite(ibp);
 		}
 	}
 	return (0);
 }
 
 /*
  * Account for a set of blocks allocated in a snapshot inode.
  */
 static int
 mapacct_ufs1(vp, oldblkp, lastblkp, fs, lblkno, expungetype)
 	struct vnode *vp;
 	ufs1_daddr_t *oldblkp, *lastblkp;
 	struct fs *fs;
 	ufs_lbn_t lblkno;
 	int expungetype;
 {
 	ufs1_daddr_t blkno;
 	struct inode *ip;
 	ino_t inum;
 	int acctit;
 
 	ip = VTOI(vp);
 	inum = ip->i_number;
 	if (lblkno == -1)
 		acctit = 0;
 	else
 		acctit = 1;
 	for ( ; oldblkp < lastblkp; oldblkp++, lblkno++) {
 		blkno = *oldblkp;
 		if (blkno == 0 || blkno == BLK_NOCOPY)
 			continue;
 		if (acctit && expungetype == BLK_SNAP && blkno != BLK_SNAP)
 			*ip->i_snapblklist++ = lblkno;
 		if (blkno == BLK_SNAP)
 			blkno = blkstofrags(fs, lblkno);
 		ffs_blkfree(ITOUMP(ip), fs, vp, blkno, fs->fs_bsize, inum,
 		    vp->v_type, NULL, SINGLETON_KEY);
 	}
 	return (0);
 }
 
 /*
  * Before expunging a snapshot inode, note all the
  * blocks that it claims with BLK_SNAP so that fsck will
  * be able to account for those blocks properly and so
  * that this snapshot knows that it need not copy them
  * if the other snapshot holding them is freed. This code
  * is reproduced once each for UFS1 and UFS2.
  */
 static int
 expunge_ufs2(snapvp, cancelip, fs, acctfunc, expungetype, clearmode)
 	struct vnode *snapvp;
 	struct inode *cancelip;
 	struct fs *fs;
 	int (*acctfunc)(struct vnode *, ufs2_daddr_t *, ufs2_daddr_t *,
 	    struct fs *, ufs_lbn_t, int);
 	int expungetype;
 	int clearmode;
 {
 	int i, error, indiroff;
 	ufs_lbn_t lbn, rlbn;
 	ufs2_daddr_t len, blkno, numblks, blksperindir;
 	struct ufs2_dinode *dip;
 	struct thread *td = curthread;
 	struct buf *bp;
 
 	/*
 	 * Prepare to expunge the inode. If its inode block has not
 	 * yet been copied, then allocate and fill the copy.
 	 */
 	lbn = fragstoblks(fs, ino_to_fsba(fs, cancelip->i_number));
 	blkno = 0;
 	if (lbn < UFS_NDADDR) {
 		blkno = VTOI(snapvp)->i_din2->di_db[lbn];
 	} else {
 		if (DOINGSOFTDEP(snapvp))
 			softdep_prealloc(snapvp, MNT_WAIT);
 		td->td_pflags |= TDP_COWINPROGRESS;
 		error = ffs_balloc_ufs2(snapvp, lblktosize(fs, (off_t)lbn),
 		   fs->fs_bsize, KERNCRED, BA_METAONLY, &bp);
 		td->td_pflags &= ~TDP_COWINPROGRESS;
 		if (error)
 			return (error);
 		indiroff = (lbn - UFS_NDADDR) % NINDIR(fs);
 		blkno = ((ufs2_daddr_t *)(bp->b_data))[indiroff];
 		bqrelse(bp);
 	}
 	if (blkno != 0) {
 		if ((error = bread(snapvp, lbn, fs->fs_bsize, KERNCRED, &bp)))
 			return (error);
 	} else {
 		error = ffs_balloc_ufs2(snapvp, lblktosize(fs, (off_t)lbn),
 		    fs->fs_bsize, KERNCRED, 0, &bp);
 		if (error)
 			return (error);
 		if ((error = readblock(snapvp, bp, lbn)) != 0)
 			return (error);
 	}
 	/*
 	 * Set a snapshot inode to be a zero length file, regular files
 	 * to be completely unallocated.
 	 */
 	dip = (struct ufs2_dinode *)bp->b_data +
 	    ino_to_fsbo(fs, cancelip->i_number);
 	dip->di_size = 0;
 	dip->di_blocks = 0;
 	dip->di_flags &= ~SF_SNAPSHOT;
 	bzero(&dip->di_db[0], (UFS_NDADDR + UFS_NIADDR) * sizeof(ufs2_daddr_t));
 	if (clearmode || cancelip->i_effnlink == 0)
 		dip->di_mode = 0;
 	else
 		ffs_update_dinode_ckhash(fs, dip);
 	bdwrite(bp);
 	/*
 	 * Now go through and expunge all the blocks in the file
 	 * using the function requested.
 	 */
 	numblks = howmany(cancelip->i_size, fs->fs_bsize);
 	if ((error = (*acctfunc)(snapvp, &cancelip->i_din2->di_db[0],
 	    &cancelip->i_din2->di_db[UFS_NDADDR], fs, 0, expungetype)))
 		return (error);
 	if ((error = (*acctfunc)(snapvp, &cancelip->i_din2->di_ib[0],
 	    &cancelip->i_din2->di_ib[UFS_NIADDR], fs, -1, expungetype)))
 		return (error);
 	blksperindir = 1;
 	lbn = -UFS_NDADDR;
 	len = numblks - UFS_NDADDR;
 	rlbn = UFS_NDADDR;
 	for (i = 0; len > 0 && i < UFS_NIADDR; i++) {
 		error = indiracct_ufs2(snapvp, ITOV(cancelip), i,
 		    cancelip->i_din2->di_ib[i], lbn, rlbn, len,
 		    blksperindir, fs, acctfunc, expungetype);
 		if (error)
 			return (error);
 		blksperindir *= NINDIR(fs);
 		lbn -= blksperindir + 1;
 		len -= blksperindir;
 		rlbn += blksperindir;
 	}
 	return (0);
 }
 
 /*
  * Descend an indirect block chain for vnode cancelvp accounting for all
  * its indirect blocks in snapvp.
  */ 
 static int
 indiracct_ufs2(snapvp, cancelvp, level, blkno, lbn, rlbn, remblks,
 	    blksperindir, fs, acctfunc, expungetype)
 	struct vnode *snapvp;
 	struct vnode *cancelvp;
 	int level;
 	ufs2_daddr_t blkno;
 	ufs_lbn_t lbn;
 	ufs_lbn_t rlbn;
 	ufs_lbn_t remblks;
 	ufs_lbn_t blksperindir;
 	struct fs *fs;
 	int (*acctfunc)(struct vnode *, ufs2_daddr_t *, ufs2_daddr_t *,
 	    struct fs *, ufs_lbn_t, int);
 	int expungetype;
 {
 	int error, num, i;
 	ufs_lbn_t subblksperindir;
 	struct indir indirs[UFS_NIADDR + 2];
 	ufs2_daddr_t last, *bap;
 	struct buf *bp;
 
 	if (blkno == 0) {
 		if (expungetype == BLK_NOCOPY)
 			return (0);
 		panic("indiracct_ufs2: missing indir");
 	}
 	if ((error = ufs_getlbns(cancelvp, rlbn, indirs, &num)) != 0)
 		return (error);
 	if (lbn != indirs[num - 1 - level].in_lbn || num < 2)
 		panic("indiracct_ufs2: botched params");
 	/*
 	 * We have to expand bread here since it will deadlock looking
 	 * up the block number for any blocks that are not in the cache.
 	 */
 	bp = getblk(cancelvp, lbn, fs->fs_bsize, 0, 0, 0);
 	bp->b_blkno = fsbtodb(fs, blkno);
 	if ((bp->b_flags & B_CACHE) == 0 &&
 	    (error = readblock(cancelvp, bp, fragstoblks(fs, blkno)))) {
 		brelse(bp);
 		return (error);
 	}
 	/*
 	 * Account for the block pointers in this indirect block.
 	 */
 	last = howmany(remblks, blksperindir);
 	if (last > NINDIR(fs))
 		last = NINDIR(fs);
 	bap = malloc(fs->fs_bsize, M_DEVBUF, M_WAITOK);
 	bcopy(bp->b_data, (caddr_t)bap, fs->fs_bsize);
 	bqrelse(bp);
 	error = (*acctfunc)(snapvp, &bap[0], &bap[last], fs,
 	    level == 0 ? rlbn : -1, expungetype);
 	if (error || level == 0)
 		goto out;
 	/*
 	 * Account for the block pointers in each of the indirect blocks
 	 * in the levels below us.
 	 */
 	subblksperindir = blksperindir / NINDIR(fs);
 	for (lbn++, level--, i = 0; i < last; i++) {
 		error = indiracct_ufs2(snapvp, cancelvp, level, bap[i], lbn,
 		    rlbn, remblks, subblksperindir, fs, acctfunc, expungetype);
 		if (error)
 			goto out;
 		rlbn += blksperindir;
 		lbn -= blksperindir;
 		remblks -= blksperindir;
 	}
 out:
 	free(bap, M_DEVBUF);
 	return (error);
 }
 
 /*
  * Do both snap accounting and map accounting.
  */
 static int
 fullacct_ufs2(vp, oldblkp, lastblkp, fs, lblkno, exptype)
 	struct vnode *vp;
 	ufs2_daddr_t *oldblkp, *lastblkp;
 	struct fs *fs;
 	ufs_lbn_t lblkno;
 	int exptype;	/* BLK_SNAP or BLK_NOCOPY */
 {
 	int error;
 
 	if ((error = snapacct_ufs2(vp, oldblkp, lastblkp, fs, lblkno, exptype)))
 		return (error);
 	return (mapacct_ufs2(vp, oldblkp, lastblkp, fs, lblkno, exptype));
 }
 
 /*
  * Identify a set of blocks allocated in a snapshot inode.
  */
 static int
 snapacct_ufs2(vp, oldblkp, lastblkp, fs, lblkno, expungetype)
 	struct vnode *vp;
 	ufs2_daddr_t *oldblkp, *lastblkp;
 	struct fs *fs;
 	ufs_lbn_t lblkno;
 	int expungetype;	/* BLK_SNAP or BLK_NOCOPY */
 {
 	struct inode *ip = VTOI(vp);
 	ufs2_daddr_t blkno, *blkp;
 	ufs_lbn_t lbn;
 	struct buf *ibp;
 	int error;
 
 	for ( ; oldblkp < lastblkp; oldblkp++) {
 		blkno = *oldblkp;
 		if (blkno == 0 || blkno == BLK_NOCOPY || blkno == BLK_SNAP)
 			continue;
 		lbn = fragstoblks(fs, blkno);
 		if (lbn < UFS_NDADDR) {
 			blkp = &ip->i_din2->di_db[lbn];
 			UFS_INODE_SET_FLAG(ip, IN_CHANGE | IN_UPDATE);
 		} else {
 			error = ffs_balloc_ufs2(vp, lblktosize(fs, (off_t)lbn),
 			    fs->fs_bsize, KERNCRED, BA_METAONLY, &ibp);
 			if (error)
 				return (error);
 			blkp = &((ufs2_daddr_t *)(ibp->b_data))
 			    [(lbn - UFS_NDADDR) % NINDIR(fs)];
 		}
 		/*
 		 * If we are expunging a snapshot vnode and we
 		 * find a block marked BLK_NOCOPY, then it is
 		 * one that has been allocated to this snapshot after
 		 * we took our current snapshot and can be ignored.
 		 */
 		if (expungetype == BLK_SNAP && *blkp == BLK_NOCOPY) {
 			if (lbn >= UFS_NDADDR)
 				brelse(ibp);
 		} else {
 			if (*blkp != 0)
 				panic("snapacct_ufs2: bad block");
 			*blkp = expungetype;
 			if (lbn >= UFS_NDADDR)
 				bdwrite(ibp);
 		}
 	}
 	return (0);
 }
 
 /*
  * Account for a set of blocks allocated in a snapshot inode.
  */
 static int
 mapacct_ufs2(vp, oldblkp, lastblkp, fs, lblkno, expungetype)
 	struct vnode *vp;
 	ufs2_daddr_t *oldblkp, *lastblkp;
 	struct fs *fs;
 	ufs_lbn_t lblkno;
 	int expungetype;
 {
 	ufs2_daddr_t blkno;
 	struct inode *ip;
 	ino_t inum;
 	int acctit;
 
 	ip = VTOI(vp);
 	inum = ip->i_number;
 	if (lblkno == -1)
 		acctit = 0;
 	else
 		acctit = 1;
 	for ( ; oldblkp < lastblkp; oldblkp++, lblkno++) {
 		blkno = *oldblkp;
 		if (blkno == 0 || blkno == BLK_NOCOPY)
 			continue;
 		if (acctit && expungetype == BLK_SNAP && blkno != BLK_SNAP)
 			*ip->i_snapblklist++ = lblkno;
 		if (blkno == BLK_SNAP)
 			blkno = blkstofrags(fs, lblkno);
 		ffs_blkfree(ITOUMP(ip), fs, vp, blkno, fs->fs_bsize, inum,
 		    vp->v_type, NULL, SINGLETON_KEY);
 	}
 	return (0);
 }
 
 /*
  * Decrement extra reference on snapshot when last name is removed.
  * It will not be freed until the last open reference goes away.
  */
 void
 ffs_snapgone(ip)
 	struct inode *ip;
 {
 	struct inode *xp;
 	struct fs *fs;
 	int snaploc;
 	struct snapdata *sn;
 	struct ufsmount *ump;
 
 	/*
 	 * Find snapshot in incore list.
 	 */
 	xp = NULL;
 	sn = ITODEVVP(ip)->v_rdev->si_snapdata;
 	if (sn != NULL)
 		TAILQ_FOREACH(xp, &sn->sn_head, i_nextsnap)
 			if (xp == ip)
 				break;
 	if (xp != NULL)
 		vrele(ITOV(ip));
 #ifdef DIAGNOSTIC
 	else if (snapdebug)
 		printf("ffs_snapgone: lost snapshot vnode %ju\n",
 		    (uintmax_t)ip->i_number);
 #endif
 	/*
 	 * Delete snapshot inode from superblock. Keep list dense.
 	 */
 	ump = ITOUMP(ip);
 	fs = ump->um_fs;
 	UFS_LOCK(ump);
 	for (snaploc = 0; snaploc < FSMAXSNAP; snaploc++)
 		if (fs->fs_snapinum[snaploc] == ip->i_number)
 			break;
 	if (snaploc < FSMAXSNAP) {
 		for (snaploc++; snaploc < FSMAXSNAP; snaploc++) {
 			if (fs->fs_snapinum[snaploc] == 0)
 				break;
 			fs->fs_snapinum[snaploc - 1] = fs->fs_snapinum[snaploc];
 		}
 		fs->fs_snapinum[snaploc - 1] = 0;
 	}
 	UFS_UNLOCK(ump);
 }
 
 /*
  * Prepare a snapshot file for being removed.
  */
 void
 ffs_snapremove(vp)
 	struct vnode *vp;
 {
 	struct inode *ip;
 	struct vnode *devvp;
 	struct buf *ibp;
 	struct fs *fs;
 	ufs2_daddr_t numblks, blkno, dblk;
 	int error, i, last, loc;
 	struct snapdata *sn;
 
 	ip = VTOI(vp);
 	fs = ITOFS(ip);
 	devvp = ITODEVVP(ip);
 	/*
 	 * If active, delete from incore list (this snapshot may
 	 * already have been in the process of being deleted, so
 	 * would not have been active).
 	 *
 	 * Clear copy-on-write flag if last snapshot.
 	 */
 	VI_LOCK(devvp);
 	if (ip->i_nextsnap.tqe_prev != 0) {
 		sn = devvp->v_rdev->si_snapdata;
 		TAILQ_REMOVE(&sn->sn_head, ip, i_nextsnap);
 		ip->i_nextsnap.tqe_prev = 0;
 		VI_UNLOCK(devvp);
 		lockmgr(&vp->v_lock, LK_EXCLUSIVE, NULL);
 		for (i = 0; i < sn->sn_lock.lk_recurse; i++)
 			lockmgr(&vp->v_lock, LK_EXCLUSIVE, NULL);
 		KASSERT(vp->v_vnlock == &sn->sn_lock,
 			("ffs_snapremove: lost lock mutation")); 
 		vp->v_vnlock = &vp->v_lock;
 		VI_LOCK(devvp);
 		while (sn->sn_lock.lk_recurse > 0)
 			lockmgr(&sn->sn_lock, LK_RELEASE, NULL);
 		lockmgr(&sn->sn_lock, LK_RELEASE, NULL);
 		try_free_snapdata(devvp);
 	} else
 		VI_UNLOCK(devvp);
 	/*
 	 * Clear all BLK_NOCOPY fields. Pass any block claims to other
 	 * snapshots that want them (see ffs_snapblkfree below).
 	 */
 	for (blkno = 1; blkno < UFS_NDADDR; blkno++) {
 		dblk = DIP(ip, i_db[blkno]);
 		if (dblk == 0)
 			continue;
 		if (dblk == BLK_NOCOPY || dblk == BLK_SNAP)
 			DIP_SET(ip, i_db[blkno], 0);
 		else if ((dblk == blkstofrags(fs, blkno) &&
 		     ffs_snapblkfree(fs, ITODEVVP(ip), dblk, fs->fs_bsize,
 		     ip->i_number, vp->v_type, NULL))) {
 			DIP_SET(ip, i_blocks, DIP(ip, i_blocks) -
 			    btodb(fs->fs_bsize));
 			DIP_SET(ip, i_db[blkno], 0);
 		}
 	}
 	numblks = howmany(ip->i_size, fs->fs_bsize);
 	for (blkno = UFS_NDADDR; blkno < numblks; blkno += NINDIR(fs)) {
 		error = UFS_BALLOC(vp, lblktosize(fs, (off_t)blkno),
 		    fs->fs_bsize, KERNCRED, BA_METAONLY, &ibp);
 		if (error)
 			continue;
 		if (fs->fs_size - blkno > NINDIR(fs))
 			last = NINDIR(fs);
 		else
 			last = fs->fs_size - blkno;
 		for (loc = 0; loc < last; loc++) {
 			if (I_IS_UFS1(ip)) {
 				dblk = ((ufs1_daddr_t *)(ibp->b_data))[loc];
 				if (dblk == 0)
 					continue;
 				if (dblk == BLK_NOCOPY || dblk == BLK_SNAP)
 					((ufs1_daddr_t *)(ibp->b_data))[loc]= 0;
 				else if ((dblk == blkstofrags(fs, blkno) &&
 				     ffs_snapblkfree(fs, ITODEVVP(ip), dblk,
 				     fs->fs_bsize, ip->i_number, vp->v_type,
 				     NULL))) {
 					ip->i_din1->di_blocks -=
 					    btodb(fs->fs_bsize);
 					((ufs1_daddr_t *)(ibp->b_data))[loc]= 0;
 				}
 				continue;
 			}
 			dblk = ((ufs2_daddr_t *)(ibp->b_data))[loc];
 			if (dblk == 0)
 				continue;
 			if (dblk == BLK_NOCOPY || dblk == BLK_SNAP)
 				((ufs2_daddr_t *)(ibp->b_data))[loc] = 0;
 			else if ((dblk == blkstofrags(fs, blkno) &&
 			     ffs_snapblkfree(fs, ITODEVVP(ip), dblk,
 			     fs->fs_bsize, ip->i_number, vp->v_type, NULL))) {
 				ip->i_din2->di_blocks -= btodb(fs->fs_bsize);
 				((ufs2_daddr_t *)(ibp->b_data))[loc] = 0;
 			}
 		}
 		bawrite(ibp);
 	}
 	/*
 	 * Clear snapshot flag and drop reference.
 	 */
 	ip->i_flags &= ~SF_SNAPSHOT;
 	DIP_SET(ip, i_flags, ip->i_flags);
 	UFS_INODE_SET_FLAG(ip, IN_CHANGE | IN_UPDATE);
 	/*
 	 * The dirtied indirects must be written out before
 	 * softdep_setup_freeblocks() is called.  Otherwise indir_trunc()
 	 * may find indirect pointers using the magic BLK_* values.
 	 */
 	if (DOINGSOFTDEP(vp))
 		ffs_syncvnode(vp, MNT_WAIT, 0);
 #ifdef QUOTA
 	/*
 	 * Reenable disk quotas for ex-snapshot file.
 	 */
 	if (!getinoquota(ip))
 		(void) chkdq(ip, DIP(ip, i_blocks), KERNCRED, FORCE);
 #endif
 }
 
 /*
  * Notification that a block is being freed. Return zero if the free
  * should be allowed to proceed. Return non-zero if the snapshot file
  * wants to claim the block. The block will be claimed if it is an
  * uncopied part of one of the snapshots. It will be freed if it is
  * either a BLK_NOCOPY or has already been copied in all of the snapshots.
  * If a fragment is being freed, then all snapshots that care about
  * it must make a copy since a snapshot file can only claim full sized
  * blocks. Note that if more than one snapshot file maps the block,
  * we can pick one at random to claim it. Since none of the snapshots
  * can change, we are assurred that they will all see the same unmodified
  * image. When deleting a snapshot file (see ffs_snapremove above), we
  * must push any of these claimed blocks to one of the other snapshots
  * that maps it. These claimed blocks are easily identified as they will
  * have a block number equal to their logical block number within the
  * snapshot. A copied block can never have this property because they
  * must always have been allocated from a BLK_NOCOPY location.
  */
 int
 ffs_snapblkfree(fs, devvp, bno, size, inum, vtype, wkhd)
 	struct fs *fs;
 	struct vnode *devvp;
 	ufs2_daddr_t bno;
 	long size;
 	ino_t inum;
 	enum vtype vtype;
 	struct workhead *wkhd;
 {
 	struct buf *ibp, *cbp, *savedcbp = NULL;
 	struct thread *td = curthread;
 	struct inode *ip;
 	struct vnode *vp = NULL;
 	ufs_lbn_t lbn;
 	ufs2_daddr_t blkno;
 	int indiroff = 0, error = 0, claimedblk = 0;
 	struct snapdata *sn;
 
 	lbn = fragstoblks(fs, bno);
 retry:
 	VI_LOCK(devvp);
 	sn = devvp->v_rdev->si_snapdata;
 	if (sn == NULL) {
 		VI_UNLOCK(devvp);
 		return (0);
 	}
 	if (lockmgr(&sn->sn_lock, LK_INTERLOCK | LK_EXCLUSIVE | LK_SLEEPFAIL,
 	    VI_MTX(devvp)) != 0)
 		goto retry;
 	TAILQ_FOREACH(ip, &sn->sn_head, i_nextsnap) {
 		vp = ITOV(ip);
 		if (DOINGSOFTDEP(vp))
 			softdep_prealloc(vp, MNT_WAIT);
 		/*
 		 * Lookup block being written.
 		 */
 		if (lbn < UFS_NDADDR) {
 			blkno = DIP(ip, i_db[lbn]);
 		} else {
 			td->td_pflags |= TDP_COWINPROGRESS;
 			error = UFS_BALLOC(vp, lblktosize(fs, (off_t)lbn),
 			    fs->fs_bsize, KERNCRED, BA_METAONLY, &ibp);
 			td->td_pflags &= ~TDP_COWINPROGRESS;
 			if (error)
 				break;
 			indiroff = (lbn - UFS_NDADDR) % NINDIR(fs);
 			if (I_IS_UFS1(ip))
 				blkno=((ufs1_daddr_t *)(ibp->b_data))[indiroff];
 			else
 				blkno=((ufs2_daddr_t *)(ibp->b_data))[indiroff];
 		}
 		/*
 		 * Check to see if block needs to be copied.
 		 */
 		if (blkno == 0) {
 			/*
 			 * A block that we map is being freed. If it has not
 			 * been claimed yet, we will claim or copy it (below).
 			 */
 			claimedblk = 1;
 		} else if (blkno == BLK_SNAP) {
 			/*
 			 * No previous snapshot claimed the block,
 			 * so it will be freed and become a BLK_NOCOPY
 			 * (don't care) for us.
 			 */
 			if (claimedblk)
 				panic("snapblkfree: inconsistent block type");
 			if (lbn < UFS_NDADDR) {
 				DIP_SET(ip, i_db[lbn], BLK_NOCOPY);
 				UFS_INODE_SET_FLAG(ip, IN_CHANGE | IN_UPDATE);
 			} else if (I_IS_UFS1(ip)) {
 				((ufs1_daddr_t *)(ibp->b_data))[indiroff] =
 				    BLK_NOCOPY;
 				bdwrite(ibp);
 			} else {
 				((ufs2_daddr_t *)(ibp->b_data))[indiroff] =
 				    BLK_NOCOPY;
 				bdwrite(ibp);
 			}
 			continue;
 		} else /* BLK_NOCOPY or default */ {
 			/*
 			 * If the snapshot has already copied the block
 			 * (default), or does not care about the block,
 			 * it is not needed.
 			 */
 			if (lbn >= UFS_NDADDR)
 				bqrelse(ibp);
 			continue;
 		}
 		/*
 		 * If this is a full size block, we will just grab it
 		 * and assign it to the snapshot inode. Otherwise we
 		 * will proceed to copy it. See explanation for this
 		 * routine as to why only a single snapshot needs to
 		 * claim this block.
 		 */
 		if (size == fs->fs_bsize) {
 #ifdef DIAGNOSTIC
 			if (snapdebug)
 				printf("%s %ju lbn %jd from inum %ju\n",
 				    "Grabonremove: snapino",
 				    (uintmax_t)ip->i_number,
 				    (intmax_t)lbn, (uintmax_t)inum);
 #endif
 			/*
 			 * If journaling is tracking this write we must add
 			 * the work to the inode or indirect being written.
 			 */
 			if (wkhd != NULL) {
 				if (lbn < UFS_NDADDR)
 					softdep_inode_append(ip,
 					    curthread->td_ucred, wkhd);
 				else
 					softdep_buf_append(ibp, wkhd);
 			}
 			if (lbn < UFS_NDADDR) {
 				DIP_SET(ip, i_db[lbn], bno);
 			} else if (I_IS_UFS1(ip)) {
 				((ufs1_daddr_t *)(ibp->b_data))[indiroff] = bno;
 				bdwrite(ibp);
 			} else {
 				((ufs2_daddr_t *)(ibp->b_data))[indiroff] = bno;
 				bdwrite(ibp);
 			}
 			DIP_SET(ip, i_blocks, DIP(ip, i_blocks) + btodb(size));
 			UFS_INODE_SET_FLAG(ip, IN_CHANGE | IN_UPDATE);
 			lockmgr(vp->v_vnlock, LK_RELEASE, NULL);
 			return (1);
 		}
 		if (lbn >= UFS_NDADDR)
 			bqrelse(ibp);
 		/*
 		 * Allocate the block into which to do the copy. Note that this
 		 * allocation will never require any additional allocations for
 		 * the snapshot inode.
 		 */
 		td->td_pflags |= TDP_COWINPROGRESS;
 		error = UFS_BALLOC(vp, lblktosize(fs, (off_t)lbn),
 		    fs->fs_bsize, KERNCRED, 0, &cbp);
 		td->td_pflags &= ~TDP_COWINPROGRESS;
 		if (error)
 			break;
 #ifdef DIAGNOSTIC
 		if (snapdebug)
 			printf("%s%ju lbn %jd %s %ju size %ld to blkno %jd\n",
 			    "Copyonremove: snapino ", (uintmax_t)ip->i_number,
 			    (intmax_t)lbn, "for inum", (uintmax_t)inum, size,
 			    (intmax_t)cbp->b_blkno);
 #endif
 		/*
 		 * If we have already read the old block contents, then
 		 * simply copy them to the new block. Note that we need
 		 * to synchronously write snapshots that have not been
 		 * unlinked, and hence will be visible after a crash,
 		 * to ensure their integrity. At a minimum we ensure the
 		 * integrity of the filesystem metadata, but use the
 		 * dopersistence sysctl-setable flag to decide on the
 		 * persistence needed for file content data.
 		 */
 		if (savedcbp != NULL) {
 			bcopy(savedcbp->b_data, cbp->b_data, fs->fs_bsize);
 			bawrite(cbp);
 			if ((vtype == VDIR || dopersistence) &&
 			    ip->i_effnlink > 0)
 				(void) ffs_syncvnode(vp, MNT_WAIT, NO_INO_UPDT);
 			continue;
 		}
 		/*
 		 * Otherwise, read the old block contents into the buffer.
 		 */
 		if ((error = readblock(vp, cbp, lbn)) != 0) {
 			bzero(cbp->b_data, fs->fs_bsize);
 			bawrite(cbp);
 			if ((vtype == VDIR || dopersistence) &&
 			    ip->i_effnlink > 0)
 				(void) ffs_syncvnode(vp, MNT_WAIT, NO_INO_UPDT);
 			break;
 		}
 		savedcbp = cbp;
 	}
 	/*
 	 * Note that we need to synchronously write snapshots that
 	 * have not been unlinked, and hence will be visible after
 	 * a crash, to ensure their integrity. At a minimum we
 	 * ensure the integrity of the filesystem metadata, but
 	 * use the dopersistence sysctl-setable flag to decide on
 	 * the persistence needed for file content data.
 	 */
 	if (savedcbp) {
 		vp = savedcbp->b_vp;
 		bawrite(savedcbp);
 		if ((vtype == VDIR || dopersistence) &&
 		    VTOI(vp)->i_effnlink > 0)
 			(void) ffs_syncvnode(vp, MNT_WAIT, NO_INO_UPDT);
 	}
 	/*
 	 * If we have been unable to allocate a block in which to do
 	 * the copy, then return non-zero so that the fragment will
 	 * not be freed. Although space will be lost, the snapshot
 	 * will stay consistent.
 	 */
 	if (error != 0 && wkhd != NULL)
 		softdep_freework(wkhd);
 	lockmgr(&sn->sn_lock, LK_RELEASE, NULL);
 	return (error);
 }
 
 /*
  * Associate snapshot files when mounting.
  */
 void
 ffs_snapshot_mount(mp)
 	struct mount *mp;
 {
 	struct ufsmount *ump = VFSTOUFS(mp);
 	struct vnode *devvp = ump->um_devvp;
 	struct fs *fs = ump->um_fs;
 	struct thread *td = curthread;
 	struct snapdata *sn;
 	struct vnode *vp;
 	struct vnode *lastvp;
 	struct inode *ip;
 	struct uio auio;
 	struct iovec aiov;
 	void *snapblklist;
 	char *reason;
 	daddr_t snaplistsize;
 	int error, snaploc, loc;
 
 	/*
 	 * XXX The following needs to be set before ffs_truncate or
 	 * VOP_READ can be called.
 	 */
 	mp->mnt_stat.f_iosize = fs->fs_bsize;
 	/*
 	 * Process each snapshot listed in the superblock.
 	 */
 	vp = NULL;
 	lastvp = NULL;
 	sn = NULL;
 	for (snaploc = 0; snaploc < FSMAXSNAP; snaploc++) {
 		if (fs->fs_snapinum[snaploc] == 0)
 			break;
 		if ((error = ffs_vget(mp, fs->fs_snapinum[snaploc],
 		    LK_EXCLUSIVE, &vp)) != 0){
 			printf("ffs_snapshot_mount: vget failed %d\n", error);
 			continue;
 		}
 		ip = VTOI(vp);
 		if (vp->v_type != VREG) {
 			reason = "non-file snapshot";
 		} else if (!IS_SNAPSHOT(ip)) {
 			reason = "non-snapshot";
 		} else if (ip->i_size ==
 		    lblktosize(fs, howmany(fs->fs_size, fs->fs_frag))) {
 			reason = "old format snapshot";
 			(void)ffs_truncate(vp, (off_t)0, 0, NOCRED);
 			(void)ffs_syncvnode(vp, MNT_WAIT, 0);
 		} else {
 			reason = NULL;
 		}
 		if (reason != NULL) {
 			printf("ffs_snapshot_mount: %s inode %d\n",
 			    reason, fs->fs_snapinum[snaploc]);
 			vput(vp);
 			vp = NULL;
 			for (loc = snaploc + 1; loc < FSMAXSNAP; loc++) {
 				if (fs->fs_snapinum[loc] == 0)
 					break;
 				fs->fs_snapinum[loc - 1] = fs->fs_snapinum[loc];
 			}
 			fs->fs_snapinum[loc - 1] = 0;
 			snaploc--;
 			continue;
 		}
 		/*
 		 * Acquire a lock on the snapdata structure, creating it if
 		 * necessary.
 		 */
 		sn = ffs_snapdata_acquire(devvp);
 		/* 
 		 * Change vnode to use shared snapshot lock instead of the
 		 * original private lock.
 		 */
 		vp->v_vnlock = &sn->sn_lock;
 		lockmgr(&vp->v_lock, LK_RELEASE, NULL);
 		/*
 		 * Link it onto the active snapshot list.
 		 */
 		VI_LOCK(devvp);
 		if (ip->i_nextsnap.tqe_prev != 0)
 			panic("ffs_snapshot_mount: %ju already on list",
 			    (uintmax_t)ip->i_number);
 		else
 			TAILQ_INSERT_TAIL(&sn->sn_head, ip, i_nextsnap);
 		vp->v_vflag |= VV_SYSTEM;
 		VI_UNLOCK(devvp);
 		VOP_UNLOCK(vp);
 		lastvp = vp;
 	}
 	vp = lastvp;
 	/*
 	 * No usable snapshots found.
 	 */
 	if (sn == NULL || vp == NULL)
 		return;
 	/*
 	 * Allocate the space for the block hints list. We always want to
 	 * use the list from the newest snapshot.
 	 */
 	auio.uio_iov = &aiov;
 	auio.uio_iovcnt = 1;
 	aiov.iov_base = (void *)&snaplistsize;
 	aiov.iov_len = sizeof(snaplistsize);
 	auio.uio_resid = aiov.iov_len;
 	auio.uio_offset =
 	    lblktosize(fs, howmany(fs->fs_size, fs->fs_frag));
 	auio.uio_segflg = UIO_SYSSPACE;
 	auio.uio_rw = UIO_READ;
 	auio.uio_td = td;
 	vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
 	if ((error = VOP_READ(vp, &auio, IO_UNIT, td->td_ucred)) != 0) {
 		printf("ffs_snapshot_mount: read_1 failed %d\n", error);
 		VOP_UNLOCK(vp);
 		return;
 	}
 	snapblklist = malloc(snaplistsize * sizeof(daddr_t),
 	    M_UFSMNT, M_WAITOK);
 	auio.uio_iovcnt = 1;
 	aiov.iov_base = snapblklist;
 	aiov.iov_len = snaplistsize * sizeof (daddr_t);
 	auio.uio_resid = aiov.iov_len;
 	auio.uio_offset -= sizeof(snaplistsize);
 	if ((error = VOP_READ(vp, &auio, IO_UNIT, td->td_ucred)) != 0) {
 		printf("ffs_snapshot_mount: read_2 failed %d\n", error);
 		VOP_UNLOCK(vp);
 		free(snapblklist, M_UFSMNT);
 		return;
 	}
 	VOP_UNLOCK(vp);
 	VI_LOCK(devvp);
 	ASSERT_VOP_LOCKED(devvp, "ffs_snapshot_mount");
 	sn->sn_listsize = snaplistsize;
 	sn->sn_blklist = (daddr_t *)snapblklist;
 	devvp->v_vflag |= VV_COPYONWRITE;
 	VI_UNLOCK(devvp);
 }
 
 /*
  * Disassociate snapshot files when unmounting.
  */
 void
 ffs_snapshot_unmount(mp)
 	struct mount *mp;
 {
 	struct vnode *devvp = VFSTOUFS(mp)->um_devvp;
 	struct snapdata *sn;
 	struct inode *xp;
 	struct vnode *vp;
 
 	VI_LOCK(devvp);
 	sn = devvp->v_rdev->si_snapdata;
 	while (sn != NULL && (xp = TAILQ_FIRST(&sn->sn_head)) != NULL) {
 		vp = ITOV(xp);
 		TAILQ_REMOVE(&sn->sn_head, xp, i_nextsnap);
 		xp->i_nextsnap.tqe_prev = 0;
 		lockmgr(&sn->sn_lock, LK_INTERLOCK | LK_EXCLUSIVE,
 		    VI_MTX(devvp));
 		lockmgr(&vp->v_lock, LK_EXCLUSIVE, NULL);
 		KASSERT(vp->v_vnlock == &sn->sn_lock,
 		("ffs_snapshot_unmount: lost lock mutation")); 
 		vp->v_vnlock = &vp->v_lock;
 		lockmgr(&vp->v_lock, LK_RELEASE, NULL);
 		lockmgr(&sn->sn_lock, LK_RELEASE, NULL);
 		if (xp->i_effnlink > 0)
 			vrele(vp);
 		VI_LOCK(devvp);
 		sn = devvp->v_rdev->si_snapdata;
 	}
 	try_free_snapdata(devvp);
 	ASSERT_VOP_LOCKED(devvp, "ffs_snapshot_unmount");
 }
 
 /*
  * Check the buffer block to be belong to device buffer that shall be
  * locked after snaplk. devvp shall be locked on entry, and will be
  * leaved locked upon exit.
  */
 static int
 ffs_bp_snapblk(devvp, bp)
 	struct vnode *devvp;
 	struct buf *bp;
 {
 	struct snapdata *sn;
 	struct fs *fs;
 	ufs2_daddr_t lbn, *snapblklist;
 	int lower, upper, mid;
 
 	ASSERT_VI_LOCKED(devvp, "ffs_bp_snapblk");
 	KASSERT(devvp->v_type == VCHR, ("Not a device %p", devvp));
 	sn = devvp->v_rdev->si_snapdata;
 	if (sn == NULL || TAILQ_FIRST(&sn->sn_head) == NULL)
 		return (0);
 	fs = ITOFS(TAILQ_FIRST(&sn->sn_head));
 	lbn = fragstoblks(fs, dbtofsb(fs, bp->b_blkno));
 	snapblklist = sn->sn_blklist;
 	upper = sn->sn_listsize - 1;
 	lower = 1;
 	while (lower <= upper) {
 		mid = (lower + upper) / 2;
 		if (snapblklist[mid] == lbn)
 			break;
 		if (snapblklist[mid] < lbn)
 			lower = mid + 1;
 		else
 			upper = mid - 1;
 	}
 	if (lower <= upper)
 		return (1);
 	return (0);
 }
 
 void
 ffs_bdflush(bo, bp)
 	struct bufobj *bo;
 	struct buf *bp;
 {
 	struct thread *td;
 	struct vnode *vp, *devvp;
 	struct buf *nbp;
 	int bp_bdskip;
 
 	if (bo->bo_dirty.bv_cnt <= dirtybufthresh)
 		return;
 
 	td = curthread;
 	vp = bp->b_vp;
 	devvp = bo2vnode(bo);
 	KASSERT(vp == devvp, ("devvp != vp %p %p", bo, bp));
 
 	VI_LOCK(devvp);
 	bp_bdskip = ffs_bp_snapblk(devvp, bp);
 	if (bp_bdskip)
 		bdwriteskip++;
 	VI_UNLOCK(devvp);
 	if (bo->bo_dirty.bv_cnt > dirtybufthresh + 10 && !bp_bdskip) {
 		(void) VOP_FSYNC(vp, MNT_NOWAIT, td);
 		altbufferflushes++;
 	} else {
 		BO_LOCK(bo);
 		/*
 		 * Try to find a buffer to flush.
 		 */
 		TAILQ_FOREACH(nbp, &bo->bo_dirty.bv_hd, b_bobufs) {
 			if ((nbp->b_vflags & BV_BKGRDINPROG) ||
 			    BUF_LOCK(nbp,
 				     LK_EXCLUSIVE | LK_NOWAIT, NULL))
 				continue;
 			if (bp == nbp)
 				panic("bdwrite: found ourselves");
 			BO_UNLOCK(bo);
 			/*
 			 * Don't countdeps with the bo lock
 			 * held.
 			 */
 			if (buf_countdeps(nbp, 0)) {
 				BO_LOCK(bo);
 				BUF_UNLOCK(nbp);
 				continue;
 			}
 			if (bp_bdskip) {
 				VI_LOCK(devvp);
 				if (!ffs_bp_snapblk(vp, nbp)) {
 					VI_UNLOCK(devvp);
 					BO_LOCK(bo);
 					BUF_UNLOCK(nbp);
 					continue;
 				}
 				VI_UNLOCK(devvp);
 			}
 			if (nbp->b_flags & B_CLUSTEROK) {
 				vfs_bio_awrite(nbp);
 			} else {
 				bremfree(nbp);
 				bawrite(nbp);
 			}
 			dirtybufferflushes++;
 			break;
 		}
 		if (nbp == NULL)
 			BO_UNLOCK(bo);
 	}
 }
 
 /*
  * Check for need to copy block that is about to be written,
  * copying the block if necessary.
  */
 int
 ffs_copyonwrite(devvp, bp)
 	struct vnode *devvp;
 	struct buf *bp;
 {
 	struct snapdata *sn;
 	struct buf *ibp, *cbp, *savedcbp = NULL;
 	struct thread *td = curthread;
 	struct fs *fs;
 	struct inode *ip;
 	struct vnode *vp = NULL;
 	ufs2_daddr_t lbn, blkno, *snapblklist;
 	int lower, upper, mid, indiroff, error = 0;
 	int launched_async_io, prev_norunningbuf;
 	long saved_runningbufspace;
 
 	if (devvp != bp->b_vp && IS_SNAPSHOT(VTOI(bp->b_vp)))
 		return (0);		/* Update on a snapshot file */
 	if (td->td_pflags & TDP_COWINPROGRESS)
 		panic("ffs_copyonwrite: recursive call");
 	/*
 	 * First check to see if it is in the preallocated list.
 	 * By doing this check we avoid several potential deadlocks.
 	 */
 	VI_LOCK(devvp);
 	sn = devvp->v_rdev->si_snapdata;
 	if (sn == NULL ||
 	    TAILQ_EMPTY(&sn->sn_head)) {
 		VI_UNLOCK(devvp);
 		return (0);		/* No snapshot */
 	}
 	ip = TAILQ_FIRST(&sn->sn_head);
 	fs = ITOFS(ip);
 	lbn = fragstoblks(fs, dbtofsb(fs, bp->b_blkno));
 	snapblklist = sn->sn_blklist;
 	upper = sn->sn_listsize - 1;
 	lower = 1;
 	while (lower <= upper) {
 		mid = (lower + upper) / 2;
 		if (snapblklist[mid] == lbn)
 			break;
 		if (snapblklist[mid] < lbn)
 			lower = mid + 1;
 		else
 			upper = mid - 1;
 	}
 	if (lower <= upper) {
 		VI_UNLOCK(devvp);
 		return (0);
 	}
 	launched_async_io = 0;
 	prev_norunningbuf = td->td_pflags & TDP_NORUNNINGBUF;
 	/*
 	 * Since I/O on bp isn't yet in progress and it may be blocked
 	 * for a long time waiting on snaplk, back it out of
 	 * runningbufspace, possibly waking other threads waiting for space.
 	 */
 	saved_runningbufspace = bp->b_runningbufspace;
 	if (saved_runningbufspace != 0)
 		runningbufwakeup(bp);
 	/*
 	 * Not in the precomputed list, so check the snapshots.
 	 */
 	while (lockmgr(&sn->sn_lock, LK_INTERLOCK | LK_EXCLUSIVE | LK_SLEEPFAIL,
 	    VI_MTX(devvp)) != 0) {
 		VI_LOCK(devvp);
 		sn = devvp->v_rdev->si_snapdata;
 		if (sn == NULL ||
 		    TAILQ_EMPTY(&sn->sn_head)) {
 			VI_UNLOCK(devvp);
 			if (saved_runningbufspace != 0) {
 				bp->b_runningbufspace = saved_runningbufspace;
 				atomic_add_long(&runningbufspace,
 					       bp->b_runningbufspace);
 			}
 			return (0);		/* Snapshot gone */
 		}
 	}
 	TAILQ_FOREACH(ip, &sn->sn_head, i_nextsnap) {
 		vp = ITOV(ip);
 		if (DOINGSOFTDEP(vp))
 			softdep_prealloc(vp, MNT_WAIT);
 		/*
 		 * We ensure that everything of our own that needs to be
 		 * copied will be done at the time that ffs_snapshot is
 		 * called. Thus we can skip the check here which can
 		 * deadlock in doing the lookup in UFS_BALLOC.
 		 */
 		if (bp->b_vp == vp)
 			continue;
 		/*
 		 * Check to see if block needs to be copied. We do not have
 		 * to hold the snapshot lock while doing this lookup as it
 		 * will never require any additional allocations for the
 		 * snapshot inode.
 		 */
 		if (lbn < UFS_NDADDR) {
 			blkno = DIP(ip, i_db[lbn]);
 		} else {
 			td->td_pflags |= TDP_COWINPROGRESS | TDP_NORUNNINGBUF;
 			error = UFS_BALLOC(vp, lblktosize(fs, (off_t)lbn),
 			   fs->fs_bsize, KERNCRED, BA_METAONLY, &ibp);
 			td->td_pflags &= ~TDP_COWINPROGRESS;
 			if (error)
 				break;
 			indiroff = (lbn - UFS_NDADDR) % NINDIR(fs);
 			if (I_IS_UFS1(ip))
 				blkno=((ufs1_daddr_t *)(ibp->b_data))[indiroff];
 			else
 				blkno=((ufs2_daddr_t *)(ibp->b_data))[indiroff];
 			bqrelse(ibp);
 		}
 #ifdef INVARIANTS
 		if (blkno == BLK_SNAP && bp->b_lblkno >= 0)
 			panic("ffs_copyonwrite: bad copy block");
 #endif
 		if (blkno != 0)
 			continue;
 		/*
 		 * Allocate the block into which to do the copy. Since
 		 * multiple processes may all try to copy the same block,
 		 * we have to recheck our need to do a copy if we sleep
 		 * waiting for the lock.
 		 *
 		 * Because all snapshots on a filesystem share a single
 		 * lock, we ensure that we will never be in competition
 		 * with another process to allocate a block.
 		 */
 		td->td_pflags |= TDP_COWINPROGRESS | TDP_NORUNNINGBUF;
 		error = UFS_BALLOC(vp, lblktosize(fs, (off_t)lbn),
 		    fs->fs_bsize, KERNCRED, 0, &cbp);
 		td->td_pflags &= ~TDP_COWINPROGRESS;
 		if (error)
 			break;
 #ifdef DIAGNOSTIC
 		if (snapdebug) {
 			printf("Copyonwrite: snapino %ju lbn %jd for ",
 			    (uintmax_t)ip->i_number, (intmax_t)lbn);
 			if (bp->b_vp == devvp)
 				printf("fs metadata");
 			else
 				printf("inum %ju",
 				    (uintmax_t)VTOI(bp->b_vp)->i_number);
 			printf(" lblkno %jd to blkno %jd\n",
 			    (intmax_t)bp->b_lblkno, (intmax_t)cbp->b_blkno);
 		}
 #endif
 		/*
 		 * If we have already read the old block contents, then
 		 * simply copy them to the new block. Note that we need
 		 * to synchronously write snapshots that have not been
 		 * unlinked, and hence will be visible after a crash,
 		 * to ensure their integrity. At a minimum we ensure the
 		 * integrity of the filesystem metadata, but use the
 		 * dopersistence sysctl-setable flag to decide on the
 		 * persistence needed for file content data.
 		 */
 		if (savedcbp != NULL) {
 			bcopy(savedcbp->b_data, cbp->b_data, fs->fs_bsize);
 			bawrite(cbp);
 			if ((devvp == bp->b_vp || bp->b_vp->v_type == VDIR ||
 			    dopersistence) && ip->i_effnlink > 0)
 				(void) ffs_syncvnode(vp, MNT_WAIT, NO_INO_UPDT);
 			else
 				launched_async_io = 1;
 			continue;
 		}
 		/*
 		 * Otherwise, read the old block contents into the buffer.
 		 */
 		if ((error = readblock(vp, cbp, lbn)) != 0) {
 			bzero(cbp->b_data, fs->fs_bsize);
 			bawrite(cbp);
 			if ((devvp == bp->b_vp || bp->b_vp->v_type == VDIR ||
 			    dopersistence) && ip->i_effnlink > 0)
 				(void) ffs_syncvnode(vp, MNT_WAIT, NO_INO_UPDT);
 			else
 				launched_async_io = 1;
 			break;
 		}
 		savedcbp = cbp;
 	}
 	/*
 	 * Note that we need to synchronously write snapshots that
 	 * have not been unlinked, and hence will be visible after
 	 * a crash, to ensure their integrity. At a minimum we
 	 * ensure the integrity of the filesystem metadata, but
 	 * use the dopersistence sysctl-setable flag to decide on
 	 * the persistence needed for file content data.
 	 */
 	if (savedcbp) {
 		vp = savedcbp->b_vp;
 		bawrite(savedcbp);
 		if ((devvp == bp->b_vp || bp->b_vp->v_type == VDIR ||
 		    dopersistence) && VTOI(vp)->i_effnlink > 0)
 			(void) ffs_syncvnode(vp, MNT_WAIT, NO_INO_UPDT);
 		else
 			launched_async_io = 1;
 	}
 	lockmgr(vp->v_vnlock, LK_RELEASE, NULL);
 	td->td_pflags = (td->td_pflags & ~TDP_NORUNNINGBUF) |
 		prev_norunningbuf;
 	if (launched_async_io && (td->td_pflags & TDP_NORUNNINGBUF) == 0)
 		waitrunningbufspace();
 	/*
 	 * I/O on bp will now be started, so count it in runningbufspace.
 	 */
 	if (saved_runningbufspace != 0) {
 		bp->b_runningbufspace = saved_runningbufspace;
 		atomic_add_long(&runningbufspace, bp->b_runningbufspace);
 	}
 	return (error);
 }
 
 /*
  * sync snapshots to force freework records waiting on snapshots to claim
  * blocks to free.
  */
 void
 ffs_sync_snap(mp, waitfor)
 	struct mount *mp;
 	int waitfor;
 {
 	struct snapdata *sn;
 	struct vnode *devvp;
 	struct vnode *vp;
 	struct inode *ip;
 
 	devvp = VFSTOUFS(mp)->um_devvp;
 	if ((devvp->v_vflag & VV_COPYONWRITE) == 0)
 		return;
 	for (;;) {
 		VI_LOCK(devvp);
 		sn = devvp->v_rdev->si_snapdata;
 		if (sn == NULL) {
 			VI_UNLOCK(devvp);
 			return;
 		}
 		if (lockmgr(&sn->sn_lock,
 		    LK_INTERLOCK | LK_EXCLUSIVE | LK_SLEEPFAIL,
 		    VI_MTX(devvp)) == 0)
 			break;
 	}
 	TAILQ_FOREACH(ip, &sn->sn_head, i_nextsnap) {
 		vp = ITOV(ip);
 		ffs_syncvnode(vp, waitfor, NO_INO_UPDT);
 	}
 	lockmgr(&sn->sn_lock, LK_RELEASE, NULL);
 }
 
 /*
  * Read the specified block into the given buffer.
  * Much of this boiler-plate comes from bwrite().
  */
 static int
 readblock(vp, bp, lbn)
 	struct vnode *vp;
 	struct buf *bp;
 	ufs2_daddr_t lbn;
 {
 	struct inode *ip;
 	struct bio *bip;
 	struct fs *fs;
 
 	ip = VTOI(vp);
 	fs = ITOFS(ip);
 
 	bip = g_alloc_bio();
 	bip->bio_cmd = BIO_READ;
 	bip->bio_offset = dbtob(fsbtodb(fs, blkstofrags(fs, lbn)));
 	bip->bio_data = bp->b_data;
 	bip->bio_length = bp->b_bcount;
 	bip->bio_done = NULL;
 
 	g_io_request(bip, ITODEVVP(ip)->v_bufobj.bo_private);
 	bp->b_error = biowait(bip, "snaprdb");
 	g_destroy_bio(bip);
 	return (bp->b_error);
 }
 
 #endif
 
 /*
  * Process file deletes that were deferred by ufs_inactive() due to
  * the file system being suspended. Transfer IN_LAZYACCESS into
  * IN_MODIFIED for vnodes that were accessed during suspension.
  */
 void
 process_deferred_inactive(struct mount *mp)
 {
 	struct vnode *vp, *mvp;
 	struct inode *ip;
 	int error;
 
 	(void) vn_start_secondary_write(NULL, &mp, V_WAIT);
  loop:
 	MNT_VNODE_FOREACH_ALL(vp, mp, mvp) {
 		/*
 		 * IN_LAZYACCESS is checked here without holding any
 		 * vnode lock, but this flag is set only while holding
 		 * vnode interlock.
 		 */
 		if (vp->v_type == VNON ||
 		    ((VTOI(vp)->i_flag & IN_LAZYACCESS) == 0 &&
 		    ((vp->v_iflag & VI_OWEINACT) == 0 || vp->v_usecount > 0))) {
 			VI_UNLOCK(vp);
 			continue;
 		}
 		vholdl(vp);
 		error = vn_lock(vp, LK_EXCLUSIVE | LK_INTERLOCK);
 		if (error != 0) {
 			vdrop(vp);
 			if (error == ENOENT)
 				continue;	/* vnode recycled */
 			MNT_VNODE_FOREACH_ALL_ABORT(mp, mvp);
 			goto loop;
 		}
 		ip = VTOI(vp);
 		if ((ip->i_flag & IN_LAZYACCESS) != 0) {
 			ip->i_flag &= ~IN_LAZYACCESS;
 			UFS_INODE_SET_FLAG(ip, IN_MODIFIED);
 		}
 		VI_LOCK(vp);
-		if ((vp->v_iflag & VI_OWEINACT) == 0 || vp->v_usecount > 0) {
-			VI_UNLOCK(vp);
-			VOP_UNLOCK(vp);
-			vdrop(vp);
-			continue;
-		}
 		vinactive(vp);
-		VNASSERT((vp->v_iflag & VI_OWEINACT) == 0, vp,
-			 ("process_deferred_inactive: got VI_OWEINACT"));
 		VI_UNLOCK(vp);
 		VOP_UNLOCK(vp);
 		vdrop(vp);
 	}
 	vn_finished_secondary_write(mp);
 }
 
 #ifndef NO_FFS_SNAPSHOT
 
 static struct snapdata *
 ffs_snapdata_alloc(void)
 {
 	struct snapdata *sn;
 
 	/*
 	 * Fetch a snapdata from the free list if there is one available.
 	 */
 	mtx_lock(&snapfree_lock);
 	sn = LIST_FIRST(&snapfree);
 	if (sn != NULL)
 		LIST_REMOVE(sn, sn_link);
 	mtx_unlock(&snapfree_lock);
 	if (sn != NULL)
 		return (sn);
 	/*
  	 * If there were no free snapdatas allocate one.
 	 */
 	sn = malloc(sizeof *sn, M_UFSMNT, M_WAITOK | M_ZERO);
 	TAILQ_INIT(&sn->sn_head);
 	lockinit(&sn->sn_lock, PVFS, "snaplk", VLKTIMEOUT,
 	    LK_CANRECURSE | LK_NOSHARE);
 	return (sn);
 }
 
 /*
  * The snapdata is never freed because we can not be certain that
  * there are no threads sleeping on the snap lock.  Persisting
  * them permanently avoids costly synchronization in ffs_lock().
  */
 static void
 ffs_snapdata_free(struct snapdata *sn)
 {
 	mtx_lock(&snapfree_lock);
 	LIST_INSERT_HEAD(&snapfree, sn, sn_link);
 	mtx_unlock(&snapfree_lock);
 }
 
 /* Try to free snapdata associated with devvp */
 static void
 try_free_snapdata(struct vnode *devvp)
 {
 	struct snapdata *sn;
 	ufs2_daddr_t *snapblklist;
 
 	ASSERT_VI_LOCKED(devvp, "try_free_snapdata");
 	sn = devvp->v_rdev->si_snapdata;
 
 	if (sn == NULL || TAILQ_FIRST(&sn->sn_head) != NULL ||
 	    (devvp->v_vflag & VV_COPYONWRITE) == 0) {
 		VI_UNLOCK(devvp);
 		return;
 	}
 
 	devvp->v_rdev->si_snapdata = NULL;
 	devvp->v_vflag &= ~VV_COPYONWRITE;
 	lockmgr(&sn->sn_lock, LK_DRAIN|LK_INTERLOCK, VI_MTX(devvp));
 	snapblklist = sn->sn_blklist;
 	sn->sn_blklist = NULL;
 	sn->sn_listsize = 0;
 	lockmgr(&sn->sn_lock, LK_RELEASE, NULL);
 	if (snapblklist != NULL)
 		free(snapblklist, M_UFSMNT);
 	ffs_snapdata_free(sn);
 }
 
 static struct snapdata *
 ffs_snapdata_acquire(struct vnode *devvp)
 {
 	struct snapdata *nsn, *sn;
 	int error;
 
 	/*
 	 * Allocate a free snapdata.  This is done before acquiring the
 	 * devvp lock to avoid allocation while the devvp interlock is
 	 * held.
 	 */
 	nsn = ffs_snapdata_alloc();
 
 	for (;;) {
 		VI_LOCK(devvp);
 		sn = devvp->v_rdev->si_snapdata;
 		if (sn == NULL) {
 			/*
 			 * This is the first snapshot on this
 			 * filesystem and we use our pre-allocated
 			 * snapdata.  Publish sn with the sn_lock
 			 * owned by us, to avoid the race.
 			 */
 			error = lockmgr(&nsn->sn_lock, LK_EXCLUSIVE |
 			    LK_NOWAIT, NULL);
 			if (error != 0)
 				panic("leaked sn, lockmgr error %d", error);
 			sn = devvp->v_rdev->si_snapdata = nsn;
 			VI_UNLOCK(devvp);
 			nsn = NULL;
 			break;
 		}
 
 		/*
 		 * There is a snapshots which already exists on this
 		 * filesystem, grab a reference to the common lock.
 		 */
 		error = lockmgr(&sn->sn_lock, LK_INTERLOCK |
 		    LK_EXCLUSIVE | LK_SLEEPFAIL, VI_MTX(devvp));
 		if (error == 0)
 			break;
 	}
 
 	/*
 	 * Free any unused snapdata.
 	 */
 	if (nsn != NULL)
 		ffs_snapdata_free(nsn);
 
 	return (sn);
 }
 
 #endif