FreeBSD/Linux Kernel Cross Reference
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. 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 $
     */
    
    /*
     * 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/file.h>
    #include <sys/kernel.h>
    #include <sys/kthread.h>
    #include <sys/malloc.h>
    #include <sys/mbuf.h>
    #include <sys/mount.h>
    #include <sys/priv.h>
    #include <sys/proc.h>
    #include <sys/reboot.h>
    #include <sys/socket.h>
    #include <sys/stat.h>
    #include <sys/sysctl.h>
    #include <sys/syslog.h>
    #include <sys/unistd.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>
    #include <sys/sysref2.h>
    #include <sys/mplock2.h>
    
    static MALLOC_DEFINE(M_NETADDR, "Export Host", "Export host address structure");
    
    int numvnodes;
    SYSCTL_INT(_debug, OID_AUTO, numvnodes, CTLFLAG_RD, &numvnodes, 0,
        "Number of vnodes allocated");
    int verbose_reclaims;
    SYSCTL_INT(_debug, OID_AUTO, verbose_reclaims, CTLFLAG_RD, &verbose_reclaims, 0,
        "Output filename of reclaimed vnode(s)");
    
    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 int reassignbufcalls;
   SYSCTL_INT(_vfs, OID_AUTO, reassignbufcalls, CTLFLAG_RW, &reassignbufcalls,
       0, "Number of times buffers have been reassigned to the proper list");
   
   static int check_buf_overlap = 2;       /* invasive check */
   SYSCTL_INT(_vfs, OID_AUTO, check_buf_overlap, CTLFLAG_RW, &check_buf_overlap,
       0, "Enable overlapping buffer checks");
   
   int     nfs_mount_type = -1;
   static struct lwkt_token spechash_token;
   struct nfs_public nfs_pub;      /* publicly exported FS */
   
   int desiredvnodes;
   SYSCTL_INT(_kern, KERN_MAXVNODES, maxvnodes, CTLFLAG_RW, 
                   &desiredvnodes, 0, "Maximum number of vnodes");
   
   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,
                                          const struct export_args *argp);
   
   /*
    * Red black tree functions
    */
   static int rb_buf_compare(struct buf *b1, struct buf *b2);
   RB_GENERATE2(buf_rb_tree, buf, b_rbnode, rb_buf_compare, off_t, b_loffset);
   RB_GENERATE2(buf_rb_hash, buf, b_rbhash, rb_buf_compare, off_t, b_loffset);
   
   static int
   rb_buf_compare(struct buf *b1, struct buf *b2)
   {
           if (b1->b_loffset < b2->b_loffset)
                   return(-1);
           if (b1->b_loffset > b2->b_loffset)
                   return(1);
           return(0);
   }
   
   /*
    * Initialize the vnode management data structures. 
    *
    * Called from vfsinit()
    */
   void
   vfs_subr_init(void)
   {
           int factor1;
           int factor2;
   
           /*
            * Desiredvnodes is kern.maxvnodes.  We want to scale it 
            * according to available system memory but we may also have
            * to limit it based on available KVM, which is capped on 32 bit
            * systems, to ~80K vnodes or so.
            *
            * WARNING!  For machines with 64-256M of ram we have to be sure
            *           that the default limit scales down well due to HAMMER
            *           taking up significantly more memory per-vnode vs UFS.
            *           We want around ~5800 on a 128M machine.
            */
           factor1 = 20 * (sizeof(struct vm_object) + sizeof(struct vnode));
           factor2 = 25 * (sizeof(struct vm_object) + sizeof(struct vnode));
           desiredvnodes =
                   imin((int64_t)vmstats.v_page_count * PAGE_SIZE / factor1,
                        KvaSize / factor2);
           desiredvnodes = imax(desiredvnodes, maxproc * 8);
   
           lwkt_token_init(&spechash_token, "spechash");
   }
   
   /*
    * 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, "Precision of file timestamps");
   
   /*
    * Get a current timestamp.
    *
    * MPSAFE
    */
   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_rmajor = VNOVAL;
           vap->va_rminor = 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;
           /* va_*_uuid fields are only valid if related flags are set */
   }
   
   /*
    * Flush out and invalidate all buffers associated with a vnode.
    *
    * vp must be locked.
    */
   static int vinvalbuf_bp(struct buf *bp, void *data);
   
   struct vinvalbuf_bp_info {
           struct vnode *vp;
           int slptimeo;
           int lkflags;
           int flags;
           int clean;
   };
   
   int
   vinvalbuf(struct vnode *vp, int flags, int slpflag, int slptimeo)
   {
           struct vinvalbuf_bp_info info;
           vm_object_t object;
           int error;
   
           lwkt_gettoken(&vp->v_token);
   
           /*
            * If we are being asked to save, call fsync to ensure that the inode
            * is updated.
            */
           if (flags & V_SAVE) {
                   error = bio_track_wait(&vp->v_track_write, slpflag, slptimeo);
                   if (error)
                           goto done;
                   if (!RB_EMPTY(&vp->v_rbdirty_tree)) {
                           if ((error = VOP_FSYNC(vp, MNT_WAIT, 0)) != 0)
                                   goto done;
   #if 0
                           /*
                            * Dirty bufs may be left or generated via races
                            * in circumstances where vinvalbuf() is called on
                            * a vnode not undergoing reclamation.   Only
                            * panic if we are trying to reclaim the vnode.
                            */
                           if ((vp->v_flag & VRECLAIMED) &&
                               (bio_track_active(&vp->v_track_write) ||
                               !RB_EMPTY(&vp->v_rbdirty_tree))) {
                                   panic("vinvalbuf: dirty bufs");
                           }
   #endif
                   }
           }
           info.slptimeo = slptimeo;
           info.lkflags = LK_EXCLUSIVE | LK_SLEEPFAIL;
           if (slpflag & PCATCH)
                   info.lkflags |= LK_PCATCH;
           info.flags = flags;
           info.vp = vp;
   
           /*
            * Flush the buffer cache until nothing is left, wait for all I/O
            * to complete.  At least one pass is required.  We might block
            * in the pip code so we have to re-check.  Order is important.
            */
           do {
                   /*
                    * Flush buffer cache
                    */
                   if (!RB_EMPTY(&vp->v_rbclean_tree)) {
                           info.clean = 1;
                           error = RB_SCAN(buf_rb_tree, &vp->v_rbclean_tree,
                                           NULL, vinvalbuf_bp, &info);
                   }
                   if (!RB_EMPTY(&vp->v_rbdirty_tree)) {
                           info.clean = 0;
                           error = RB_SCAN(buf_rb_tree, &vp->v_rbdirty_tree,
                                           NULL, vinvalbuf_bp, &info);
                   }
   
                   /*
                    * Wait for I/O completion.
                    */
                   bio_track_wait(&vp->v_track_write, 0, 0);
                   if ((object = vp->v_object) != NULL)
                           refcount_wait(&object->paging_in_progress, "vnvlbx");
           } while (bio_track_active(&vp->v_track_write) ||
                    !RB_EMPTY(&vp->v_rbclean_tree) ||
                    !RB_EMPTY(&vp->v_rbdirty_tree));
   
           /*
            * Destroy the copy in the VM cache, too.
            */
           if ((object = vp->v_object) != NULL) {
                   vm_object_page_remove(object, 0, 0,
                           (flags & V_SAVE) ? TRUE : FALSE);
           }
   
           if (!RB_EMPTY(&vp->v_rbdirty_tree) || !RB_EMPTY(&vp->v_rbclean_tree))
                   panic("vinvalbuf: flush failed");
           if (!RB_EMPTY(&vp->v_rbhash_tree))
                   panic("vinvalbuf: flush failed, buffers still present");
           error = 0;
   done:
           lwkt_reltoken(&vp->v_token);
           return (error);
   }
   
   static int
   vinvalbuf_bp(struct buf *bp, void *data)
   {
           struct vinvalbuf_bp_info *info = data;
           int error;
   
           if (BUF_LOCK(bp, LK_EXCLUSIVE | LK_NOWAIT)) {
                   atomic_add_int(&bp->b_refs, 1);
                   error = BUF_TIMELOCK(bp, info->lkflags,
                                        "vinvalbuf", info->slptimeo);
                   atomic_subtract_int(&bp->b_refs, 1);
                   if (error == 0) {
                           BUF_UNLOCK(bp);
                           error = ENOLCK;
                   }
                   if (error == ENOLCK)
                           return(0);
                   return (-error);
           }
           KKASSERT(bp->b_vp == info->vp);
   
           /*
            * Must check clean/dirty status after successfully locking as
            * it may race.
            */
           if ((info->clean && (bp->b_flags & B_DELWRI)) ||
               (info->clean == 0 && (bp->b_flags & B_DELWRI) == 0)) {
                   BUF_UNLOCK(bp);
                   return(0);
           }
   
           /*
            * NOTE:  NO B_LOCKED CHECK.  Also no buf_checkwrite()
            * check.  This code will write out the buffer, period.
            */
           bremfree(bp);
           if (((bp->b_flags & (B_DELWRI | B_INVAL)) == B_DELWRI) &&
               (info->flags & V_SAVE)) {
                   cluster_awrite(bp);
           } else if (info->flags & V_SAVE) {
                   /*
                    * Cannot set B_NOCACHE on a clean buffer as this will
                    * destroy the VM backing store which might actually
                    * be dirty (and unsynchronized).
                    */
                   bp->b_flags |= (B_INVAL | B_RELBUF);
                   brelse(bp);
           } else {
                   bp->b_flags |= (B_INVAL | B_NOCACHE | B_RELBUF);
                   brelse(bp);
           }
           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.
    *
    * The vnode must be locked.
    */
   static int vtruncbuf_bp_trunc_cmp(struct buf *bp, void *data);
   static int vtruncbuf_bp_trunc(struct buf *bp, void *data);
   static int vtruncbuf_bp_metasync_cmp(struct buf *bp, void *data);
   static int vtruncbuf_bp_metasync(struct buf *bp, void *data);
   
   struct vtruncbuf_info {
           struct vnode *vp;
           off_t   truncloffset;
           int     clean;
   };
   
   int
   vtruncbuf(struct vnode *vp, off_t length, int blksize)
   {
           struct vtruncbuf_info info;
           const char *filename;
           int count;
   
           /*
            * Round up to the *next* block, then destroy the buffers in question.  
            * Since we are only removing some of the buffers we must rely on the
            * scan count to determine whether a loop is necessary.
            */
           if ((count = (int)(length % blksize)) != 0)
                   info.truncloffset = length + (blksize - count);
           else
                   info.truncloffset = length;
           info.vp = vp;
   
           lwkt_gettoken(&vp->v_token);
           do {
                   info.clean = 1;
                   count = RB_SCAN(buf_rb_tree, &vp->v_rbclean_tree, 
                                   vtruncbuf_bp_trunc_cmp,
                                   vtruncbuf_bp_trunc, &info);
                   info.clean = 0;
                   count += RB_SCAN(buf_rb_tree, &vp->v_rbdirty_tree,
                                   vtruncbuf_bp_trunc_cmp,
                                   vtruncbuf_bp_trunc, &info);
           } while(count);
   
           /*
            * For safety, fsync any remaining metadata if the file is not being
            * truncated to 0.  Since the metadata does not represent the entire
            * dirty list we have to rely on the hit count to ensure that we get
            * all of it.
            */
           if (length > 0) {
                   do {
                           count = RB_SCAN(buf_rb_tree, &vp->v_rbdirty_tree,
                                           vtruncbuf_bp_metasync_cmp,
                                           vtruncbuf_bp_metasync, &info);
                   } while (count);
           }
   
           /*
            * Clean out any left over VM backing store.
            *
            * It is possible to have in-progress I/O from buffers that were
            * not part of the truncation.  This should not happen if we
            * are truncating to 0-length.
            */
           vnode_pager_setsize(vp, length);
           bio_track_wait(&vp->v_track_write, 0, 0);
   
           /*
            * Debugging only
            */
           spin_lock(&vp->v_spin);
           filename = TAILQ_FIRST(&vp->v_namecache) ?
                      TAILQ_FIRST(&vp->v_namecache)->nc_name : "?";
           spin_unlock(&vp->v_spin);
   
           /*
            * Make sure no buffers were instantiated while we were trying
            * to clean out the remaining VM pages.  This could occur due
            * to busy dirty VM pages being flushed out to disk.
            */
           do {
                   info.clean = 1;
                   count = RB_SCAN(buf_rb_tree, &vp->v_rbclean_tree, 
                                   vtruncbuf_bp_trunc_cmp,
                                   vtruncbuf_bp_trunc, &info);
                   info.clean = 0;
                   count += RB_SCAN(buf_rb_tree, &vp->v_rbdirty_tree,
                                   vtruncbuf_bp_trunc_cmp,
                                   vtruncbuf_bp_trunc, &info);
                   if (count) {
                           kprintf("Warning: vtruncbuf():  Had to re-clean %d "
                                  "left over buffers in %s\n", count, filename);
                   }
           } while(count);
   
           lwkt_reltoken(&vp->v_token);
   
           return (0);
   }
   
   /*
    * The callback buffer is beyond the new file EOF and must be destroyed.
    * Note that the compare function must conform to the RB_SCAN's requirements.
    */
   static
   int
   vtruncbuf_bp_trunc_cmp(struct buf *bp, void *data)
   {
           struct vtruncbuf_info *info = data;
   
           if (bp->b_loffset >= info->truncloffset)
                   return(0);
           return(-1);
   }
   
   static 
   int 
   vtruncbuf_bp_trunc(struct buf *bp, void *data)
   {
           struct vtruncbuf_info *info = data;
   
           /*
            * Do not try to use a buffer we cannot immediately lock, but sleep
            * anyway to prevent a livelock.  The code will loop until all buffers
            * can be acted upon.
            *
            * We must always revalidate the buffer after locking it to deal
            * with MP races.
            */
           if (BUF_LOCK(bp, LK_EXCLUSIVE | LK_NOWAIT)) {
                   atomic_add_int(&bp->b_refs, 1);
                   if (BUF_LOCK(bp, LK_EXCLUSIVE|LK_SLEEPFAIL) == 0)
                           BUF_UNLOCK(bp);
                   atomic_subtract_int(&bp->b_refs, 1);
           } else if ((info->clean && (bp->b_flags & B_DELWRI)) ||
                      (info->clean == 0 && (bp->b_flags & B_DELWRI) == 0) ||
                      bp->b_vp != info->vp ||
                      vtruncbuf_bp_trunc_cmp(bp, data)) {
                   BUF_UNLOCK(bp);
           } else {
                   bremfree(bp);
                   bp->b_flags |= (B_INVAL | B_RELBUF | B_NOCACHE);
                   brelse(bp);
           }
           return(1);
   }
   
   /*
    * Fsync all meta-data after truncating a file to be non-zero.  Only metadata
    * blocks (with a negative loffset) are scanned.
    * Note that the compare function must conform to the RB_SCAN's requirements.
    */
   static int
   vtruncbuf_bp_metasync_cmp(struct buf *bp, void *data __unused)
   {
           if (bp->b_loffset < 0)
                   return(0);
           return(1);
   }
   
   static int
   vtruncbuf_bp_metasync(struct buf *bp, void *data)
   {
           struct vtruncbuf_info *info = data;
   
           if (BUF_LOCK(bp, LK_EXCLUSIVE | LK_NOWAIT)) {
                   atomic_add_int(&bp->b_refs, 1);
                   if (BUF_LOCK(bp, LK_EXCLUSIVE|LK_SLEEPFAIL) == 0)
                           BUF_UNLOCK(bp);
                   atomic_subtract_int(&bp->b_refs, 1);
           } else if ((bp->b_flags & B_DELWRI) == 0 ||
                      bp->b_vp != info->vp ||
                      vtruncbuf_bp_metasync_cmp(bp, data)) {
                   BUF_UNLOCK(bp);
           } else {
                   bremfree(bp);
                   if (bp->b_vp == info->vp)
                           bawrite(bp);
                   else
                           bwrite(bp);
           }
           return(1);
   }
   
   /*
    * vfsync - implements a multipass fsync on a file which understands
    * dependancies and meta-data.  The passed vnode must be locked.  The 
    * waitfor argument may be MNT_WAIT or MNT_NOWAIT, or MNT_LAZY.
    *
    * When fsyncing data asynchronously just do one consolidated pass starting
    * with the most negative block number.  This may not get all the data due
    * to dependancies.
    *
    * When fsyncing data synchronously do a data pass, then a metadata pass,
    * then do additional data+metadata passes to try to get all the data out.
    */
   static int vfsync_wait_output(struct vnode *vp, 
                               int (*waitoutput)(struct vnode *, struct thread *));
   static int vfsync_dummy_cmp(struct buf *bp __unused, void *data __unused);
   static int vfsync_data_only_cmp(struct buf *bp, void *data);
   static int vfsync_meta_only_cmp(struct buf *bp, void *data);
   static int vfsync_lazy_range_cmp(struct buf *bp, void *data);
   static int vfsync_bp(struct buf *bp, void *data);
   
   struct vfsync_info {
           struct vnode *vp;
           int synchronous;
           int syncdeps;
           int lazycount;
           int lazylimit;
           int skippedbufs;
           int (*checkdef)(struct buf *);
           int (*cmpfunc)(struct buf *, void *);
   };
   
   int
   vfsync(struct vnode *vp, int waitfor, int passes,
           int (*checkdef)(struct buf *),
           int (*waitoutput)(struct vnode *, struct thread *))
   {
           struct vfsync_info info;
           int error;
   
           bzero(&info, sizeof(info));
           info.vp = vp;
           if ((info.checkdef = checkdef) == NULL)
                   info.syncdeps = 1;
   
           lwkt_gettoken(&vp->v_token);
   
           switch(waitfor) {
           case MNT_LAZY | MNT_NOWAIT:
           case MNT_LAZY:
                   /*
                    * Lazy (filesystem syncer typ) Asynchronous plus limit the
                    * number of data (not meta) pages we try to flush to 1MB.
                    * A non-zero return means that lazy limit was reached.
                    */
                   info.lazylimit = 1024 * 1024;
                   info.syncdeps = 1;
                   info.cmpfunc = vfsync_lazy_range_cmp;
                   error = RB_SCAN(buf_rb_tree, &vp->v_rbdirty_tree, 
                                   vfsync_lazy_range_cmp, vfsync_bp, &info);
                   info.cmpfunc = vfsync_meta_only_cmp;
                   RB_SCAN(buf_rb_tree, &vp->v_rbdirty_tree, 
                           vfsync_meta_only_cmp, vfsync_bp, &info);
                   if (error == 0)
                           vp->v_lazyw = 0;
                   else if (!RB_EMPTY(&vp->v_rbdirty_tree))
                           vn_syncer_add(vp, 1);
                   error = 0;
                   break;
           case MNT_NOWAIT:
                   /*
                    * Asynchronous.  Do a data-only pass and a meta-only pass.
                    */
                   info.syncdeps = 1;
                   info.cmpfunc = vfsync_data_only_cmp;
                   RB_SCAN(buf_rb_tree, &vp->v_rbdirty_tree, vfsync_data_only_cmp, 
                           vfsync_bp, &info);
                   info.cmpfunc = vfsync_meta_only_cmp;
                   RB_SCAN(buf_rb_tree, &vp->v_rbdirty_tree, vfsync_meta_only_cmp, 
                           vfsync_bp, &info);
                   error = 0;
                   break;
           default:
                   /*
                    * Synchronous.  Do a data-only pass, then a meta-data+data
                    * pass, then additional integrated passes to try to get
                    * all the dependancies flushed.
                    */
                   info.cmpfunc = vfsync_data_only_cmp;
                   RB_SCAN(buf_rb_tree, &vp->v_rbdirty_tree, vfsync_data_only_cmp,
                           vfsync_bp, &info);
                   error = vfsync_wait_output(vp, waitoutput);
                   if (error == 0) {
                           info.skippedbufs = 0;
                           info.cmpfunc = vfsync_dummy_cmp;
                           RB_SCAN(buf_rb_tree, &vp->v_rbdirty_tree, NULL,
                                   vfsync_bp, &info);
                           error = vfsync_wait_output(vp, waitoutput);
                           if (info.skippedbufs) {
                                   kprintf("Warning: vfsync skipped %d dirty "
                                           "bufs in pass2!\n", info.skippedbufs);
                           }
                   }
                   while (error == 0 && passes > 0 &&
                          !RB_EMPTY(&vp->v_rbdirty_tree)
                   ) {
                           if (--passes == 0) {
                                   info.synchronous = 1;
                                   info.syncdeps = 1;
                           }
                           info.cmpfunc = vfsync_dummy_cmp;
                           error = RB_SCAN(buf_rb_tree, &vp->v_rbdirty_tree, NULL,
                                           vfsync_bp, &info);
                           if (error < 0)
                                   error = -error;
                           info.syncdeps = 1;
                           if (error == 0)
                                   error = vfsync_wait_output(vp, waitoutput);
                   }
                   break;
           }
           lwkt_reltoken(&vp->v_token);
           return(error);
   }
   
   static int
   vfsync_wait_output(struct vnode *vp,
                      int (*waitoutput)(struct vnode *, struct thread *))
   {
           int error;
   
           error = bio_track_wait(&vp->v_track_write, 0, 0);
           if (waitoutput)
                   error = waitoutput(vp, curthread);
           return(error);
   }
   
   static int
   vfsync_dummy_cmp(struct buf *bp __unused, void *data __unused)
   {
           return(0);
   }
   
   static int
   vfsync_data_only_cmp(struct buf *bp, void *data)
   {
           if (bp->b_loffset < 0)
                   return(-1);
           return(0);
   }
   
   static int
   vfsync_meta_only_cmp(struct buf *bp, void *data)
   {
           if (bp->b_loffset < 0)
                   return(0);
           return(1);
   }
   
   static int
   vfsync_lazy_range_cmp(struct buf *bp, void *data)
   {
           struct vfsync_info *info = data;
   
           if (bp->b_loffset < info->vp->v_lazyw)
                   return(-1);
           return(0);
   }
   
   static int
   vfsync_bp(struct buf *bp, void *data)
   {
           struct vfsync_info *info = data;
           struct vnode *vp = info->vp;
           int error;
   
           /*
            * Ignore buffers that we cannot immediately lock.
            */
           if (BUF_LOCK(bp, LK_EXCLUSIVE | LK_NOWAIT)) {
                   ++info->skippedbufs;
                   return(0);
           }
   
           /*
            * We must revalidate the buffer after locking.
            */
           if ((bp->b_flags & B_DELWRI) == 0 ||
               bp->b_vp != info->vp ||
               info->cmpfunc(bp, data)) {
                   BUF_UNLOCK(bp);
                   return(0);
           }
   
           /*
            * If syncdeps is not set we do not try to write buffers which have
            * dependancies.
            */
           if (!info->synchronous && info->syncdeps == 0 && info->checkdef(bp)) {
                   BUF_UNLOCK(bp);
                   return(0);
           }
   
           /*
            * B_NEEDCOMMIT (primarily used by NFS) is a state where the buffer
            * has been written but an additional handshake with the device
            * is required before we can dispose of the buffer.  We have no idea
            * how to do this so we have to skip these buffers.
            */
           if (bp->b_flags & B_NEEDCOMMIT) {
                   BUF_UNLOCK(bp);
                   return(0);
           }
   
           /*
            * Ask bioops if it is ok to sync.  If not the VFS may have
            * set B_LOCKED so we have to cycle the buffer.
            */
           if (LIST_FIRST(&bp->b_dep) != NULL && buf_checkwrite(bp)) {
                   bremfree(bp);
                   brelse(bp);
                   return(0);
           }
   
           if (info->synchronous) {
                   /*
                    * Synchronous flushing.  An error may be returned.
                    */
                   bremfree(bp);
                   error = bwrite(bp);
           } else { 
                   /*
                    * Asynchronous flushing.  A negative return value simply
                    * stops the scan and is not considered an error.  We use
                    * this to support limited MNT_LAZY flushes.
                    */
                   vp->v_lazyw = bp->b_loffset;
                   bremfree(bp);
                   info->lazycount += cluster_awrite(bp);
                   waitrunningbufspace();
                   vm_wait_nominal();
                   if (info->lazylimit && info->lazycount >= info->lazylimit)
                           error = 1;
                   else
                           error = 0;
           }
           return(-error);
   }
   
   /*
    * Associate a buffer with a vnode.
    *
    * MPSAFE
    */
   int
   bgetvp(struct vnode *vp, struct buf *bp, int testsize)
   {
           KASSERT(bp->b_vp == NULL, ("bgetvp: not free"));
           KKASSERT((bp->b_flags & (B_HASHED|B_DELWRI|B_VNCLEAN|B_VNDIRTY)) == 0);
   
           /*
            * Insert onto list for new vnode.
            */
           lwkt_gettoken(&vp->v_token);
   
           if (buf_rb_hash_RB_INSERT(&vp->v_rbhash_tree, bp)) {
                   lwkt_reltoken(&vp->v_token);
                   return (EEXIST);
           }
   
           /*
            * Diagnostics (mainly for HAMMER debugging).  Check for
            * overlapping buffers.
            */
           if (check_buf_overlap) {
                   struct buf *bx;
                   bx = buf_rb_hash_RB_PREV(bp);
                   if (bx) {
                           if (bx->b_loffset + bx->b_bufsize > bp->b_loffset) {
                                   kprintf("bgetvp: overlapl %016jx/%d %016jx "
                                           "bx %p bp %p\n",
                                           (intmax_t)bx->b_loffset,
                                           bx->b_bufsize,
                                           (intmax_t)bp->b_loffset,
                                           bx, bp);
                                   if (check_buf_overlap > 1)
                                           panic("bgetvp - overlapping buffer");
                           }
                   }
                   bx = buf_rb_hash_RB_NEXT(bp);
                   if (bx) {
                           if (bp->b_loffset + testsize > bx->b_loffset) {
                                   kprintf("bgetvp: overlapr %016jx/%d %016jx "
                                           "bp %p bx %p\n",
                                           (intmax_t)bp->b_loffset,
                                           testsize,
                                           (intmax_t)bx->b_loffset,
                                           bp, bx);
                                   if (check_buf_overlap > 1)
                                           panic("bgetvp - overlapping buffer");
                           }
                   }
           }
           bp->b_vp = vp;
           bp->b_flags |= B_HASHED;
           bp->b_flags |= B_VNCLEAN;
           if (buf_rb_tree_RB_INSERT(&vp->v_rbclean_tree, bp))
                   panic("reassignbuf: dup lblk/clean vp %p bp %p", vp, bp);
           /*vhold(vp);*/
           lwkt_reltoken(&vp->v_token);
           return(0);
   }
   
   /*
    * Disassociate a buffer from a vnode.
    *
    * MPSAFE
    */
   void
   brelvp(struct buf *bp)
   {
           struct vnode *vp;
   
           KASSERT(bp->b_vp != NULL, ("brelvp: NULL"));
   
           /*
            * Delete from old vnode list, if on one.
            */
           vp = bp->b_vp;
           lwkt_gettoken(&vp->v_token);
           if (bp->b_flags & (B_VNDIRTY | B_VNCLEAN)) {
                   if (bp->b_flags & B_VNDIRTY)
                           buf_rb_tree_RB_REMOVE(&vp->v_rbdirty_tree, bp);
                   else
                           buf_rb_tree_RB_REMOVE(&vp->v_rbclean_tree, bp);
                   bp->b_flags &= ~(B_VNDIRTY | B_VNCLEAN);
           }
           if (bp->b_flags & B_HASHED) {
                   buf_rb_hash_RB_REMOVE(&vp->v_rbhash_tree, bp);
                   bp->b_flags &= ~B_HASHED;
           }
   
           /*
            * Only remove from synclist when no dirty buffers are left AND
            * the VFS has not flagged the vnode's inode as being dirty.
            */
           if ((vp->v_flag & (VONWORKLST | VISDIRTY | VOBJDIRTY)) == VONWORKLST &&
               RB_EMPTY(&vp->v_rbdirty_tree)) {
                   vn_syncer_remove(vp);
           }
           bp->b_vp = NULL;
   
           lwkt_reltoken(&vp->v_token);
   
           /*vdrop(vp);*/
   }
   
   /*
    * Reassign the buffer to the proper clean/dirty list based on B_DELWRI.
    * This routine is called when the state of the B_DELWRI bit is changed.
    *
    * Must be called with vp->v_token held.
    * MPSAFE
    */
   void
   reassignbuf(struct buf *bp)
   {
           struct vnode *vp = bp->b_vp;
           int delay;
   
           ASSERT_LWKT_TOKEN_HELD(&vp->v_token);
           ++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");
   
           if (bp->b_flags & B_DELWRI) {
                   /*
                    * Move to the dirty list, add the vnode to the worklist
                    */
                   if (bp->b_flags & B_VNCLEAN) {
                           buf_rb_tree_RB_REMOVE(&vp->v_rbclean_tree, bp);
                           bp->b_flags &= ~B_VNCLEAN;
                   }
                   if ((bp->b_flags & B_VNDIRTY) == 0) {
                           if (buf_rb_tree_RB_INSERT(&vp->v_rbdirty_tree, bp)) {
                                   panic("reassignbuf: dup lblk vp %p bp %p",
                                         vp, bp);
                           }
                           bp->b_flags |= B_VNDIRTY;
                   }
                   if ((vp->v_flag & VONWORKLST) == 0) {
                           switch (vp->v_type) {
                           case VDIR:
                                   delay = dirdelay;
                                   break;
                           case VCHR:
                           case VBLK:
                                   if (vp->v_rdev && 
                                       vp->v_rdev->si_mountpoint != NULL) {
                                           delay = metadelay;
                                           break;
                                  }
                                  /* fall through */
                          default:
                                  delay = filedelay;
                          }
                          vn_syncer_add(vp, delay);
                  }
          } else {
                  /*
                   * Move to the clean list, remove the vnode from the worklist
                   * if no dirty blocks remain.
                   */
                  if (bp->b_flags & B_VNDIRTY) {
                          buf_rb_tree_RB_REMOVE(&vp->v_rbdirty_tree, bp);
                          bp->b_flags &= ~B_VNDIRTY;
                  }
                  if ((bp->b_flags & B_VNCLEAN) == 0) {
                          if (buf_rb_tree_RB_INSERT(&vp->v_rbclean_tree, bp)) {
                                  panic("reassignbuf: dup lblk vp %p bp %p",
                                        vp, bp);
                          }
                          bp->b_flags |= B_VNCLEAN;
                  }
  
                  /*
                   * Only remove from synclist when no dirty buffers are left
                   * AND the VFS has not flagged the vnode's inode as being
                   * dirty.
                   */
                  if ((vp->v_flag & (VONWORKLST | VISDIRTY | VOBJDIRTY)) ==
                       VONWORKLST &&
                      RB_EMPTY(&vp->v_rbdirty_tree)) {
                          vn_syncer_remove(vp);
                  }
          }
  }
  
  /*
   * Create a vnode for a block device.  Used for mounting the root file
   * system.
   *
   * A vref()'d vnode is returned.
   */
  extern struct vop_ops *devfs_vnode_dev_vops_p;
  int
  bdevvp(cdev_t dev, struct vnode **vpp)
  {
          struct vnode *vp;
          struct vnode *nvp;
          int error;
  
          if (dev == NULL) {
                  *vpp = NULLVP;
                  return (ENXIO);
          }
          error = getspecialvnode(VT_NON, NULL, &devfs_vnode_dev_vops_p,
                                  &nvp, 0, 0);
          if (error) {
                  *vpp = NULLVP;
                  return (error);
          }
          vp = nvp;
          vp->v_type = VCHR;
  #if 0
          vp->v_rdev = dev;
  #endif
          v_associate_rdev(vp, dev);
          vp->v_umajor = dev->si_umajor;
          vp->v_uminor = dev->si_uminor;
          vx_unlock(vp);
          *vpp = vp;
          return (0);
  }
  
  int
  v_associate_rdev(struct vnode *vp, cdev_t dev)
  {
          if (dev == NULL)
                  return(ENXIO);
          if (dev_is_good(dev) == 0)
                  return(ENXIO);
          KKASSERT(vp->v_rdev == NULL);
          vp->v_rdev = reference_dev(dev);
          lwkt_gettoken(&spechash_token);
          SLIST_INSERT_HEAD(&dev->si_hlist, vp, v_cdevnext);
          lwkt_reltoken(&spechash_token);
          return(0);
  }
  
  void
  v_release_rdev(struct vnode *vp)
  {
          cdev_t dev;
  
          if ((dev = vp->v_rdev) != NULL) {
                  lwkt_gettoken(&spechash_token);
                  SLIST_REMOVE(&dev->si_hlist, vp, vnode, v_cdevnext);
                  vp->v_rdev = NULL;
                  release_dev(dev);
                  lwkt_reltoken(&spechash_token);
          }
  }
  
  /*
   * Add a vnode to the alias list hung off the cdev_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, int x, int y)
  {
          if (nvp->v_type != VBLK && nvp->v_type != VCHR)
                  panic("addaliasu on non-special vnode");
          nvp->v_umajor = x;
          nvp->v_uminor = y;
  }
  
  /*
   * Simple call that a filesystem can make to try to get rid of a
   * vnode.  It will fail if anyone is referencing the vnode (including
   * the caller).
   *
   * The filesystem can check whether its in-memory inode structure still
   * references the vp on return.
   *
   * May only be called if the vnode is in a known state (i.e. being prevented
   * from being deallocated by some other condition such as a vfs inode hold).
   */
  void
  vclean_unlocked(struct vnode *vp)
  {
          vx_get(vp);
          if (VREFCNT(vp) <= 0)
                  vgone_vxlocked(vp);
          vx_put(vp);
  }
  
  /*
   * Disassociate a vnode from its underlying filesystem. 
   *
   * The vnode must be VX locked and referenced.  In all normal situations
   * there are no active references.  If vclean_vxlocked() is called while
   * there are active references, the vnode is being ripped out and we have
   * to call VOP_CLOSE() as appropriate before we can reclaim it.
   */
  void
  vclean_vxlocked(struct vnode *vp, int flags)
  {
          int active;
          int n;
          vm_object_t object;
          struct namecache *ncp;
  
          /*
           * If the vnode has already been reclaimed we have nothing to do.
           */
          if (vp->v_flag & VRECLAIMED)
                  return;
  
          /*
           * Set flag to interlock operation, flag finalization to ensure
           * that the vnode winds up on the inactive list, and set v_act to 0.
           */
          vsetflags(vp, VRECLAIMED);
          atomic_set_int(&vp->v_refcnt, VREF_FINALIZE);
          vp->v_act = 0;
  
          if (verbose_reclaims) {
                  if ((ncp = TAILQ_FIRST(&vp->v_namecache)) != NULL)
                          kprintf("Debug: reclaim %p %s\n", vp, ncp->nc_name);
          }
  
          /*
           * Scrap the vfs cache
           */
          while (cache_inval_vp(vp, 0) != 0) {
                  kprintf("Warning: vnode %p clean/cache_resolution "
                          "race detected\n", vp);
                  tsleep(vp, 0, "vclninv", 2);
          }
  
          /*
           * 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.
           */
          active = (VREFCNT(vp) > 0);
  
          /*
           * Clean out any buffers associated with the vnode and destroy its
           * object, if it has one. 
           */
          vinvalbuf(vp, V_SAVE, 0, 0);
          KKASSERT(lockcountnb(&vp->v_lock) == 1);
  
          /*
           * If purging an active vnode (typically during a forced unmount
           * or reboot), it must be closed and deactivated before being
           * reclaimed.  This isn't really all that safe, but what can
           * we do? XXX.
           *
           * Note that neither of these routines unlocks the vnode.
           */
          if (active && (flags & DOCLOSE)) {
                  while ((n = vp->v_opencount) != 0) {
                          if (vp->v_writecount)
                                  VOP_CLOSE(vp, FWRITE|FNONBLOCK);
                          else
                                  VOP_CLOSE(vp, FNONBLOCK);
                          if (vp->v_opencount == n) {
                                  kprintf("Warning: unable to force-close"
                                         " vnode %p\n", vp);
                                  break;
                          }
                  }
          }
  
          /*
           * If the vnode has not been deactivated, deactivated it.  Deactivation
           * can create new buffers and VM pages so we have to call vinvalbuf()
           * again to make sure they all get flushed.
           *
           * This can occur if a file with a link count of 0 needs to be
           * truncated.
           *
           * If the vnode is already dead don't try to deactivate it.
           */
          if ((vp->v_flag & VINACTIVE) == 0) {
                  vsetflags(vp, VINACTIVE);
                  if (vp->v_mount)
                          VOP_INACTIVE(vp);
                  vinvalbuf(vp, V_SAVE, 0, 0);
          }
          KKASSERT(lockcountnb(&vp->v_lock) == 1);
  
          /*
           * If the vnode has an object, destroy it.
           */
          while ((object = vp->v_object) != NULL) {
                  vm_object_hold(object);
                  if (object == vp->v_object)
                          break;
                  vm_object_drop(object);
          }
  
          if (object != NULL) {
                  if (object->ref_count == 0) {
                          if ((object->flags & OBJ_DEAD) == 0)
                                  vm_object_terminate(object);
                          vm_object_drop(object);
                          vclrflags(vp, VOBJBUF);
                  } else {
                          vm_pager_deallocate(object);
                          vclrflags(vp, VOBJBUF);
                          vm_object_drop(object);
                  }
          }
          KKASSERT((vp->v_flag & VOBJBUF) == 0);
  
          /*
           * Reclaim the vnode if not already dead.
           */
          if (vp->v_mount && VOP_RECLAIM(vp))
                  panic("vclean: cannot reclaim");
  
          /*
           * Done with purge, notify sleepers of the grim news.
           */
          vp->v_ops = &dead_vnode_vops_p;
          vn_gone(vp);
          vp->v_tag = VT_NON;
  
          /*
           * If we are destroying an active vnode, reactivate it now that
           * we have reassociated it with deadfs.  This prevents the system
           * from crashing on the vnode due to it being unexpectedly marked
           * as inactive or reclaimed.
           */
          if (active && (flags & DOCLOSE)) {
                  vclrflags(vp, VINACTIVE | VRECLAIMED);
          }
  }
  
  /*
   * Eliminate all activity associated with the requested vnode
   * and with all vnodes aliased to the requested vnode.
   *
   * The vnode must be referenced but should not be locked.
   */
  int
  vrevoke(struct vnode *vp, struct ucred *cred)
  {
          struct vnode *vq;
          struct vnode *vqn;
          cdev_t dev;
          int error;
  
          /*
           * 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.
           *
           * The passed vp will probably show up in the list, do not VX lock
           * it twice!
           *
           * Releasing the vnode's rdev here can mess up specfs's call to
           * device close, so don't do it.  The vnode has been disassociated
           * and the device will be closed after the last ref on the related
           * fp goes away (if not still open by e.g. the kernel).
           */
          if (vp->v_type != VCHR) {
                  error = fdrevoke(vp, DTYPE_VNODE, cred);
                  return (error);
          }
          if ((dev = vp->v_rdev) == NULL) {
                  return(0);
          }
          reference_dev(dev);
          lwkt_gettoken(&spechash_token);
  
  restart:
          vqn = SLIST_FIRST(&dev->si_hlist);
          if (vqn)
                  vhold(vqn);
          while ((vq = vqn) != NULL) {
                  if (VREFCNT(vq) > 0) {
                          vref(vq);
                          fdrevoke(vq, DTYPE_VNODE, cred);
                          /*v_release_rdev(vq);*/
                          vrele(vq);
                          if (vq->v_rdev != dev) {
                                  vdrop(vq);
                                  goto restart;
                          }
                  }
                  vqn = SLIST_NEXT(vq, v_cdevnext);
                  if (vqn)
                          vhold(vqn);
                  vdrop(vq);
          }
          lwkt_reltoken(&spechash_token);
          dev_drevoke(dev);
          release_dev(dev);
          return (0);
  }
  
  /*
   * This is called when the object underlying a vnode is being destroyed,
   * such as in a remove().  Try to recycle the vnode immediately if the
   * only active reference is our reference.
   *
   * Directory vnodes in the namecache with children cannot be immediately
   * recycled because numerous VOP_N*() ops require them to be stable.
   *
   * To avoid recursive recycling from VOP_INACTIVE implemenetations this
   * function is a NOP if VRECLAIMED is already set.
   */
  int
  vrecycle(struct vnode *vp)
  {
          if (VREFCNT(vp) <= 1 && (vp->v_flag & VRECLAIMED) == 0) {
                  if (cache_inval_vp_nonblock(vp))
                          return(0);
                  vgone_vxlocked(vp);
                  return (1);
          }
          return (0);
  }
  
  /*
   * Return the maximum I/O size allowed for strategy calls on VP.
   *
   * If vp is VCHR or VBLK we dive the device, otherwise we use
   * the vp's mount info.
   *
   * The returned value is clamped at MAXPHYS as most callers cannot use
   * buffers larger than that size.
   */
  int
  vmaxiosize(struct vnode *vp)
  {
          int maxiosize;
  
          if (vp->v_type == VBLK || vp->v_type == VCHR)
                  maxiosize = vp->v_rdev->si_iosize_max;
          else
                  maxiosize = vp->v_mount->mnt_iosize_max;
  
          if (maxiosize > MAXPHYS)
                  maxiosize = MAXPHYS;
          return (maxiosize);
  }
  
  /*
   * Eliminate all activity associated with a vnode in preparation for
   * destruction.
   *
   * The vnode must be VX locked and refd and will remain VX locked and refd
   * on return.  This routine may be called with the vnode in any state, as
   * long as it is VX locked.  The vnode will be cleaned out and marked
   * VRECLAIMED but will not actually be reused until all existing refs and
   * holds go away.
   *
   * NOTE: This routine may be called on a vnode which has not yet been
   * already been deactivated (VOP_INACTIVE), or on a vnode which has
   * already been reclaimed.
   *
   * This routine is not responsible for placing us back on the freelist. 
   * Instead, it happens automatically when the caller releases the VX lock
   * (assuming there aren't any other references).
   */
  void
  vgone_vxlocked(struct vnode *vp)
  {
          /*
           * assert that the VX lock is held.  This is an absolute requirement
           * now for vgone_vxlocked() to be called.
           */
          KKASSERT(lockcountnb(&vp->v_lock) == 1);
  
          /*
           * Clean out the filesystem specific data and set the VRECLAIMED
           * bit.  Also deactivate the vnode if necessary. 
           *
           * The vnode should have automatically been removed from the syncer
           * list as syncer/dirty flags cleared during the cleaning.
           */
          vclean_vxlocked(vp, DOCLOSE);
          KKASSERT((vp->v_flag & VONWORKLST) == 0);
  
          /*
           * Delete from old mount point vnode list, if on one.
           */
          if (vp->v_mount != NULL) {
                  KKASSERT(vp->v_data == NULL);
                  insmntque(vp, NULL);
          }
  
          /*
           * 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);
          }
  
          /*
           * Set us to VBAD
           */
          vp->v_type = VBAD;
  }
  
  /*
   * Lookup a vnode by device number.
   *
   * Returns non-zero and *vpp set to a vref'd vnode on success.
   * Returns zero on failure.
   */
  int
  vfinddev(cdev_t dev, enum vtype type, struct vnode **vpp)
  {
          struct vnode *vp;
  
          lwkt_gettoken(&spechash_token);
          SLIST_FOREACH(vp, &dev->si_hlist, v_cdevnext) {
                  if (type == vp->v_type) {
                          *vpp = vp;
                          vref(vp);
                          lwkt_reltoken(&spechash_token);
                          return (1);
                  }
          }
          lwkt_reltoken(&spechash_token);
          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 NULL, we have
   * to check for a NULL v_rdev.
   */
  int
  count_dev(cdev_t dev)
  {
          struct vnode *vp;
          int count = 0;
  
          if (SLIST_FIRST(&dev->si_hlist)) {
                  lwkt_gettoken(&spechash_token);
                  SLIST_FOREACH(vp, &dev->si_hlist, v_cdevnext) {
                          count += vp->v_opencount;
                  }
                  lwkt_reltoken(&spechash_token);
          }
          return(count);
  }
  
  int
  vcount(struct vnode *vp)
  {
          if (vp->v_rdev == NULL)
                  return(0);
          return(count_dev(vp->v_rdev));
  }
  
  /*
   * Initialize VMIO for a vnode.  This routine MUST be called before a
   * VFS can issue buffer cache ops on a vnode.  It is typically called
   * when a vnode is initialized from its inode.
   */
  int
  vinitvmio(struct vnode *vp, off_t filesize, int blksize, int boff)
  {
          vm_object_t object;
          int error = 0;
  
          object = vp->v_object;
          if (object) {
                  vm_object_hold(object);
                  KKASSERT(vp->v_object == object);
          }
  
          if (object == NULL) {
                  object = vnode_pager_alloc(vp, filesize, 0, 0, blksize, boff);
  
                  /*
                   * Dereference the reference we just created.  This assumes
                   * that the object is associated with the vp.  Allow it to
                   * have zero refs.  It cannot be destroyed as long as it
                   * is associated with the vnode.
                   */
                  vm_object_hold(object);
                  atomic_add_int(&object->ref_count, -1);
                  vrele(vp);
          } else {
                  KKASSERT((object->flags & OBJ_DEAD) == 0);
          }
          KASSERT(vp->v_object != NULL, ("vinitvmio: NULL object"));
          vsetflags(vp, VOBJBUF);
          vm_object_drop(object);
  
          return (error);
  }
  
  
  /*
   * 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)
                  kprintf("%s: %p: ", label, (void *)vp);
          else
                  kprintf("%p: ", (void *)vp);
          kprintf("type %s, refcnt %08x, writecount %d, holdcnt %d,",
                  typename[vp->v_type],
                  vp->v_refcnt, vp->v_writecount, vp->v_auxrefs);
          buf[0] = '\0';
          if (vp->v_flag & VROOT)
                  strcat(buf, "|VROOT");
          if (vp->v_flag & VPFSROOT)
                  strcat(buf, "|VPFSROOT");
          if (vp->v_flag & VTEXT)
                  strcat(buf, "|VTEXT");
          if (vp->v_flag & VSYSTEM)
                  strcat(buf, "|VSYSTEM");
          if (vp->v_flag & VOBJBUF)
                  strcat(buf, "|VOBJBUF");
          if (buf[0] != '\0')
                  kprintf(" flags (%s)", &buf[1]);
          if (vp->v_data == NULL) {
                  kprintf("\n");
          } else {
                  kprintf("\n\t");
                  VOP_PRINT(vp);
          }
  }
  
  /*
   * Do the usual access checking.
   * file_mode, uid and gid are from the vnode in question,
   * while acc_mode and cred are from the VOP_ACCESS parameter list
   */
  int
  vaccess(enum vtype type, mode_t file_mode, uid_t uid, gid_t gid,
      mode_t acc_mode, struct ucred *cred)
  {
          mode_t mask;
          int ismember;
  
          /*
           * Super-user always gets read/write access, but execute access depends
           * on at least one execute bit being set.
           */
          if (priv_check_cred(cred, PRIV_ROOT, 0) == 0) {
                  if ((acc_mode & VEXEC) && type != VDIR &&
                      (file_mode & (S_IXUSR|S_IXGRP|S_IXOTH)) == 0)
                          return (EACCES);
                  return (0);
          }
  
          mask = 0;
  
          /* Otherwise, check the owner. */
          if (cred->cr_uid == uid) {
                  if (acc_mode & VEXEC)
                          mask |= S_IXUSR;
                  if (acc_mode & VREAD)
                          mask |= S_IRUSR;
                  if (acc_mode & VWRITE)
                          mask |= S_IWUSR;
                  return ((file_mode & mask) == mask ? 0 : EACCES);
          }
  
          /* Otherwise, check the groups. */
          ismember = groupmember(gid, cred);
          if (cred->cr_svgid == gid || ismember) {
                  if (acc_mode & VEXEC)
                          mask |= S_IXGRP;
                  if (acc_mode & VREAD)
                          mask |= S_IRGRP;
                  if (acc_mode & VWRITE)
                          mask |= S_IWGRP;
                  return ((file_mode & mask) == mask ? 0 : EACCES);
          }
  
          /* Otherwise, check everyone else. */
          if (acc_mode & VEXEC)
                  mask |= S_IXOTH;
          if (acc_mode & VREAD)
                  mask |= S_IROTH;
          if (acc_mode & VWRITE)
                  mask |= S_IWOTH;
          return ((file_mode & mask) == mask ? 0 : EACCES);
  }
  
  #ifdef DDB
  #include <ddb/ddb.h>
  
  static int db_show_locked_vnodes(struct mount *mp, void *data);
  
  /*
   * List all of the locked vnodes in the system.
   * Called when debugging the kernel.
   */
  DB_SHOW_COMMAND(lockedvnodes, lockedvnodes)
  {
          kprintf("Locked vnodes\n");
          mountlist_scan(db_show_locked_vnodes, NULL, 
                          MNTSCAN_FORWARD|MNTSCAN_NOBUSY);
  }
  
  static int
  db_show_locked_vnodes(struct mount *mp, void *data __unused)
  {
          struct vnode *vp;
  
          TAILQ_FOREACH(vp, &mp->mnt_nvnodelist, v_nmntvnodes) {
                  if (vn_islocked(vp))
                          vprint(NULL, vp);
          }
          return(0);
  }
  #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;
          int maxtypenum;
  
  #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) {
                  vfsp = vfsconf_find_by_typenum(name[0]);
                  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);
                  maxtypenum = vfsconf_get_maxtypenum();
                  return (SYSCTL_OUT(req, &maxtypenum, sizeof(maxtypenum)));
          case VFS_CONF:
                  if (namelen != 3)
                          return (ENOTDIR);       /* overloaded */
                  vfsp = vfsconf_find_by_typenum(name[2]);
                  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_iter(struct vfsconf *vfsp, void *data)
  {
          int error;
          struct ovfsconf ovfs;
          struct sysctl_req *req = (struct sysctl_req*) data;
  
          bzero(&ovfs, sizeof(ovfs));
          ovfs.vfc_vfsops = vfsp->vfc_vfsops;     /* XXX used as flag */
          strcpy(ovfs.vfc_name, vfsp->vfc_name);
          ovfs.vfc_index = vfsp->vfc_typenum;
          ovfs.vfc_refcount = vfsp->vfc_refcount;
          ovfs.vfc_flags = vfsp->vfc_flags;
          error = SYSCTL_OUT(req, &ovfs, sizeof ovfs);
          if (error)
                  return error; /* abort iteration with error code */
          else
                  return 0; /* continue iterating with next element */
  }
  
  static int
  sysctl_ovfs_conf(SYSCTL_HANDLER_ARGS)
  {
          return vfsconf_each(sysctl_ovfs_conf_iter, (void*)req);
  }
  
  #endif /* 1 || COMPAT_PRELITE2 */
  
  /*
   * Check to see if a filesystem is mounted on a block device.
   */
  int
  vfs_mountedon(struct vnode *vp)
  {
          cdev_t dev;
  
          if ((dev = vp->v_rdev) == NULL) {
  /*              if (vp->v_type != VBLK)
                          dev = get_dev(vp->v_uminor, vp->v_umajor); */
          }
          if (dev != NULL && dev->si_mountpoint)
                  return (EBUSY);
          return (0);
  }
  
  /*
   * Unmount all filesystems. The list is traversed in reverse order
   * of mounting to avoid dependencies.
   */
  
  static int vfs_umountall_callback(struct mount *mp, void *data);
  
  void
  vfs_unmountall(void)
  {
          int count;
  
          do {
                  count = mountlist_scan(vfs_umountall_callback, 
                                          NULL, MNTSCAN_REVERSE|MNTSCAN_NOBUSY);
          } while (count);
  }
  
  static
  int
  vfs_umountall_callback(struct mount *mp, void *data)
  {
          int error;
  
          error = dounmount(mp, MNT_FORCE);
          if (error) {
                  mountlist_remove(mp);
                  kprintf("unmount of filesystem mounted from %s failed (", 
                          mp->mnt_stat.f_mntfromname);
                  if (error == EBUSY)
                          kprintf("BUSY)\n");
                  else
                          kprintf("%d)\n", error);
          }
          return(1);
  }
  
  /*
   * Checks the mount flags for parameter mp and put the names comma-separated
   * into a string buffer buf with a size limit specified by len.
   *
   * It returns the number of bytes written into buf, and (*errorp) will be
   * set to 0, EINVAL (if passed length is 0), or ENOSPC (supplied buffer was
   * not large enough).  The buffer will be 0-terminated if len was not 0.
   */
  size_t
  vfs_flagstostr(int flags, const struct mountctl_opt *optp,
                 char *buf, size_t len, int *errorp)
  {
          static const struct mountctl_opt optnames[] = {
                  { MNT_ASYNC,            "asynchronous" },
                  { MNT_EXPORTED,         "NFS exported" },
                  { MNT_LOCAL,            "local" },
                  { MNT_NOATIME,          "noatime" },
                  { MNT_NODEV,            "nodev" },
                  { MNT_NOEXEC,           "noexec" },
                  { MNT_NOSUID,           "nosuid" },
                  { MNT_NOSYMFOLLOW,      "nosymfollow" },
                  { MNT_QUOTA,            "with-quotas" },
                  { MNT_RDONLY,           "read-only" },
                  { MNT_SYNCHRONOUS,      "synchronous" },
                  { MNT_UNION,            "union" },
                  { MNT_NOCLUSTERR,       "noclusterr" },
                  { MNT_NOCLUSTERW,       "noclusterw" },
                  { MNT_SUIDDIR,          "suiddir" },
                  { MNT_SOFTDEP,          "soft-updates" },
                  { MNT_IGNORE,           "ignore" },
                  { 0,                    NULL}
          };
          int bwritten;
          int bleft;
          int optlen;
          int actsize;
  
          *errorp = 0;
          bwritten = 0;
          bleft = len - 1;        /* leave room for trailing \0 */
  
          /*
           * Checks the size of the string. If it contains
           * any data, then we will append the new flags to
           * it.
           */
          actsize = strlen(buf);
          if (actsize > 0)
                  buf += actsize;
  
          /* Default flags if no flags passed */
          if (optp == NULL)
                  optp = optnames;
  
          if (bleft < 0) {        /* degenerate case, 0-length buffer */
                  *errorp = EINVAL;
                  return(0);
          }
  
          for (; flags && optp->o_opt; ++optp) {
                  if ((flags & optp->o_opt) == 0)
                          continue;
                  optlen = strlen(optp->o_name);
                  if (bwritten || actsize > 0) {
                          if (bleft < 2) {
                                  *errorp = ENOSPC;
                                  break;
                          }
                          buf[bwritten++] = ',';
                          buf[bwritten++] = ' ';
                          bleft -= 2;
                  }
                  if (bleft < optlen) {
                          *errorp = ENOSPC;
                          break;
                  }
                  bcopy(optp->o_name, buf + bwritten, optlen);
                  bwritten += optlen;
                  bleft -= optlen;
                  flags &= ~optp->o_opt;
          }
  
          /*
           * Space already reserved for trailing \0
           */
          buf[bwritten] = 0;
          return (bwritten);
  }
  
  /*
   * 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,
                  const struct export_args *argp)
  {
          struct netcred *np;
          struct radix_node_head *rnh;
          int i;
          struct radix_node *rn;
          struct sockaddr *saddr, *smask = NULL;
          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 *) kmalloc(i, M_NETADDR, M_WAITOK | M_ZERO);
          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]) == NULL) {
                  /*
                   * Seems silly to initialize every AF when most are not used,
                   * do so on demand here
                   */
                  SLIST_FOREACH(dom, &domains, 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]) == NULL) {
                          error = ENOBUFS;
                          goto out;
                  }
          }
          rn = (*rnh->rnh_addaddr) ((char *) saddr, (char *) smask, rnh,
              np->netc_rnodes);
          if (rn == NULL || 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:
          kfree(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);
          kfree((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);
                          kfree((caddr_t) rnh, M_RTABLE);
                          nep->ne_rtable[i] = 0;
                  }
  }
  
  int
  vfs_export(struct mount *mp, struct netexport *nep,
             const 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,
                  const 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) {
                                  kfree(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) {
                  int namelen;
  
                  error = vn_get_namelen(rvp, &namelen);
                  if (error)
                          return (error);
                  nfs_pub.np_index = kmalloc(namelen, M_TEMP, M_WAITOK);
                  error = copyinstr(argp->ex_indexfile, nfs_pub.np_index,
                      namelen, NULL);
                  if (!error) {
                          /*
                           * Check for illegal filenames.
                           */
                          for (cp = nfs_pub.np_index; *cp; cp++) {
                                  if (*cp == '/') {
                                          error = EINVAL;
                                          break;
                                  }
                          }
                  }
                  if (error) {
                          kfree(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)((char *)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.
   *
   * NOTE: XXX VOP_PUTPAGES and friends requires that the vnode be locked,
   * but vnode_pager_putpages() doesn't lock the vnode.  We have to do it
   * way up in this high level function.
   */
  static int vfs_msync_scan1(struct mount *mp, struct vnode *vp, void *data);
  static int vfs_msync_scan2(struct mount *mp, struct vnode *vp, void *data);
  
  void
  vfs_msync(struct mount *mp, int flags) 
  {
          int vmsc_flags;
  
          /*
           * tmpfs sets this flag to prevent msync(), sync, and the
           * filesystem periodic syncer from trying to flush VM pages
           * to swap.  Only pure memory pressure flushes tmpfs VM pages
           * to swap.
           */
          if (mp->mnt_kern_flag & MNTK_NOMSYNC)
                  return;
  
          /*
           * Ok, scan the vnodes for work.  If the filesystem is using the
           * syncer thread feature we can use vsyncscan() instead of
           * vmntvnodescan(), which is much faster.
           */
          vmsc_flags = VMSC_GETVP;
          if (flags != MNT_WAIT)
                  vmsc_flags |= VMSC_NOWAIT;
  
          if (mp->mnt_kern_flag & MNTK_THR_SYNC) {
                  vsyncscan(mp, vmsc_flags, vfs_msync_scan2,
                            (void *)(intptr_t)flags);
          } else {
                  vmntvnodescan(mp, vmsc_flags,
                                vfs_msync_scan1, vfs_msync_scan2,
                                (void *)(intptr_t)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)(intptr_t)data;
  
          if ((vp->v_flag & VRECLAIMED) == 0) {
                  if (vp->v_auxrefs == 0 && VREFCNT(vp) <= 0 &&
                      vp->v_object) {
                          return(0);      /* call scan2 */
                  }
                  if ((mp->mnt_flag & MNT_RDONLY) == 0 &&
                      (vp->v_flag & VOBJDIRTY) &&
                      (flags == MNT_WAIT || vn_islocked(vp) == 0)) {
                          return(0);      /* call scan2 */
                  }
          }
  
          /*
           * do not call scan2, continue the loop
           */
          return(-1);
  }
  
  /*
   * This callback is handed a locked vnode.
   */
  static
  int
  vfs_msync_scan2(struct mount *mp, struct vnode *vp, void *data)
  {
          vm_object_t obj;
          int flags = (int)(intptr_t)data;
  
          if (vp->v_flag & VRECLAIMED)
                  return(0);
  
          if ((mp->mnt_flag & MNT_RDONLY) == 0 && (vp->v_flag & VOBJDIRTY)) {
                  if ((obj = vp->v_object) != NULL) {
                          vm_object_page_clean(obj, 0, 0, 
                           flags == MNT_WAIT ? OBJPC_SYNC : OBJPC_NOSYNC);
                  }
          }
          return(0);
  }
  
  /*
   * Wake up anyone interested in vp because it is being revoked.
   */
  void
  vn_gone(struct vnode *vp)
  {
          lwkt_gettoken(&vp->v_token);
          KNOTE(&vp->v_pollinfo.vpi_kqinfo.ki_note, NOTE_REVOKE);
          lwkt_reltoken(&vp->v_token);
  }
  
  /*
   * extract the cdev_t from a VBLK or VCHR.  The vnode must have been opened
   * (or v_rdev might be NULL).
   */
  cdev_t
  vn_todev(struct vnode *vp)
  {
          if (vp->v_type != VBLK && vp->v_type != VCHR)
                  return (NULL);
          KKASSERT(vp->v_rdev != NULL);
          return (vp->v_rdev);
  }
  
  /*
   * Check if vnode represents a disk device.  The vnode does not need to be
   * opened.
   *
   * MPALMOSTSAFE
   */
  int
  vn_isdisk(struct vnode *vp, int *errp)
  {
          cdev_t dev;
  
          if (vp->v_type != VCHR) {
                  if (errp != NULL)
                          *errp = ENOTBLK;
                  return (0);
          }
  
          dev = vp->v_rdev;
  
          if (dev == NULL) {
                  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);
  }
  
  int
  vn_get_namelen(struct vnode *vp, int *namelen)
  {
          int error;
          register_t retval[2];
  
          error = VOP_PATHCONF(vp, _PC_NAME_MAX, retval);
          if (error)
                  return (error);
          *namelen = (int)retval[0];
          return (0);
  }
  
  int
  vop_write_dirent(int *error, struct uio *uio, ino_t d_ino, uint8_t d_type, 
                  uint16_t d_namlen, const char *d_name)
  {
          struct dirent *dp;
          size_t len;
  
          len = _DIRENT_RECLEN(d_namlen);
          if (len > uio->uio_resid)
                  return(1);
  
          dp = kmalloc(len, M_TEMP, M_WAITOK | M_ZERO);
  
          dp->d_ino = d_ino;
          dp->d_namlen = d_namlen;
          dp->d_type = d_type;
          bcopy(d_name, dp->d_name, d_namlen);
  
          *error = uiomove((caddr_t)dp, len, uio);
  
          kfree(dp, M_TEMP);
  
          return(0);
  }
  
  void
  vn_mark_atime(struct vnode *vp, struct thread *td)
  {
          struct proc *p = td->td_proc;
          struct ucred *cred = p ? p->p_ucred : proc0.p_ucred;
  
          if ((vp->v_mount->mnt_flag & (MNT_NOATIME | MNT_RDONLY)) == 0) {
                  VOP_MARKATIME(vp, cred);
          }
  }

Cache object: 33e21ea0bc28117d2299e985d8a42768