[apple/xnu.git] / bsd / vfs / vfs_subr.c

/*
 * Copyright (c) 2000-2001 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 * 
 * The contents of this file constitute Original Code as defined in and
 * are subject to the Apple Public Source License Version 1.1 (the
 * "License").  You may not use this file except in compliance with the
 * License.  Please obtain a copy of the License at
 * http://www.apple.com/publicsource and read it before using this file.
 * 
 * This Original Code and all software distributed under the License are
 * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT.  Please see the
 * License for the specific language governing rights and limitations
 * under the License.
 * 
 * @APPLE_LICENSE_HEADER_END@
 */
/* Copyright (c) 1995 NeXT Computer, Inc. All Rights Reserved */
/*
 * 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
 */

/*
 * External virtual filesystem routines
 */

#undef  DIAGNOSTIC
#define DIAGNOSTIC 1

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/proc.h>
#include <sys/mount.h>
#include <sys/time.h>
#include <sys/vnode.h>
#include <sys/stat.h>
#include <sys/namei.h>
#include <sys/ucred.h>
#include <sys/buf.h>
#include <sys/errno.h>
#include <sys/malloc.h>
#include <sys/domain.h>
#include <sys/mbuf.h>
#include <sys/syslog.h>
#include <sys/ubc.h>
#include <sys/vm.h>
#include <sys/sysctl.h>

#include <kern/assert.h>

#include <miscfs/specfs/specdev.h>

#include <mach/mach_types.h>
#include <mach/memory_object_types.h>


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 void vfree(struct vnode *vp);
static void vinactive(struct vnode *vp);
static int vnreclaim(int count);
extern kern_return_t 
        adjust_vm_object_cache(vm_size_t oval, vm_size_t nval);

TAILQ_HEAD(freelst, vnode) vnode_free_list;     /* vnode free list */
TAILQ_HEAD(inactivelst, vnode) vnode_inactive_list;     /* vnode inactive list */
struct mntlist mountlist;                       /* mounted filesystem list */

#if DIAGNOSTIC
#define VLISTCHECK(fun, vp, list)       \
        if ((vp)->v_freelist.tqe_prev == (struct vnode **)0xdeadb) \
                panic("%s: %s vnode not on %slist", (fun), (list), (list));

#define VINACTIVECHECK(fun, vp, expected)       \
        do {    \
                int __is_inactive = ISSET((vp)->v_flag, VUINACTIVE);    \
                if (__is_inactive ^ expected)   \
                        panic("%s: %sinactive vnode, expected %s", (fun),       \
                                __is_inactive? "" : "not ",     \
                                expected? "inactive": "not inactive"); \
        } while(0)
#else
#define VLISTCHECK(fun, vp, list)
#define VINACTIVECHECK(fun, vp, expected)
#endif /* DIAGNOSTIC */

#define VLISTNONE(vp)   \
        do {    \
                (vp)->v_freelist.tqe_next = (struct vnode *)0;  \
                (vp)->v_freelist.tqe_prev = (struct vnode **)0xdeadb;   \
        } while(0)

#define VONLIST(vp)     \
        ((vp)->v_freelist.tqe_prev != (struct vnode **)0xdeadb)

/* remove a vnode from free vnode list */
#define VREMFREE(fun, vp)       \
        do {    \
                VLISTCHECK((fun), (vp), "free");        \
                TAILQ_REMOVE(&vnode_free_list, (vp), v_freelist);       \
                VLISTNONE((vp));        \
                freevnodes--;   \
        } while(0)

/* remove a vnode from inactive vnode list */
#define VREMINACTIVE(fun, vp)   \
        do {    \
                VLISTCHECK((fun), (vp), "inactive"); \
                VINACTIVECHECK((fun), (vp), VUINACTIVE); \
                TAILQ_REMOVE(&vnode_inactive_list, (vp), v_freelist); \
                CLR((vp)->v_flag, VUINACTIVE); \
                VLISTNONE((vp));        \
                inactivevnodes--;       \
        } while(0)

#define VORECLAIM_ENABLE(vp)   \
        do {    \
                if (ISSET((vp)->v_flag, VORECLAIM))     \
                        panic("vm object raclaim already");     \
                SET((vp)->v_flag, VORECLAIM);   \
        } while(0)

#define VORECLAIM_DISABLE(vp)   \
        do {    \
                CLR((vp)->v_flag, VORECLAIM);   \
                if (ISSET((vp)->v_flag, VXWANT)) {      \
                        CLR((vp)->v_flag, VXWANT);      \
                        wakeup((caddr_t)(vp));  \
                }       \
        } while(0)

/*
 * Have to declare first two locks as actual data even if !MACH_SLOCKS, since
 * a pointers to them get passed around.
 */
simple_lock_data_t mountlist_slock;
simple_lock_data_t mntvnode_slock;
decl_simple_lock_data(,mntid_slock);
decl_simple_lock_data(,vnode_free_list_slock);
decl_simple_lock_data(,spechash_slock);

/*
 * vnodetarget is the amount of vnodes we expect to get back 
 * from the the inactive vnode list and VM object cache.
 * As vnreclaim() is a mainly cpu bound operation for faster 
 * processers this number could be higher.
 * Having this number too high introduces longer delays in 
 * the execution of getnewvnode().
 */
unsigned long vnodetarget;              /* target for vnreclaim() */
#define VNODE_FREE_TARGET       20      /* Default value for vnodetarget */

/*
 * We need quite a few vnodes on the free list to sustain the
 * rapid stat() the compilation process does, and still benefit from the name
 * cache. Having too few vnodes on the free list causes serious disk
 * thrashing as we cycle through them.
 */
#define VNODE_FREE_MIN          300     /* freelist should have at least these many */

/*
 * We need to get vnodes back from the VM object cache when a certain #
 * of vnodes are reused from the freelist. This is essential for the
 * caching to be effective in the namecache and the buffer cache [for the
 * metadata].
 */
#define VNODE_TOOMANY_REUSED    (VNODE_FREE_MIN/4)

/*
 * If we have enough vnodes on the freelist we do not want to reclaim
 * the vnodes from the VM object cache.
 */
#define VNODE_FREE_ENOUGH       (VNODE_FREE_MIN + (VNODE_FREE_MIN/2))

/*
 * Initialize the vnode management data structures.
 */
__private_extern__ void
vntblinit()
{
        extern struct lock__bsd__       exchangelock;

        simple_lock_init(&mountlist_slock);
        simple_lock_init(&mntvnode_slock);
        simple_lock_init(&mntid_slock);
        simple_lock_init(&spechash_slock);
        TAILQ_INIT(&vnode_free_list);
        simple_lock_init(&vnode_free_list_slock);
        TAILQ_INIT(&vnode_inactive_list);
        CIRCLEQ_INIT(&mountlist);
    lockinit(&exchangelock, PVFS, "exchange", 0, 0);

        if (!vnodetarget)
                vnodetarget = VNODE_FREE_TARGET;

        /*
         * Scale the vm_object_cache to accomodate the vnodes 
         * we want to cache
         */
        (void) adjust_vm_object_cache(0, desiredvnodes - VNODE_FREE_MIN);
}

/* Reset the VM Object Cache with the values passed in */
__private_extern__ kern_return_t
reset_vmobjectcache(unsigned int val1, unsigned int val2)
{
        vm_size_t oval = val1 - VNODE_FREE_MIN;
        vm_size_t nval;
        
        if(val2 < VNODE_FREE_MIN)
                nval = 0;
        else
                nval = val2 - VNODE_FREE_MIN;

        return(adjust_vm_object_cache(oval, nval));
}

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

        if (mp->mnt_kern_flag & MNTK_UNMOUNT) {
                if (flags & LK_NOWAIT)
                        return (ENOENT);
                mp->mnt_kern_flag |= MNTK_MWAIT;
                if (interlkp)
                        simple_unlock(interlkp);
                /*
                 * 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.
                 */
                sleep((caddr_t)mp, PVFS);
                if (interlkp)
                        simple_lock(interlkp);
                return (ENOENT);
        }
        lkflags = LK_SHARED;
        if (interlkp)
                lkflags |= LK_INTERLOCK;
        if (lockmgr(&mp->mnt_lock, lkflags, interlkp, p))
                panic("vfs_busy: unexpected lock failure");
        return (0);
}

/*
 * Free a busy filesystem.
 */
void
vfs_unbusy(mp, p)
        struct mount *mp;
        struct proc *p;
{

        lockmgr(&mp->mnt_lock, LK_RELEASE, NULL, p);
}

/*
 * 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(fstypename, devname, mpp)
        char *fstypename;
        char *devname;
        struct mount **mpp;
{
        struct proc *p = current_proc();        /* XXX */
        struct vfsconf *vfsp;
        struct mount *mp;

        for (vfsp = vfsconf; vfsp; vfsp = vfsp->vfc_next)
                if (!strcmp(vfsp->vfc_name, fstypename))
                        break;
        if (vfsp == NULL)
                return (ENODEV);
        mp = _MALLOC_ZONE((u_long)sizeof(struct mount), M_MOUNT, M_WAITOK);
        bzero((char *)mp, (u_long)sizeof(struct mount));

    /* Initialize the default IO constraints */
    mp->mnt_maxreadcnt = mp->mnt_maxwritecnt = MAXPHYS;
    mp->mnt_segreadcnt = mp->mnt_segwritecnt = 32;

        lockinit(&mp->mnt_lock, PVFS, "vfslock", 0, 0);
        (void)vfs_busy(mp, LK_NOWAIT, 0, p);
        LIST_INIT(&mp->mnt_vnodelist);
        mp->mnt_vfc = vfsp;
        mp->mnt_op = vfsp->vfc_vfsops;
        mp->mnt_flag = MNT_RDONLY;
        mp->mnt_vnodecovered = NULLVP;
        vfsp->vfc_refcount++;
        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] = '/';
        (void) copystr(devname, mp->mnt_stat.f_mntfromname, MNAMELEN - 1, 0);
        *mpp = mp;
        return (0);
}

/*
 * Find an appropriate filesystem to use for the root. If a filesystem
 * has not been preselected, walk through the list of known filesystems
 * trying those that have mountroot routines, and try them until one
 * works or we have tried them all.
 */
int
vfs_mountroot()
{
        struct vfsconf *vfsp;
        extern int (*mountroot)(void);
        int error;

        if (mountroot != NULL) {
                error = (*mountroot)();
                return (error);
        }
        
        for (vfsp = vfsconf; vfsp; vfsp = vfsp->vfc_next) {
                if (vfsp->vfc_mountroot == NULL)
                        continue;
                if ((error = (*vfsp->vfc_mountroot)()) == 0)
                        return (0);
                if (error != EINVAL)
                        printf("%s_mountroot failed: %d\n", vfsp->vfc_name, error);
        }
        return (ENODEV);
}

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

        simple_lock(&mountlist_slock);
        for (mp = mountlist.cqh_first; mp != (void *)&mountlist;
             mp = mp->mnt_list.cqe_next) {
                if (mp->mnt_stat.f_fsid.val[0] == fsid->val[0] &&
                    mp->mnt_stat.f_fsid.val[1] == fsid->val[1]) {
                        simple_unlock(&mountlist_slock);
                        return (mp);
                }
        }
        simple_unlock(&mountlist_slock);
        return ((struct mount *)0);
}

/*
 * Get a new unique fsid
 */
void
vfs_getnewfsid(mp)
        struct mount *mp;
{
static u_short xxxfs_mntid;

        fsid_t tfsid;
        int mtype;

        simple_lock(&mntid_slock);
        mtype = mp->mnt_vfc->vfc_typenum;
        mp->mnt_stat.f_fsid.val[0] = makedev(nblkdev + mtype, 0);
        mp->mnt_stat.f_fsid.val[1] = mtype;
        if (xxxfs_mntid == 0)
                ++xxxfs_mntid;
        tfsid.val[0] = makedev(nblkdev + mtype, xxxfs_mntid);
        tfsid.val[1] = mtype;
        if (mountlist.cqh_first != (void *)&mountlist) {
                while (vfs_getvfs(&tfsid)) {
                        tfsid.val[0]++;
                        xxxfs_mntid++;
                }
        }
        mp->mnt_stat.f_fsid.val[0] = tfsid.val[0];
        simple_unlock(&mntid_slock);
}

/*
 * Set vnode attributes to VNOVAL
 */
void
vattr_null(vap)
        register struct vattr *vap;
{

        vap->va_type = VNON;
        vap->va_size = vap->va_bytes = VNOVAL;
        vap->va_mode = vap->va_nlink = vap->va_uid = vap->va_gid =
                vap->va_fsid = vap->va_fileid =
                vap->va_blocksize = vap->va_rdev =
                vap->va_atime.tv_sec = vap->va_atime.tv_nsec =
                vap->va_mtime.tv_sec = vap->va_mtime.tv_nsec =
                vap->va_ctime.tv_sec = vap->va_ctime.tv_nsec =
                vap->va_flags = vap->va_gen = VNOVAL;
        vap->va_vaflags = 0;
}

/*
 * Routines having to do with the management of the vnode table.
 */
extern int (**dead_vnodeop_p)(void *);
static void vclean __P((struct vnode *vp, int flag, struct proc *p));
extern void vgonel __P((struct vnode *vp, struct proc *p));
long numvnodes, freevnodes;
long inactivevnodes;
long vnode_reclaim_tried;
long vnode_objects_reclaimed;


extern struct vattr va_null;

/*
 * Return the next vnode from the free list.
 */
int
getnewvnode(tag, mp, vops, vpp)
        enum vtagtype tag;
        struct mount *mp;
        int (**vops)(void *);
        struct vnode **vpp;
{
        struct proc *p = current_proc();        /* XXX */
        struct vnode *vp;
        int cnt, didretry = 0;
        static int reused = 0;                          /* track the reuse rate */
        int reclaimhits = 0;

retry:
        simple_lock(&vnode_free_list_slock);
        /*
         * MALLOC a vnode if the number of vnodes has not reached the desired
         * value and the number on the free list is still reasonable...
         * reuse from the freelist even though we may evict a name cache entry
         * to reduce the number of vnodes that accumulate.... vnodes tie up
         * wired memory and are never garbage collected
         */
        if (numvnodes < desiredvnodes && (freevnodes < (2 * VNODE_FREE_MIN))) {
                numvnodes++;
                simple_unlock(&vnode_free_list_slock);
                MALLOC_ZONE(vp, struct vnode *, sizeof *vp, M_VNODE, M_WAITOK);
                bzero((char *)vp, sizeof *vp);
                VLISTNONE(vp);          /* avoid double queue removal */
                simple_lock_init(&vp->v_interlock);
                goto done;
        }

        /*
         * Once the desired number of vnodes are allocated,
         * we start reusing the vnodes.
         */
        if (freevnodes < VNODE_FREE_MIN) {
                /*
                 * if we are low on vnodes on the freelist attempt to get
                 * some back from the inactive list and VM object cache
                 */
                simple_unlock(&vnode_free_list_slock);
                (void)vnreclaim(vnodetarget);
                simple_lock(&vnode_free_list_slock);
        }
        if (numvnodes >= desiredvnodes && reused > VNODE_TOOMANY_REUSED) {
                reused = 0;
                if (freevnodes < VNODE_FREE_ENOUGH) {
                        simple_unlock(&vnode_free_list_slock);
                        (void)vnreclaim(vnodetarget);
                        simple_lock(&vnode_free_list_slock);
                }
        }

        for (cnt = 0, vp = vnode_free_list.tqh_first;
                        vp != NULLVP; cnt++, vp = vp->v_freelist.tqe_next) {
                if (simple_lock_try(&vp->v_interlock)) {
                        /* got the interlock */
                        if (ISSET(vp->v_flag, VORECLAIM)) {
                                /* skip over the vnodes that are being reclaimed */
                                simple_unlock(&vp->v_interlock);
                                reclaimhits++;
                        } else
                        break;
        }
        }

        /*
         * Unless this is a bad time of the month, at most
         * the first NCPUS items on the free list are
         * locked, so this is close enough to being empty.
         */
        if (vp == NULLVP) {
                simple_unlock(&vnode_free_list_slock);
                if (!(didretry++) && (vnreclaim(vnodetarget) > 0))
                        goto retry;
                tablefull("vnode");
                log(LOG_EMERG, "%d vnodes locked, %d desired, %d numvnodes, "
                        "%d free, %d inactive, %d being reclaimed\n",
                        cnt, desiredvnodes, numvnodes, freevnodes, inactivevnodes,
                        reclaimhits);
                *vpp = 0;
                return (ENFILE);
        }

        if (vp->v_usecount)
                panic("free vnode isn't: v_type = %d, v_usecount = %d?",
                                vp->v_type, vp->v_usecount);

        VREMFREE("getnewvnode", vp);
        reused++;
        simple_unlock(&vnode_free_list_slock);
        vp->v_lease = NULL;
        cache_purge(vp);
        if (vp->v_type != VBAD)
                vgonel(vp, p);  /* clean and reclaim the vnode */
        else
                simple_unlock(&vp->v_interlock);
#if DIAGNOSTIC
        if (vp->v_data)
                panic("cleaned vnode isn't");
        {
        int s = splbio();
        if (vp->v_numoutput)
                panic("Clean vnode has pending I/O's");
        splx(s);
        }
#endif
        if (UBCINFOEXISTS(vp))
                panic("getnewvnode: ubcinfo not cleaned");
        else
                vp->v_ubcinfo = 0;

        vp->v_lastr = -1;
        vp->v_ralen = 0;
        vp->v_maxra = 0;
        vp->v_lastw = 0;
        vp->v_ciosiz = 0;
        vp->v_cstart = 0;
        vp->v_clen = 0;
        vp->v_socket = 0;

done:
        vp->v_flag = VSTANDARD;
        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;
        return (0);
}

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

        simple_lock(&mntvnode_slock);
        /*
         * Delete from old mount point vnode list, if on one.
         */
        if (vp->v_mount != NULL)
                LIST_REMOVE(vp, v_mntvnodes);
        /*
         * Insert into list of vnodes for the new mount point, if available.
         */
        if ((vp->v_mount = mp) != NULL)
                LIST_INSERT_HEAD(&mp->mnt_vnodelist, vp, v_mntvnodes);
        simple_unlock(&mntvnode_slock);
}

__inline void
vpwakeup(struct vnode *vp)
{
        if (vp) {
                if (--vp->v_numoutput < 0)
                        panic("vpwakeup: neg numoutput");
                if ((vp->v_flag & VBWAIT || vp->v_flag & VTHROTTLED)
                    && vp->v_numoutput <= 0) {
                        vp->v_flag &= ~(VBWAIT|VTHROTTLED);
                        wakeup((caddr_t)&vp->v_numoutput);
                }
        }
}

/*
 * Update outstanding I/O count and do wakeup if requested.
 */
void
vwakeup(bp)
        register struct buf *bp;
{
        CLR(bp->b_flags, B_WRITEINPROG);
        vpwakeup(bp->b_vp);
}

/*
 * Flush out and invalidate all buffers associated with a vnode.
 * Called with the underlying object locked.
 */
int
vinvalbuf(vp, flags, cred, p, slpflag, slptimeo)
        register struct vnode *vp;
        int flags;
        struct ucred *cred;
        struct proc *p;
        int slpflag, slptimeo;
{
        register struct buf *bp;
        struct buf *nbp, *blist;
        int s, error = 0;

        if (flags & V_SAVE) {
                if (error = VOP_FSYNC(vp, cred, MNT_WAIT, p)) {
                        return (error);
                }
                if (vp->v_dirtyblkhd.lh_first)
                        panic("vinvalbuf: dirty bufs");
        }

        for (;;) {
                if ((blist = vp->v_cleanblkhd.lh_first) && flags & V_SAVEMETA)
                        while (blist && blist->b_lblkno < 0)
                                blist = blist->b_vnbufs.le_next;
                if (!blist && (blist = vp->v_dirtyblkhd.lh_first) &&
                    (flags & V_SAVEMETA))
                        while (blist && blist->b_lblkno < 0)
                                blist = blist->b_vnbufs.le_next;
                if (!blist)
                        break;

                for (bp = blist; bp; bp = nbp) {
                        nbp = bp->b_vnbufs.le_next;
                        if (flags & V_SAVEMETA && bp->b_lblkno < 0)
                                continue;
                        s = splbio();
                        if (ISSET(bp->b_flags, B_BUSY)) {
                                SET(bp->b_flags, B_WANTED);
                                error = tsleep((caddr_t)bp,
                                        slpflag | (PRIBIO + 1), "vinvalbuf",
                                        slptimeo);
                                splx(s);
                                if (error) {
                                        return (error);
                                }
                                break;
                        }
                        bremfree(bp);
                        SET(bp->b_flags, B_BUSY);
                        splx(s);
                        /*
                         * XXX Since there are no node locks for NFS, I believe
                         * there is a slight chance that a delayed write will
                         * occur while sleeping just above, so check for it.
                         */
                        if (ISSET(bp->b_flags, B_DELWRI) && (flags & V_SAVE)) {
                                (void) VOP_BWRITE(bp);
                                break;
                        }
                        SET(bp->b_flags, B_INVAL);
                        brelse(bp);
                }
        }
        if (!(flags & V_SAVEMETA) &&
            (vp->v_dirtyblkhd.lh_first || vp->v_cleanblkhd.lh_first))
                panic("vinvalbuf: flush failed");
        return (0);
}

/*
 * Create a vnode for a block device.
 * Used for root filesystem, argdev, and swap areas.
 * Also used for memory file system special devices.
 */
int
bdevvp(dev, vpp)
        dev_t dev;
        struct vnode **vpp;
{
        register struct vnode *vp;
        struct vnode *nvp;
        int error;

        if (dev == NODEV) {
                *vpp = NULLVP;
                return (ENODEV);
        }
        error = getnewvnode(VT_NON, (struct mount *)0, spec_vnodeop_p, &nvp);
        if (error) {
                *vpp = NULLVP;
                return (error);
        }
        vp = nvp;
        vp->v_type = VBLK;
        if (nvp = checkalias(vp, dev, (struct mount *)0)) {
                vput(vp);
                vp = nvp;
        }
        *vpp = vp;
        return (0);
}

/*
 * Check to see if the new vnode represents a special device
 * for which we already have a vnode (either because of
 * bdevvp() or because of a different vnode representing
 * the same block device). If such an alias exists, deallocate
 * the existing contents and return the aliased vnode. The
 * caller is responsible for filling it with its new contents.
 */
struct vnode *
checkalias(nvp, nvp_rdev, mp)
        register struct vnode *nvp;
        dev_t nvp_rdev;
        struct mount *mp;
{
        struct proc *p = current_proc();        /* XXX */
        struct vnode *vp;
        struct vnode **vpp;
        struct specinfo * bufhold;
        int buffree = 1;

        if (nvp->v_type != VBLK && nvp->v_type != VCHR)
                return (NULLVP);

        bufhold = (struct specinfo *)_MALLOC_ZONE(sizeof(struct specinfo),
                        M_VNODE, M_WAITOK);
        vpp = &speclisth[SPECHASH(nvp_rdev)];
loop:
        simple_lock(&spechash_slock);
        for (vp = *vpp; vp; vp = vp->v_specnext) {
                if (nvp_rdev != vp->v_rdev || nvp->v_type != vp->v_type)
                        continue;
                /*
                 * Alias, but not in use, so flush it out.
                 */
                simple_lock(&vp->v_interlock);
                if (vp->v_usecount == 0) {
                        simple_unlock(&spechash_slock);
                        vgonel(vp, p);
                        goto loop;
                }
                if (vget(vp, LK_EXCLUSIVE | LK_INTERLOCK, p)) {
                        simple_unlock(&spechash_slock);
                        goto loop;
                }
                break;
        }
        if (vp == NULL || vp->v_tag != VT_NON) {
                nvp->v_specinfo = bufhold;
                buffree = 0;    /* buffer used */
                bzero(nvp->v_specinfo, sizeof(struct specinfo));
                nvp->v_rdev = nvp_rdev;
                nvp->v_hashchain = vpp;
                nvp->v_specnext = *vpp;
                nvp->v_specflags = 0;
                simple_unlock(&spechash_slock);
                *vpp = nvp;
                if (vp != NULLVP) {
                        nvp->v_flag |= VALIASED;
                        vp->v_flag |= VALIASED;
                        vput(vp);
                }
                /* Since buffer is used just return */
                return (NULLVP);
        }
        simple_unlock(&spechash_slock);
        VOP_UNLOCK(vp, 0, p);
        simple_lock(&vp->v_interlock);
        vclean(vp, 0, p);
        vp->v_op = nvp->v_op;
        vp->v_tag = nvp->v_tag;
        nvp->v_type = VNON;
        insmntque(vp, mp);
        if (buffree)
                _FREE_ZONE((void *)bufhold, sizeof (struct specinfo), M_VNODE);
        return (vp);
}

/*
 * Get a reference on a particular vnode and lock it if requested.
 * If the vnode was on the inactive list, remove it from the list.
 * If the vnode was on the free list, remove it from the list and
 * move it to inactive list as needed.
 * 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).
 */
int
vget(vp, flags, p)
        struct vnode *vp;
        int flags;
        struct proc *p;
{
        int error = 0;

retry:

        /*
         * 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.
         */
        if ((flags & LK_INTERLOCK) == 0)
                simple_lock(&vp->v_interlock);
        if ((vp->v_flag & VXLOCK) || (vp->v_flag & VORECLAIM)) {
                vp->v_flag |= VXWANT;
                simple_unlock(&vp->v_interlock);
                (void)tsleep((caddr_t)vp, PINOD, "vget", 0);
                return (ENOENT);
        }

        /* 
         * vnode is being terminated.
         * wait for vnode_pager_no_senders() to clear VTERMINATE
         */
        if (ISSET(vp->v_flag, VTERMINATE)) {
                SET(vp->v_flag, VTERMWANT);
                simple_unlock(&vp->v_interlock);
                (void)tsleep((caddr_t)&vp->v_ubcinfo, PINOD, "vclean", 0);
                return (ENOENT);
        }

        /*
         * if the vnode is being initialized,
         * wait for it to finish initialization
         */
        if (ISSET(vp->v_flag,  VUINIT)) {
                if (ISSET(vp->v_flag,  VUINIT)) {
                        SET(vp->v_flag, VUWANT);
                        simple_unlock(&vp->v_interlock);
                        (void) tsleep((caddr_t)vp, PINOD, "vget2", 0);
                        goto retry;
                }
        }

        simple_lock(&vnode_free_list_slock);
        if (vp->v_usecount == 0) {
                /* If on the free list, remove it from there */
                if (VONLIST(vp))
                        VREMFREE("vget", vp);
        } else {
                /* If on the inactive list, remove it from there */
                if ((vp->v_usecount == 1) && UBCINFOEXISTS(vp)) {
                        if (VONLIST(vp))
                                VREMINACTIVE("vget", vp);
                }
        }

        /* The vnode should not be on the inactive list here */
        VINACTIVECHECK("vget", vp, 0);

        simple_unlock(&vnode_free_list_slock);

        if (++vp->v_usecount <= 0)
                panic("vget: v_usecount");                     

        /*
         * Recover named reference as needed
         */
        if (UBCISVALID(vp) && !ubc_issetflags(vp, UI_HASOBJREF)) {
                simple_unlock(&vp->v_interlock);
                if (ubc_getobject(vp, UBC_HOLDOBJECT)) {
                        error = ENOENT;
                        goto errout;
                }
                simple_lock(&vp->v_interlock);
        }

        if (flags & LK_TYPE_MASK) {
                if (error = vn_lock(vp, flags | LK_INTERLOCK, p))
                        goto errout;
                return (0);
        }

        if ((flags & LK_INTERLOCK) == 0)
                simple_unlock(&vp->v_interlock);
        return (0);

errout:
        /*
         * If the vnode was not active in the first place
         * must not call vrele() as VOP_INACTIVE() is not
         * required.
         * So inlined part of vrele() here.
         */
        simple_lock(&vp->v_interlock);
        if (--vp->v_usecount == 1) {
                if (UBCINFOEXISTS(vp)) {
                        vinactive(vp);
                        simple_unlock(&vp->v_interlock);
                        return (error);
                }
        }
        if (vp->v_usecount > 0) {
                simple_unlock(&vp->v_interlock);
                return (error);
        }
        if (vp->v_usecount < 0)
                panic("vget: negative usecount (%d)", vp->v_usecount);
        vfree(vp);
        simple_unlock(&vp->v_interlock);
        return (error);
}

/*
 * Get a pager reference on the particular vnode.
 *
 * This is called from ubc_info_init() and it is asumed that
 * the vnode is neither on the free list on on the inactive list.
 * It is also assumed that the vnode is neither being recycled
 * by vgonel nor being terminated by vnode_pager_vrele().
 *
 * The vnode interlock is NOT held by the caller.
 */
__private_extern__ int
vnode_pager_vget(vp)
        struct vnode *vp;
{
        simple_lock(&vp->v_interlock);
        if (UBCINFOMISSING(vp))
                panic("vnode_pager_vget: stolen ubc_info");

        if (!UBCINFOEXISTS(vp))
                panic("vnode_pager_vget: lost ubc_info");

        if ((vp->v_flag & VXLOCK) || (vp->v_flag & VORECLAIM))
                panic("vnode_pager_vget: already being reclaimd");

        if (ISSET(vp->v_flag, VTERMINATE))
                panic("vnode_pager_vget: already being terminated");

        simple_lock(&vnode_free_list_slock);
        /* The vnode should not be on ANY list */
        if (VONLIST(vp))
                panic("vnode_pager_vget: still on the list");

        /* The vnode should not be on the inactive list here */
        VINACTIVECHECK("vnode_pager_vget", vp, 0);
        simple_unlock(&vnode_free_list_slock);

        /* After all those checks, now do the real work :-) */
        if (++vp->v_usecount <= 0)
                panic("vnode_pager_vget: v_usecount");                     
        simple_unlock(&vp->v_interlock);

        return (0);
}

/*
 * Stubs to use when there is no locking to be done on the underlying object.
 * A minimal shared lock is necessary to ensure that the underlying object
 * is not revoked while an operation is in progress. So, an active shared
 * count is maintained in an auxillary vnode lock structure.
 */
int
vop_nolock(ap)
        struct vop_lock_args /* {
                struct vnode *a_vp;
                int a_flags;
                struct proc *a_p;
        } */ *ap;
{
#ifdef notyet
        /*
         * This code cannot be used until all the non-locking filesystems
         * (notably NFS) are converted to properly lock and release nodes.
         * Also, certain vnode operations change the locking state within
         * the operation (create, mknod, remove, link, rename, mkdir, rmdir,
         * and symlink). Ideally these operations should not change the
         * lock state, but should be changed to let the caller of the
         * function unlock them. Otherwise all intermediate vnode layers
         * (such as union, umapfs, etc) must catch these functions to do
         * the necessary locking at their layer. Note that the inactive
         * and lookup operations also change their lock state, but this 
         * cannot be avoided, so these two operations will always need
         * to be handled in intermediate layers.
         */
        struct vnode *vp = ap->a_vp;
        int vnflags, flags = ap->a_flags;

        if (vp->v_vnlock == NULL) {
                if ((flags & LK_TYPE_MASK) == LK_DRAIN)
                        return (0);
                MALLOC_ZONE(vp->v_vnlock, struct lock__bsd__ *,
                                sizeof(struct lock__bsd__), M_VNODE, M_WAITOK);
                lockinit(vp->v_vnlock, PVFS, "vnlock", 0, 0);
        }
        switch (flags & LK_TYPE_MASK) {
        case LK_DRAIN:
                vnflags = LK_DRAIN;
                break;
        case LK_EXCLUSIVE:
        case LK_SHARED:
                vnflags = LK_SHARED;
                break;
        case LK_UPGRADE:
        case LK_EXCLUPGRADE:
        case LK_DOWNGRADE:
                return (0);
        case LK_RELEASE:
        default:
                panic("vop_nolock: bad operation %d", flags & LK_TYPE_MASK);
        }
        if (flags & LK_INTERLOCK)
                vnflags |= LK_INTERLOCK;
        return(lockmgr(vp->v_vnlock, vnflags, &vp->v_interlock, ap->a_p));
#else /* for now */
        /*
         * Since we are not using the lock manager, we must clear
         * the interlock here.
         */
        if (ap->a_flags & LK_INTERLOCK)
                simple_unlock(&ap->a_vp->v_interlock);
        return (0);
#endif
}

/*
 * Decrement the active use count.
 */
int
vop_nounlock(ap)
        struct vop_unlock_args /* {
                struct vnode *a_vp;
                int a_flags;
                struct proc *a_p;
        } */ *ap;
{
        struct vnode *vp = ap->a_vp;

        if (vp->v_vnlock == NULL)
                return (0);
        return (lockmgr(vp->v_vnlock, LK_RELEASE, NULL, ap->a_p));
}

/*
 * Return whether or not the node is in use.
 */
int
vop_noislocked(ap)
        struct vop_islocked_args /* {
                struct vnode *a_vp;
        } */ *ap;
{
        struct vnode *vp = ap->a_vp;

        if (vp->v_vnlock == NULL)
                return (0);
        return (lockstatus(vp->v_vnlock));
}

/*
 * Vnode reference.
 */
void
vref(vp)
        struct vnode *vp;
{

        simple_lock(&vp->v_interlock);
        if (vp->v_usecount <= 0)
                panic("vref used where vget required");

        /* If on the inactive list, remove it from there */
        if ((vp->v_usecount == 1) && UBCINFOEXISTS(vp)) {
                if (VONLIST(vp)) {
                        simple_lock(&vnode_free_list_slock);
                        VREMINACTIVE("vref", vp);
                        simple_unlock(&vnode_free_list_slock);
                }
        }
        /* The vnode should not be on the inactive list here */
        VINACTIVECHECK("vref", vp, 0);

        if (++vp->v_usecount <= 0)
                panic("vref v_usecount");                     
        simple_unlock(&vp->v_interlock);
}

/*
 * put the vnode on appropriate free list.
 * called with v_interlock held.
 */
static void
vfree(vp)
        struct vnode *vp;
{
        /*
         * if the vnode is not obtained by calling getnewvnode() we
         * are not responsible for the cleanup. Just return.
         */
        if (!(vp->v_flag & VSTANDARD)) {
                return;
        }

        if (vp->v_usecount != 0)
                panic("vfree: v_usecount");

        /* insert at tail of LRU list or at head if VAGE is set */
        simple_lock(&vnode_free_list_slock);

        if (VONLIST(vp))
                 panic("vfree: vnode still on list");

        if (vp->v_flag & VAGE) {
                TAILQ_INSERT_HEAD(&vnode_free_list, vp, v_freelist);
                vp->v_flag &= ~VAGE;
        } else
                TAILQ_INSERT_TAIL(&vnode_free_list, vp, v_freelist);
        freevnodes++;
        simple_unlock(&vnode_free_list_slock);
        return;
}

/*
 * put the vnode on the inactive list.
 * called with v_interlock held
 */
static void
vinactive(vp)
        struct vnode *vp;
{
        if (!UBCINFOEXISTS(vp))
                panic("vinactive: not a UBC vnode");

        if (vp->v_usecount != 1)
                panic("vinactive: v_usecount");

        simple_lock(&vnode_free_list_slock);

        if (VONLIST(vp))
                 panic("vinactive: vnode still on list");
        VINACTIVECHECK("vinactive", vp, 0);

        TAILQ_INSERT_TAIL(&vnode_inactive_list, vp, v_freelist);
        SET(vp->v_flag, VUINACTIVE);
        CLR(vp->v_flag, (VNOCACHE_DATA | VRAOFF));

        inactivevnodes++;
        simple_unlock(&vnode_free_list_slock);
        return;
}


/*
 * vput(), just unlock and vrele()
 */
void
vput(vp)
        struct vnode *vp;
{
        struct proc *p = current_proc();        /* XXX */

        simple_lock(&vp->v_interlock);
        if (--vp->v_usecount == 1) {
                if (UBCINFOEXISTS(vp)) {
                        vinactive(vp);
                        simple_unlock(&vp->v_interlock);
                        VOP_UNLOCK(vp, 0, p);
                        return;
                }
        }
        if (vp->v_usecount > 0) {
                simple_unlock(&vp->v_interlock);
                VOP_UNLOCK(vp, 0, p);
                return;
        }
#if DIAGNOSTIC
        if (vp->v_usecount < 0 || vp->v_writecount != 0) {
                vprint("vput: bad ref count", vp);
                panic("vput: v_usecount = %d, v_writecount = %d",
                        vp->v_usecount, vp->v_writecount);
        }
#endif
        if (ISSET((vp)->v_flag, VUINACTIVE) && VONLIST(vp))
                VREMINACTIVE("vrele", vp);

        simple_unlock(&vp->v_interlock);
        VOP_INACTIVE(vp, p);
        /*
         * The interlock is not held and
         * VOP_INCATIVE releases the vnode lock.
         * We could block and the vnode might get reactivated
         * Can not just call vfree without checking the state
         */
        simple_lock(&vp->v_interlock);
        if (!VONLIST(vp)) {
                if (vp->v_usecount == 0) 
                        vfree(vp);
                else if ((vp->v_usecount == 1) && UBCINFOEXISTS(vp))
                        vinactive(vp);
        }
        simple_unlock(&vp->v_interlock);
}

/*
 * Vnode release.
 * If count drops to zero, call inactive routine and return to freelist.
 */
void
vrele(vp)
        struct vnode *vp;
{
        struct proc *p = current_proc();        /* XXX */

        simple_lock(&vp->v_interlock);
        if (--vp->v_usecount == 1) {
                if (UBCINFOEXISTS(vp)) {
                        vinactive(vp);
                        simple_unlock(&vp->v_interlock);
                        return;
                }
        }
        if (vp->v_usecount > 0) {
                simple_unlock(&vp->v_interlock);
                return;
        }
#if DIAGNOSTIC
        if (vp->v_usecount < 0 || vp->v_writecount != 0) {
                vprint("vrele: bad ref count", vp);
                panic("vrele: ref cnt");
        }
#endif
        if (ISSET((vp)->v_flag, VUINACTIVE) && VONLIST(vp))
                VREMINACTIVE("vrele", vp);


        if ((vp->v_flag & VXLOCK) || (vp->v_flag & VORECLAIM)) {
                /* vnode is being cleaned, just return */
                vfree(vp);
                simple_unlock(&vp->v_interlock);
                return;
        }

        if (vn_lock(vp, LK_EXCLUSIVE | LK_INTERLOCK, p) == 0) {
                VOP_INACTIVE(vp, p);
                /*
                 * vn_lock releases the interlock and
                 * VOP_INCATIVE releases the vnode lock.
                 * We could block and the vnode might get reactivated
                 * Can not just call vfree without checking the state
                 */
                simple_lock(&vp->v_interlock);
                if (!VONLIST(vp)) {
                        if (vp->v_usecount == 0) 
                                vfree(vp);
                        else if ((vp->v_usecount == 1) && UBCINFOEXISTS(vp))
                                vinactive(vp);
                }
                simple_unlock(&vp->v_interlock);
        }
#if 0
        else {
                vfree(vp);
                simple_unlock(&vp->v_interlock);
                kprintf("vrele: vn_lock() failed for vp = 0x%08x\n", vp);
        }
#endif
}

void
vagevp(vp)
        struct vnode *vp;
{
        simple_lock(&vp->v_interlock);
        vp->v_flag |= VAGE;
        simple_unlock(&vp->v_interlock);
        return;
}

/*
 * Page or buffer structure gets a reference.
 */
void
vhold(vp)
        register struct vnode *vp;
{

        simple_lock(&vp->v_interlock);
        vp->v_holdcnt++;
        simple_unlock(&vp->v_interlock);
}

/*
 * Page or buffer structure frees a reference.
 */
void
holdrele(vp)
        register struct vnode *vp;
{

        simple_lock(&vp->v_interlock);
        if (vp->v_holdcnt <= 0)
                panic("holdrele: holdcnt");
        vp->v_holdcnt--;
        simple_unlock(&vp->v_interlock);
}

/*
 * Remove any vnodes in the vnode table belonging to mount point mp.
 *
 * If MNT_NOFORCE is 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 MNT_FORCE is specified, detach any active vnodes
 * that are found.
 */
#if DIAGNOSTIC
int busyprt = 0;        /* print out busy vnodes */
#if 0
struct ctldebug debug1 = { "busyprt", &busyprt };
#endif /* 0 */
#endif

int
vflush(mp, skipvp, flags)
        struct mount *mp;
        struct vnode *skipvp;
        int flags;
{
        struct proc *p = current_proc();
        struct vnode *vp, *nvp;
        int busy = 0;

        simple_lock(&mntvnode_slock);
loop:
        for (vp = mp->mnt_vnodelist.lh_first; vp; vp = nvp) {
                if (vp->v_mount != mp)
                        goto loop;
                nvp = vp->v_mntvnodes.le_next;
                /*
                 * Skip over a selected vnode.
                 */
                if (vp == skipvp)
                        continue;

                simple_lock(&vp->v_interlock);
                /*
                 * Skip over a vnodes marked VSYSTEM or VNOFLUSH.
                 */
                if ((flags & SKIPSYSTEM) && ((vp->v_flag & VSYSTEM) || (vp->v_flag & VNOFLUSH))) {
                        simple_unlock(&vp->v_interlock);
                        continue;
                }
                /*
                 * Skip over a vnodes marked VSWAP.
                 */
                if ((flags & SKIPSWAP) && (vp->v_flag & VSWAP)) {
                        simple_unlock(&vp->v_interlock);
                        continue;
                }
                /*
                 * If WRITECLOSE is set, only flush out regular file
                 * vnodes open for writing.
                 */
                if ((flags & WRITECLOSE) &&
                    (vp->v_writecount == 0 || vp->v_type != VREG)) {
                        simple_unlock(&vp->v_interlock);
                        continue;
                }
                /*
                 * 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) {
                        simple_unlock(&mntvnode_slock);
                        vgonel(vp, p);
                        simple_lock(&mntvnode_slock);
                        continue;
                }
                /*
                 * 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 (flags & FORCECLOSE) {
                        simple_unlock(&mntvnode_slock);
                        if (vp->v_type != VBLK && vp->v_type != VCHR) {
                                vgonel(vp, p);
                        } else {
                                vclean(vp, 0, p);
                                vp->v_op = spec_vnodeop_p;
                                insmntque(vp, (struct mount *)0);
                        }
                        simple_lock(&mntvnode_slock);
                        continue;
                }
#if DIAGNOSTIC
                if (busyprt)
                        vprint("vflush: busy vnode", vp);
#endif
                simple_unlock(&vp->v_interlock);
                busy++;
        }
        simple_unlock(&mntvnode_slock);
        if (busy && ((flags & FORCECLOSE)==0))
                return (EBUSY);
        return (0);
}

/*
 * Disassociate the underlying file system from a vnode.
 * The vnode interlock is held on entry.
 */
static void
vclean(vp, flags, p)
        struct vnode *vp;
        int flags;
        struct proc *p;
{
        int active;
        int removed = 0;
        int didhold;

        /*
         * if the vnode is not obtained by calling getnewvnode() we
         * are not responsible for the cleanup. Just return.
         */
        if (!(vp->v_flag & VSTANDARD)) {
                simple_unlock(&vp->v_interlock);
                return;
        }

        /*
         * 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)
                if (++vp->v_usecount <= 0)
                        panic("vclean: 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;

        /*
         * 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.
         */
        VOP_LOCK(vp, LK_DRAIN | LK_INTERLOCK, p);

        /*
         * if this vnode is on the inactive list 
         * take it off the list.
         */
        if ((active == 1) && 
                (ISSET((vp)->v_flag, VUINACTIVE) && VONLIST(vp))) {
                simple_lock(&vnode_free_list_slock);
                VREMINACTIVE("vclean", vp);
                simple_unlock(&vnode_free_list_slock);
                removed++;
        }

        /* Clean the pages in VM. */
        if (active && (flags & DOCLOSE))
                VOP_CLOSE(vp, IO_NDELAY, NOCRED, p);

        /* Clean the pages in VM. */
        didhold = ubc_hold(vp);
        if ((active) && (didhold))
                (void)ubc_clean(vp, 0); /* do not invalidate */

        /*
         * Clean out any buffers associated with the vnode.
         */
        if (flags & DOCLOSE) {
                if (vp->v_tag == VT_NFS)
            nfs_vinvalbuf(vp, V_SAVE, NOCRED, p, 0);
        else
            vinvalbuf(vp, V_SAVE, NOCRED, p, 0, 0);
    }

        if (active)
                VOP_INACTIVE(vp, p);
        else
                VOP_UNLOCK(vp, 0, p);

        /* Destroy ubc named reference */
    if (didhold) {
        ubc_rele(vp);
                ubc_destroy_named(vp);
        }

        /*
         * Reclaim the vnode.
         */
        if (VOP_RECLAIM(vp, p))
                panic("vclean: cannot reclaim");
        cache_purge(vp);
        if (vp->v_vnlock) {
                if ((vp->v_vnlock->lk_flags & LK_DRAINED) == 0)
                        vprint("vclean: lock not drained", vp);
                FREE_ZONE(vp->v_vnlock, sizeof (struct lock__bsd__), M_VNODE);
                vp->v_vnlock = NULL;
        }

        /* It's dead, Jim! */
        vp->v_op = dead_vnodeop_p;
        vp->v_tag = VT_NON;

        /*
         * Done with purge, notify sleepers of the grim news.
         */
        vp->v_flag &= ~VXLOCK;
        if (vp->v_flag & VXWANT) {
                vp->v_flag &= ~VXWANT;
                wakeup((caddr_t)vp);
        }

        if (active)
                vrele(vp);
}

/*
 * Eliminate all activity associated with  the requested vnode
 * and with all vnodes aliased to the requested vnode.
 */
int
vop_revoke(ap)
        struct vop_revoke_args /* {
                struct vnode *a_vp;
                int a_flags;
        } */ *ap;
{
        struct vnode *vp, *vq;
        struct proc *p = current_proc();

#if DIAGNOSTIC
        if ((ap->a_flags & REVOKEALL) == 0)
                panic("vop_revoke");
#endif

        vp = ap->a_vp;
        simple_lock(&vp->v_interlock);

        if (vp->v_flag & VALIASED) {
                /*
                 * If a vgone (or vclean) is already in progress,
                 * wait until it is done and return.
                 */
                if (vp->v_flag & VXLOCK) {
                        while (vp->v_flag & VXLOCK) {
                                vp->v_flag |= VXWANT;
                                simple_unlock(&vp->v_interlock);
                                (void)tsleep((caddr_t)vp, PINOD, "vop_revokeall", 0);
                        }
                        return (0);
                }
                /*
                 * Ensure that vp will not be vgone'd while we
                 * are eliminating its aliases.
                 */
                vp->v_flag |= VXLOCK;
                simple_unlock(&vp->v_interlock);
                while (vp->v_flag & VALIASED) {
                        simple_lock(&spechash_slock);
                        for (vq = *vp->v_hashchain; vq; vq = vq->v_specnext) {
                                if (vq->v_rdev != vp->v_rdev ||
                                    vq->v_type != vp->v_type || vp == vq)
                                        continue;
                                simple_unlock(&spechash_slock);
                                vgone(vq);
                                break;
                        }
                        if (vq == NULLVP)
                                simple_unlock(&spechash_slock);
                }
                /*
                 * Remove the lock so that vgone below will
                 * really eliminate the vnode after which time
                 * vgone will awaken any sleepers.
                 */
                simple_lock(&vp->v_interlock);
                vp->v_flag &= ~VXLOCK;
        }
        vgonel(vp, p);
        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(vp, inter_lkp, p)
        struct vnode *vp;
        struct slock *inter_lkp;
        struct proc *p;
{

        simple_lock(&vp->v_interlock);
        if (vp->v_usecount == 0) {
                if (inter_lkp)
                        simple_unlock(inter_lkp);
                vgonel(vp, p);
                return (1);
        }
        simple_unlock(&vp->v_interlock);
        return (0);
}

/*
 * Eliminate all activity associated with a vnode
 * in preparation for reuse.
 */
void
vgone(vp)
        struct vnode *vp;
{
        struct proc *p = current_proc();

        simple_lock(&vp->v_interlock);
        vgonel(vp, p);
}

/*
 * vgone, with the vp interlock held.
 */
void
vgonel(vp, p)
        struct vnode *vp;
        struct proc *p;
{
        struct vnode *vq;
        struct vnode *vx;

        /*
         * if the vnode is not obtained by calling getnewvnode() we
         * are not responsible for the cleanup. Just return.
         */
        if (!(vp->v_flag & VSTANDARD)) {
                simple_unlock(&vp->v_interlock);
                return;
        }

        /*
         * If a vgone (or vclean) is already in progress,
         * wait until it is done and return.
         */
        if (vp->v_flag & VXLOCK) {
                while (vp->v_flag & VXLOCK) {
                        vp->v_flag |= VXWANT;
                        simple_unlock(&vp->v_interlock);
                        (void)tsleep((caddr_t)vp, PINOD, "vgone", 0);
                }
                return;
        }
        /*
         * Clean out the filesystem specific data.
         */
        vclean(vp, DOCLOSE, p);
        /*
         * 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.
         */
        if ((vp->v_type == VBLK || vp->v_type == VCHR) && vp->v_specinfo != 0) {
                simple_lock(&spechash_slock);
                if (*vp->v_hashchain == vp) {
                        *vp->v_hashchain = vp->v_specnext;
                } else {
                        for (vq = *vp->v_hashchain; vq; vq = vq->v_specnext) {
                                if (vq->v_specnext != vp)
                                        continue;
                                vq->v_specnext = vp->v_specnext;
                                break;
                        }
                        if (vq == NULL)
                                panic("missing bdev");
                }
                if (vp->v_flag & VALIASED) {
                        vx = NULL;
                        for (vq = *vp->v_hashchain; vq; vq = vq->v_specnext) {
                                if (vq->v_rdev != vp->v_rdev ||
                                    vq->v_type != vp->v_type)
                                        continue;
                                if (vx)
                                        break;
                                vx = vq;
                        }
                        if (vx == NULL)
                                panic("missing alias");
                        if (vq == NULL)
                                vx->v_flag &= ~VALIASED;
                        vp->v_flag &= ~VALIASED;
                }
                simple_unlock(&spechash_slock);
                FREE_ZONE(vp->v_specinfo, sizeof (struct specinfo), M_VNODE);
                vp->v_specinfo = NULL;
        }
        /*
         * If it is on the freelist and not already at the head,
         * move it to the head of the list. The test of the back
         * pointer 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.
         * So, the back pointer is explicitly set to `0xdeadb' in
         * getnewvnode after removing it from the freelist to ensure
         * that we do not try to move it here.
         */
        if (vp->v_usecount == 0) {
                simple_lock(&vnode_free_list_slock);
                if ((vp->v_freelist.tqe_prev != (struct vnode **)0xdeadb) &&
                    vnode_free_list.tqh_first != vp) {
                        TAILQ_REMOVE(&vnode_free_list, vp, v_freelist);
                        TAILQ_INSERT_HEAD(&vnode_free_list, vp, v_freelist);
                }
                simple_unlock(&vnode_free_list_slock);
        }
        vp->v_type = VBAD;
}

/*
 * Lookup a vnode by device number.
 */
int
vfinddev(dev, type, vpp)
        dev_t dev;
        enum vtype type;
        struct vnode **vpp;
{
        struct vnode *vp;
        int rc = 0;

        simple_lock(&spechash_slock);
        for (vp = speclisth[SPECHASH(dev)]; vp; vp = vp->v_specnext) {
                if (dev != vp->v_rdev || type != vp->v_type)
                        continue;
                *vpp = vp;
                rc = 1;
                break;
        }
        simple_unlock(&spechash_slock);
        return (rc);
}

/*
 * Calculate the total number of references to a special device.
 */
int
vcount(vp)
        struct vnode *vp;
{
        struct vnode *vq, *vnext;
        int count;

loop:
        if ((vp->v_flag & VALIASED) == 0)
                return (vp->v_usecount);
        simple_lock(&spechash_slock);
        for (count = 0, vq = *vp->v_hashchain; vq; vq = vnext) {
                vnext = vq->v_specnext;
                if (vq->v_rdev != vp->v_rdev || vq->v_type != vp->v_type)
                        continue;
                /*
                 * Alias, but not in use, so flush it out.
                 */
                if (vq->v_usecount == 0 && vq != vp) {
                        simple_unlock(&spechash_slock);
                        vgone(vq);
                        goto loop;
                }
                count += vq->v_usecount;
        }
        simple_unlock(&spechash_slock);
        return (count);
}

int     prtactive = 0;          /* 1 => print out reclaim of active vnodes */

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

void
vprint(label, vp)
        char *label;
        register struct vnode *vp;
{
        char buf[64];

        if (label != NULL)
                printf("%s: ", label);
        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 & VNOFLUSH)
                strcat(buf, "|VNOFLUSH");
        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 & VALIASED)
                strcat(buf, "|VALIASED");
        if (buf[0] != '\0')
                printf(" flags (%s)", &buf[1]);
        if (vp->v_data == NULL) {
                printf("\n");
        } else {
                printf("\n\t");
                VOP_PRINT(vp);
        }
}

#ifdef DEBUG
/*
 * List all of the locked vnodes in the system.
 * Called when debugging the kernel.
 */
void
printlockedvnodes()
{
        struct proc *p = current_proc();
        struct mount *mp, *nmp;
        struct vnode *vp;

        printf("Locked vnodes\n");
        simple_lock(&mountlist_slock);
        for (mp = mountlist.cqh_first; mp != (void *)&mountlist; mp = nmp) {
                if (vfs_busy(mp, LK_NOWAIT, &mountlist_slock, p)) {
                        nmp = mp->mnt_list.cqe_next;
                        continue;
                }
                for (vp = mp->mnt_vnodelist.lh_first;
                     vp != NULL;
                     vp = vp->v_mntvnodes.le_next) {
                        if (VOP_ISLOCKED(vp))
                                vprint((char *)0, vp);
                }
                simple_lock(&mountlist_slock);
                nmp = mp->mnt_list.cqe_next;
                vfs_unbusy(mp, p);
        }
        simple_unlock(&mountlist_slock);
}
#endif

/*
 * Top level filesystem related information gathering.
 */
int
vfs_sysctl(name, namelen, oldp, oldlenp, newp, newlen, p)
        int *name;
        u_int namelen;
        void *oldp;
        size_t *oldlenp;
        void *newp;
        size_t newlen;
        struct proc *p;
{
        struct vfsconf *vfsp;

        /*
         * The VFS_NUMMNTOPS shouldn't be at name[0] since
         * is a VFS generic variable. So now we must check
         * namelen so we don't end up covering any UFS
         * variables (sinc UFS vfc_typenum is 1).
         *
         * It should have been:
         *    name[0]:  VFS_GENERIC
         *    name[1]:  VFS_NUMMNTOPS
         */
        if (namelen == 1 && name[0] == VFS_NUMMNTOPS) {
                extern unsigned int vfs_nummntops;
                return (sysctl_rdint(oldp, oldlenp, newp, vfs_nummntops));
        }

        /* 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));
        }
        switch (name[1]) {
        case VFS_MAXTYPENUM:
                return (sysctl_rdint(oldp, oldlenp, newp, maxvfsconf));
        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_rdstruct(oldp, oldlenp, newp, vfsp,
                    sizeof(struct vfsconf)));
        }
        return (EOPNOTSUPP);
}

int kinfo_vdebug = 1;
#define KINFO_VNODESLOP 10
/*
 * Dump vnode list (via sysctl).
 * Copyout address of vnode followed by vnode.
 */
/* ARGSUSED */
int
sysctl_vnode(where, sizep, p)
        char *where;
        size_t *sizep;
        struct proc *p;
{
        struct mount *mp, *nmp;
        struct vnode *nvp, *vp;
        char *bp = where, *savebp;
        char *ewhere;
        int error;

#define VPTRSZ  sizeof (struct vnode *)
#define VNODESZ sizeof (struct vnode)
        if (where == NULL) {
                *sizep = (numvnodes + KINFO_VNODESLOP) * (VPTRSZ + VNODESZ);
                return (0);
        }
        ewhere = where + *sizep;
                
        simple_lock(&mountlist_slock);
        for (mp = mountlist.cqh_first; mp != (void *)&mountlist; mp = nmp) {
                if (vfs_busy(mp, LK_NOWAIT, &mountlist_slock, p)) {
                        nmp = mp->mnt_list.cqe_next;
                        continue;
                }
                savebp = bp;
again:
                simple_lock(&mntvnode_slock);
                for (vp = mp->mnt_vnodelist.lh_first;
                     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) {
                                simple_unlock(&mntvnode_slock);
                                if (kinfo_vdebug)
                                        printf("kinfo: vp changed\n");
                                bp = savebp;
                                goto again;
                        }
                        nvp = vp->v_mntvnodes.le_next;
                        if (bp + VPTRSZ + VNODESZ > ewhere) {
                                simple_unlock(&mntvnode_slock);
                                *sizep = bp - where;
                                return (ENOMEM);
                        }
                        simple_unlock(&mntvnode_slock);
                        if ((error = copyout((caddr_t)&vp, bp, VPTRSZ)) ||
                           (error = copyout((caddr_t)vp, bp + VPTRSZ, VNODESZ)))
                                return (error);
                        bp += VPTRSZ + VNODESZ;
                        simple_lock(&mntvnode_slock);
                }
                simple_unlock(&mntvnode_slock);
                simple_lock(&mountlist_slock);
                nmp = mp->mnt_list.cqe_next;
                vfs_unbusy(mp, p);
        }
        simple_unlock(&mountlist_slock);

        *sizep = bp - where;
        return (0);
}

/*
 * Check to see if a filesystem is mounted on a block device.
 */
int
vfs_mountedon(vp)
        struct vnode *vp;
{
        struct vnode *vq;
        int error = 0;

        if (vp->v_specflags & SI_MOUNTEDON)
                return (EBUSY);
        if (vp->v_flag & VALIASED) {
                simple_lock(&spechash_slock);
                for (vq = *vp->v_hashchain; vq; vq = vq->v_specnext) {
                        if (vq->v_rdev != vp->v_rdev ||
                            vq->v_type != vp->v_type)
                                continue;
                        if (vq->v_specflags & SI_MOUNTEDON) {
                                error = EBUSY;
                                break;
                        }
                }
                simple_unlock(&spechash_slock);
        }
        return (error);
}

/*
 * Unmount all filesystems. The list is traversed in reverse order
 * of mounting to avoid dependencies.
 */
__private_extern__ void
vfs_unmountall()
{
        struct mount *mp, *nmp;
        struct proc *p = current_proc();

        /*
         * Since this only runs when rebooting, it is not interlocked.
         */
        for (mp = mountlist.cqh_last; mp != (void *)&mountlist; mp = nmp) {
                nmp = mp->mnt_list.cqe_prev;
                (void) dounmount(mp, MNT_FORCE, p);
        }
}

/*
 * Build hash lists of net addresses and hang them off the mount point.
 * Called by vfs_export() to set up the lists of export addresses.
 */
static int
vfs_hang_addrlist(mp, nep, argp)
        struct mount *mp;
        struct netexport *nep;
        struct export_args *argp;
{
        register struct netcred *np;
        register struct radix_node_head *rnh;
        register 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);
        }
        i = sizeof(struct netcred) + argp->ex_addrlen + argp->ex_masklen;
        MALLOC(np, struct netcred *, 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_addr, (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) {
                /*
                 * One of the reasons that rnh_addaddr may fail is that
                 * the entry already exists. To check for this case, we
                 * look up the entry to see if it is there. If so, we
                 * do not need to make a new entry but do return success.
                 */
                _FREE(np, M_NETADDR);
                rn = (*rnh->rnh_matchaddr)((caddr_t)saddr, rnh);
                if (rn != 0 && (rn->rn_flags & RNF_ROOT) == 0 &&
                    ((struct netcred *)rn)->netc_exflags == argp->ex_flags &&
                    !bcmp((caddr_t)&((struct netcred *)rn)->netc_anon,
                            (caddr_t)&argp->ex_anon, sizeof(struct ucred)))
                        return (0);
                return (EPERM);
        }
        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(rn, w)
        struct radix_node *rn;
        caddr_t w;
{
        register 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(nep)
        struct netexport *nep;
{
        register int i;
        register 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(mp, nep, argp)
        struct mount *mp;
        struct netexport *nep;
        struct export_args *argp;
{
        int error;

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

struct netcred *
vfs_export_lookup(mp, nep, nam)
        register struct mount *mp;
        struct netexport *nep;
        struct mbuf *nam;
{
        register struct netcred *np;
        register 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 = mtod(nam, struct sockaddr *);
                        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);
}

/*
 * try to reclaim vnodes from the memory 
 * object cache
 */
static int
vm_object_cache_reclaim(int count)
{
        int cnt;
        void vnode_pager_release_from_cache(int *);

        /* attempt to reclaim vnodes from VM object cache */
        cnt = count;
        vnode_pager_release_from_cache(&cnt);
        return(cnt);
}

/*
 * Release memory object reference held by inactive vnodes
 * and then try to reclaim some vnodes from the memory 
 * object cache
 */
static int
vnreclaim(int count)
{
        int i, loopcnt;
        struct vnode *vp;
        int err;
        struct proc *p;

        i = 0;
        loopcnt = 0;

        /* Try to release "count" vnodes from the inactive list */
restart:
        if (++loopcnt > inactivevnodes) {
                /*
                 * I did my best trying to reclaim the vnodes.
                 * Do not try any more as that would only lead to 
                 * long latencies. Also in the worst case 
                 * this can get totally CPU bound.
                 * Just fall though and attempt a reclaim of VM
                 * object cache
                 */
                goto out;
        }

        simple_lock(&vnode_free_list_slock);
        for (vp = TAILQ_FIRST(&vnode_inactive_list);
                        (vp != NULLVP) && (i < count);
                        vp = TAILQ_NEXT(vp, v_freelist)) {
                
                if (!simple_lock_try(&vp->v_interlock))
                        continue;

                if (vp->v_usecount != 1)
                        panic("vnreclaim: v_usecount");

                if(!UBCINFOEXISTS(vp)) {
                        if (vp->v_type == VBAD) {
                                VREMINACTIVE("vnreclaim", vp);
                                simple_unlock(&vp->v_interlock);
                                continue;
                        } else
                                panic("non UBC vnode on inactive list");
                                /* Should not reach here */
                }

                /* If vnode is already being reclaimed, wait */
                if ((vp->v_flag & VXLOCK) || (vp->v_flag & VORECLAIM)) {
                        vp->v_flag |= VXWANT;
                        simple_unlock(&vp->v_interlock);
                        simple_unlock(&vnode_free_list_slock);
                        (void)tsleep((caddr_t)vp, PINOD, "vocr", 0);
                        goto restart;
                }

                VREMINACTIVE("vnreclaim", vp);
                simple_unlock(&vnode_free_list_slock);

                if (ubc_issetflags(vp, UI_WASMAPPED)) {
                        /*
                         * We should not reclaim as it is likely
                         * to be in use. Let it die a natural death.
                         * Release the UBC reference if one exists
                         * and put it back at the tail.
                         */
                        simple_unlock(&vp->v_interlock);
                        if (ubc_release_named(vp)) {
                                if (UBCINFOEXISTS(vp)) {
                                        simple_lock(&vp->v_interlock);
                                        if (vp->v_usecount == 1 && !VONLIST(vp))
                                                vinactive(vp);
                                        simple_unlock(&vp->v_interlock);
                                }
                        } else {
                            simple_lock(&vp->v_interlock);
                                vinactive(vp);
                                simple_unlock(&vp->v_interlock);
                        }
                } else {
                        int didhold;

                        VORECLAIM_ENABLE(vp);

                        /*
                         * scrub the dirty pages and invalidate the buffers
                         */
                        p = current_proc();
                        err = vn_lock(vp, LK_EXCLUSIVE|LK_INTERLOCK, p); 
                        if (err) {
                                /* cannot reclaim */
                                simple_lock(&vp->v_interlock);
                                vinactive(vp);
                                VORECLAIM_DISABLE(vp);
                                i++;
                                simple_unlock(&vp->v_interlock);
                                goto restart;
                        }

                        /* keep the vnode alive so we can kill it */
                        simple_lock(&vp->v_interlock);
                        if(vp->v_usecount != 1)
                                panic("VOCR: usecount race");
                        vp->v_usecount++;
                        simple_unlock(&vp->v_interlock);

                        /* clean up the state in VM without invalidating */
                        didhold = ubc_hold(vp);
                        if (didhold)
                                (void)ubc_clean(vp, 0);

                        /* flush and invalidate buffers associated with the vnode */
                        if (vp->v_tag == VT_NFS)
                                nfs_vinvalbuf(vp, V_SAVE, NOCRED, p, 0);
                        else
                                vinvalbuf(vp, V_SAVE, NOCRED, p, 0, 0);

                        /*
                         * Note: for the v_usecount == 2 case, VOP_INACTIVE
                         * has not yet been called.  Call it now while vp is
                         * still locked, it will also release the lock.
                         */
                        if (vp->v_usecount == 2)
                                VOP_INACTIVE(vp, p);
                        else
                                VOP_UNLOCK(vp, 0, p);

                        if (didhold)
                                ubc_rele(vp);

                        /*
                         * destroy the ubc named reference.
                         * If we can't because it is held for I/Os
                         * in progress, just put it back on the inactive
                         * list and move on.  Otherwise, the paging reference
                         * is toast (and so is this vnode?).
                         */
                        if (ubc_destroy_named(vp)) {
                            i++;
                        }
                        simple_lock(&vp->v_interlock);
                        VORECLAIM_DISABLE(vp);
                        simple_unlock(&vp->v_interlock);
                        vrele(vp);  /* release extra use we added here */
                }
                /* inactive list lock was released, must restart */
                goto restart;
        }
        simple_unlock(&vnode_free_list_slock);

        vnode_reclaim_tried += i;
out:
        i = vm_object_cache_reclaim(count);
        vnode_objects_reclaimed += i;

        return(i);
}

/*  
 * This routine is called from vnode_pager_no_senders()
 * which in turn can be called with vnode locked by vnode_uncache()
 * But it could also get called as a result of vm_object_cache_trim().
 * In that case lock state is unknown.
 * AGE the vnode so that it gets recycled quickly.
 * Check lock status to decide whether to call vput() or vrele().
 */
__private_extern__ void
vnode_pager_vrele(struct vnode *vp)
{

        boolean_t       funnel_state;
        int isvnreclaim = 1;

        if (vp == (struct vnode *) NULL) 
                panic("vnode_pager_vrele: null vp");

        funnel_state = thread_funnel_set(kernel_flock, TRUE);

        /* Mark the vnode to be recycled */
        vagevp(vp);

        simple_lock(&vp->v_interlock);
        /*
         * If a vgone (or vclean) is already in progress,
         * Do not bother with the ubc_info cleanup.
         * Let the vclean deal with it.
         */
        if (vp->v_flag & VXLOCK) {
                CLR(vp->v_flag, VTERMINATE);
                if (ISSET(vp->v_flag, VTERMWANT)) {
                        CLR(vp->v_flag, VTERMWANT);
                        wakeup((caddr_t)&vp->v_ubcinfo);
                }
                simple_unlock(&vp->v_interlock);
                vrele(vp);
                (void) thread_funnel_set(kernel_flock, funnel_state);
                return;
        }

        /* It's dead, Jim! */
        if (!ISSET(vp->v_flag, VORECLAIM)) {
                /*
                 * called as a result of eviction of the memory
                 * object from the memory object cache
                 */
                isvnreclaim = 0;

                /* So serialize vnode operations */
                VORECLAIM_ENABLE(vp);
        }
        if (!ISSET(vp->v_flag, VTERMINATE))
                SET(vp->v_flag, VTERMINATE);
        if (UBCINFOEXISTS(vp)) {
                struct ubc_info *uip = vp->v_ubcinfo;

                if (ubc_issetflags(vp, UI_WASMAPPED))
                        SET(vp->v_flag, VWASMAPPED);

                vp->v_ubcinfo = UBC_NOINFO;  /* catch bad accesses */
                simple_unlock(&vp->v_interlock);
                ubc_info_deallocate(uip);
        } else {
                if ((vp->v_type == VBAD) && ((vp)->v_ubcinfo != UBC_INFO_NULL) 
                        && ((vp)->v_ubcinfo != UBC_NOINFO)) {
                        struct ubc_info *uip = vp->v_ubcinfo;

                        vp->v_ubcinfo = UBC_NOINFO;  /* catch bad accesses */
                        simple_unlock(&vp->v_interlock);
                        ubc_info_deallocate(uip);
                } else {
                        simple_unlock(&vp->v_interlock);
                }
        }

        CLR(vp->v_flag, VTERMINATE);

        if (vp->v_type != VBAD){
                vgone(vp);      /* revoke the vnode */
                vrele(vp);      /* and drop the reference */
        } else
                vrele(vp);

        if (ISSET(vp->v_flag, VTERMWANT)) {
                CLR(vp->v_flag, VTERMWANT);
                wakeup((caddr_t)&vp->v_ubcinfo);
        }
        if (!isvnreclaim)
                VORECLAIM_DISABLE(vp);
        (void) thread_funnel_set(kernel_flock, funnel_state);
        return;
}


#if DIAGNOSTIC
int walk_vnodes_debug=0;

void
walk_allvnodes()
{
        struct mount *mp, *nmp;
        struct vnode *vp;
        int cnt = 0;

        for (mp = mountlist.cqh_first; mp != (void *)&mountlist; mp = nmp) {
                for (vp = mp->mnt_vnodelist.lh_first;
                     vp != NULL;
                     vp = vp->v_mntvnodes.le_next) {
                        if (vp->v_usecount < 0){
                                if(walk_vnodes_debug) {
                                        printf("vp is %x\n",vp);
                                }
                        }
                }
                nmp = mp->mnt_list.cqe_next;
        }
        for (cnt = 0, vp = vnode_free_list.tqh_first;
                vp != NULLVP; cnt++, vp = vp->v_freelist.tqe_next) {
                if ((vp->v_usecount < 0) && walk_vnodes_debug) {
                        if(walk_vnodes_debug) {
                                printf("vp is %x\n",vp);
                        }
                }
        }
        printf("%d - free\n", cnt);

        for (cnt = 0, vp = vnode_inactive_list.tqh_first;
                vp != NULLVP; cnt++, vp = vp->v_freelist.tqe_next) {
                if ((vp->v_usecount < 0) && walk_vnodes_debug) {
                        if(walk_vnodes_debug) {
                                printf("vp is %x\n",vp);
                        }
                }
        }
        printf("%d - inactive\n", cnt);
}
#endif /* DIAGNOSTIC */

void
vfs_io_attributes(vp, flags, iosize, vectors)
        struct vnode    *vp;
        int     flags;  /* B_READ or B_WRITE */
        int     *iosize;
        int     *vectors;
{
        struct mount *mp;

        /* start with "reasonable" defaults */
        *iosize = MAXPHYS;
        *vectors = 32;

        mp = vp->v_mount;
        if (mp != NULL) {
                switch (flags) {
                case B_READ:
                        *iosize = mp->mnt_maxreadcnt;
                        *vectors = mp->mnt_segreadcnt;
                        break;
                case B_WRITE:
                        *iosize = mp->mnt_maxwritecnt;
                        *vectors = mp->mnt_segwritecnt;
                        break;
                default:
                        break;
                }
        }

        return;
}

#include <dev/disk.h>

int
vfs_init_io_attributes(devvp, mp)
        struct vnode *devvp;
        struct mount *mp;
{
        int error;
        off_t readblockcnt;
        off_t writeblockcnt;
        off_t readsegcnt;
        off_t writesegcnt;
        u_long blksize;

        u_int64_t temp;

        struct proc *p = current_proc();
        struct  ucred *cred = p->p_ucred;

        if ((error = VOP_IOCTL(devvp, DKIOCGETMAXBLOCKCOUNTREAD,
                                (caddr_t)&readblockcnt, 0, cred, p)))
                return (error);

        if ((error = VOP_IOCTL(devvp, DKIOCGETMAXBLOCKCOUNTWRITE,
                                (caddr_t)&writeblockcnt, 0, cred, p)))
                return (error);

        if ((error = VOP_IOCTL(devvp, DKIOCGETMAXSEGMENTCOUNTREAD,
                                (caddr_t)&readsegcnt, 0, cred, p)))
                return (error);

        if ((error = VOP_IOCTL(devvp, DKIOCGETMAXSEGMENTCOUNTWRITE,
                                (caddr_t)&writesegcnt, 0, cred, p)))
                return (error);

        if ((error = VOP_IOCTL(devvp, DKIOCGETBLOCKSIZE,
                                (caddr_t)&blksize, 0, cred, p)))
                return (error);

        temp = readblockcnt * blksize;
        temp = (temp > UINT32_MAX) ? (UINT32_MAX / blksize) * blksize : temp;
        mp->mnt_maxreadcnt = (u_int32_t)temp;

        temp = writeblockcnt * blksize;
        temp = (temp > UINT32_MAX) ? (UINT32_MAX / blksize) * blksize : temp;
        mp->mnt_maxwritecnt = (u_int32_t)temp;

        temp = (readsegcnt > UINT16_MAX) ? UINT16_MAX : readsegcnt;
        mp->mnt_segreadcnt = (u_int16_t)temp;

        temp = (writesegcnt > UINT16_MAX) ? UINT16_MAX : writesegcnt;
        mp->mnt_segwritecnt = (u_int16_t)temp;

#if 0
        printf("--- IO attributes for mount point 0x%08x ---\n", mp);
        printf("\tmnt_maxreadcnt = 0x%x", mp->mnt_maxreadcnt);
        printf("\tmnt_maxwritecnt = 0x%x\n", mp->mnt_maxwritecnt);
        printf("\tmnt_segreadcnt = 0x%x", mp->mnt_segreadcnt);
        printf("\tmnt_segwritecnt = 0x%x\n", mp->mnt_segwritecnt);
#endif /* 0 */

        return (error);
}