Fix a race with the clearing of p->p_session->s_ttyvp. NULL the pointer

[dragonfly.git] / sys / kern / vfs_subr.c

/*
 * 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *      @(#)vfs_subr.c  8.31 (Berkeley) 5/26/95
 * $FreeBSD: src/sys/kern/vfs_subr.c,v 1.249.2.30 2003/04/04 20:35:57 tegge Exp $
 * $DragonFly: src/sys/kern/vfs_subr.c,v 1.33 2004/06/15 00:30:53 dillon Exp $
 */

/*
 * External virtual filesystem routines
 */
#include "opt_ddb.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/buf.h>
#include <sys/conf.h>
#include <sys/dirent.h>
#include <sys/domain.h>
#include <sys/eventhandler.h>
#include <sys/fcntl.h>
#include <sys/kernel.h>
#include <sys/kthread.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/mount.h>
#include <sys/proc.h>
#include <sys/namei.h>
#include <sys/reboot.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/sysctl.h>
#include <sys/syslog.h>
#include <sys/vmmeter.h>
#include <sys/vnode.h>

#include <machine/limits.h>

#include <vm/vm.h>
#include <vm/vm_object.h>
#include <vm/vm_extern.h>
#include <vm/vm_kern.h>
#include <vm/pmap.h>
#include <vm/vm_map.h>
#include <vm/vm_page.h>
#include <vm/vm_pager.h>
#include <vm/vnode_pager.h>
#include <vm/vm_zone.h>

#include <sys/buf2.h>
#include <sys/thread2.h>

static MALLOC_DEFINE(M_NETADDR, "Export Host", "Export host address structure");

static void     insmntque (struct vnode *vp, struct mount *mp);
static void     vclean (struct vnode *vp, lwkt_tokref_t vlock, 
                        int flags, struct thread *td);

static unsigned long numvnodes;
SYSCTL_INT(_debug, OID_AUTO, numvnodes, CTLFLAG_RD, &numvnodes, 0, "");

enum vtype iftovt_tab[16] = {
        VNON, VFIFO, VCHR, VNON, VDIR, VNON, VBLK, VNON,
        VREG, VNON, VLNK, VNON, VSOCK, VNON, VNON, VBAD,
};
int vttoif_tab[9] = {
        0, S_IFREG, S_IFDIR, S_IFBLK, S_IFCHR, S_IFLNK,
        S_IFSOCK, S_IFIFO, S_IFMT,
};

static TAILQ_HEAD(freelst, vnode) vnode_free_list;      /* vnode free list */

static u_long wantfreevnodes = 25;
SYSCTL_INT(_debug, OID_AUTO, wantfreevnodes, CTLFLAG_RW,
                &wantfreevnodes, 0, "");
static u_long freevnodes = 0;
SYSCTL_INT(_debug, OID_AUTO, freevnodes, CTLFLAG_RD,
                &freevnodes, 0, "");

static int reassignbufcalls;
SYSCTL_INT(_vfs, OID_AUTO, reassignbufcalls, CTLFLAG_RW,
                &reassignbufcalls, 0, "");
static int reassignbufloops;
SYSCTL_INT(_vfs, OID_AUTO, reassignbufloops, CTLFLAG_RW,
                &reassignbufloops, 0, "");
static int reassignbufsortgood;
SYSCTL_INT(_vfs, OID_AUTO, reassignbufsortgood, CTLFLAG_RW,
                &reassignbufsortgood, 0, "");
static int reassignbufsortbad;
SYSCTL_INT(_vfs, OID_AUTO, reassignbufsortbad, CTLFLAG_RW,
                &reassignbufsortbad, 0, "");
static int reassignbufmethod = 1;
SYSCTL_INT(_vfs, OID_AUTO, reassignbufmethod, CTLFLAG_RW,
                &reassignbufmethod, 0, "");

#ifdef ENABLE_VFS_IOOPT
int vfs_ioopt = 0;
SYSCTL_INT(_vfs, OID_AUTO, ioopt, CTLFLAG_RW, &vfs_ioopt, 0, "");
#endif

struct mntlist mountlist = TAILQ_HEAD_INITIALIZER(mountlist); /* mounted fs */
struct lwkt_token mountlist_token;
struct lwkt_token mntvnode_token;
int     nfs_mount_type = -1;
static struct lwkt_token mntid_token;
static struct lwkt_token vnode_free_list_token;
static struct lwkt_token spechash_token;
struct nfs_public nfs_pub;      /* publicly exported FS */
static vm_zone_t vnode_zone;

/*
 * The workitem queue.
 */
#define SYNCER_MAXDELAY         32
static int syncer_maxdelay = SYNCER_MAXDELAY;   /* maximum delay time */
time_t syncdelay = 30;          /* max time to delay syncing data */
SYSCTL_INT(_kern, OID_AUTO, syncdelay, CTLFLAG_RW,
                &syncdelay, 0, "VFS data synchronization delay");
time_t filedelay = 30;          /* time to delay syncing files */
SYSCTL_INT(_kern, OID_AUTO, filedelay, CTLFLAG_RW,
                &filedelay, 0, "File synchronization delay");
time_t dirdelay = 29;           /* time to delay syncing directories */
SYSCTL_INT(_kern, OID_AUTO, dirdelay, CTLFLAG_RW,
                &dirdelay, 0, "Directory synchronization delay");
time_t metadelay = 28;          /* time to delay syncing metadata */
SYSCTL_INT(_kern, OID_AUTO, metadelay, CTLFLAG_RW,
                &metadelay, 0, "VFS metadata synchronization delay");
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, "");

static int syncer_delayno = 0;
static long syncer_mask; 
LIST_HEAD(synclist, vnode);
static struct synclist *syncer_workitem_pending;

int desiredvnodes;
SYSCTL_INT(_kern, KERN_MAXVNODES, maxvnodes, CTLFLAG_RW, 
                &desiredvnodes, 0, "Maximum number of vnodes");
static int minvnodes;
SYSCTL_INT(_kern, OID_AUTO, minvnodes, CTLFLAG_RW, 
                &minvnodes, 0, "Minimum number of vnodes");
static int vnlru_nowhere = 0;
SYSCTL_INT(_debug, OID_AUTO, vnlru_nowhere, CTLFLAG_RW,
                &vnlru_nowhere, 0,
                "Number of times the vnlru process ran without success");

static void     vfs_free_addrlist (struct netexport *nep);
static int      vfs_free_netcred (struct radix_node *rn, void *w);
static int      vfs_hang_addrlist (struct mount *mp, struct netexport *nep,
                                       struct export_args *argp);

#define VSHOULDFREE(vp) \
        (!((vp)->v_flag & (VFREE|VDOOMED)) && \
         !(vp)->v_holdcnt && !(vp)->v_usecount && \
         (!(vp)->v_object || \
          !((vp)->v_object->ref_count || (vp)->v_object->resident_page_count)))
 
#define VMIGHTFREE(vp) \
        (((vp)->v_flag & (VFREE|VDOOMED|VXLOCK)) == 0 &&   \
         cache_leaf_test(vp) == 0 && (vp)->v_usecount == 0)
 
#define VSHOULDBUSY(vp) \
        (((vp)->v_flag & VFREE) && \
         ((vp)->v_holdcnt || (vp)->v_usecount))

static void vbusy(struct vnode *vp);
static void vfree(struct vnode *vp);
static void vmaybefree(struct vnode *vp);

extern int dev_ref_debug;

/*
 * NOTE: the vnode interlock must be held on call.
 */
static __inline void
vmaybefree(struct vnode *vp)
{
        if (VSHOULDFREE(vp))
                vfree(vp);
}
 
/*
 * Initialize the vnode management data structures.
 */
void
vntblinit(void)
{

        /*
         * Desired vnodes is a result of the physical page count
         * and the size of kernel's heap.  It scales in proportion
         * to the amount of available physical memory.  This can
         * cause trouble on 64-bit and large memory platforms.
         */
        /* desiredvnodes = maxproc + vmstats.v_page_count / 4; */
        desiredvnodes =
                min(maxproc + vmstats.v_page_count /4,
                    2 * (VM_MAX_KERNEL_ADDRESS - VM_MIN_KERNEL_ADDRESS) /
                    (5 * (sizeof(struct vm_object) + sizeof(struct vnode))));

        minvnodes = desiredvnodes / 4;
        lwkt_token_init(&mountlist_token);
        lwkt_token_init(&mntvnode_token);
        lwkt_token_init(&mntid_token);
        lwkt_token_init(&spechash_token);
        TAILQ_INIT(&vnode_free_list);
        lwkt_token_init(&vnode_free_list_token);
        vnode_zone = zinit("VNODE", sizeof (struct vnode), 0, 0, 5);
        /*
         * Initialize the filesystem syncer.
         */     
        syncer_workitem_pending = hashinit(syncer_maxdelay, M_VNODE, 
                &syncer_mask);
        syncer_maxdelay = syncer_mask + 1;
}

/*
 * Mark a mount point as busy. Used to synchronize access and to delay
 * unmounting. Interlock is not released on failure.
 */
int
vfs_busy(struct mount *mp, int flags,
        lwkt_tokref_t interlkp, struct thread *td)
{
        int lkflags;

        if (mp->mnt_kern_flag & MNTK_UNMOUNT) {
                if (flags & LK_NOWAIT)
                        return (ENOENT);
                mp->mnt_kern_flag |= MNTK_MWAIT;
                /*
                 * Since all busy locks are shared except the exclusive
                 * lock granted when unmounting, the only place that a
                 * wakeup needs to be done is at the release of the
                 * exclusive lock at the end of dounmount.
                 *
                 * note: interlkp is a serializer and thus can be safely
                 * held through any sleep
                 */
                tsleep((caddr_t)mp, 0, "vfs_busy", 0);
                return (ENOENT);
        }
        lkflags = LK_SHARED | LK_NOPAUSE;
        if (interlkp)
                lkflags |= LK_INTERLOCK;
        if (lockmgr(&mp->mnt_lock, lkflags, interlkp, td))
                panic("vfs_busy: unexpected lock failure");
        return (0);
}

/*
 * Free a busy filesystem.
 */
void
vfs_unbusy(struct mount *mp, struct thread *td)
{
        lockmgr(&mp->mnt_lock, LK_RELEASE, NULL, td);
}

/*
 * Lookup a filesystem type, and if found allocate and initialize
 * a mount structure for it.
 *
 * Devname is usually updated by mount(8) after booting.
 */
int
vfs_rootmountalloc(char *fstypename, char *devname, struct mount **mpp)
{
        struct thread *td = curthread;  /* XXX */
        struct vfsconf *vfsp;
        struct mount *mp;

        if (fstypename == NULL)
                return (ENODEV);
        for (vfsp = vfsconf; vfsp; vfsp = vfsp->vfc_next)
                if (!strcmp(vfsp->vfc_name, fstypename))
                        break;
        if (vfsp == NULL)
                return (ENODEV);
        mp = malloc((u_long)sizeof(struct mount), M_MOUNT, M_WAITOK);
        bzero((char *)mp, (u_long)sizeof(struct mount));
        lockinit(&mp->mnt_lock, 0, "vfslock", VLKTIMEOUT, LK_NOPAUSE);
        vfs_busy(mp, LK_NOWAIT, NULL, td);
        TAILQ_INIT(&mp->mnt_nvnodelist);
        TAILQ_INIT(&mp->mnt_reservedvnlist);
        mp->mnt_nvnodelistsize = 0;
        mp->mnt_vfc = vfsp;
        mp->mnt_op = vfsp->vfc_vfsops;
        mp->mnt_flag = MNT_RDONLY;
        mp->mnt_vnodecovered = NULLVP;
        vfsp->vfc_refcount++;
        mp->mnt_iosize_max = DFLTPHYS;
        mp->mnt_stat.f_type = vfsp->vfc_typenum;
        mp->mnt_flag |= vfsp->vfc_flags & MNT_VISFLAGMASK;
        strncpy(mp->mnt_stat.f_fstypename, vfsp->vfc_name, MFSNAMELEN);
        mp->mnt_stat.f_mntonname[0] = '/';
        mp->mnt_stat.f_mntonname[1] = 0;
        (void) copystr(devname, mp->mnt_stat.f_mntfromname, MNAMELEN - 1, 0);
        *mpp = mp;
        return (0);
}

/*
 * Lookup a mount point by filesystem identifier.
 */
struct mount *
vfs_getvfs(fsid_t *fsid)
{
        struct mount *mp;
        lwkt_tokref ilock;

        lwkt_gettoken(&ilock, &mountlist_token);
        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]) {
                        break;
            }
        }
        lwkt_reltoken(&ilock);
        return (mp);
}

/*
 * 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 u_int16_t mntid_base;
        lwkt_tokref ilock;
        fsid_t tfsid;
        int mtype;

        lwkt_gettoken(&ilock, &mntid_token);
        mtype = mp->mnt_vfc->vfc_typenum;
        tfsid.val[1] = mtype;
        mtype = (mtype & 0xFF) << 24;
        for (;;) {
                tfsid.val[0] = makeudev(255,
                    mtype | ((mntid_base & 0xFF00) << 8) | (mntid_base & 0xFF));
                mntid_base++;
                if (vfs_getvfs(&tfsid) == NULL)
                        break;
        }
        mp->mnt_stat.f_fsid.val[0] = tfsid.val[0];
        mp->mnt_stat.f_fsid.val[1] = tfsid.val[1];
        lwkt_reltoken(&ilock);
}

/*
 * 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_SEC;
SYSCTL_INT(_vfs, OID_AUTO, timestamp_precision, CTLFLAG_RW,
                &timestamp_precision, 0, "");

/*
 * 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_flags = VNOVAL;
        vap->va_gen = VNOVAL;
        vap->va_vaflags = 0;
}

/*
 * 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
 * desireable 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.
 */
static int
vlrureclaim(struct mount *mp)
{
        struct vnode *vp;
        lwkt_tokref ilock;
        lwkt_tokref vlock;
        int done;
        int trigger;
        int usevnodes;
        int count;

        /*
         * Calculate the trigger point, don't allow user
         * screwups to blow us up.   This prevents us from
         * recycling vnodes with lots of resident pages.  We
         * aren't trying to free memory, we are trying to
         * free vnodes.
         */
        usevnodes = desiredvnodes;
        if (usevnodes <= 0)
                usevnodes = 1;
        trigger = vmstats.v_page_count * 2 / usevnodes;

        done = 0;
        lwkt_gettoken(&ilock, &mntvnode_token);
        count = mp->mnt_nvnodelistsize / 10 + 1;
        while (count && (vp = TAILQ_FIRST(&mp->mnt_nvnodelist)) != NULL) {
                /*
                 * __VNODESCAN__
                 *
                 * The VP will stick around while we hold mntvnode_token,
                 * at least until we block, so we can safely do an initial
                 * check.  But we have to check again after obtaining
                 * the vnode interlock.  vp->v_interlock points to stable
                 * storage so it's ok if the vp gets ripped out from
                 * under us while we are blocked.
                 */
                if (vp->v_type == VNON ||
                    vp->v_type == VBAD ||
                    !VMIGHTFREE(vp) ||          /* critical path opt */
                    (vp->v_object &&
                     vp->v_object->resident_page_count >= trigger)
                ) {
                        TAILQ_REMOVE(&mp->mnt_nvnodelist, vp, v_nmntvnodes);
                        TAILQ_INSERT_TAIL(&mp->mnt_nvnodelist,vp, v_nmntvnodes);
                        --count;
                        continue;
                }

                /*
                 * Get the interlock, delay moving the node to the tail so
                 * we don't race against new additions to the mountlist.
                 */
                lwkt_gettoken(&vlock, vp->v_interlock);
                if (TAILQ_FIRST(&mp->mnt_nvnodelist) != vp) {
                        lwkt_reltoken(&vlock);
                        continue;
                }
                TAILQ_REMOVE(&mp->mnt_nvnodelist, vp, v_nmntvnodes);
                TAILQ_INSERT_TAIL(&mp->mnt_nvnodelist,vp, v_nmntvnodes);

                /*
                 * Must check again
                 */
                if (vp->v_type == VNON ||
                    vp->v_type == VBAD ||
                    !VMIGHTFREE(vp) ||          /* critical path opt */
                    (vp->v_object &&
                     vp->v_object->resident_page_count >= trigger)
                ) {
                        lwkt_reltoken(&vlock);
                        --count;
                        continue;
                }
                vgonel(vp, &vlock, curthread);
                ++done;
                --count;
        }
        lwkt_reltoken(&ilock);
        return done;
}

/*
 * Attempt to recycle vnodes in a context that is always safe to block.
 * Calling vlrurecycle() from the bowels of file system code has some
 * interesting deadlock problems.
 */
static struct thread *vnlruthread;
static int vnlruproc_sig;

static void 
vnlru_proc(void)
{
        struct mount *mp, *nmp;
        lwkt_tokref ilock;
        int s;
        int done;
        struct thread *td = curthread;

        EVENTHANDLER_REGISTER(shutdown_pre_sync, shutdown_kproc, td,
            SHUTDOWN_PRI_FIRST);   

        s = splbio();
        for (;;) {
                kproc_suspend_loop();
                if (numvnodes - freevnodes <= desiredvnodes * 9 / 10) {
                        vnlruproc_sig = 0;
                        wakeup(&vnlruproc_sig);
                        tsleep(td, 0, "vlruwt", hz);
                        continue;
                }
                done = 0;
                lwkt_gettoken(&ilock, &mountlist_token);
                for (mp = TAILQ_FIRST(&mountlist); mp != NULL; mp = nmp) {
                        if (vfs_busy(mp, LK_NOWAIT, &ilock, td)) {
                                nmp = TAILQ_NEXT(mp, mnt_list);
                                continue;
                        }
                        done += vlrureclaim(mp);
                        lwkt_gettokref(&ilock);
                        nmp = TAILQ_NEXT(mp, mnt_list);
                        vfs_unbusy(mp, td);
                }
                lwkt_reltoken(&ilock);
                if (done == 0) {
                        vnlru_nowhere++;
                        tsleep(td, 0, "vlrup", hz * 3);
                }
        }
        splx(s);
}

static struct kproc_desc vnlru_kp = {
        "vnlru",
        vnlru_proc,
        &vnlruthread
};
SYSINIT(vnlru, SI_SUB_KTHREAD_UPDATE, SI_ORDER_FIRST, kproc_start, &vnlru_kp)

/*
 * Routines having to do with the management of the vnode table.
 */
extern vop_t **dead_vnodeop_p;

/*
 * Return the next vnode from the free list.
 */
int
getnewvnode(enum vtagtype tag, struct mount *mp, 
            vop_t **vops, struct vnode **vpp)
{
        int s;
        struct thread *td = curthread;  /* XXX */
        struct vnode *vp = NULL;
        struct vnode *xvp;
        vm_object_t object;
        lwkt_tokref ilock;
        lwkt_tokref vlock;

        s = splbio();

        /*
         * Try to reuse vnodes if we hit the max.  This situation only
         * occurs in certain large-memory (2G+) situations.  We cannot
         * attempt to directly reclaim vnodes due to nasty recursion
         * problems.
         */
        while (numvnodes - freevnodes > desiredvnodes) {
                if (vnlruproc_sig == 0) {
                        vnlruproc_sig = 1;      /* avoid unnecessary wakeups */
                        wakeup(vnlruthread);
                }
                tsleep(&vnlruproc_sig, 0, "vlruwk", hz);
        }


        /*
         * Attempt to reuse a vnode already on the free list, allocating
         * a new vnode if we can't find one or if we have not reached a
         * good minimum for good LRU performance.
         */
        lwkt_gettoken(&ilock, &vnode_free_list_token);
        if (freevnodes >= wantfreevnodes && numvnodes >= minvnodes) {
                int count;

                for (count = 0; count < freevnodes; count++) {
                        /*
                         * __VNODESCAN__
                         *
                         * Pull the next vnode off the free list and do some
                         * sanity checks.  Note that regardless of how we
                         * block, if freevnodes is non-zero there had better
                         * be something on the list.
                         */
                        vp = TAILQ_FIRST(&vnode_free_list);
                        if (vp == NULL)
                                panic("getnewvnode: free vnode isn't");

                        /*
                         * Move the vnode to the end of the list so other
                         * processes do not double-block trying to recycle
                         * the same vnode (as an optimization), then get
                         * the interlock.
                         */
                        TAILQ_REMOVE(&vnode_free_list, vp, v_freelist);
                        TAILQ_INSERT_TAIL(&vnode_free_list, vp, v_freelist);

                        /*
                         * Skip vnodes that are in the process of being
                         * held or referenced.  Since the act of adding or
                         * removing a vnode on the freelist requires a token
                         * and may block, the ref count may be adjusted
                         * prior to its addition or removal.
                         */
                        if (VSHOULDBUSY(vp)) {
                                vp = NULL;
                                continue;
                        }


                        /*
                         * Obtain the vnode interlock and check that the
                         * vnode is still on the free list.
                         *
                         * This normally devolves into a degenerate case so
                         * it is optimal.   Loop up if it isn't.  Note that
                         * the vnode could be in the middle of being moved
                         * off the free list (the VSHOULDBUSY() check) and
                         * must be skipped if so.
                         */
                        lwkt_gettoken(&vlock, vp->v_interlock);
                        TAILQ_FOREACH_REVERSE(xvp, &vnode_free_list, 
                            freelst, v_freelist) {
                                if (vp == xvp)
                                        break;
                        }
                        if (vp != xvp || VSHOULDBUSY(vp)) {
                                vp = NULL;
                                continue;
                        }

                        /*
                         * We now safely own the vnode.  If the vnode has
                         * an object do not recycle it if its VM object
                         * has resident pages or references.
                         */
                        if ((VOP_GETVOBJECT(vp, &object) == 0 &&
                            (object->resident_page_count || object->ref_count))
                        ) {
                                lwkt_reltoken(&vlock);
                                vp = NULL;
                                continue;
                        }

                        /*
                         * We can almost reuse this vnode.  But we don't want
                         * to recycle it if the vnode has children in the
                         * namecache because that breaks the namecache's
                         * path element chain.  (YYY use nc_refs for the
                         * check?)
                         */
                        KKASSERT(vp->v_flag & VFREE);
                        TAILQ_REMOVE(&vnode_free_list, vp, v_freelist);

                        if (TAILQ_FIRST(&vp->v_namecache) == NULL ||
                            cache_leaf_test(vp) >= 0) {
                                /* ok, we can reuse this vnode */
                                break;
                        }
                        lwkt_reltoken(&vlock);
                        TAILQ_INSERT_TAIL(&vnode_free_list, vp, v_freelist);
                        vp = NULL;
                }
        }

        /*
         * If vp is non-NULL we hold it's interlock.
         */
        if (vp) {
                vp->v_flag |= VDOOMED;
                vp->v_flag &= ~VFREE;
                freevnodes--;
                lwkt_reltoken(&ilock);
                cache_purge(vp);        /* YYY may block */
                vp->v_lease = NULL;
                if (vp->v_type != VBAD) {
                        vgonel(vp, &vlock, td);
                } else {
                        lwkt_reltoken(&vlock);
                }

#ifdef INVARIANTS
                {
                        int s;

                        if (vp->v_data)
                                panic("cleaned vnode isn't");
                        s = splbio();
                        if (vp->v_numoutput)
                                panic("Clean vnode has pending I/O's");
                        splx(s);
                }
#endif
                vp->v_flag = 0;
                vp->v_lastw = 0;
                vp->v_lasta = 0;
                vp->v_cstart = 0;
                vp->v_clen = 0;
                vp->v_socket = 0;
                vp->v_writecount = 0;   /* XXX */
        } else {
                lwkt_reltoken(&ilock);
                vp = zalloc(vnode_zone);
                bzero(vp, sizeof(*vp));
                vp->v_interlock = lwkt_token_pool_get(vp);
                lwkt_token_init(&vp->v_pollinfo.vpi_token);
                cache_purge(vp);
                TAILQ_INIT(&vp->v_namecache);
                numvnodes++;
        }

        TAILQ_INIT(&vp->v_cleanblkhd);
        TAILQ_INIT(&vp->v_dirtyblkhd);
        vp->v_type = VNON;
        vp->v_tag = tag;
        vp->v_op = vops;
        insmntque(vp, mp);
        *vpp = vp;
        vp->v_usecount = 1;
        vp->v_data = 0;
        splx(s);

        vfs_object_create(vp, td);
        return (0);
}

/*
 * Move a vnode from one mount queue to another.
 */
static void
insmntque(struct vnode *vp, struct mount *mp)
{
        lwkt_tokref ilock;

        lwkt_gettoken(&ilock, &mntvnode_token);
        /*
         * Delete from old mount point vnode list, if on one.
         */
        if (vp->v_mount != NULL) {
                KASSERT(vp->v_mount->mnt_nvnodelistsize > 0,
                        ("bad mount point vnode list size"));
                TAILQ_REMOVE(&vp->v_mount->mnt_nvnodelist, vp, v_nmntvnodes);
                vp->v_mount->mnt_nvnodelistsize--;
        }
        /*
         * Insert into list of vnodes for the new mount point, if available.
         */
        if ((vp->v_mount = mp) == NULL) {
                lwkt_reltoken(&ilock);
                return;
        }
        TAILQ_INSERT_TAIL(&mp->mnt_nvnodelist, vp, v_nmntvnodes);
        mp->mnt_nvnodelistsize++;
        lwkt_reltoken(&ilock);
}

/*
 * Update outstanding I/O count and do wakeup if requested.
 */
void
vwakeup(struct buf *bp)
{
        struct vnode *vp;

        bp->b_flags &= ~B_WRITEINPROG;
        if ((vp = bp->b_vp)) {
                vp->v_numoutput--;
                if (vp->v_numoutput < 0)
                        panic("vwakeup: neg numoutput");
                if ((vp->v_numoutput == 0) && (vp->v_flag & VBWAIT)) {
                        vp->v_flag &= ~VBWAIT;
                        wakeup((caddr_t) &vp->v_numoutput);
                }
        }
}

/*
 * Flush out and invalidate all buffers associated with a vnode.
 * Called with the underlying object locked.
 */
int
vinvalbuf(struct vnode *vp, int flags, struct thread *td,
        int slpflag, int slptimeo)
{
        struct buf *bp;
        struct buf *nbp, *blist;
        int s, error;
        vm_object_t object;
        lwkt_tokref vlock;

        if (flags & V_SAVE) {
                s = splbio();
                while (vp->v_numoutput) {
                        vp->v_flag |= VBWAIT;
                        error = tsleep((caddr_t)&vp->v_numoutput,
                            slpflag, "vinvlbuf", slptimeo);
                        if (error) {
                                splx(s);
                                return (error);
                        }
                }
                if (!TAILQ_EMPTY(&vp->v_dirtyblkhd)) {
                        splx(s);
                        if ((error = VOP_FSYNC(vp, MNT_WAIT, td)) != 0)
                                return (error);
                        s = splbio();
                        if (vp->v_numoutput > 0 ||
                            !TAILQ_EMPTY(&vp->v_dirtyblkhd))
                                panic("vinvalbuf: dirty bufs");
                }
                splx(s);
        }
        s = splbio();
        for (;;) {
                blist = TAILQ_FIRST(&vp->v_cleanblkhd);
                if (!blist)
                        blist = TAILQ_FIRST(&vp->v_dirtyblkhd);
                if (!blist)
                        break;

                for (bp = blist; bp; bp = nbp) {
                        nbp = TAILQ_NEXT(bp, b_vnbufs);
                        if (BUF_LOCK(bp, LK_EXCLUSIVE | LK_NOWAIT)) {
                                error = BUF_TIMELOCK(bp,
                                    LK_EXCLUSIVE | LK_SLEEPFAIL,
                                    "vinvalbuf", slpflag, slptimeo);
                                if (error == ENOLCK)
                                        break;
                                splx(s);
                                return (error);
                        }
                        /*
                         * 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.  Note that vfs_bio_awrite expects
                         * buffers to reside on a queue, while VOP_BWRITE and
                         * brelse do not.
                         */
                        if (((bp->b_flags & (B_DELWRI | B_INVAL)) == B_DELWRI) &&
                                (flags & V_SAVE)) {

                                if (bp->b_vp == vp) {
                                        if (bp->b_flags & B_CLUSTEROK) {
                                                BUF_UNLOCK(bp);
                                                vfs_bio_awrite(bp);
                                        } else {
                                                bremfree(bp);
                                                bp->b_flags |= B_ASYNC;
                                                VOP_BWRITE(bp->b_vp, bp);
                                        }
                                } else {
                                        bremfree(bp);
                                        (void) VOP_BWRITE(bp->b_vp, bp);
                                }
                                break;
                        }
                        bremfree(bp);
                        bp->b_flags |= (B_INVAL | B_NOCACHE | B_RELBUF);
                        bp->b_flags &= ~B_ASYNC;
                        brelse(bp);
                }
        }

        /*
         * 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 {
                while (vp->v_numoutput > 0) {
                        vp->v_flag |= VBWAIT;
                        tsleep(&vp->v_numoutput, 0, "vnvlbv", 0);
                }
                if (VOP_GETVOBJECT(vp, &object) == 0) {
                        while (object->paging_in_progress)
                                vm_object_pip_sleep(object, "vnvlbx");
                }
        } while (vp->v_numoutput > 0);

        splx(s);

        /*
         * Destroy the copy in the VM cache, too.
         */
        lwkt_gettoken(&vlock, vp->v_interlock);
        if (VOP_GETVOBJECT(vp, &object) == 0) {
                vm_object_page_remove(object, 0, 0,
                        (flags & V_SAVE) ? TRUE : FALSE);
        }
        lwkt_reltoken(&vlock);

        if (!TAILQ_EMPTY(&vp->v_dirtyblkhd) || !TAILQ_EMPTY(&vp->v_cleanblkhd))
                panic("vinvalbuf: flush failed");
        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, struct thread *td, off_t length, int blksize)
{
        struct buf *bp;
        struct buf *nbp;
        int s, anyfreed;
        int trunclbn;

        /*
         * Round up to the *next* lbn.
         */
        trunclbn = (length + blksize - 1) / blksize;

        s = splbio();
restart:
        anyfreed = 1;
        for (;anyfreed;) {
                anyfreed = 0;
                for (bp = TAILQ_FIRST(&vp->v_cleanblkhd); bp; bp = nbp) {
                        nbp = TAILQ_NEXT(bp, b_vnbufs);
                        if (bp->b_lblkno >= trunclbn) {
                                if (BUF_LOCK(bp, LK_EXCLUSIVE | LK_NOWAIT)) {
                                        BUF_LOCK(bp, LK_EXCLUSIVE|LK_SLEEPFAIL);
                                        goto restart;
                                } else {
                                        bremfree(bp);
                                        bp->b_flags |= (B_INVAL | B_RELBUF);
                                        bp->b_flags &= ~B_ASYNC;
                                        brelse(bp);
                                        anyfreed = 1;
                                }
                                if (nbp &&
                                    (((nbp->b_xflags & BX_VNCLEAN) == 0) ||
                                    (nbp->b_vp != vp) ||
                                    (nbp->b_flags & B_DELWRI))) {
                                        goto restart;
                                }
                        }
                }

                for (bp = TAILQ_FIRST(&vp->v_dirtyblkhd); bp; bp = nbp) {
                        nbp = TAILQ_NEXT(bp, b_vnbufs);
                        if (bp->b_lblkno >= trunclbn) {
                                if (BUF_LOCK(bp, LK_EXCLUSIVE | LK_NOWAIT)) {
                                        BUF_LOCK(bp, LK_EXCLUSIVE|LK_SLEEPFAIL);
                                        goto restart;
                                } else {
                                        bremfree(bp);
                                        bp->b_flags |= (B_INVAL | B_RELBUF);
                                        bp->b_flags &= ~B_ASYNC;
                                        brelse(bp);
                                        anyfreed = 1;
                                }
                                if (nbp &&
                                    (((nbp->b_xflags & BX_VNDIRTY) == 0) ||
                                    (nbp->b_vp != vp) ||
                                    (nbp->b_flags & B_DELWRI) == 0)) {
                                        goto restart;
                                }
                        }
                }
        }

        if (length > 0) {
restartsync:
                for (bp = TAILQ_FIRST(&vp->v_dirtyblkhd); bp; bp = nbp) {
                        nbp = TAILQ_NEXT(bp, b_vnbufs);
                        if ((bp->b_flags & B_DELWRI) && (bp->b_lblkno < 0)) {
                                if (BUF_LOCK(bp, LK_EXCLUSIVE | LK_NOWAIT)) {
                                        BUF_LOCK(bp, LK_EXCLUSIVE|LK_SLEEPFAIL);
                                        goto restart;
                                } else {
                                        bremfree(bp);
                                        if (bp->b_vp == vp) {
                                                bp->b_flags |= B_ASYNC;
                                        } else {
                                                bp->b_flags &= ~B_ASYNC;
                                        }
                                        VOP_BWRITE(bp->b_vp, bp);
                                }
                                goto restartsync;
                        }

                }
        }

        while (vp->v_numoutput > 0) {
                vp->v_flag |= VBWAIT;
                tsleep(&vp->v_numoutput, 0, "vbtrunc", 0);
        }

        splx(s);

        vnode_pager_setsize(vp, length);

        return (0);
}

/*
 * Associate a buffer with a vnode.
 */
void
bgetvp(struct vnode *vp, struct buf *bp)
{
        int s;

        KASSERT(bp->b_vp == NULL, ("bgetvp: not free"));

        vhold(vp);
        bp->b_vp = vp;
        bp->b_dev = vn_todev(vp);
        /*
         * Insert onto list for new vnode.
         */
        s = splbio();
        bp->b_xflags |= BX_VNCLEAN;
        bp->b_xflags &= ~BX_VNDIRTY;
        TAILQ_INSERT_TAIL(&vp->v_cleanblkhd, bp, b_vnbufs);
        splx(s);
}

/*
 * Disassociate a buffer from a vnode.
 */
void
brelvp(struct buf *bp)
{
        struct vnode *vp;
        struct buflists *listheadp;
        int s;

        KASSERT(bp->b_vp != NULL, ("brelvp: NULL"));

        /*
         * Delete from old vnode list, if on one.
         */
        vp = bp->b_vp;
        s = splbio();
        if (bp->b_xflags & (BX_VNDIRTY | BX_VNCLEAN)) {
                if (bp->b_xflags & BX_VNDIRTY)
                        listheadp = &vp->v_dirtyblkhd;
                else 
                        listheadp = &vp->v_cleanblkhd;
                TAILQ_REMOVE(listheadp, bp, b_vnbufs);
                bp->b_xflags &= ~(BX_VNDIRTY | BX_VNCLEAN);
        }
        if ((vp->v_flag & VONWORKLST) && TAILQ_EMPTY(&vp->v_dirtyblkhd)) {
                vp->v_flag &= ~VONWORKLST;
                LIST_REMOVE(vp, v_synclist);
        }
        splx(s);
        bp->b_vp = (struct vnode *) 0;
        vdrop(vp);
}

/*
 * 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]
 *
 */

/*
 * Add an item to the syncer work queue.
 */
static void
vn_syncer_add_to_worklist(struct vnode *vp, int delay)
{
        int s, slot;

        s = splbio();

        if (vp->v_flag & VONWORKLST) {
                LIST_REMOVE(vp, v_synclist);
        }

        if (delay > syncer_maxdelay - 2)
                delay = syncer_maxdelay - 2;
        slot = (syncer_delayno + delay) & syncer_mask;

        LIST_INSERT_HEAD(&syncer_workitem_pending[slot], vp, v_synclist);
        vp->v_flag |= VONWORKLST;
        splx(s);
}

struct  thread *updatethread;
static void sched_sync (void);
static struct kproc_desc up_kp = {
        "syncer",
        sched_sync,
        &updatethread
};
SYSINIT(syncer, SI_SUB_KTHREAD_UPDATE, SI_ORDER_FIRST, kproc_start, &up_kp)

/*
 * System filesystem synchronizer daemon.
 */
void 
sched_sync(void)
{
        struct synclist *slp;
        struct vnode *vp;
        long starttime;
        int s;
        struct thread *td = curthread;

        EVENTHANDLER_REGISTER(shutdown_pre_sync, shutdown_kproc, td,
            SHUTDOWN_PRI_LAST);   

        for (;;) {
                kproc_suspend_loop();

                starttime = time_second;

                /*
                 * Push files whose dirty time has expired.  Be careful
                 * of interrupt race on slp queue.
                 */
                s = splbio();
                slp = &syncer_workitem_pending[syncer_delayno];
                syncer_delayno += 1;
                if (syncer_delayno == syncer_maxdelay)
                        syncer_delayno = 0;
                splx(s);

                while ((vp = LIST_FIRST(slp)) != NULL) {
                        if (VOP_ISLOCKED(vp, NULL) == 0) {
                                vn_lock(vp, NULL, LK_EXCLUSIVE | LK_RETRY, td);
                                (void) VOP_FSYNC(vp, MNT_LAZY, td);
                                VOP_UNLOCK(vp, NULL, 0, td);
                        }
                        s = splbio();
                        if (LIST_FIRST(slp) == vp) {
                                /*
                                 * Note: v_tag VT_VFS vps can remain on the
                                 * worklist too with no dirty blocks, but 
                                 * since sync_fsync() moves it to a different 
                                 * slot we are safe.
                                 */
                                if (TAILQ_EMPTY(&vp->v_dirtyblkhd) &&
                                    !vn_isdisk(vp, NULL))
                                        panic("sched_sync: fsync failed vp %p tag %d", vp, vp->v_tag);
                                /*
                                 * 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(vp, syncdelay);
                        }
                        splx(s);
                }

                /*
                 * Do soft update processing.
                 */
                if (bioops.io_sync)
                        (*bioops.io_sync)(NULL);

                /*
                 * 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;
                }
                /*
                 * 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 (time_second == starttime)
                        tsleep(&lbolt, 0, "syncer", 0);
        }
}

/*
 * 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.
 *
 * YYY wchan field protected by the BGL.
 */
int
speedup_syncer(void)
{
        crit_enter();
        if (updatethread->td_wchan == &lbolt) { /* YYY */
                unsleep(updatethread);
                lwkt_schedule(updatethread);
        }
        crit_exit();
        if (rushjob < syncdelay / 2) {
                rushjob += 1;
                stat_rush_requests += 1;
                return (1);
        }
        return(0);
}

/*
 * Associate a p-buffer with a vnode.
 *
 * Also sets B_PAGING flag to indicate that vnode is not fully associated
 * with the buffer.  i.e. the bp has not been linked into the vnode or
 * ref-counted.
 */
void
pbgetvp(struct vnode *vp, struct buf *bp)
{
        KASSERT(bp->b_vp == NULL, ("pbgetvp: not free"));

        bp->b_vp = vp;
        bp->b_flags |= B_PAGING;
        bp->b_dev = vn_todev(vp);
}

/*
 * Disassociate a p-buffer from a vnode.
 */
void
pbrelvp(struct buf *bp)
{
        KASSERT(bp->b_vp != NULL, ("pbrelvp: NULL"));

        /* XXX REMOVE ME */
        if (TAILQ_NEXT(bp, b_vnbufs) != NULL) {
                panic(
                    "relpbuf(): b_vp was probably reassignbuf()d %p %x", 
                    bp,
                    (int)bp->b_flags
                );
        }
        bp->b_vp = (struct vnode *) 0;
        bp->b_flags &= ~B_PAGING;
}

void
pbreassignbuf(struct buf *bp, struct vnode *newvp)
{
        if ((bp->b_flags & B_PAGING) == 0) {
                panic(
                    "pbreassignbuf() on non phys bp %p", 
                    bp
                );
        }
        bp->b_vp = newvp;
}

/*
 * 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 *newvp)
{
        struct buflists *listheadp;
        int delay;
        int s;

        if (newvp == NULL) {
                printf("reassignbuf: NULL");
                return;
        }
        ++reassignbufcalls;

        /*
         * 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");

        s = splbio();
        /*
         * Delete from old vnode list, if on one.
         */
        if (bp->b_xflags & (BX_VNDIRTY | BX_VNCLEAN)) {
                if (bp->b_xflags & BX_VNDIRTY)
                        listheadp = &bp->b_vp->v_dirtyblkhd;
                else 
                        listheadp = &bp->b_vp->v_cleanblkhd;
                TAILQ_REMOVE(listheadp, bp, b_vnbufs);
                bp->b_xflags &= ~(BX_VNDIRTY | BX_VNCLEAN);
                if (bp->b_vp != newvp) {
                        vdrop(bp->b_vp);
                        bp->b_vp = NULL;        /* for clarification */
                }
        }
        /*
         * If dirty, put on list of dirty buffers; otherwise insert onto list
         * of clean buffers.
         */
        if (bp->b_flags & B_DELWRI) {
                struct buf *tbp;

                listheadp = &newvp->v_dirtyblkhd;
                if ((newvp->v_flag & VONWORKLST) == 0) {
                        switch (newvp->v_type) {
                        case VDIR:
                                delay = dirdelay;
                                break;
                        case VCHR:
                        case VBLK:
                                if (newvp->v_rdev && 
                                    newvp->v_rdev->si_mountpoint != NULL) {
                                        delay = metadelay;
                                        break;
                                }
                                /* fall through */
                        default:
                                delay = filedelay;
                        }
                        vn_syncer_add_to_worklist(newvp, delay);
                }
                bp->b_xflags |= BX_VNDIRTY;
                tbp = TAILQ_FIRST(listheadp);
                if (tbp == NULL ||
                    bp->b_lblkno == 0 ||
                    (bp->b_lblkno > 0 && tbp->b_lblkno < 0) ||
                    (bp->b_lblkno > 0 && bp->b_lblkno < tbp->b_lblkno)) {
                        TAILQ_INSERT_HEAD(listheadp, bp, b_vnbufs);
                        ++reassignbufsortgood;
                } else if (bp->b_lblkno < 0) {
                        TAILQ_INSERT_TAIL(listheadp, bp, b_vnbufs);
                        ++reassignbufsortgood;
                } else if (reassignbufmethod == 1) {
                        /*
                         * New sorting algorithm, only handle sequential case,
                         * otherwise append to end (but before metadata)
                         */
                        if ((tbp = gbincore(newvp, bp->b_lblkno - 1)) != NULL &&
                            (tbp->b_xflags & BX_VNDIRTY)) {
                                /*
                                 * Found the best place to insert the buffer
                                 */
                                TAILQ_INSERT_AFTER(listheadp, tbp, bp, b_vnbufs);
                                ++reassignbufsortgood;
                        } else {
                                /*
                                 * Missed, append to end, but before meta-data.
                                 * We know that the head buffer in the list is
                                 * not meta-data due to prior conditionals.
                                 *
                                 * Indirect effects:  NFS second stage write
                                 * tends to wind up here, giving maximum 
                                 * distance between the unstable write and the
                                 * commit rpc.
                                 */
                                tbp = TAILQ_LAST(listheadp, buflists);
                                while (tbp && tbp->b_lblkno < 0)
                                        tbp = TAILQ_PREV(tbp, buflists, b_vnbufs);
                                TAILQ_INSERT_AFTER(listheadp, tbp, bp, b_vnbufs);
                                ++reassignbufsortbad;
                        }
                } else {
                        /*
                         * Old sorting algorithm, scan queue and insert
                         */
                        struct buf *ttbp;
                        while ((ttbp = TAILQ_NEXT(tbp, b_vnbufs)) &&
                            (ttbp->b_lblkno < bp->b_lblkno)) {
                                ++reassignbufloops;
                                tbp = ttbp;
                        }
                        TAILQ_INSERT_AFTER(listheadp, tbp, bp, b_vnbufs);
                }
        } else {
                bp->b_xflags |= BX_VNCLEAN;
                TAILQ_INSERT_TAIL(&newvp->v_cleanblkhd, bp, b_vnbufs);
                if ((newvp->v_flag & VONWORKLST) &&
                    TAILQ_EMPTY(&newvp->v_dirtyblkhd)) {
                        newvp->v_flag &= ~VONWORKLST;
                        LIST_REMOVE(newvp, v_synclist);
                }
        }
        if (bp->b_vp != newvp) {
                bp->b_vp = newvp;
                vhold(bp->b_vp);
        }
        splx(s);
}

/*
 * Create a vnode for a block device.
 * Used for mounting the root file system.
 */
int
bdevvp(dev_t dev, struct vnode **vpp)
{
        struct vnode *vp;
        struct vnode *nvp;
        int error;

        if (dev == NODEV) {
                *vpp = NULLVP;
                return (ENXIO);
        }
        error = getnewvnode(VT_NON, (struct mount *)0, spec_vnodeop_p, &nvp);
        if (error) {
                *vpp = NULLVP;
                return (error);
        }
        vp = nvp;
        vp->v_type = VCHR;
        vp->v_udev = dev->si_udev;
        *vpp = vp;
        return (0);
}

int
v_associate_rdev(struct vnode *vp, dev_t dev)
{
        lwkt_tokref ilock;

        if (dev == NULL || dev == NODEV)
                return(ENXIO);
        if (dev_is_good(dev) == 0)
                return(ENXIO);
        KKASSERT(vp->v_rdev == NULL);
        if (dev_ref_debug)
                printf("Z1");
        vp->v_rdev = reference_dev(dev);
        lwkt_gettoken(&ilock, &spechash_token);
        SLIST_INSERT_HEAD(&dev->si_hlist, vp, v_specnext);
        lwkt_reltoken(&ilock);
        return(0);
}

void
v_release_rdev(struct vnode *vp)
{
        lwkt_tokref ilock;
        dev_t dev;

        if ((dev = vp->v_rdev) != NULL) {
                lwkt_gettoken(&ilock, &spechash_token);
                SLIST_REMOVE(&dev->si_hlist, vp, vnode, v_specnext);
                if (dev_ref_debug && vp->v_opencount != 0) {
                        printf("releasing rdev with non-0 "
                                "v_opencount(%d) (revoked?)\n",
                                vp->v_opencount);
                }
                vp->v_rdev = NULL;
                vp->v_opencount = 0;
                release_dev(dev);
                lwkt_reltoken(&ilock);
        }
}

/*
 * Add a vnode to the alias list hung off the dev_t.  We only associate
 * the device number with the vnode.  The actual device is not associated
 * until the vnode is opened (usually in spec_open()), and will be 
 * disassociated on last close.
 */
void
addaliasu(struct vnode *nvp, udev_t nvp_udev)
{
        if (nvp->v_type != VBLK && nvp->v_type != VCHR)
                panic("addaliasu on non-special vnode");
        nvp->v_udev = nvp_udev;
}

/*
 * Grab a particular vnode from the free list, increment its
 * reference count and lock it. The vnode lock bit is set if the
 * vnode is being eliminated in vgone. The process is awakened
 * when the transition is completed, and an error returned to
 * indicate that the vnode is no longer usable (possibly having
 * been changed to a new file system type).
 *
 * This code is very sensitive.  We are depending on the vnode interlock
 * to be maintained through to the vn_lock() call, which means that we
 * cannot block which means that we cannot call vbusy() until after vn_lock().
 * If the interlock is not maintained, the VXLOCK check will not properly
 * interlock against a vclean()'s LK_DRAIN operation on the lock.
 */
int
vget(struct vnode *vp, lwkt_tokref_t vlock, int flags, thread_t td)
{
        int error;
        lwkt_tokref vvlock;

        /*
         * We need the interlock to safely modify the v_ fields.  ZZZ it is
         * only legal to pass (1) the vnode's interlock and (2) only pass
         * NULL w/o LK_INTERLOCK if the vnode is *ALREADY* referenced or
         * held.
         */
        if ((flags & LK_INTERLOCK) == 0) {
                lwkt_gettoken(&vvlock, vp->v_interlock);
                vlock = &vvlock;
        }

        /*
         * If the vnode is in the process of being cleaned out for
         * another use, we wait for the cleaning to finish and then
         * return failure. Cleaning is determined by checking that
         * the VXLOCK flag is set.  It is possible for the vnode to be
         * self-referenced during the cleaning operation.
         */
        if (vp->v_flag & VXLOCK) {
                if (vp->v_vxthread == curthread) {
#if 0
                        /* this can now occur in normal operation */
                        log(LOG_INFO, "VXLOCK interlock avoided\n");
#endif
                } else {
                        vp->v_flag |= VXWANT;
                        lwkt_reltoken(vlock);
                        tsleep((caddr_t)vp, 0, "vget", 0);
                        return (ENOENT);
                }
        }

        /*
         * Bump v_usecount to prevent the vnode from being recycled.  The
         * usecount needs to be bumped before we successfully get our lock.
         */
        vp->v_usecount++;
        if (flags & LK_TYPE_MASK) {
                if ((error = vn_lock(vp, vlock, flags | LK_INTERLOCK, td)) != 0) {
                        /*
                         * must expand vrele here because we do not want
                         * to call VOP_INACTIVE if the reference count
                         * drops back to zero since it was never really
                         * active. We must remove it from the free list
                         * before sleeping so that multiple processes do
                         * not try to recycle it.
                         */
                        lwkt_gettokref(vlock);
                        vp->v_usecount--;
                        vmaybefree(vp);
                        lwkt_reltoken(vlock);
                }
                return (error);
        }
        if (VSHOULDBUSY(vp))
                vbusy(vp);      /* interlock must be held on call */
        lwkt_reltoken(vlock);
        return (0);
}

void
vref(struct vnode *vp)
{
        crit_enter();   /* YYY use crit section for moment / BGL protected */
        vp->v_usecount++;
        crit_exit();
}

/*
 * Vnode put/release.
 * If count drops to zero, call inactive routine and return to freelist.
 */
void
vrele(struct vnode *vp)
{
        struct thread *td = curthread;  /* XXX */
        lwkt_tokref vlock;

        KASSERT(vp != NULL && vp->v_usecount >= 0,
            ("vrele: null vp or <=0 v_usecount"));

        lwkt_gettoken(&vlock, vp->v_interlock);

        if (vp->v_usecount > 1) {
                vp->v_usecount--;
                lwkt_reltoken(&vlock);
                return;
        }

        if (vp->v_usecount == 1) {
                vp->v_usecount--;
                /*
                 * We must call VOP_INACTIVE with the node locked and the
                 * usecount 0.  If we are doing a vpu, the node is already
                 * locked, but, in the case of vrele, we must explicitly lock
                 * the vnode before calling VOP_INACTIVE.
                 */

                if (vn_lock(vp, NULL, LK_EXCLUSIVE, td) == 0)
                        VOP_INACTIVE(vp, td);
                vmaybefree(vp);
                lwkt_reltoken(&vlock);
        } else {
#ifdef DIAGNOSTIC
                vprint("vrele: negative ref count", vp);
#endif
                lwkt_reltoken(&vlock);
                panic("vrele: negative ref cnt");
        }
}

void
vput(struct vnode *vp)
{
        struct thread *td = curthread;  /* XXX */
        lwkt_tokref vlock;

        KASSERT(vp != NULL, ("vput: null vp"));

        lwkt_gettoken(&vlock, vp->v_interlock);

        if (vp->v_usecount > 1) {
                vp->v_usecount--;
                VOP_UNLOCK(vp, &vlock, LK_INTERLOCK, td);
                return;
        }

        if (vp->v_usecount == 1) {
                vp->v_usecount--;
                /*
                 * We must call VOP_INACTIVE with the node locked.
                 * If we are doing a vpu, the node is already locked,
                 * so we just need to release the vnode mutex.
                 */
                VOP_INACTIVE(vp, td);
                vmaybefree(vp);
                lwkt_reltoken(&vlock);
        } else {
#ifdef DIAGNOSTIC
                vprint("vput: negative ref count", vp);
#endif
                lwkt_reltoken(&vlock);
                panic("vput: negative ref cnt");
        }
}

/*
 * Somebody doesn't want the vnode recycled. ZZZ vnode interlock should
 * be held but isn't.
 */
void
vhold(struct vnode *vp)
{
        int s;

        s = splbio();
        vp->v_holdcnt++;
        if (VSHOULDBUSY(vp))
                vbusy(vp);      /* interlock must be held on call */
        splx(s);
}

/*
 * One less who cares about this vnode.
 */
void
vdrop(struct vnode *vp)
{
        lwkt_tokref vlock;

        lwkt_gettoken(&vlock, vp->v_interlock);
        if (vp->v_holdcnt <= 0)
                panic("vdrop: holdcnt");
        vp->v_holdcnt--;
        vmaybefree(vp);
        lwkt_reltoken(&vlock);
}

int
vmntvnodescan(
    struct mount *mp, 
    int (*fastfunc)(struct mount *mp, struct vnode *vp, void *data),
    int (*slowfunc)(struct mount *mp, struct vnode *vp, 
                    lwkt_tokref_t vlock, void *data),
    void *data
) {
        lwkt_tokref ilock;
        lwkt_tokref vlock;
        struct vnode *pvp;
        struct vnode *vp;
        int r = 0;

        /*
         * Scan the vnodes on the mount's vnode list.  Use a placemarker
         */
        pvp = zalloc(vnode_zone);
        pvp->v_flag |= VPLACEMARKER;

        lwkt_gettoken(&ilock, &mntvnode_token);
        TAILQ_INSERT_HEAD(&mp->mnt_nvnodelist, pvp, v_nmntvnodes);

        while ((vp = TAILQ_NEXT(pvp, v_nmntvnodes)) != NULL) {
                /*
                 * Move the placemarker and skip other placemarkers we
                 * encounter.  The nothing can get in our way so the
                 * mount point on the vp must be valid.
                 */
                TAILQ_REMOVE(&mp->mnt_nvnodelist, pvp, v_nmntvnodes);
                TAILQ_INSERT_AFTER(&mp->mnt_nvnodelist, vp, pvp, v_nmntvnodes);
                if (vp->v_flag & VPLACEMARKER)
                        continue;
                KKASSERT(vp->v_mount == mp);

                /*
                 * Quick test
                 */
                if (fastfunc) {
                        if ((r = fastfunc(mp, vp, data)) < 0)
                                continue;
                        if (r)
                                break;
                }

                /*
                 * Get the vnodes interlock and make sure it is still on the
                 * mount list.  Skip it if it has moved (we may encounter it
                 * later).  Then do the with-interlock test.  The callback
                 * is responsible for releasing the vnode interlock.
                 *
                 * The interlock is type-stable.
                 */
                if (slowfunc) {
                        lwkt_gettoken(&vlock, vp->v_interlock);
                        if (vp != TAILQ_PREV(pvp, vnodelst, v_nmntvnodes)) {
                                printf("vmntvnodescan (debug info only): f=%p vp=%p vnode ripped out from under us\n", slowfunc, vp);
                                lwkt_reltoken(&vlock);
                                continue;
                        }
                        if ((r = slowfunc(mp, vp, &vlock, data)) != 0) {
                                KKASSERT(lwkt_havetokref(&vlock) == 0);
                                break;
                        }
                        KKASSERT(lwkt_havetokref(&vlock) == 0);
                }
        }
        TAILQ_REMOVE(&mp->mnt_nvnodelist, pvp, v_nmntvnodes);
        zfree(vnode_zone, pvp);
        lwkt_reltoken(&ilock);
        return(r);
}

/*
 * 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 VSYSTEM 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()
 * 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, "");
#endif

static int vflush_scan(struct mount *mp, struct vnode *vp,
                        lwkt_tokref_t vlock, void *data);

struct vflush_info {
        int flags;
        int busy;
        thread_t td;
};

int
vflush(struct mount *mp, int rootrefs, int flags)
{
        struct thread *td = curthread;  /* XXX */
        struct vnode *rootvp = NULL;
        int error;
        lwkt_tokref vlock;
        struct vflush_info vflush_info;

        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, &rootvp)) != 0)
                        return (error);
                vput(rootvp);
        }

        vflush_info.busy = 0;
        vflush_info.flags = flags;
        vflush_info.td = td;
        vmntvnodescan(mp, NULL, vflush_scan, &vflush_info);

        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.
                 */
                lwkt_gettoken(&vlock, rootvp->v_interlock);
                KASSERT(vflush_info.busy > 0, ("vflush: not busy"));
                KASSERT(rootvp->v_usecount >= rootrefs, ("vflush: rootrefs"));
                if (vflush_info.busy == 1 && rootvp->v_usecount == rootrefs) {
                        vgonel(rootvp, &vlock, td);
                        vflush_info.busy = 0;
                } else {
                        lwkt_reltoken(&vlock);
                }
        }
        if (vflush_info.busy)
                return (EBUSY);
        for (; rootrefs > 0; rootrefs--)
                vrele(rootvp);
        return (0);
}

/*
 * The scan callback is made with an interlocked vnode.
 */
static int
vflush_scan(struct mount *mp, struct vnode *vp,
            lwkt_tokref_t vlock, void *data)
{
        struct vflush_info *info = data;
        struct vattr vattr;

        /*
         * Skip over a vnodes marked VSYSTEM.
         */
        if ((info->flags & SKIPSYSTEM) && (vp->v_flag & VSYSTEM)) {
                lwkt_reltoken(vlock);
                return(0);
        }

        /*
         * 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 ((info->flags & WRITECLOSE) &&
            (vp->v_type == VNON ||
            (VOP_GETATTR(vp, &vattr, info->td) == 0 &&
            vattr.va_nlink > 0)) &&
            (vp->v_writecount == 0 || vp->v_type != VREG)) {
                lwkt_reltoken(vlock);
                return(0);
        }

        /*
         * With v_usecount == 0, all we need to do is clear out the
         * vnode data structures and we are done.
         */
        if (vp->v_usecount == 0) {
                vgonel(vp, vlock, info->td);
                return(0);
        }

        /*
         * If FORCECLOSE is set, forcibly close the vnode. For block
         * or character devices, revert to an anonymous device. For
         * all other files, just kill them.
         */
        if (info->flags & FORCECLOSE) {
                if (vp->v_type != VBLK && vp->v_type != VCHR) {
                        vgonel(vp, vlock, info->td);
                } else {
                        vclean(vp, vlock, 0, info->td);
                        vp->v_op = spec_vnodeop_p;
                        insmntque(vp, (struct mount *) 0);
                }
                return(0);
        }
#ifdef DIAGNOSTIC
        if (busyprt)
                vprint("vflush: busy vnode", vp);
#endif
        lwkt_reltoken(vlock);
        ++info->busy;
        return(0);
}

/*
 * Disassociate the underlying file system from a vnode.
 */
static void
vclean(struct vnode *vp, lwkt_tokref_t vlock, int flags, struct thread *td)
{
        int active;

        /*
         * Check to see if the vnode is in use. If so we have to reference it
         * before we clean it out so that its count cannot fall to zero and
         * generate a race against ourselves to recycle it.
         */
        if ((active = vp->v_usecount))
                vp->v_usecount++;

        /*
         * Prevent the vnode from being recycled or brought into use while we
         * clean it out.
         */
        if (vp->v_flag & VXLOCK)
                panic("vclean: deadlock");
        vp->v_flag |= VXLOCK;
        vp->v_vxthread = curthread;

        /*
         * Even if the count is zero, the VOP_INACTIVE routine may still
         * have the object locked while it cleans it out. The VOP_LOCK
         * ensures that the VOP_INACTIVE routine is done with its work.
         * For active vnodes, it ensures that no other activity can
         * occur while the underlying object is being cleaned out.
         *
         * NOTE: we continue to hold the vnode interlock through to the
         * end of vclean().
         */
        VOP_LOCK(vp, NULL, LK_DRAIN, td);

        /*
         * Clean out any buffers associated with the vnode.
         */
        vinvalbuf(vp, V_SAVE, td, 0, 0);
        VOP_DESTROYVOBJECT(vp);

        /*
         * If purging an active vnode, it must be closed and
         * deactivated before being reclaimed. Note that the
         * VOP_INACTIVE will unlock the vnode.
         */
        if (active) {
                if (flags & DOCLOSE)
                        VOP_CLOSE(vp, FNONBLOCK, td);
                VOP_INACTIVE(vp, td);
        } else {
                /*
                 * Any other processes trying to obtain this lock must first
                 * wait for VXLOCK to clear, then call the new lock operation.
                 */
                VOP_UNLOCK(vp, NULL, 0, td);
        }
        /*
         * Reclaim the vnode.
         */
        if (VOP_RECLAIM(vp, td))
                panic("vclean: cannot reclaim");

        if (active) {
                /*
                 * Inline copy of vrele() since VOP_INACTIVE
                 * has already been called.
                 */
                if (--vp->v_usecount <= 0) {
#ifdef DIAGNOSTIC
                        if (vp->v_usecount < 0 || vp->v_writecount != 0) {
                                vprint("vclean: bad ref count", vp);
                                panic("vclean: ref cnt");
                        }
#endif
                        vfree(vp);
                }
        }

        cache_purge(vp);
        vp->v_vnlock = NULL;
        vmaybefree(vp);
        
        /*
         * Done with purge, notify sleepers of the grim news.
         */
        vp->v_op = dead_vnodeop_p;
        vn_pollgone(vp);
        vp->v_tag = VT_NON;
        vp->v_flag &= ~VXLOCK;
        vp->v_vxthread = NULL;
        if (vp->v_flag & VXWANT) {
                vp->v_flag &= ~VXWANT;
                wakeup((caddr_t) vp);
        }
        lwkt_reltoken(vlock);
}

/*
 * Eliminate all activity associated with the requested vnode
 * and with all vnodes aliased to the requested vnode.
 *
 * revoke { struct vnode *a_vp, int a_flags }
 */
int
vop_revoke(struct vop_revoke_args *ap)
{
        struct vnode *vp, *vq;
        lwkt_tokref ilock;
        dev_t dev;

        KASSERT((ap->a_flags & REVOKEALL) != 0, ("vop_revoke"));

        vp = ap->a_vp;
        /*
         * If a vgone (or vclean) is already in progress,
         * wait until it is done and return.
         */
        if (vp->v_flag & VXLOCK) {
                vp->v_flag |= VXWANT;
                /*lwkt_reltoken(vlock); ZZZ */
                tsleep((caddr_t)vp, 0, "vop_revokeall", 0);
                return (0);
        }

        /*
         * If the vnode has a device association, scrap all vnodes associated
         * with the device.  Don't let the device disappear on us while we
         * are scrapping the vnodes.
         */
        if (vp->v_type != VCHR && vp->v_type != VBLK)
                return(0);
        if ((dev = vp->v_rdev) == NULL) {
                if ((dev = udev2dev(vp->v_udev, vp->v_type == VBLK)) == NODEV)
                        return(0);
        }
        reference_dev(dev);
        for (;;) {
                lwkt_gettoken(&ilock, &spechash_token);
                vq = SLIST_FIRST(&dev->si_hlist);
                lwkt_reltoken(&ilock);
                if (vq == NULL)
                        break;
                vgone(vq);
        }
        release_dev(dev);
        return (0);
}

/*
 * Recycle an unused vnode to the front of the free list.
 * Release the passed interlock if the vnode will be recycled.
 */
int
vrecycle(struct vnode *vp, lwkt_tokref_t inter_lkp, struct thread *td)
{
        lwkt_tokref vlock;

        lwkt_gettoken(&vlock, vp->v_interlock);
        if (vp->v_usecount == 0) {
                if (inter_lkp)
                        lwkt_reltoken(inter_lkp);
                vgonel(vp, &vlock, td);
                return (1);
        }
        lwkt_reltoken(&vlock);
        return (0);
}

/*
 * Eliminate all activity associated with a vnode
 * in preparation for reuse.
 */
void
vgone(struct vnode *vp)
{
        struct thread *td = curthread;  /* XXX */
        lwkt_tokref vlock;

        lwkt_gettoken(&vlock, vp->v_interlock);
        vgonel(vp, &vlock, td);
}

/*
 * vgone, with the vp interlock held.
 */
void
vgonel(struct vnode *vp, lwkt_tokref_t vlock, struct thread *td)
{
        lwkt_tokref ilock;
        int s;

        /*
         * If a vgone (or vclean) is already in progress,
         * wait until it is done and return.
         */
        if (vp->v_flag & VXLOCK) {
                vp->v_flag |= VXWANT;
                lwkt_reltoken(vlock);
                tsleep((caddr_t)vp, 0, "vgone", 0);
                return;
        }

        /*
         * Clean out the filesystem specific data.
         */
        vclean(vp, vlock, DOCLOSE, td);
        lwkt_gettokref(vlock);

        /*
         * Delete from old mount point vnode list, if on one.
         */
        if (vp->v_mount != NULL)
                insmntque(vp, (struct mount *)0);

        /*
         * If special device, remove it from special device alias list
         * if it is on one.  This should normally only occur if a vnode is
         * being revoked as the device should otherwise have been released
         * naturally.
         */
        if ((vp->v_type == VBLK || vp->v_type == VCHR) && vp->v_rdev != NULL) {
                v_release_rdev(vp);
        }

        /*
         * If it is on the freelist and not already at the head,
         * move it to the head of the list. The test of the
         * VDOOMED flag and the reference count of zero is because
         * it will be removed from the free list by getnewvnode,
         * but will not have its reference count incremented until
         * after calling vgone. If the reference count were
         * incremented first, vgone would (incorrectly) try to
         * close the previous instance of the underlying object.
         */
        if (vp->v_usecount == 0 && !(vp->v_flag & VDOOMED)) {
                s = splbio();
                lwkt_gettoken(&ilock, &vnode_free_list_token);
                if (vp->v_flag & VFREE)
                        TAILQ_REMOVE(&vnode_free_list, vp, v_freelist);
                else
                        freevnodes++;
                vp->v_flag |= VFREE;
                TAILQ_INSERT_HEAD(&vnode_free_list, vp, v_freelist);
                lwkt_reltoken(&ilock);
                splx(s);
        }
        vp->v_type = VBAD;
        lwkt_reltoken(vlock);
}

/*
 * Lookup a vnode by device number.
 */
int
vfinddev(dev_t dev, enum vtype type, struct vnode **vpp)
{
        lwkt_tokref ilock;
        struct vnode *vp;

        lwkt_gettoken(&ilock, &spechash_token);
        SLIST_FOREACH(vp, &dev->si_hlist, v_specnext) {
                if (type == vp->v_type) {
                        *vpp = vp;
                        lwkt_reltoken(&ilock);
                        return (1);
                }
        }
        lwkt_reltoken(&ilock);
        return (0);
}

/*
 * Calculate the total number of references to a special device.  This
 * routine may only be called for VBLK and VCHR vnodes since v_rdev is
 * an overloaded field.  Since udev2dev can now return NODEV, we have
 * to check for a NULL v_rdev.
 */
int
count_dev(dev_t dev)
{
        lwkt_tokref ilock;
        struct vnode *vp;
        int count = 0;

        if (SLIST_FIRST(&dev->si_hlist)) {
                lwkt_gettoken(&ilock, &spechash_token);
                SLIST_FOREACH(vp, &dev->si_hlist, v_specnext) {
                        count += vp->v_usecount;
                }
                lwkt_reltoken(&ilock);
        }
        return(count);
}

int
count_udev(udev_t udev)
{
        dev_t dev;

        if ((dev = udev2dev(udev, 0)) == NODEV)
                return(0);
        return(count_dev(dev));
}

int
vcount(struct vnode *vp)
{
        if (vp->v_rdev == NULL)
                return(0);
        return(count_dev(vp->v_rdev));
}

/*
 * Print out a description of a vnode.
 */
static char *typename[] =
{"VNON", "VREG", "VDIR", "VBLK", "VCHR", "VLNK", "VSOCK", "VFIFO", "VBAD"};

void
vprint(char *label, struct vnode *vp)
{
        char buf[96];

        if (label != NULL)
                printf("%s: %p: ", label, (void *)vp);
        else
                printf("%p: ", (void *)vp);
        printf("type %s, usecount %d, writecount %d, refcount %d,",
            typename[vp->v_type], vp->v_usecount, vp->v_writecount,
            vp->v_holdcnt);
        buf[0] = '\0';
        if (vp->v_flag & VROOT)
                strcat(buf, "|VROOT");
        if (vp->v_flag & VTEXT)
                strcat(buf, "|VTEXT");
        if (vp->v_flag & VSYSTEM)
                strcat(buf, "|VSYSTEM");
        if (vp->v_flag & VXLOCK)
                strcat(buf, "|VXLOCK");
        if (vp->v_flag & VXWANT)
                strcat(buf, "|VXWANT");
        if (vp->v_flag & VBWAIT)
                strcat(buf, "|VBWAIT");
        if (vp->v_flag & VDOOMED)
                strcat(buf, "|VDOOMED");
        if (vp->v_flag & VFREE)
                strcat(buf, "|VFREE");
        if (vp->v_flag & VOBJBUF)
                strcat(buf, "|VOBJBUF");
        if (buf[0] != '\0')
                printf(" flags (%s)", &buf[1]);
        if (vp->v_data == NULL) {
                printf("\n");
        } else {
                printf("\n\t");
                VOP_PRINT(vp);
        }
}

#ifdef DDB
#include <ddb/ddb.h>
/*
 * List all of the locked vnodes in the system.
 * Called when debugging the kernel.
 */
DB_SHOW_COMMAND(lockedvnodes, lockedvnodes)
{
        struct thread *td = curthread;  /* XXX */
        lwkt_tokref ilock;
        struct mount *mp, *nmp;
        struct vnode *vp;

        printf("Locked vnodes\n");
        lwkt_gettoken(&ilock, &mountlist_token);
        for (mp = TAILQ_FIRST(&mountlist); mp != NULL; mp = nmp) {
                if (vfs_busy(mp, LK_NOWAIT, &ilock, td)) {
                        nmp = TAILQ_NEXT(mp, mnt_list);
                        continue;
                }
                TAILQ_FOREACH(vp, &mp->mnt_nvnodelist, v_nmntvnodes) {
                        if (VOP_ISLOCKED(vp, NULL))
                                vprint((char *)0, vp);
                }
                lwkt_gettokref(&ilock);
                nmp = TAILQ_NEXT(mp, mnt_list);
                vfs_unbusy(mp, td);
        }
        lwkt_reltoken(&ilock);
}
#endif

/*
 * Top level filesystem related information gathering.
 */
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;

#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

#ifdef notyet
        /* all sysctl names at this level are at least name and field */
        if (namelen < 2)
                return (ENOTDIR);               /* overloaded */
        if (name[0] != VFS_GENERIC) {
                for (vfsp = vfsconf; vfsp; vfsp = vfsp->vfc_next)
                        if (vfsp->vfc_typenum == name[0])
                                break;
                if (vfsp == NULL)
                        return (EOPNOTSUPP);
                return ((*vfsp->vfc_vfsops->vfs_sysctl)(&name[1], namelen - 1,
                    oldp, oldlenp, newp, newlen, p));
        }
#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 */
                for (vfsp = vfsconf; vfsp; vfsp = vfsp->vfc_next)
                        if (vfsp->vfc_typenum == name[2])
                                break;
                if (vfsp == NULL)
                        return (EOPNOTSUPP);
                return (SYSCTL_OUT(req, vfsp, sizeof *vfsp));
        }
        return (EOPNOTSUPP);
}

SYSCTL_NODE(_vfs, VFS_GENERIC, generic, CTLFLAG_RD, 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;

        for (vfsp = vfsconf; vfsp; vfsp = vfsp->vfc_next) {
                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)
                        return error;
        }
        return 0;
}

#endif /* 1 || COMPAT_PRELITE2 */

#if 0
#define KINFO_VNODESLOP 10
/*
 * Dump vnode list (via sysctl).
 * Copyout address of vnode followed by vnode.
 */
/* ARGSUSED */
static int
sysctl_vnode(SYSCTL_HANDLER_ARGS)
{
        struct proc *p = curproc;       /* XXX */
        struct mount *mp, *nmp;
        struct vnode *nvp, *vp;
        lwkt_tokref ilock;
        lwkt_tokref jlock;
        int error;

#define VPTRSZ  sizeof (struct vnode *)
#define VNODESZ sizeof (struct vnode)

        req->lock = 0;
        if (!req->oldptr) /* Make an estimate */
                return (SYSCTL_OUT(req, 0,
                        (numvnodes + KINFO_VNODESLOP) * (VPTRSZ + VNODESZ)));

        lwkt_gettoken(&ilock, &mountlist_token);
        for (mp = TAILQ_FIRST(&mountlist); mp != NULL; mp = nmp) {
                if (vfs_busy(mp, LK_NOWAIT, &ilock, p)) {
                        nmp = TAILQ_NEXT(mp, mnt_list);
                        continue;
                }
                lwkt_gettoken(&jlock, &mntvnode_token);
again:
                for (vp = TAILQ_FIRST(&mp->mnt_nvnodelist);
                     vp != NULL;
                     vp = nvp) {
                        /*
                         * Check that the vp is still associated with
                         * this filesystem.  RACE: could have been
                         * recycled onto the same filesystem.
                         */
                        if (vp->v_mount != mp)
                                goto again;
                        nvp = TAILQ_NEXT(vp, v_nmntvnodes);
                        if ((error = SYSCTL_OUT(req, &vp, VPTRSZ)) ||
                            (error = SYSCTL_OUT(req, vp, VNODESZ))) {
                                lwkt_reltoken(&jlock);
                                return (error);
                        }
                }
                lwkt_reltoken(&jlock);
                lwkt_gettokref(&ilock);
                nmp = TAILQ_NEXT(mp, mnt_list); /* ZZZ */
                vfs_unbusy(mp, p);
        }
        lwkt_reltoken(&ilock);

        return (0);
}
#endif

/*
 * XXX
 * Exporting the vnode list on large systems causes them to crash.
 * Exporting the vnode list on medium systems causes sysctl to coredump.
 */
#if 0
SYSCTL_PROC(_kern, KERN_VNODE, vnode, CTLTYPE_OPAQUE|CTLFLAG_RD,
        0, 0, sysctl_vnode, "S,vnode", "");
#endif

/*
 * Check to see if a filesystem is mounted on a block device.
 */
int
vfs_mountedon(struct vnode *vp)
{
        dev_t dev;

        if ((dev = vp->v_rdev) == NULL)
                dev = udev2dev(vp->v_udev, (vp->v_type == VBLK));
        if (dev != NODEV && dev->si_mountpoint)
                return (EBUSY);
        return (0);
}

/*
 * Unmount all filesystems. The list is traversed in reverse order
 * of mounting to avoid dependencies.
 */
void
vfs_unmountall(void)
{
        struct mount *mp;
        struct thread *td = curthread;
        int error;

        if (td->td_proc == NULL)
                td = initproc->p_thread;        /* XXX XXX use proc0 instead? */

        /*
         * Since this only runs when rebooting, it is not interlocked.
         */
        while(!TAILQ_EMPTY(&mountlist)) {
                mp = TAILQ_LAST(&mountlist, mntlist);
                error = dounmount(mp, MNT_FORCE, td);
                if (error) {
                        TAILQ_REMOVE(&mountlist, mp, mnt_list);
                        printf("unmount of %s failed (",
                            mp->mnt_stat.f_mntonname);
                        if (error == EBUSY)
                                printf("BUSY)\n");
                        else
                                printf("%d)\n", error);
                } else {
                        /* The unmount has removed mp from the mountlist */
                }
        }
}

/*
 * Build hash lists of net addresses and hang them off the mount point.
 * Called by ufs_mount() to set up the lists of export addresses.
 */
static int
vfs_hang_addrlist(struct mount *mp, struct netexport *nep,
                struct export_args *argp)
{
        struct netcred *np;
        struct radix_node_head *rnh;
        int i;
        struct radix_node *rn;
        struct sockaddr *saddr, *smask = 0;
        struct domain *dom;
        int error;

        if (argp->ex_addrlen == 0) {
                if (mp->mnt_flag & MNT_DEFEXPORTED)
                        return (EPERM);
                np = &nep->ne_defexported;
                np->netc_exflags = argp->ex_flags;
                np->netc_anon = argp->ex_anon;
                np->netc_anon.cr_ref = 1;
                mp->mnt_flag |= MNT_DEFEXPORTED;
                return (0);
        }

        if (argp->ex_addrlen < 0 || argp->ex_addrlen > MLEN)
                return (EINVAL);
        if (argp->ex_masklen < 0 || argp->ex_masklen > MLEN)
                return (EINVAL);

        i = sizeof(struct netcred) + argp->ex_addrlen + argp->ex_masklen;
        np = (struct netcred *) malloc(i, M_NETADDR, M_WAITOK);
        bzero((caddr_t) np, i);
        saddr = (struct sockaddr *) (np + 1);
        if ((error = copyin(argp->ex_addr, (caddr_t) saddr, argp->ex_addrlen)))
                goto out;
        if (saddr->sa_len > argp->ex_addrlen)
                saddr->sa_len = argp->ex_addrlen;
        if (argp->ex_masklen) {
                smask = (struct sockaddr *)((caddr_t)saddr + argp->ex_addrlen);
                error = copyin(argp->ex_mask, (caddr_t)smask, argp->ex_masklen);
                if (error)
                        goto out;
                if (smask->sa_len > argp->ex_masklen)
                        smask->sa_len = argp->ex_masklen;
        }
        i = saddr->sa_family;
        if ((rnh = nep->ne_rtable[i]) == 0) {
                /*
                 * Seems silly to initialize every AF when most are not used,
                 * do so on demand here
                 */
                for (dom = domains; dom; dom = dom->dom_next)
                        if (dom->dom_family == i && dom->dom_rtattach) {
                                dom->dom_rtattach((void **) &nep->ne_rtable[i],
                                    dom->dom_rtoffset);
                                break;
                        }
                if ((rnh = nep->ne_rtable[i]) == 0) {
                        error = ENOBUFS;
                        goto out;
                }
        }
        rn = (*rnh->rnh_addaddr) ((caddr_t) saddr, (caddr_t) smask, rnh,
            np->netc_rnodes);
        if (rn == 0 || np != (struct netcred *) rn) {   /* already exists */
                error = EPERM;
                goto out;
        }
        np->netc_exflags = argp->ex_flags;
        np->netc_anon = argp->ex_anon;
        np->netc_anon.cr_ref = 1;
        return (0);
out:
        free(np, M_NETADDR);
        return (error);
}

/* ARGSUSED */
static int
vfs_free_netcred(struct radix_node *rn, void *w)
{
        struct radix_node_head *rnh = (struct radix_node_head *) w;

        (*rnh->rnh_deladdr) (rn->rn_key, rn->rn_mask, rnh);
        free((caddr_t) rn, M_NETADDR);
        return (0);
}

/*
 * Free the net address hash lists that are hanging off the mount points.
 */
static void
vfs_free_addrlist(struct netexport *nep)
{
        int i;
        struct radix_node_head *rnh;

        for (i = 0; i <= AF_MAX; i++)
                if ((rnh = nep->ne_rtable[i])) {
                        (*rnh->rnh_walktree) (rnh, vfs_free_netcred,
                            (caddr_t) rnh);
                        free((caddr_t) rnh, M_RTABLE);
                        nep->ne_rtable[i] = 0;
                }
}

int
vfs_export(struct mount *mp, struct netexport *nep, struct export_args *argp)
{
        int error;

        if (argp->ex_flags & MNT_DELEXPORT) {
                if (mp->mnt_flag & MNT_EXPUBLIC) {
                        vfs_setpublicfs(NULL, NULL, NULL);
                        mp->mnt_flag &= ~MNT_EXPUBLIC;
                }
                vfs_free_addrlist(nep);
                mp->mnt_flag &= ~(MNT_EXPORTED | MNT_DEFEXPORTED);
        }
        if (argp->ex_flags & MNT_EXPORTED) {
                if (argp->ex_flags & MNT_EXPUBLIC) {
                        if ((error = vfs_setpublicfs(mp, nep, argp)) != 0)
                                return (error);
                        mp->mnt_flag |= MNT_EXPUBLIC;
                }
                if ((error = vfs_hang_addrlist(mp, nep, argp)))
                        return (error);
                mp->mnt_flag |= MNT_EXPORTED;
        }
        return (0);
}


/*
 * Set the publicly exported filesystem (WebNFS). Currently, only
 * one public filesystem is possible in the spec (RFC 2054 and 2055)
 */
int
vfs_setpublicfs(struct mount *mp, struct netexport *nep,
                struct export_args *argp)
{
        int error;
        struct vnode *rvp;
        char *cp;

        /*
         * mp == NULL -> invalidate the current info, the FS is
         * no longer exported. May be called from either vfs_export
         * or unmount, so check if it hasn't already been done.
         */
        if (mp == NULL) {
                if (nfs_pub.np_valid) {
                        nfs_pub.np_valid = 0;
                        if (nfs_pub.np_index != NULL) {
                                FREE(nfs_pub.np_index, M_TEMP);
                                nfs_pub.np_index = NULL;
                        }
                }
                return (0);
        }

        /*
         * Only one allowed at a time.
         */
        if (nfs_pub.np_valid != 0 && mp != nfs_pub.np_mount)
                return (EBUSY);

        /*
         * Get real filehandle for root of exported FS.
         */
        bzero((caddr_t)&nfs_pub.np_handle, sizeof(nfs_pub.np_handle));
        nfs_pub.np_handle.fh_fsid = mp->mnt_stat.f_fsid;

        if ((error = VFS_ROOT(mp, &rvp)))
                return (error);

        if ((error = VFS_VPTOFH(rvp, &nfs_pub.np_handle.fh_fid)))
                return (error);

        vput(rvp);

        /*
         * If an indexfile was specified, pull it in.
         */
        if (argp->ex_indexfile != NULL) {
                MALLOC(nfs_pub.np_index, char *, MAXNAMLEN + 1, M_TEMP,
                    M_WAITOK);
                error = copyinstr(argp->ex_indexfile, nfs_pub.np_index,
                    MAXNAMLEN, (size_t *)0);
                if (!error) {
                        /*
                         * Check for illegal filenames.
                         */
                        for (cp = nfs_pub.np_index; *cp; cp++) {
                                if (*cp == '/') {
                                        error = EINVAL;
                                        break;
                                }
                        }
                }
                if (error) {
                        FREE(nfs_pub.np_index, M_TEMP);
                        return (error);
                }
        }

        nfs_pub.np_mount = mp;
        nfs_pub.np_valid = 1;
        return (0);
}

struct netcred *
vfs_export_lookup(struct mount *mp, struct netexport *nep,
                struct sockaddr *nam)
{
        struct netcred *np;
        struct radix_node_head *rnh;
        struct sockaddr *saddr;

        np = NULL;
        if (mp->mnt_flag & MNT_EXPORTED) {
                /*
                 * Lookup in the export list first.
                 */
                if (nam != NULL) {
                        saddr = nam;
                        rnh = nep->ne_rtable[saddr->sa_family];
                        if (rnh != NULL) {
                                np = (struct netcred *)
                                        (*rnh->rnh_matchaddr)((caddr_t)saddr,
                                                              rnh);
                                if (np && np->netc_rnodes->rn_flags & RNF_ROOT)
                                        np = NULL;
                        }
                }
                /*
                 * If no address match, use the default if it exists.
                 */
                if (np == NULL && mp->mnt_flag & MNT_DEFEXPORTED)
                        np = &nep->ne_defexported;
        }
        return (np);
}

/*
 * perform msync on all vnodes under a mount point.  The mount point must
 * be locked.  This code is also responsible for lazy-freeing unreferenced
 * vnodes whos VM objects no longer contain pages.
 *
 * NOTE: MNT_WAIT still skips vnodes in the VXLOCK state.
 */
static int vfs_msync_scan1(struct mount *mp, struct vnode *vp, void *data);
static int vfs_msync_scan2(struct mount *mp, struct vnode *vp, 
                            lwkt_tokref_t vlock, void *data);

void
vfs_msync(struct mount *mp, int flags) 
{
        vmntvnodescan(mp, vfs_msync_scan1, vfs_msync_scan2, (void *)flags);
}

/*
 * scan1 is a fast pre-check.  There could be hundreds of thousands of
 * vnodes, we cannot afford to do anything heavy weight until we have a
 * fairly good indication that there is work to do.
 */
static
int
vfs_msync_scan1(struct mount *mp, struct vnode *vp, void *data)
{
        int flags = (int)data;

        if ((vp->v_flag & VXLOCK) == 0) {
                if (VSHOULDFREE(vp))
                        return(0);
                if ((mp->mnt_flag & MNT_RDONLY) == 0 &&
                    (vp->v_flag & VOBJDIRTY) &&
                    (flags == MNT_WAIT || VOP_ISLOCKED(vp, NULL) == 0)) {
                        return(0);
                }
        }
        return(-1);
}

static
int
vfs_msync_scan2(struct mount *mp, struct vnode *vp, 
                lwkt_tokref_t vlock, void *data)
{
        vm_object_t obj;
        int error;
        int flags = (int)data;

        if (vp->v_flag & VXLOCK)
                return(0);

        if ((mp->mnt_flag & MNT_RDONLY) == 0 &&
            (vp->v_flag & VOBJDIRTY) &&
            (flags == MNT_WAIT || VOP_ISLOCKED(vp, NULL) == 0)) {
                error = vget(vp, vlock, LK_EXCLUSIVE | LK_RETRY | LK_NOOBJ | LK_INTERLOCK, curthread);
                if (error == 0) {
                        if (VOP_GETVOBJECT(vp, &obj) == 0) {
                                vm_object_page_clean(obj, 0, 0, 
                                 flags == MNT_WAIT ? OBJPC_SYNC : OBJPC_NOSYNC);
                        }
                        vput(vp);
                }
                return(0);
        }
        vmaybefree(vp);
        lwkt_reltoken(vlock);
        return(0);
}

/*
 * Create the VM object needed for VMIO and mmap support.  This
 * is done for all VREG files in the system.  Some filesystems might
 * afford the additional metadata buffering capability of the
 * VMIO code by making the device node be VMIO mode also.
 *
 * vp must be locked when vfs_object_create is called.
 */
int
vfs_object_create(struct vnode *vp, struct thread *td)
{
        return (VOP_CREATEVOBJECT(vp, td));
}

/*
 * NOTE: the vnode interlock must be held during the call.  We have to recheck
 * the VFREE flag since the vnode may have been removed from the free list
 * while we were blocked on vnode_free_list_token.  The use or hold count
 * must have already been bumped by the caller.
 */
static void
vbusy(struct vnode *vp)
{
        lwkt_tokref ilock;

        lwkt_gettoken(&ilock, &vnode_free_list_token);
        if ((vp->v_flag & VFREE) != 0) {
            TAILQ_REMOVE(&vnode_free_list, vp, v_freelist);
            freevnodes--;
            vp->v_flag &= ~(VFREE|VAGE);
        }
        lwkt_reltoken(&ilock);
}

/*
 * NOTE: the vnode interlock must be held during the call.  The use or hold
 * count must have already been bumped by the caller.  We use a VINFREE to
 * interlock against other calls to vfree() which might occur while we 
 * are blocked.  The vnode cannot be reused until it has actually been
 * placed on the free list, so there are no other races even though the
 * use and hold counts are 0.
 */
static void
vfree(struct vnode *vp)
{
        lwkt_tokref ilock;

        if ((vp->v_flag & VINFREE) == 0) {
                vp->v_flag |= VINFREE;
                lwkt_gettoken(&ilock, &vnode_free_list_token); /* can block */
                KASSERT((vp->v_flag & VFREE) == 0, ("vnode already free"));
                if (vp->v_flag & VAGE) {
                        TAILQ_INSERT_HEAD(&vnode_free_list, vp, v_freelist);
                } else {
                        TAILQ_INSERT_TAIL(&vnode_free_list, vp, v_freelist);
                }
                freevnodes++;
                vp->v_flag &= ~(VAGE|VINFREE);
                vp->v_flag |= VFREE;
                lwkt_reltoken(&ilock);  /* can block */
        }
}


/*
 * 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)
{
        lwkt_tokref ilock;

        lwkt_gettoken(&ilock, &vp->v_pollinfo.vpi_token);
        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;

                lwkt_reltoken(&ilock);
                return events;
        }
        vp->v_pollinfo.vpi_events |= events;
        selrecord(td, &vp->v_pollinfo.vpi_selinfo);
        lwkt_reltoken(&ilock);
        return 0;
}

/*
 * Note the occurrence of an event.  If the VN_POLLEVENT macro is used,
 * it is possible for us to miss an event due to race conditions, but
 * that condition is expected to be rare, so for the moment it is the
 * preferred interface.
 */
void
vn_pollevent(struct vnode *vp, int events)
{
        lwkt_tokref ilock;

        lwkt_gettoken(&ilock, &vp->v_pollinfo.vpi_token);
        if (vp->v_pollinfo.vpi_events & events) {
                /*
                 * We clear vpi_events so that we don't
                 * call selwakeup() twice if two events are
                 * posted before the polling process(es) is
                 * awakened.  This also ensures that we take at
                 * most one selwakeup() if the polling process
                 * is no longer interested.  However, it does
                 * mean that only one event can be noticed at
                 * a time.  (Perhaps we should only clear those
                 * event bits which we note?) XXX
                 */
                vp->v_pollinfo.vpi_events = 0;  /* &= ~events ??? */
                vp->v_pollinfo.vpi_revents |= events;
                selwakeup(&vp->v_pollinfo.vpi_selinfo);
        }
        lwkt_reltoken(&ilock);
}

/*
 * Wake up anyone polling on vp because it is being revoked.
 * This depends on dead_poll() returning POLLHUP for correct
 * behavior.
 */
void
vn_pollgone(struct vnode *vp)
{
        lwkt_tokref ilock;

        lwkt_gettoken(&ilock, &vp->v_pollinfo.vpi_token);
        if (vp->v_pollinfo.vpi_events) {
                vp->v_pollinfo.vpi_events = 0;
                selwakeup(&vp->v_pollinfo.vpi_selinfo);
        }
        lwkt_reltoken(&ilock);
}



/*
 * 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 *);
#define sync_lock ((int (*) (struct  vop_lock_args *))vop_nolock)
#define sync_unlock ((int (*) (struct  vop_unlock_args *))vop_nounlock)
static int      sync_print (struct vop_print_args *);
#define sync_islocked ((int(*) (struct vop_islocked_args *))vop_noislocked)

static vop_t **sync_vnodeop_p;
static struct vnodeopv_entry_desc sync_vnodeop_entries[] = {
        { &vop_default_desc,    (vop_t *) vop_eopnotsupp },
        { &vop_close_desc,      (vop_t *) sync_close },         /* close */
        { &vop_fsync_desc,      (vop_t *) sync_fsync },         /* fsync */
        { &vop_inactive_desc,   (vop_t *) sync_inactive },      /* inactive */
        { &vop_reclaim_desc,    (vop_t *) sync_reclaim },       /* reclaim */
        { &vop_lock_desc,       (vop_t *) sync_lock },          /* lock */
        { &vop_unlock_desc,     (vop_t *) sync_unlock },        /* unlock */
        { &vop_print_desc,      (vop_t *) sync_print },         /* print */
        { &vop_islocked_desc,   (vop_t *) sync_islocked },      /* islocked */
        { NULL, NULL }
};
static struct vnodeopv_desc sync_vnodeop_opv_desc =
        { &sync_vnodeop_p, sync_vnodeop_entries };

VNODEOP_SET(sync_vnodeop_opv_desc);

/*
 * Create a new filesystem syncer vnode for the specified mount point.
 * This vnode is placed on the worklist and is responsible for sync'ing
 * the filesystem.
 *
 * NOTE: read-only mounts are also placed on the worklist.  The filesystem
 * sync code is also responsible for cleaning up vnodes.
 */
int
vfs_allocate_syncvnode(struct mount *mp)
{
        struct vnode *vp;
        static long start, incr, next;
        int error;

        /* Allocate a new vnode */
        if ((error = getnewvnode(VT_VFS, mp, sync_vnodeop_p, &vp)) != 0) {
                mp->mnt_syncer = NULL;
                return (error);
        }
        vp->v_type = VNON;
        /*
         * 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;
        }
        vn_syncer_add_to_worklist(vp, syncdelay > 0 ? next % syncdelay : 0);
        mp->mnt_syncer = vp;
        return (0);
}

/*
 * Do a lazy sync of the filesystem.
 *
 * sync_fsync { struct vnode *a_vp, struct ucred *a_cred, int a_waitfor,
 *              struct thread *a_td }
 */
static int
sync_fsync(struct vop_fsync_args *ap)
{
        struct vnode *syncvp = ap->a_vp;
        struct mount *mp = syncvp->v_mount;
        struct thread *td = ap->a_td;
        lwkt_tokref ilock;
        int asyncflag;

        /*
         * 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.
         */
        vn_syncer_add_to_worklist(syncvp, syncdelay);

        /*
         * Walk the list of vnodes pushing all that are dirty and
         * not already on the sync list, and freeing vnodes which have
         * no refs and whos VM objects are empty.  vfs_msync() handles
         * the VM issues and must be called whether the mount is readonly
         * or not.
         */
        lwkt_gettoken(&ilock, &mountlist_token);
        if (vfs_busy(mp, LK_EXCLUSIVE | LK_NOWAIT, &ilock, td) != 0) {
                lwkt_reltoken(&ilock);
                return (0);
        }
        if (mp->mnt_flag & MNT_RDONLY) {
                vfs_msync(mp, MNT_NOWAIT);
        } else {
                asyncflag = mp->mnt_flag & MNT_ASYNC;
                mp->mnt_flag &= ~MNT_ASYNC;     /* ZZZ hack */
                vfs_msync(mp, MNT_NOWAIT);
                VFS_SYNC(mp, MNT_LAZY, td);
                if (asyncflag)
                        mp->mnt_flag |= MNT_ASYNC;
        }
        vfs_unbusy(mp, td);
        return (0);
}

/*
 * The syncer vnode is no referenced.
 *
 * sync_inactive { struct vnode *a_vp, struct proc *a_p }
 */
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 at splbio().
 *
 *      sync_reclaim { struct vnode *a_vp }
 */
static int
sync_reclaim(struct vop_reclaim_args *ap)
{
        struct vnode *vp = ap->a_vp;
        int s;

        s = splbio();
        vp->v_mount->mnt_syncer = NULL;
        if (vp->v_flag & VONWORKLST) {
                LIST_REMOVE(vp, v_synclist);
                vp->v_flag &= ~VONWORKLST;
        }
        splx(s);

        return (0);
}

/*
 * Print out a syncer vnode.
 *
 *      sync_print { struct vnode *a_vp }
 */
static int
sync_print(struct vop_print_args *ap)
{
        struct vnode *vp = ap->a_vp;

        printf("syncer vnode");
        if (vp->v_vnlock != NULL)
                lockmgr_printinfo(vp->v_vnlock);
        printf("\n");
        return (0);
}

/*
 * extract the dev_t from a VBLK or VCHR.  The vnode must have been opened
 * (or v_rdev might be NULL).
 */
dev_t
vn_todev(struct vnode *vp)
{
        if (vp->v_type != VBLK && vp->v_type != VCHR)
                return (NODEV);
        KKASSERT(vp->v_rdev != NULL);
        return (vp->v_rdev);
}

/*
 * Check if vnode represents a disk device.  The vnode does not need to be
 * opened.
 */
int
vn_isdisk(struct vnode *vp, int *errp)
{
        dev_t dev;

        if (vp->v_type != VBLK && vp->v_type != VCHR) {
                if (errp != NULL)
                        *errp = ENOTBLK;
                return (0);
        }

        if ((dev = vp->v_rdev) == NULL)
                dev = udev2dev(vp->v_udev, (vp->v_type == VBLK));
        if (dev == NULL || dev == NODEV) {
                if (errp != NULL)
                        *errp = ENXIO;
                return (0);
        }
        if (dev_is_good(dev) == 0) {
                if (errp != NULL)
                        *errp = ENXIO;
                return (0);
        }
        if ((dev_dflags(dev) & D_DISK) == 0) {
                if (errp != NULL)
                        *errp = ENOTBLK;
                return (0);
        }
        if (errp != NULL)
                *errp = 0;
        return (1);
}

void
NDFREE(struct nameidata *ndp, const uint flags)
{
        if (!(flags & NDF_NO_FREE_PNBUF) &&
            (ndp->ni_cnd.cn_flags & CNP_HASBUF)) {
                zfree(namei_zone, ndp->ni_cnd.cn_pnbuf);
                ndp->ni_cnd.cn_flags &= ~CNP_HASBUF;
        }
        if (!(flags & NDF_NO_DNCP_RELE) &&
            (ndp->ni_cnd.cn_flags & CNP_WANTDNCP) &&
            ndp->ni_dncp) {
                cache_drop(ndp->ni_dncp);
                ndp->ni_dncp = NULL;
        }
        if (!(flags & NDF_NO_NCP_RELE) &&
            (ndp->ni_cnd.cn_flags & CNP_WANTNCP) &&
            ndp->ni_ncp) {
                cache_drop(ndp->ni_ncp);
                ndp->ni_ncp = NULL;
        }
        if (!(flags & NDF_NO_DVP_UNLOCK) &&
            (ndp->ni_cnd.cn_flags & CNP_LOCKPARENT) &&
            ndp->ni_dvp != ndp->ni_vp) {
                VOP_UNLOCK(ndp->ni_dvp, NULL, 0, ndp->ni_cnd.cn_td);
        }
        if (!(flags & NDF_NO_DVP_RELE) &&
            (ndp->ni_cnd.cn_flags & (CNP_LOCKPARENT|CNP_WANTPARENT))) {
                vrele(ndp->ni_dvp);
                ndp->ni_dvp = NULL;
        }
        if (!(flags & NDF_NO_VP_UNLOCK) &&
            (ndp->ni_cnd.cn_flags & CNP_LOCKLEAF) && ndp->ni_vp) {
                VOP_UNLOCK(ndp->ni_vp, NULL, 0, ndp->ni_cnd.cn_td);
        }
        if (!(flags & NDF_NO_VP_RELE) &&
            ndp->ni_vp) {
                vrele(ndp->ni_vp);
                ndp->ni_vp = NULL;
        }
        if (!(flags & NDF_NO_STARTDIR_RELE) &&
            (ndp->ni_cnd.cn_flags & CNP_SAVESTART)) {
                vrele(ndp->ni_startdir);
                ndp->ni_startdir = NULL;
        }
}

#ifdef DEBUG_VFS_LOCKS

void
assert_vop_locked(struct vnode *vp, const char *str)
{
        if (vp && IS_LOCKING_VFS(vp) && !VOP_ISLOCKED(vp, NULL)) {
                panic("%s: %p is not locked shared but should be", str, vp);
        }
}

void
assert_vop_unlocked(struct vnode *vp, const char *str)
{
        if (vp && IS_LOCKING_VFS(vp)) {
                if (VOP_ISLOCKED(vp, curthread) == LK_EXCLUSIVE) {
                        panic("%s: %p is locked but should not be", str, vp);
                }
        }
}

#endif