FreeBSD/Linux Kernel Cross Reference
sys/ufs/ffs/ffs_alloc.c

     /*-
      * Copyright (c) 2002 Networks Associates Technology, Inc.
      * All rights reserved.
      *
      * This software was developed for the FreeBSD Project by Marshall
      * Kirk McKusick and Network Associates Laboratories, the Security
      * Research Division of Network Associates, Inc. under DARPA/SPAWAR
      * contract N66001-01-C-8035 ("CBOSS"), as part of the DARPA CHATS
      * research program
     *
     * Redistribution and use in source and binary forms, with or without
     * modification, are permitted provided that the following conditions
     * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     *
     * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     * SUCH DAMAGE.
     *
     * Copyright (c) 1982, 1986, 1989, 1993
     *      The Regents of the University of California.  All rights reserved.
     *
     * Redistribution and use in source and binary forms, with or without
     * modification, are permitted provided that the following conditions
     * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     * 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.
     *
     *      @(#)ffs_alloc.c 8.18 (Berkeley) 5/26/95
     */
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD: releng/10.0/sys/ufs/ffs/ffs_alloc.c 255219 2013-09-05 00:09:56Z pjd $");
    
    #include "opt_quota.h"
    
    #include <sys/param.h>
    #include <sys/capability.h>
    #include <sys/systm.h>
    #include <sys/bio.h>
    #include <sys/buf.h>
    #include <sys/conf.h>
    #include <sys/fcntl.h>
    #include <sys/file.h>
    #include <sys/filedesc.h>
    #include <sys/priv.h>
    #include <sys/proc.h>
    #include <sys/vnode.h>
    #include <sys/mount.h>
    #include <sys/kernel.h>
    #include <sys/syscallsubr.h>
    #include <sys/sysctl.h>
    #include <sys/syslog.h>
    #include <sys/taskqueue.h>
    
    #include <security/audit/audit.h>
    
    #include <geom/geom.h>
    
    #include <ufs/ufs/dir.h>
    #include <ufs/ufs/extattr.h>
    #include <ufs/ufs/quota.h>
    #include <ufs/ufs/inode.h>
    #include <ufs/ufs/ufs_extern.h>
    #include <ufs/ufs/ufsmount.h>
    
    #include <ufs/ffs/fs.h>
    #include <ufs/ffs/ffs_extern.h>
    #include <ufs/ffs/softdep.h>
   
   typedef ufs2_daddr_t allocfcn_t(struct inode *ip, u_int cg, ufs2_daddr_t bpref,
                                     int size, int rsize);
   
   static ufs2_daddr_t ffs_alloccg(struct inode *, u_int, ufs2_daddr_t, int, int);
   static ufs2_daddr_t
                 ffs_alloccgblk(struct inode *, struct buf *, ufs2_daddr_t, int);
   static void     ffs_blkfree_cg(struct ufsmount *, struct fs *,
                       struct vnode *, ufs2_daddr_t, long, ino_t,
                       struct workhead *);
   static void     ffs_blkfree_trim_completed(struct bio *);
   static void     ffs_blkfree_trim_task(void *ctx, int pending __unused);
   #ifdef INVARIANTS
   static int      ffs_checkblk(struct inode *, ufs2_daddr_t, long);
   #endif
   static ufs2_daddr_t ffs_clusteralloc(struct inode *, u_int, ufs2_daddr_t, int,
                       int);
   static ino_t    ffs_dirpref(struct inode *);
   static ufs2_daddr_t ffs_fragextend(struct inode *, u_int, ufs2_daddr_t,
                       int, int);
   static ufs2_daddr_t     ffs_hashalloc
                   (struct inode *, u_int, ufs2_daddr_t, int, int, allocfcn_t *);
   static ufs2_daddr_t ffs_nodealloccg(struct inode *, u_int, ufs2_daddr_t, int,
                       int);
   static ufs1_daddr_t ffs_mapsearch(struct fs *, struct cg *, ufs2_daddr_t, int);
   static int      ffs_reallocblks_ufs1(struct vop_reallocblks_args *);
   static int      ffs_reallocblks_ufs2(struct vop_reallocblks_args *);
   
   /*
    * Allocate a block in the filesystem.
    *
    * The size of the requested block is given, which must be some
    * multiple of fs_fsize and <= fs_bsize.
    * A preference may be optionally specified. If a preference is given
    * the following hierarchy is used to allocate a block:
    *   1) allocate the requested block.
    *   2) allocate a rotationally optimal block in the same cylinder.
    *   3) allocate a block in the same cylinder group.
    *   4) quadradically rehash into other cylinder groups, until an
    *      available block is located.
    * If no block preference is given the following hierarchy is used
    * to allocate a block:
    *   1) allocate a block in the cylinder group that contains the
    *      inode for the file.
    *   2) quadradically rehash into other cylinder groups, until an
    *      available block is located.
    */
   int
   ffs_alloc(ip, lbn, bpref, size, flags, cred, bnp)
           struct inode *ip;
           ufs2_daddr_t lbn, bpref;
           int size, flags;
           struct ucred *cred;
           ufs2_daddr_t *bnp;
   {
           struct fs *fs;
           struct ufsmount *ump;
           ufs2_daddr_t bno;
           u_int cg, reclaimed;
           static struct timeval lastfail;
           static int curfail;
           int64_t delta;
   #ifdef QUOTA
           int error;
   #endif
   
           *bnp = 0;
           fs = ip->i_fs;
           ump = ip->i_ump;
           mtx_assert(UFS_MTX(ump), MA_OWNED);
   #ifdef INVARIANTS
           if ((u_int)size > fs->fs_bsize || fragoff(fs, size) != 0) {
                   printf("dev = %s, bsize = %ld, size = %d, fs = %s\n",
                       devtoname(ip->i_dev), (long)fs->fs_bsize, size,
                       fs->fs_fsmnt);
                   panic("ffs_alloc: bad size");
           }
           if (cred == NOCRED)
                   panic("ffs_alloc: missing credential");
   #endif /* INVARIANTS */
           reclaimed = 0;
   retry:
   #ifdef QUOTA
           UFS_UNLOCK(ump);
           error = chkdq(ip, btodb(size), cred, 0);
           if (error)
                   return (error);
           UFS_LOCK(ump);
   #endif
           if (size == fs->fs_bsize && fs->fs_cstotal.cs_nbfree == 0)
                   goto nospace;
           if (priv_check_cred(cred, PRIV_VFS_BLOCKRESERVE, 0) &&
               freespace(fs, fs->fs_minfree) - numfrags(fs, size) < 0)
                   goto nospace;
           if (bpref >= fs->fs_size)
                   bpref = 0;
           if (bpref == 0)
                   cg = ino_to_cg(fs, ip->i_number);
           else
                   cg = dtog(fs, bpref);
           bno = ffs_hashalloc(ip, cg, bpref, size, size, ffs_alloccg);
           if (bno > 0) {
                   delta = btodb(size);
                   DIP_SET(ip, i_blocks, DIP(ip, i_blocks) + delta);
                   if (flags & IO_EXT)
                           ip->i_flag |= IN_CHANGE;
                   else
                           ip->i_flag |= IN_CHANGE | IN_UPDATE;
                   *bnp = bno;
                   return (0);
           }
   nospace:
   #ifdef QUOTA
           UFS_UNLOCK(ump);
           /*
            * Restore user's disk quota because allocation failed.
            */
           (void) chkdq(ip, -btodb(size), cred, FORCE);
           UFS_LOCK(ump);
   #endif
           if (reclaimed == 0 && (flags & IO_BUFLOCKED) == 0) {
                   reclaimed = 1;
                   softdep_request_cleanup(fs, ITOV(ip), cred, FLUSH_BLOCKS_WAIT);
                   goto retry;
           }
           UFS_UNLOCK(ump);
           if (reclaimed > 0 && ppsratecheck(&lastfail, &curfail, 1)) {
                   ffs_fserr(fs, ip->i_number, "filesystem full");
                   uprintf("\n%s: write failed, filesystem is full\n",
                       fs->fs_fsmnt);
           }
           return (ENOSPC);
   }
   
   /*
    * Reallocate a fragment to a bigger size
    *
    * The number and size of the old block is given, and a preference
    * and new size is also specified. The allocator attempts to extend
    * the original block. Failing that, the regular block allocator is
    * invoked to get an appropriate block.
    */
   int
   ffs_realloccg(ip, lbprev, bprev, bpref, osize, nsize, flags, cred, bpp)
           struct inode *ip;
           ufs2_daddr_t lbprev;
           ufs2_daddr_t bprev;
           ufs2_daddr_t bpref;
           int osize, nsize, flags;
           struct ucred *cred;
           struct buf **bpp;
   {
           struct vnode *vp;
           struct fs *fs;
           struct buf *bp;
           struct ufsmount *ump;
           u_int cg, request, reclaimed;
           int error, gbflags;
           ufs2_daddr_t bno;
           static struct timeval lastfail;
           static int curfail;
           int64_t delta;
   
           *bpp = 0;
           vp = ITOV(ip);
           fs = ip->i_fs;
           bp = NULL;
           ump = ip->i_ump;
           gbflags = (flags & BA_UNMAPPED) != 0 ? GB_UNMAPPED : 0;
   
           mtx_assert(UFS_MTX(ump), MA_OWNED);
   #ifdef INVARIANTS
           if (vp->v_mount->mnt_kern_flag & MNTK_SUSPENDED)
                   panic("ffs_realloccg: allocation on suspended filesystem");
           if ((u_int)osize > fs->fs_bsize || fragoff(fs, osize) != 0 ||
               (u_int)nsize > fs->fs_bsize || fragoff(fs, nsize) != 0) {
                   printf(
                   "dev = %s, bsize = %ld, osize = %d, nsize = %d, fs = %s\n",
                       devtoname(ip->i_dev), (long)fs->fs_bsize, osize,
                       nsize, fs->fs_fsmnt);
                   panic("ffs_realloccg: bad size");
           }
           if (cred == NOCRED)
                   panic("ffs_realloccg: missing credential");
   #endif /* INVARIANTS */
           reclaimed = 0;
   retry:
           if (priv_check_cred(cred, PRIV_VFS_BLOCKRESERVE, 0) &&
               freespace(fs, fs->fs_minfree) -  numfrags(fs, nsize - osize) < 0) {
                   goto nospace;
           }
           if (bprev == 0) {
                   printf("dev = %s, bsize = %ld, bprev = %jd, fs = %s\n",
                       devtoname(ip->i_dev), (long)fs->fs_bsize, (intmax_t)bprev,
                       fs->fs_fsmnt);
                   panic("ffs_realloccg: bad bprev");
           }
           UFS_UNLOCK(ump);
           /*
            * Allocate the extra space in the buffer.
            */
           error = bread_gb(vp, lbprev, osize, NOCRED, gbflags, &bp);
           if (error) {
                   brelse(bp);
                   return (error);
           }
   
           if (bp->b_blkno == bp->b_lblkno) {
                   if (lbprev >= NDADDR)
                           panic("ffs_realloccg: lbprev out of range");
                   bp->b_blkno = fsbtodb(fs, bprev);
           }
   
   #ifdef QUOTA
           error = chkdq(ip, btodb(nsize - osize), cred, 0);
           if (error) {
                   brelse(bp);
                   return (error);
           }
   #endif
           /*
            * Check for extension in the existing location.
            */
           cg = dtog(fs, bprev);
           UFS_LOCK(ump);
           bno = ffs_fragextend(ip, cg, bprev, osize, nsize);
           if (bno) {
                   if (bp->b_blkno != fsbtodb(fs, bno))
                           panic("ffs_realloccg: bad blockno");
                   delta = btodb(nsize - osize);
                   DIP_SET(ip, i_blocks, DIP(ip, i_blocks) + delta);
                   if (flags & IO_EXT)
                           ip->i_flag |= IN_CHANGE;
                   else
                           ip->i_flag |= IN_CHANGE | IN_UPDATE;
                   allocbuf(bp, nsize);
                   bp->b_flags |= B_DONE;
                   vfs_bio_bzero_buf(bp, osize, nsize - osize);
                   if ((bp->b_flags & (B_MALLOC | B_VMIO)) == B_VMIO)
                           vfs_bio_set_valid(bp, osize, nsize - osize);
                   *bpp = bp;
                   return (0);
           }
           /*
            * Allocate a new disk location.
            */
           if (bpref >= fs->fs_size)
                   bpref = 0;
           switch ((int)fs->fs_optim) {
           case FS_OPTSPACE:
                   /*
                    * Allocate an exact sized fragment. Although this makes
                    * best use of space, we will waste time relocating it if
                    * the file continues to grow. If the fragmentation is
                    * less than half of the minimum free reserve, we choose
                    * to begin optimizing for time.
                    */
                   request = nsize;
                   if (fs->fs_minfree <= 5 ||
                       fs->fs_cstotal.cs_nffree >
                       (off_t)fs->fs_dsize * fs->fs_minfree / (2 * 100))
                           break;
                   log(LOG_NOTICE, "%s: optimization changed from SPACE to TIME\n",
                           fs->fs_fsmnt);
                   fs->fs_optim = FS_OPTTIME;
                   break;
           case FS_OPTTIME:
                   /*
                    * At this point we have discovered a file that is trying to
                    * grow a small fragment to a larger fragment. To save time,
                    * we allocate a full sized block, then free the unused portion.
                    * If the file continues to grow, the `ffs_fragextend' call
                    * above will be able to grow it in place without further
                    * copying. If aberrant programs cause disk fragmentation to
                    * grow within 2% of the free reserve, we choose to begin
                    * optimizing for space.
                    */
                   request = fs->fs_bsize;
                   if (fs->fs_cstotal.cs_nffree <
                       (off_t)fs->fs_dsize * (fs->fs_minfree - 2) / 100)
                           break;
                   log(LOG_NOTICE, "%s: optimization changed from TIME to SPACE\n",
                           fs->fs_fsmnt);
                   fs->fs_optim = FS_OPTSPACE;
                   break;
           default:
                   printf("dev = %s, optim = %ld, fs = %s\n",
                       devtoname(ip->i_dev), (long)fs->fs_optim, fs->fs_fsmnt);
                   panic("ffs_realloccg: bad optim");
                   /* NOTREACHED */
           }
           bno = ffs_hashalloc(ip, cg, bpref, request, nsize, ffs_alloccg);
           if (bno > 0) {
                   bp->b_blkno = fsbtodb(fs, bno);
                   if (!DOINGSOFTDEP(vp))
                           ffs_blkfree(ump, fs, ip->i_devvp, bprev, (long)osize,
                               ip->i_number, vp->v_type, NULL);
                   delta = btodb(nsize - osize);
                   DIP_SET(ip, i_blocks, DIP(ip, i_blocks) + delta);
                   if (flags & IO_EXT)
                           ip->i_flag |= IN_CHANGE;
                   else
                           ip->i_flag |= IN_CHANGE | IN_UPDATE;
                   allocbuf(bp, nsize);
                   bp->b_flags |= B_DONE;
                   vfs_bio_bzero_buf(bp, osize, nsize - osize);
                   if ((bp->b_flags & (B_MALLOC | B_VMIO)) == B_VMIO)
                           vfs_bio_set_valid(bp, osize, nsize - osize);
                   *bpp = bp;
                   return (0);
           }
   #ifdef QUOTA
           UFS_UNLOCK(ump);
           /*
            * Restore user's disk quota because allocation failed.
            */
           (void) chkdq(ip, -btodb(nsize - osize), cred, FORCE);
           UFS_LOCK(ump);
   #endif
   nospace:
           /*
            * no space available
            */
           if (reclaimed == 0 && (flags & IO_BUFLOCKED) == 0) {
                   reclaimed = 1;
                   UFS_UNLOCK(ump);
                   if (bp) {
                           brelse(bp);
                           bp = NULL;
                   }
                   UFS_LOCK(ump);
                   softdep_request_cleanup(fs, vp, cred, FLUSH_BLOCKS_WAIT);
                   goto retry;
           }
           UFS_UNLOCK(ump);
           if (bp)
                   brelse(bp);
           if (reclaimed > 0 && ppsratecheck(&lastfail, &curfail, 1)) {
                   ffs_fserr(fs, ip->i_number, "filesystem full");
                   uprintf("\n%s: write failed, filesystem is full\n",
                       fs->fs_fsmnt);
           }
           return (ENOSPC);
   }
   
   /*
    * Reallocate a sequence of blocks into a contiguous sequence of blocks.
    *
    * The vnode and an array of buffer pointers for a range of sequential
    * logical blocks to be made contiguous is given. The allocator attempts
    * to find a range of sequential blocks starting as close as possible
    * from the end of the allocation for the logical block immediately
    * preceding the current range. If successful, the physical block numbers
    * in the buffer pointers and in the inode are changed to reflect the new
    * allocation. If unsuccessful, the allocation is left unchanged. The
    * success in doing the reallocation is returned. Note that the error
    * return is not reflected back to the user. Rather the previous block
    * allocation will be used.
    */
   
   SYSCTL_NODE(_vfs, OID_AUTO, ffs, CTLFLAG_RW, 0, "FFS filesystem");
   
   static int doasyncfree = 1;
   SYSCTL_INT(_vfs_ffs, OID_AUTO, doasyncfree, CTLFLAG_RW, &doasyncfree, 0, "");
   
   static int doreallocblks = 1;
   SYSCTL_INT(_vfs_ffs, OID_AUTO, doreallocblks, CTLFLAG_RW, &doreallocblks, 0, "");
   
   #ifdef DEBUG
   static volatile int prtrealloc = 0;
   #endif
   
   int
   ffs_reallocblks(ap)
           struct vop_reallocblks_args /* {
                   struct vnode *a_vp;
                   struct cluster_save *a_buflist;
           } */ *ap;
   {
   
           if (doreallocblks == 0)
                   return (ENOSPC);
           /*
            * We can't wait in softdep prealloc as it may fsync and recurse
            * here.  Instead we simply fail to reallocate blocks if this
            * rare condition arises.
            */
           if (DOINGSOFTDEP(ap->a_vp))
                   if (softdep_prealloc(ap->a_vp, MNT_NOWAIT) != 0)
                           return (ENOSPC);
           if (VTOI(ap->a_vp)->i_ump->um_fstype == UFS1)
                   return (ffs_reallocblks_ufs1(ap));
           return (ffs_reallocblks_ufs2(ap));
   }
           
   static int
   ffs_reallocblks_ufs1(ap)
           struct vop_reallocblks_args /* {
                   struct vnode *a_vp;
                   struct cluster_save *a_buflist;
           } */ *ap;
   {
           struct fs *fs;
           struct inode *ip;
           struct vnode *vp;
           struct buf *sbp, *ebp;
           ufs1_daddr_t *bap, *sbap, *ebap = 0;
           struct cluster_save *buflist;
           struct ufsmount *ump;
           ufs_lbn_t start_lbn, end_lbn;
           ufs1_daddr_t soff, newblk, blkno;
           ufs2_daddr_t pref;
           struct indir start_ap[NIADDR + 1], end_ap[NIADDR + 1], *idp;
           int i, len, start_lvl, end_lvl, ssize;
   
           vp = ap->a_vp;
           ip = VTOI(vp);
           fs = ip->i_fs;
           ump = ip->i_ump;
           /*
            * If we are not tracking block clusters or if we have less than 2%
            * free blocks left, then do not attempt to cluster. Running with
            * less than 5% free block reserve is not recommended and those that
            * choose to do so do not expect to have good file layout.
            */
           if (fs->fs_contigsumsize <= 0 || freespace(fs, 2) < 0)
                   return (ENOSPC);
           buflist = ap->a_buflist;
           len = buflist->bs_nchildren;
           start_lbn = buflist->bs_children[0]->b_lblkno;
           end_lbn = start_lbn + len - 1;
   #ifdef INVARIANTS
           for (i = 0; i < len; i++)
                   if (!ffs_checkblk(ip,
                      dbtofsb(fs, buflist->bs_children[i]->b_blkno), fs->fs_bsize))
                           panic("ffs_reallocblks: unallocated block 1");
           for (i = 1; i < len; i++)
                   if (buflist->bs_children[i]->b_lblkno != start_lbn + i)
                           panic("ffs_reallocblks: non-logical cluster");
           blkno = buflist->bs_children[0]->b_blkno;
           ssize = fsbtodb(fs, fs->fs_frag);
           for (i = 1; i < len - 1; i++)
                   if (buflist->bs_children[i]->b_blkno != blkno + (i * ssize))
                           panic("ffs_reallocblks: non-physical cluster %d", i);
   #endif
           /*
            * If the cluster crosses the boundary for the first indirect
            * block, leave space for the indirect block. Indirect blocks
            * are initially laid out in a position after the last direct
            * block. Block reallocation would usually destroy locality by
            * moving the indirect block out of the way to make room for
            * data blocks if we didn't compensate here. We should also do
            * this for other indirect block boundaries, but it is only
            * important for the first one.
            */
           if (start_lbn < NDADDR && end_lbn >= NDADDR)
                   return (ENOSPC);
           /*
            * If the latest allocation is in a new cylinder group, assume that
            * the filesystem has decided to move and do not force it back to
            * the previous cylinder group.
            */
           if (dtog(fs, dbtofsb(fs, buflist->bs_children[0]->b_blkno)) !=
               dtog(fs, dbtofsb(fs, buflist->bs_children[len - 1]->b_blkno)))
                   return (ENOSPC);
           if (ufs_getlbns(vp, start_lbn, start_ap, &start_lvl) ||
               ufs_getlbns(vp, end_lbn, end_ap, &end_lvl))
                   return (ENOSPC);
           /*
            * Get the starting offset and block map for the first block.
            */
           if (start_lvl == 0) {
                   sbap = &ip->i_din1->di_db[0];
                   soff = start_lbn;
           } else {
                   idp = &start_ap[start_lvl - 1];
                   if (bread(vp, idp->in_lbn, (int)fs->fs_bsize, NOCRED, &sbp)) {
                           brelse(sbp);
                           return (ENOSPC);
                   }
                   sbap = (ufs1_daddr_t *)sbp->b_data;
                   soff = idp->in_off;
           }
           /*
            * If the block range spans two block maps, get the second map.
            */
           if (end_lvl == 0 || (idp = &end_ap[end_lvl - 1])->in_off + 1 >= len) {
                   ssize = len;
           } else {
   #ifdef INVARIANTS
                   if (start_lvl > 0 &&
                       start_ap[start_lvl - 1].in_lbn == idp->in_lbn)
                           panic("ffs_reallocblk: start == end");
   #endif
                   ssize = len - (idp->in_off + 1);
                   if (bread(vp, idp->in_lbn, (int)fs->fs_bsize, NOCRED, &ebp))
                           goto fail;
                   ebap = (ufs1_daddr_t *)ebp->b_data;
           }
           /*
            * Find the preferred location for the cluster.
            */
           UFS_LOCK(ump);
           pref = ffs_blkpref_ufs1(ip, start_lbn, soff, sbap);
           /*
            * Search the block map looking for an allocation of the desired size.
            */
           if ((newblk = ffs_hashalloc(ip, dtog(fs, pref), pref,
               len, len, ffs_clusteralloc)) == 0) {
                   UFS_UNLOCK(ump);
                   goto fail;
           }
           /*
            * We have found a new contiguous block.
            *
            * First we have to replace the old block pointers with the new
            * block pointers in the inode and indirect blocks associated
            * with the file.
            */
   #ifdef DEBUG
           if (prtrealloc)
                   printf("realloc: ino %ju, lbns %jd-%jd\n\told:",
                       (uintmax_t)ip->i_number,
                       (intmax_t)start_lbn, (intmax_t)end_lbn);
   #endif
           blkno = newblk;
           for (bap = &sbap[soff], i = 0; i < len; i++, blkno += fs->fs_frag) {
                   if (i == ssize) {
                           bap = ebap;
                           soff = -i;
                   }
   #ifdef INVARIANTS
                   if (!ffs_checkblk(ip,
                      dbtofsb(fs, buflist->bs_children[i]->b_blkno), fs->fs_bsize))
                           panic("ffs_reallocblks: unallocated block 2");
                   if (dbtofsb(fs, buflist->bs_children[i]->b_blkno) != *bap)
                           panic("ffs_reallocblks: alloc mismatch");
   #endif
   #ifdef DEBUG
                   if (prtrealloc)
                           printf(" %d,", *bap);
   #endif
                   if (DOINGSOFTDEP(vp)) {
                           if (sbap == &ip->i_din1->di_db[0] && i < ssize)
                                   softdep_setup_allocdirect(ip, start_lbn + i,
                                       blkno, *bap, fs->fs_bsize, fs->fs_bsize,
                                       buflist->bs_children[i]);
                           else
                                   softdep_setup_allocindir_page(ip, start_lbn + i,
                                       i < ssize ? sbp : ebp, soff + i, blkno,
                                       *bap, buflist->bs_children[i]);
                   }
                   *bap++ = blkno;
           }
           /*
            * Next we must write out the modified inode and indirect blocks.
            * For strict correctness, the writes should be synchronous since
            * the old block values may have been written to disk. In practise
            * they are almost never written, but if we are concerned about
            * strict correctness, the `doasyncfree' flag should be set to zero.
            *
            * The test on `doasyncfree' should be changed to test a flag
            * that shows whether the associated buffers and inodes have
            * been written. The flag should be set when the cluster is
            * started and cleared whenever the buffer or inode is flushed.
            * We can then check below to see if it is set, and do the
            * synchronous write only when it has been cleared.
            */
           if (sbap != &ip->i_din1->di_db[0]) {
                   if (doasyncfree)
                           bdwrite(sbp);
                   else
                           bwrite(sbp);
           } else {
                   ip->i_flag |= IN_CHANGE | IN_UPDATE;
                   if (!doasyncfree)
                           ffs_update(vp, 1);
           }
           if (ssize < len) {
                   if (doasyncfree)
                           bdwrite(ebp);
                   else
                           bwrite(ebp);
           }
           /*
            * Last, free the old blocks and assign the new blocks to the buffers.
            */
   #ifdef DEBUG
           if (prtrealloc)
                   printf("\n\tnew:");
   #endif
           for (blkno = newblk, i = 0; i < len; i++, blkno += fs->fs_frag) {
                   if (!DOINGSOFTDEP(vp))
                           ffs_blkfree(ump, fs, ip->i_devvp,
                               dbtofsb(fs, buflist->bs_children[i]->b_blkno),
                               fs->fs_bsize, ip->i_number, vp->v_type, NULL);
                   buflist->bs_children[i]->b_blkno = fsbtodb(fs, blkno);
   #ifdef INVARIANTS
                   if (!ffs_checkblk(ip,
                      dbtofsb(fs, buflist->bs_children[i]->b_blkno), fs->fs_bsize))
                           panic("ffs_reallocblks: unallocated block 3");
   #endif
   #ifdef DEBUG
                   if (prtrealloc)
                           printf(" %d,", blkno);
   #endif
           }
   #ifdef DEBUG
           if (prtrealloc) {
                   prtrealloc--;
                   printf("\n");
           }
   #endif
           return (0);
   
   fail:
           if (ssize < len)
                   brelse(ebp);
           if (sbap != &ip->i_din1->di_db[0])
                   brelse(sbp);
           return (ENOSPC);
   }
   
   static int
   ffs_reallocblks_ufs2(ap)
           struct vop_reallocblks_args /* {
                   struct vnode *a_vp;
                   struct cluster_save *a_buflist;
           } */ *ap;
   {
           struct fs *fs;
           struct inode *ip;
           struct vnode *vp;
           struct buf *sbp, *ebp;
           ufs2_daddr_t *bap, *sbap, *ebap = 0;
           struct cluster_save *buflist;
           struct ufsmount *ump;
           ufs_lbn_t start_lbn, end_lbn;
           ufs2_daddr_t soff, newblk, blkno, pref;
           struct indir start_ap[NIADDR + 1], end_ap[NIADDR + 1], *idp;
           int i, len, start_lvl, end_lvl, ssize;
   
           vp = ap->a_vp;
           ip = VTOI(vp);
           fs = ip->i_fs;
           ump = ip->i_ump;
           /*
            * If we are not tracking block clusters or if we have less than 2%
            * free blocks left, then do not attempt to cluster. Running with
            * less than 5% free block reserve is not recommended and those that
            * choose to do so do not expect to have good file layout.
            */
           if (fs->fs_contigsumsize <= 0 || freespace(fs, 2) < 0)
                   return (ENOSPC);
           buflist = ap->a_buflist;
           len = buflist->bs_nchildren;
           start_lbn = buflist->bs_children[0]->b_lblkno;
           end_lbn = start_lbn + len - 1;
   #ifdef INVARIANTS
           for (i = 0; i < len; i++)
                   if (!ffs_checkblk(ip,
                      dbtofsb(fs, buflist->bs_children[i]->b_blkno), fs->fs_bsize))
                           panic("ffs_reallocblks: unallocated block 1");
           for (i = 1; i < len; i++)
                   if (buflist->bs_children[i]->b_lblkno != start_lbn + i)
                           panic("ffs_reallocblks: non-logical cluster");
           blkno = buflist->bs_children[0]->b_blkno;
           ssize = fsbtodb(fs, fs->fs_frag);
           for (i = 1; i < len - 1; i++)
                   if (buflist->bs_children[i]->b_blkno != blkno + (i * ssize))
                           panic("ffs_reallocblks: non-physical cluster %d", i);
   #endif
           /*
            * If the cluster crosses the boundary for the first indirect
            * block, do not move anything in it. Indirect blocks are
            * usually initially laid out in a position between the data
            * blocks. Block reallocation would usually destroy locality by
            * moving the indirect block out of the way to make room for
            * data blocks if we didn't compensate here. We should also do
            * this for other indirect block boundaries, but it is only
            * important for the first one.
            */
           if (start_lbn < NDADDR && end_lbn >= NDADDR)
                   return (ENOSPC);
           /*
            * If the latest allocation is in a new cylinder group, assume that
            * the filesystem has decided to move and do not force it back to
            * the previous cylinder group.
            */
           if (dtog(fs, dbtofsb(fs, buflist->bs_children[0]->b_blkno)) !=
               dtog(fs, dbtofsb(fs, buflist->bs_children[len - 1]->b_blkno)))
                   return (ENOSPC);
           if (ufs_getlbns(vp, start_lbn, start_ap, &start_lvl) ||
               ufs_getlbns(vp, end_lbn, end_ap, &end_lvl))
                   return (ENOSPC);
           /*
            * Get the starting offset and block map for the first block.
            */
           if (start_lvl == 0) {
                   sbap = &ip->i_din2->di_db[0];
                   soff = start_lbn;
           } else {
                   idp = &start_ap[start_lvl - 1];
                   if (bread(vp, idp->in_lbn, (int)fs->fs_bsize, NOCRED, &sbp)) {
                           brelse(sbp);
                           return (ENOSPC);
                   }
                   sbap = (ufs2_daddr_t *)sbp->b_data;
                   soff = idp->in_off;
           }
           /*
            * If the block range spans two block maps, get the second map.
            */
           if (end_lvl == 0 || (idp = &end_ap[end_lvl - 1])->in_off + 1 >= len) {
                   ssize = len;
           } else {
   #ifdef INVARIANTS
                   if (start_lvl > 0 &&
                       start_ap[start_lvl - 1].in_lbn == idp->in_lbn)
                           panic("ffs_reallocblk: start == end");
   #endif
                   ssize = len - (idp->in_off + 1);
                   if (bread(vp, idp->in_lbn, (int)fs->fs_bsize, NOCRED, &ebp))
                           goto fail;
                   ebap = (ufs2_daddr_t *)ebp->b_data;
           }
           /*
            * Find the preferred location for the cluster.
            */
           UFS_LOCK(ump);
           pref = ffs_blkpref_ufs2(ip, start_lbn, soff, sbap);
           /*
            * Search the block map looking for an allocation of the desired size.
            */
           if ((newblk = ffs_hashalloc(ip, dtog(fs, pref), pref,
               len, len, ffs_clusteralloc)) == 0) {
                   UFS_UNLOCK(ump);
                   goto fail;
           }
           /*
            * We have found a new contiguous block.
            *
            * First we have to replace the old block pointers with the new
            * block pointers in the inode and indirect blocks associated
            * with the file.
            */
   #ifdef DEBUG
           if (prtrealloc)
                   printf("realloc: ino %d, lbns %jd-%jd\n\told:", ip->i_number,
                       (intmax_t)start_lbn, (intmax_t)end_lbn);
   #endif
           blkno = newblk;
           for (bap = &sbap[soff], i = 0; i < len; i++, blkno += fs->fs_frag) {
                   if (i == ssize) {
                           bap = ebap;
                           soff = -i;
                   }
   #ifdef INVARIANTS
                   if (!ffs_checkblk(ip,
                      dbtofsb(fs, buflist->bs_children[i]->b_blkno), fs->fs_bsize))
                           panic("ffs_reallocblks: unallocated block 2");
                   if (dbtofsb(fs, buflist->bs_children[i]->b_blkno) != *bap)
                           panic("ffs_reallocblks: alloc mismatch");
   #endif
   #ifdef DEBUG
                   if (prtrealloc)
                           printf(" %jd,", (intmax_t)*bap);
   #endif
                   if (DOINGSOFTDEP(vp)) {
                           if (sbap == &ip->i_din2->di_db[0] && i < ssize)
                                   softdep_setup_allocdirect(ip, start_lbn + i,
                                       blkno, *bap, fs->fs_bsize, fs->fs_bsize,
                                       buflist->bs_children[i]);
                           else
                                   softdep_setup_allocindir_page(ip, start_lbn + i,
                                       i < ssize ? sbp : ebp, soff + i, blkno,
                                       *bap, buflist->bs_children[i]);
                   }
                   *bap++ = blkno;
           }
           /*
            * Next we must write out the modified inode and indirect blocks.
            * For strict correctness, the writes should be synchronous since
            * the old block values may have been written to disk. In practise
            * they are almost never written, but if we are concerned about
            * strict correctness, the `doasyncfree' flag should be set to zero.
            *
            * The test on `doasyncfree' should be changed to test a flag
            * that shows whether the associated buffers and inodes have
            * been written. The flag should be set when the cluster is
            * started and cleared whenever the buffer or inode is flushed.
            * We can then check below to see if it is set, and do the
            * synchronous write only when it has been cleared.
            */
           if (sbap != &ip->i_din2->di_db[0]) {
                   if (doasyncfree)
                           bdwrite(sbp);
                   else
                           bwrite(sbp);
           } else {
                   ip->i_flag |= IN_CHANGE | IN_UPDATE;
                   if (!doasyncfree)
                           ffs_update(vp, 1);
           }
           if (ssize < len) {
                   if (doasyncfree)
                           bdwrite(ebp);
                   else
                           bwrite(ebp);
           }
           /*
            * Last, free the old blocks and assign the new blocks to the buffers.
            */
   #ifdef DEBUG
           if (prtrealloc)
                   printf("\n\tnew:");
   #endif
           for (blkno = newblk, i = 0; i < len; i++, blkno += fs->fs_frag) {
                   if (!DOINGSOFTDEP(vp))
                           ffs_blkfree(ump, fs, ip->i_devvp,
                               dbtofsb(fs, buflist->bs_children[i]->b_blkno),
                               fs->fs_bsize, ip->i_number, vp->v_type, NULL);
                   buflist->bs_children[i]->b_blkno = fsbtodb(fs, blkno);
   #ifdef INVARIANTS
                   if (!ffs_checkblk(ip,
                      dbtofsb(fs, buflist->bs_children[i]->b_blkno), fs->fs_bsize))
                           panic("ffs_reallocblks: unallocated block 3");
   #endif
   #ifdef DEBUG
                   if (prtrealloc)
                           printf(" %jd,", (intmax_t)blkno);
   #endif
           }
   #ifdef DEBUG
           if (prtrealloc) {
                   prtrealloc--;
                   printf("\n");
           }
   #endif
           return (0);
   
   fail:
           if (ssize < len)
                   brelse(ebp);
           if (sbap != &ip->i_din2->di_db[0])
                   brelse(sbp);
           return (ENOSPC);
   }
   
   /*
    * Allocate an inode in the filesystem.
    *
    * If allocating a directory, use ffs_dirpref to select the inode.
    * If allocating in a directory, the following hierarchy is followed:
    *   1) allocate the preferred inode.
    *   2) allocate an inode in the same cylinder group.
    *   3) quadradically rehash into other cylinder groups, until an
    *      available inode is located.
    * If no inode preference is given the following hierarchy is used
    * to allocate an inode:
    *   1) allocate an inode in cylinder group 0.
    *   2) quadradically rehash into other cylinder groups, until an
    *      available inode is located.
    */
   int
   ffs_valloc(pvp, mode, cred, vpp)
           struct vnode *pvp;
           int mode;
           struct ucred *cred;
           struct vnode **vpp;
   {
           struct inode *pip;
           struct fs *fs;
           struct inode *ip;
           struct timespec ts;
           struct ufsmount *ump;
           ino_t ino, ipref;
           u_int cg;
           int error, error1, reclaimed;
           static struct timeval lastfail;
           static int curfail;
   
           *vpp = NULL;
           pip = VTOI(pvp);
           fs = pip->i_fs;
           ump = pip->i_ump;
   
           UFS_LOCK(ump);
           reclaimed = 0;
   retry:
           if (fs->fs_cstotal.cs_nifree == 0)
                   goto noinodes;
   
           if ((mode & IFMT) == IFDIR)
                   ipref = ffs_dirpref(pip);
           else
                   ipref = pip->i_number;
           if (ipref >= fs->fs_ncg * fs->fs_ipg)
                   ipref = 0;
           cg = ino_to_cg(fs, ipref);
          /*
           * Track number of dirs created one after another
           * in a same cg without intervening by files.
           */
          if ((mode & IFMT) == IFDIR) {
                  if (fs->fs_contigdirs[cg] < 255)
                          fs->fs_contigdirs[cg]++;
          } else {
                  if (fs->fs_contigdirs[cg] > 0)
                          fs->fs_contigdirs[cg]--;
          }
          ino = (ino_t)ffs_hashalloc(pip, cg, ipref, mode, 0,
                                          (allocfcn_t *)ffs_nodealloccg);
          if (ino == 0)
                  goto noinodes;
          error = ffs_vget(pvp->v_mount, ino, LK_EXCLUSIVE, vpp);
          if (error) {
                  error1 = ffs_vgetf(pvp->v_mount, ino, LK_EXCLUSIVE, vpp,
                      FFSV_FORCEINSMQ);
                  ffs_vfree(pvp, ino, mode);
                  if (error1 == 0) {
                          ip = VTOI(*vpp);
                          if (ip->i_mode)
                                  goto dup_alloc;
                          ip->i_flag |= IN_MODIFIED;
                          vput(*vpp);
                  }
                  return (error);
          }
          ip = VTOI(*vpp);
          if (ip->i_mode) {
  dup_alloc:
                  printf("mode = 0%o, inum = %lu, fs = %s\n",
                      ip->i_mode, (u_long)ip->i_number, fs->fs_fsmnt);
                  panic("ffs_valloc: dup alloc");
          }
          if (DIP(ip, i_blocks) && (fs->fs_flags & FS_UNCLEAN) == 0) {  /* XXX */
                  printf("free inode %s/%lu had %ld blocks\n",
                      fs->fs_fsmnt, (u_long)ino, (long)DIP(ip, i_blocks));
                  DIP_SET(ip, i_blocks, 0);
          }
          ip->i_flags = 0;
          DIP_SET(ip, i_flags, 0);
          /*
           * Set up a new generation number for this inode.
           */
          if (ip->i_gen == 0 || ++ip->i_gen == 0)
                  ip->i_gen = arc4random() / 2 + 1;
          DIP_SET(ip, i_gen, ip->i_gen);
          if (fs->fs_magic == FS_UFS2_MAGIC) {
                  vfs_timestamp(&ts);
                  ip->i_din2->di_birthtime = ts.tv_sec;
                  ip->i_din2->di_birthnsec = ts.tv_nsec;
          }
          ufs_prepare_reclaim(*vpp);
          ip->i_flag = 0;
          (*vpp)->v_vflag = 0;
          (*vpp)->v_type = VNON;
          if (fs->fs_magic == FS_UFS2_MAGIC)
                  (*vpp)->v_op = &ffs_vnodeops2;
          else
                  (*vpp)->v_op = &ffs_vnodeops1;
          return (0);
  noinodes:
          if (reclaimed == 0) {
                  reclaimed = 1;
                  softdep_request_cleanup(fs, pvp, cred, FLUSH_INODES_WAIT);
                  goto retry;
          }
          UFS_UNLOCK(ump);
          if (ppsratecheck(&lastfail, &curfail, 1)) {
                  ffs_fserr(fs, pip->i_number, "out of inodes");
                  uprintf("\n%s: create/symlink failed, no inodes free\n",
                      fs->fs_fsmnt);
          }
          return (ENOSPC);
  }
  
  /*
   * Find a cylinder group to place a directory.
   *
   * The policy implemented by this algorithm is to allocate a
   * directory inode in the same cylinder group as its parent
   * directory, but also to reserve space for its files inodes
   * and data. Restrict the number of directories which may be
   * allocated one after another in the same cylinder group
   * without intervening allocation of files.
   *
   * If we allocate a first level directory then force allocation
   * in another cylinder group.
   */
  static ino_t
  ffs_dirpref(pip)
          struct inode *pip;
  {
          struct fs *fs;
          int cg, prefcg, dirsize, cgsize;
          u_int avgifree, avgbfree, avgndir, curdirsize;
          u_int minifree, minbfree, maxndir;
          u_int mincg, minndir;
          u_int maxcontigdirs;
  
          mtx_assert(UFS_MTX(pip->i_ump), MA_OWNED);
          fs = pip->i_fs;
  
          avgifree = fs->fs_cstotal.cs_nifree / fs->fs_ncg;
          avgbfree = fs->fs_cstotal.cs_nbfree / fs->fs_ncg;
          avgndir = fs->fs_cstotal.cs_ndir / fs->fs_ncg;
  
          /*
           * Force allocation in another cg if creating a first level dir.
           */
          ASSERT_VOP_LOCKED(ITOV(pip), "ffs_dirpref");
          if (ITOV(pip)->v_vflag & VV_ROOT) {
                  prefcg = arc4random() % fs->fs_ncg;
                  mincg = prefcg;
                  minndir = fs->fs_ipg;
                  for (cg = prefcg; cg < fs->fs_ncg; cg++)
                          if (fs->fs_cs(fs, cg).cs_ndir < minndir &&
                              fs->fs_cs(fs, cg).cs_nifree >= avgifree &&
                              fs->fs_cs(fs, cg).cs_nbfree >= avgbfree) {
                                  mincg = cg;
                                  minndir = fs->fs_cs(fs, cg).cs_ndir;
                          }
                  for (cg = 0; cg < prefcg; cg++)
                          if (fs->fs_cs(fs, cg).cs_ndir < minndir &&
                              fs->fs_cs(fs, cg).cs_nifree >= avgifree &&
                              fs->fs_cs(fs, cg).cs_nbfree >= avgbfree) {
                                  mincg = cg;
                                  minndir = fs->fs_cs(fs, cg).cs_ndir;
                          }
                  return ((ino_t)(fs->fs_ipg * mincg));
          }
  
          /*
           * Count various limits which used for
           * optimal allocation of a directory inode.
           */
          maxndir = min(avgndir + fs->fs_ipg / 16, fs->fs_ipg);
          minifree = avgifree - avgifree / 4;
          if (minifree < 1)
                  minifree = 1;
          minbfree = avgbfree - avgbfree / 4;
          if (minbfree < 1)
                  minbfree = 1;
          cgsize = fs->fs_fsize * fs->fs_fpg;
          dirsize = fs->fs_avgfilesize * fs->fs_avgfpdir;
          curdirsize = avgndir ? (cgsize - avgbfree * fs->fs_bsize) / avgndir : 0;
          if (dirsize < curdirsize)
                  dirsize = curdirsize;
          if (dirsize <= 0)
                  maxcontigdirs = 0;              /* dirsize overflowed */
          else
                  maxcontigdirs = min((avgbfree * fs->fs_bsize) / dirsize, 255);
          if (fs->fs_avgfpdir > 0)
                  maxcontigdirs = min(maxcontigdirs,
                                      fs->fs_ipg / fs->fs_avgfpdir);
          if (maxcontigdirs == 0)
                  maxcontigdirs = 1;
  
          /*
           * Limit number of dirs in one cg and reserve space for 
           * regular files, but only if we have no deficit in
           * inodes or space.
           *
           * We are trying to find a suitable cylinder group nearby
           * our preferred cylinder group to place a new directory.
           * We scan from our preferred cylinder group forward looking
           * for a cylinder group that meets our criterion. If we get
           * to the final cylinder group and do not find anything,
           * we start scanning backwards from our preferred cylinder
           * group. The ideal would be to alternate looking forward
           * and backward, but that is just too complex to code for
           * the gain it would get. The most likely place where the
           * backward scan would take effect is when we start near
           * the end of the filesystem and do not find anything from
           * where we are to the end. In that case, scanning backward
           * will likely find us a suitable cylinder group much closer
           * to our desired location than if we were to start scanning
           * forward from the beginning of the filesystem.
           */
          prefcg = ino_to_cg(fs, pip->i_number);
          for (cg = prefcg; cg < fs->fs_ncg; cg++)
                  if (fs->fs_cs(fs, cg).cs_ndir < maxndir &&
                      fs->fs_cs(fs, cg).cs_nifree >= minifree &&
                      fs->fs_cs(fs, cg).cs_nbfree >= minbfree) {
                          if (fs->fs_contigdirs[cg] < maxcontigdirs)
                                  return ((ino_t)(fs->fs_ipg * cg));
                  }
          for (cg = 0; cg < prefcg; cg++)
                  if (fs->fs_cs(fs, cg).cs_ndir < maxndir &&
                      fs->fs_cs(fs, cg).cs_nifree >= minifree &&
                      fs->fs_cs(fs, cg).cs_nbfree >= minbfree) {
                          if (fs->fs_contigdirs[cg] < maxcontigdirs)
                                  return ((ino_t)(fs->fs_ipg * cg));
                  }
          /*
           * This is a backstop when we have deficit in space.
           */
          for (cg = prefcg; cg < fs->fs_ncg; cg++)
                  if (fs->fs_cs(fs, cg).cs_nifree >= avgifree)
                          return ((ino_t)(fs->fs_ipg * cg));
          for (cg = 0; cg < prefcg; cg++)
                  if (fs->fs_cs(fs, cg).cs_nifree >= avgifree)
                          break;
          return ((ino_t)(fs->fs_ipg * cg));
  }
  
  /*
   * Select the desired position for the next block in a file.  The file is
   * logically divided into sections. The first section is composed of the
   * direct blocks and the next fs_maxbpg blocks. Each additional section
   * contains fs_maxbpg blocks.
   *
   * If no blocks have been allocated in the first section, the policy is to
   * request a block in the same cylinder group as the inode that describes
   * the file. The first indirect is allocated immediately following the last
   * direct block and the data blocks for the first indirect immediately
   * follow it.
   *
   * If no blocks have been allocated in any other section, the indirect 
   * block(s) are allocated in the same cylinder group as its inode in an
   * area reserved immediately following the inode blocks. The policy for
   * the data blocks is to place them in a cylinder group with a greater than
   * average number of free blocks. An appropriate cylinder group is found
   * by using a rotor that sweeps the cylinder groups. When a new group of
   * blocks is needed, the sweep begins in the cylinder group following the
   * cylinder group from which the previous allocation was made. The sweep
   * continues until a cylinder group with greater than the average number
   * of free blocks is found. If the allocation is for the first block in an
   * indirect block or the previous block is a hole, then the information on
   * the previous allocation is unavailable; here a best guess is made based
   * on the logical block number being allocated.
   *
   * If a section is already partially allocated, the policy is to
   * allocate blocks contiguously within the section if possible.
   */
  ufs2_daddr_t
  ffs_blkpref_ufs1(ip, lbn, indx, bap)
          struct inode *ip;
          ufs_lbn_t lbn;
          int indx;
          ufs1_daddr_t *bap;
  {
          struct fs *fs;
          u_int cg, inocg;
          u_int avgbfree, startcg;
          ufs2_daddr_t pref;
  
          KASSERT(indx <= 0 || bap != NULL, ("need non-NULL bap"));
          mtx_assert(UFS_MTX(ip->i_ump), MA_OWNED);
          fs = ip->i_fs;
          /*
           * Allocation of indirect blocks is indicated by passing negative
           * values in indx: -1 for single indirect, -2 for double indirect,
           * -3 for triple indirect. As noted below, we attempt to allocate
           * the first indirect inline with the file data. For all later
           * indirect blocks, the data is often allocated in other cylinder
           * groups. However to speed random file access and to speed up
           * fsck, the filesystem reserves the first fs_metaspace blocks
           * (typically half of fs_minfree) of the data area of each cylinder
           * group to hold these later indirect blocks.
           */
          inocg = ino_to_cg(fs, ip->i_number);
          if (indx < 0) {
                  /*
                   * Our preference for indirect blocks is the zone at the
                   * beginning of the inode's cylinder group data area that
                   * we try to reserve for indirect blocks.
                   */
                  pref = cgmeta(fs, inocg);
                  /*
                   * If we are allocating the first indirect block, try to
                   * place it immediately following the last direct block.
                   */
                  if (indx == -1 && lbn < NDADDR + NINDIR(fs) &&
                      ip->i_din1->di_db[NDADDR - 1] != 0)
                          pref = ip->i_din1->di_db[NDADDR - 1] + fs->fs_frag;
                  return (pref);
          }
          /*
           * If we are allocating the first data block in the first indirect
           * block and the indirect has been allocated in the data block area,
           * try to place it immediately following the indirect block.
           */
          if (lbn == NDADDR) {
                  pref = ip->i_din1->di_ib[0];
                  if (pref != 0 && pref >= cgdata(fs, inocg) &&
                      pref < cgbase(fs, inocg + 1))
                          return (pref + fs->fs_frag);
          }
          /*
           * If we are at the beginning of a file, or we have already allocated
           * the maximum number of blocks per cylinder group, or we do not
           * have a block allocated immediately preceeding us, then we need
           * to decide where to start allocating new blocks.
           */
          if (indx % fs->fs_maxbpg == 0 || bap[indx - 1] == 0) {
                  /*
                   * If we are allocating a directory data block, we want
                   * to place it in the metadata area.
                   */
                  if ((ip->i_mode & IFMT) == IFDIR)
                          return (cgmeta(fs, inocg));
                  /*
                   * Until we fill all the direct and all the first indirect's
                   * blocks, we try to allocate in the data area of the inode's
                   * cylinder group.
                   */
                  if (lbn < NDADDR + NINDIR(fs))
                          return (cgdata(fs, inocg));
                  /*
                   * Find a cylinder with greater than average number of
                   * unused data blocks.
                   */
                  if (indx == 0 || bap[indx - 1] == 0)
                          startcg = inocg + lbn / fs->fs_maxbpg;
                  else
                          startcg = dtog(fs, bap[indx - 1]) + 1;
                  startcg %= fs->fs_ncg;
                  avgbfree = fs->fs_cstotal.cs_nbfree / fs->fs_ncg;
                  for (cg = startcg; cg < fs->fs_ncg; cg++)
                          if (fs->fs_cs(fs, cg).cs_nbfree >= avgbfree) {
                                  fs->fs_cgrotor = cg;
                                  return (cgdata(fs, cg));
                          }
                  for (cg = 0; cg <= startcg; cg++)
                          if (fs->fs_cs(fs, cg).cs_nbfree >= avgbfree) {
                                  fs->fs_cgrotor = cg;
                                  return (cgdata(fs, cg));
                          }
                  return (0);
          }
          /*
           * Otherwise, we just always try to lay things out contiguously.
           */
          return (bap[indx - 1] + fs->fs_frag);
  }
  
  /*
   * Same as above, but for UFS2
   */
  ufs2_daddr_t
  ffs_blkpref_ufs2(ip, lbn, indx, bap)
          struct inode *ip;
          ufs_lbn_t lbn;
          int indx;
          ufs2_daddr_t *bap;
  {
          struct fs *fs;
          u_int cg, inocg;
          u_int avgbfree, startcg;
          ufs2_daddr_t pref;
  
          KASSERT(indx <= 0 || bap != NULL, ("need non-NULL bap"));
          mtx_assert(UFS_MTX(ip->i_ump), MA_OWNED);
          fs = ip->i_fs;
          /*
           * Allocation of indirect blocks is indicated by passing negative
           * values in indx: -1 for single indirect, -2 for double indirect,
           * -3 for triple indirect. As noted below, we attempt to allocate
           * the first indirect inline with the file data. For all later
           * indirect blocks, the data is often allocated in other cylinder
           * groups. However to speed random file access and to speed up
           * fsck, the filesystem reserves the first fs_metaspace blocks
           * (typically half of fs_minfree) of the data area of each cylinder
           * group to hold these later indirect blocks.
           */
          inocg = ino_to_cg(fs, ip->i_number);
          if (indx < 0) {
                  /*
                   * Our preference for indirect blocks is the zone at the
                   * beginning of the inode's cylinder group data area that
                   * we try to reserve for indirect blocks.
                   */
                  pref = cgmeta(fs, inocg);
                  /*
                   * If we are allocating the first indirect block, try to
                   * place it immediately following the last direct block.
                   */
                  if (indx == -1 && lbn < NDADDR + NINDIR(fs) &&
                      ip->i_din2->di_db[NDADDR - 1] != 0)
                          pref = ip->i_din2->di_db[NDADDR - 1] + fs->fs_frag;
                  return (pref);
          }
          /*
           * If we are allocating the first data block in the first indirect
           * block and the indirect has been allocated in the data block area,
           * try to place it immediately following the indirect block.
           */
          if (lbn == NDADDR) {
                  pref = ip->i_din2->di_ib[0];
                  if (pref != 0 && pref >= cgdata(fs, inocg) &&
                      pref < cgbase(fs, inocg + 1))
                          return (pref + fs->fs_frag);
          }
          /*
           * If we are at the beginning of a file, or we have already allocated
           * the maximum number of blocks per cylinder group, or we do not
           * have a block allocated immediately preceeding us, then we need
           * to decide where to start allocating new blocks.
           */
          if (indx % fs->fs_maxbpg == 0 || bap[indx - 1] == 0) {
                  /*
                   * If we are allocating a directory data block, we want
                   * to place it in the metadata area.
                   */
                  if ((ip->i_mode & IFMT) == IFDIR)
                          return (cgmeta(fs, inocg));
                  /*
                   * Until we fill all the direct and all the first indirect's
                   * blocks, we try to allocate in the data area of the inode's
                   * cylinder group.
                   */
                  if (lbn < NDADDR + NINDIR(fs))
                          return (cgdata(fs, inocg));
                  /*
                   * Find a cylinder with greater than average number of
                   * unused data blocks.
                   */
                  if (indx == 0 || bap[indx - 1] == 0)
                          startcg = inocg + lbn / fs->fs_maxbpg;
                  else
                          startcg = dtog(fs, bap[indx - 1]) + 1;
                  startcg %= fs->fs_ncg;
                  avgbfree = fs->fs_cstotal.cs_nbfree / fs->fs_ncg;
                  for (cg = startcg; cg < fs->fs_ncg; cg++)
                          if (fs->fs_cs(fs, cg).cs_nbfree >= avgbfree) {
                                  fs->fs_cgrotor = cg;
                                  return (cgdata(fs, cg));
                          }
                  for (cg = 0; cg <= startcg; cg++)
                          if (fs->fs_cs(fs, cg).cs_nbfree >= avgbfree) {
                                  fs->fs_cgrotor = cg;
                                  return (cgdata(fs, cg));
                          }
                  return (0);
          }
          /*
           * Otherwise, we just always try to lay things out contiguously.
           */
          return (bap[indx - 1] + fs->fs_frag);
  }
  
  /*
   * Implement the cylinder overflow algorithm.
   *
   * The policy implemented by this algorithm is:
   *   1) allocate the block in its requested cylinder group.
   *   2) quadradically rehash on the cylinder group number.
   *   3) brute force search for a free block.
   *
   * Must be called with the UFS lock held.  Will release the lock on success
   * and return with it held on failure.
   */
  /*VARARGS5*/
  static ufs2_daddr_t
  ffs_hashalloc(ip, cg, pref, size, rsize, allocator)
          struct inode *ip;
          u_int cg;
          ufs2_daddr_t pref;
          int size;       /* Search size for data blocks, mode for inodes */
          int rsize;      /* Real allocated size. */
          allocfcn_t *allocator;
  {
          struct fs *fs;
          ufs2_daddr_t result;
          u_int i, icg = cg;
  
          mtx_assert(UFS_MTX(ip->i_ump), MA_OWNED);
  #ifdef INVARIANTS
          if (ITOV(ip)->v_mount->mnt_kern_flag & MNTK_SUSPENDED)
                  panic("ffs_hashalloc: allocation on suspended filesystem");
  #endif
          fs = ip->i_fs;
          /*
           * 1: preferred cylinder group
           */
          result = (*allocator)(ip, cg, pref, size, rsize);
          if (result)
                  return (result);
          /*
           * 2: quadratic rehash
           */
          for (i = 1; i < fs->fs_ncg; i *= 2) {
                  cg += i;
                  if (cg >= fs->fs_ncg)
                          cg -= fs->fs_ncg;
                  result = (*allocator)(ip, cg, 0, size, rsize);
                  if (result)
                          return (result);
          }
          /*
           * 3: brute force search
           * Note that we start at i == 2, since 0 was checked initially,
           * and 1 is always checked in the quadratic rehash.
           */
          cg = (icg + 2) % fs->fs_ncg;
          for (i = 2; i < fs->fs_ncg; i++) {
                  result = (*allocator)(ip, cg, 0, size, rsize);
                  if (result)
                          return (result);
                  cg++;
                  if (cg == fs->fs_ncg)
                          cg = 0;
          }
          return (0);
  }
  
  /*
   * Determine whether a fragment can be extended.
   *
   * Check to see if the necessary fragments are available, and
   * if they are, allocate them.
   */
  static ufs2_daddr_t
  ffs_fragextend(ip, cg, bprev, osize, nsize)
          struct inode *ip;
          u_int cg;
          ufs2_daddr_t bprev;
          int osize, nsize;
  {
          struct fs *fs;
          struct cg *cgp;
          struct buf *bp;
          struct ufsmount *ump;
          int nffree;
          long bno;
          int frags, bbase;
          int i, error;
          u_int8_t *blksfree;
  
          ump = ip->i_ump;
          fs = ip->i_fs;
          if (fs->fs_cs(fs, cg).cs_nffree < numfrags(fs, nsize - osize))
                  return (0);
          frags = numfrags(fs, nsize);
          bbase = fragnum(fs, bprev);
          if (bbase > fragnum(fs, (bprev + frags - 1))) {
                  /* cannot extend across a block boundary */
                  return (0);
          }
          UFS_UNLOCK(ump);
          error = bread(ip->i_devvp, fsbtodb(fs, cgtod(fs, cg)),
                  (int)fs->fs_cgsize, NOCRED, &bp);
          if (error)
                  goto fail;
          cgp = (struct cg *)bp->b_data;
          if (!cg_chkmagic(cgp))
                  goto fail;
          bp->b_xflags |= BX_BKGRDWRITE;
          cgp->cg_old_time = cgp->cg_time = time_second;
          bno = dtogd(fs, bprev);
          blksfree = cg_blksfree(cgp);
          for (i = numfrags(fs, osize); i < frags; i++)
                  if (isclr(blksfree, bno + i))
                          goto fail;
          /*
           * the current fragment can be extended
           * deduct the count on fragment being extended into
           * increase the count on the remaining fragment (if any)
           * allocate the extended piece
           */
          for (i = frags; i < fs->fs_frag - bbase; i++)
                  if (isclr(blksfree, bno + i))
                          break;
          cgp->cg_frsum[i - numfrags(fs, osize)]--;
          if (i != frags)
                  cgp->cg_frsum[i - frags]++;
          for (i = numfrags(fs, osize), nffree = 0; i < frags; i++) {
                  clrbit(blksfree, bno + i);
                  cgp->cg_cs.cs_nffree--;
                  nffree++;
          }
          UFS_LOCK(ump);
          fs->fs_cstotal.cs_nffree -= nffree;
          fs->fs_cs(fs, cg).cs_nffree -= nffree;
          fs->fs_fmod = 1;
          ACTIVECLEAR(fs, cg);
          UFS_UNLOCK(ump);
          if (DOINGSOFTDEP(ITOV(ip)))
                  softdep_setup_blkmapdep(bp, UFSTOVFS(ump), bprev,
                      frags, numfrags(fs, osize));
          bdwrite(bp);
          return (bprev);
  
  fail:
          brelse(bp);
          UFS_LOCK(ump);
          return (0);
  
  }
  
  /*
   * Determine whether a block can be allocated.
   *
   * Check to see if a block of the appropriate size is available,
   * and if it is, allocate it.
   */
  static ufs2_daddr_t
  ffs_alloccg(ip, cg, bpref, size, rsize)
          struct inode *ip;
          u_int cg;
          ufs2_daddr_t bpref;
          int size;
          int rsize;
  {
          struct fs *fs;
          struct cg *cgp;
          struct buf *bp;
          struct ufsmount *ump;
          ufs1_daddr_t bno;
          ufs2_daddr_t blkno;
          int i, allocsiz, error, frags;
          u_int8_t *blksfree;
  
          ump = ip->i_ump;
          fs = ip->i_fs;
          if (fs->fs_cs(fs, cg).cs_nbfree == 0 && size == fs->fs_bsize)
                  return (0);
          UFS_UNLOCK(ump);
          error = bread(ip->i_devvp, fsbtodb(fs, cgtod(fs, cg)),
                  (int)fs->fs_cgsize, NOCRED, &bp);
          if (error)
                  goto fail;
          cgp = (struct cg *)bp->b_data;
          if (!cg_chkmagic(cgp) ||
              (cgp->cg_cs.cs_nbfree == 0 && size == fs->fs_bsize))
                  goto fail;
          bp->b_xflags |= BX_BKGRDWRITE;
          cgp->cg_old_time = cgp->cg_time = time_second;
          if (size == fs->fs_bsize) {
                  UFS_LOCK(ump);
                  blkno = ffs_alloccgblk(ip, bp, bpref, rsize);
                  ACTIVECLEAR(fs, cg);
                  UFS_UNLOCK(ump);
                  bdwrite(bp);
                  return (blkno);
          }
          /*
           * check to see if any fragments are already available
           * allocsiz is the size which will be allocated, hacking
           * it down to a smaller size if necessary
           */
          blksfree = cg_blksfree(cgp);
          frags = numfrags(fs, size);
          for (allocsiz = frags; allocsiz < fs->fs_frag; allocsiz++)
                  if (cgp->cg_frsum[allocsiz] != 0)
                          break;
          if (allocsiz == fs->fs_frag) {
                  /*
                   * no fragments were available, so a block will be
                   * allocated, and hacked up
                   */
                  if (cgp->cg_cs.cs_nbfree == 0)
                          goto fail;
                  UFS_LOCK(ump);
                  blkno = ffs_alloccgblk(ip, bp, bpref, rsize);
                  ACTIVECLEAR(fs, cg);
                  UFS_UNLOCK(ump);
                  bdwrite(bp);
                  return (blkno);
          }
          KASSERT(size == rsize,
              ("ffs_alloccg: size(%d) != rsize(%d)", size, rsize));
          bno = ffs_mapsearch(fs, cgp, bpref, allocsiz);
          if (bno < 0)
                  goto fail;
          for (i = 0; i < frags; i++)
                  clrbit(blksfree, bno + i);
          cgp->cg_cs.cs_nffree -= frags;
          cgp->cg_frsum[allocsiz]--;
          if (frags != allocsiz)
                  cgp->cg_frsum[allocsiz - frags]++;
          UFS_LOCK(ump);
          fs->fs_cstotal.cs_nffree -= frags;
          fs->fs_cs(fs, cg).cs_nffree -= frags;
          fs->fs_fmod = 1;
          blkno = cgbase(fs, cg) + bno;
          ACTIVECLEAR(fs, cg);
          UFS_UNLOCK(ump);
          if (DOINGSOFTDEP(ITOV(ip)))
                  softdep_setup_blkmapdep(bp, UFSTOVFS(ump), blkno, frags, 0);
          bdwrite(bp);
          return (blkno);
  
  fail:
          brelse(bp);
          UFS_LOCK(ump);
          return (0);
  }
  
  /*
   * Allocate a block in a cylinder group.
   *
   * This algorithm implements the following policy:
   *   1) allocate the requested block.
   *   2) allocate a rotationally optimal block in the same cylinder.
   *   3) allocate the next available block on the block rotor for the
   *      specified cylinder group.
   * Note that this routine only allocates fs_bsize blocks; these
   * blocks may be fragmented by the routine that allocates them.
   */
  static ufs2_daddr_t
  ffs_alloccgblk(ip, bp, bpref, size)
          struct inode *ip;
          struct buf *bp;
          ufs2_daddr_t bpref;
          int size;
  {
          struct fs *fs;
          struct cg *cgp;
          struct ufsmount *ump;
          ufs1_daddr_t bno;
          ufs2_daddr_t blkno;
          u_int8_t *blksfree;
          int i, cgbpref;
  
          fs = ip->i_fs;
          ump = ip->i_ump;
          mtx_assert(UFS_MTX(ump), MA_OWNED);
          cgp = (struct cg *)bp->b_data;
          blksfree = cg_blksfree(cgp);
          if (bpref == 0) {
                  bpref = cgbase(fs, cgp->cg_cgx) + cgp->cg_rotor + fs->fs_frag;
          } else if ((cgbpref = dtog(fs, bpref)) != cgp->cg_cgx) {
                  /* map bpref to correct zone in this cg */
                  if (bpref < cgdata(fs, cgbpref))
                          bpref = cgmeta(fs, cgp->cg_cgx);
                  else
                          bpref = cgdata(fs, cgp->cg_cgx);
          }
          /*
           * if the requested block is available, use it
           */
          bno = dtogd(fs, blknum(fs, bpref));
          if (ffs_isblock(fs, blksfree, fragstoblks(fs, bno)))
                  goto gotit;
          /*
           * Take the next available block in this cylinder group.
           */
          bno = ffs_mapsearch(fs, cgp, bpref, (int)fs->fs_frag);
          if (bno < 0)
                  return (0);
          /* Update cg_rotor only if allocated from the data zone */
          if (bno >= dtogd(fs, cgdata(fs, cgp->cg_cgx)))
                  cgp->cg_rotor = bno;
  gotit:
          blkno = fragstoblks(fs, bno);
          ffs_clrblock(fs, blksfree, (long)blkno);
          ffs_clusteracct(fs, cgp, blkno, -1);
          cgp->cg_cs.cs_nbfree--;
          fs->fs_cstotal.cs_nbfree--;
          fs->fs_cs(fs, cgp->cg_cgx).cs_nbfree--;
          fs->fs_fmod = 1;
          blkno = cgbase(fs, cgp->cg_cgx) + bno;
          /*
           * If the caller didn't want the whole block free the frags here.
           */
          size = numfrags(fs, size);
          if (size != fs->fs_frag) {
                  bno = dtogd(fs, blkno);
                  for (i = size; i < fs->fs_frag; i++)
                          setbit(blksfree, bno + i);
                  i = fs->fs_frag - size;
                  cgp->cg_cs.cs_nffree += i;
                  fs->fs_cstotal.cs_nffree += i;
                  fs->fs_cs(fs, cgp->cg_cgx).cs_nffree += i;
                  fs->fs_fmod = 1;
                  cgp->cg_frsum[i]++;
          }
          /* XXX Fixme. */
          UFS_UNLOCK(ump);
          if (DOINGSOFTDEP(ITOV(ip)))
                  softdep_setup_blkmapdep(bp, UFSTOVFS(ump), blkno,
                      size, 0);
          UFS_LOCK(ump);
          return (blkno);
  }
  
  /*
   * Determine whether a cluster can be allocated.
   *
   * We do not currently check for optimal rotational layout if there
   * are multiple choices in the same cylinder group. Instead we just
   * take the first one that we find following bpref.
   */
  static ufs2_daddr_t
  ffs_clusteralloc(ip, cg, bpref, len, unused)
          struct inode *ip;
          u_int cg;
          ufs2_daddr_t bpref;
          int len;
          int unused;
  {
          struct fs *fs;
          struct cg *cgp;
          struct buf *bp;
          struct ufsmount *ump;
          int i, run, bit, map, got;
          ufs2_daddr_t bno;
          u_char *mapp;
          int32_t *lp;
          u_int8_t *blksfree;
  
          fs = ip->i_fs;
          ump = ip->i_ump;
          if (fs->fs_maxcluster[cg] < len)
                  return (0);
          UFS_UNLOCK(ump);
          if (bread(ip->i_devvp, fsbtodb(fs, cgtod(fs, cg)), (int)fs->fs_cgsize,
              NOCRED, &bp))
                  goto fail_lock;
          cgp = (struct cg *)bp->b_data;
          if (!cg_chkmagic(cgp))
                  goto fail_lock;
          bp->b_xflags |= BX_BKGRDWRITE;
          /*
           * Check to see if a cluster of the needed size (or bigger) is
           * available in this cylinder group.
           */
          lp = &cg_clustersum(cgp)[len];
          for (i = len; i <= fs->fs_contigsumsize; i++)
                  if (*lp++ > 0)
                          break;
          if (i > fs->fs_contigsumsize) {
                  /*
                   * This is the first time looking for a cluster in this
                   * cylinder group. Update the cluster summary information
                   * to reflect the true maximum sized cluster so that
                   * future cluster allocation requests can avoid reading
                   * the cylinder group map only to find no clusters.
                   */
                  lp = &cg_clustersum(cgp)[len - 1];
                  for (i = len - 1; i > 0; i--)
                          if (*lp-- > 0)
                                  break;
                  UFS_LOCK(ump);
                  fs->fs_maxcluster[cg] = i;
                  goto fail;
          }
          /*
           * Search the cluster map to find a big enough cluster.
           * We take the first one that we find, even if it is larger
           * than we need as we prefer to get one close to the previous
           * block allocation. We do not search before the current
           * preference point as we do not want to allocate a block
           * that is allocated before the previous one (as we will
           * then have to wait for another pass of the elevator
           * algorithm before it will be read). We prefer to fail and
           * be recalled to try an allocation in the next cylinder group.
           */
          if (dtog(fs, bpref) != cg)
                  bpref = cgdata(fs, cg);
          else
                  bpref = blknum(fs, bpref);
          bpref = fragstoblks(fs, dtogd(fs, bpref));
          mapp = &cg_clustersfree(cgp)[bpref / NBBY];
          map = *mapp++;
          bit = 1 << (bpref % NBBY);
          for (run = 0, got = bpref; got < cgp->cg_nclusterblks; got++) {
                  if ((map & bit) == 0) {
                          run = 0;
                  } else {
                          run++;
                          if (run == len)
                                  break;
                  }
                  if ((got & (NBBY - 1)) != (NBBY - 1)) {
                          bit <<= 1;
                  } else {
                          map = *mapp++;
                          bit = 1;
                  }
          }
          if (got >= cgp->cg_nclusterblks)
                  goto fail_lock;
          /*
           * Allocate the cluster that we have found.
           */
          blksfree = cg_blksfree(cgp);
          for (i = 1; i <= len; i++)
                  if (!ffs_isblock(fs, blksfree, got - run + i))
                          panic("ffs_clusteralloc: map mismatch");
          bno = cgbase(fs, cg) + blkstofrags(fs, got - run + 1);
          if (dtog(fs, bno) != cg)
                  panic("ffs_clusteralloc: allocated out of group");
          len = blkstofrags(fs, len);
          UFS_LOCK(ump);
          for (i = 0; i < len; i += fs->fs_frag)
                  if (ffs_alloccgblk(ip, bp, bno + i, fs->fs_bsize) != bno + i)
                          panic("ffs_clusteralloc: lost block");
          ACTIVECLEAR(fs, cg);
          UFS_UNLOCK(ump);
          bdwrite(bp);
          return (bno);
  
  fail_lock:
          UFS_LOCK(ump);
  fail:
          brelse(bp);
          return (0);
  }
  
  static inline struct buf *
  getinobuf(struct inode *ip, u_int cg, u_int32_t cginoblk, int gbflags)
  {
          struct fs *fs;
  
          fs = ip->i_fs;
          return (getblk(ip->i_devvp, fsbtodb(fs, ino_to_fsba(fs,
              cg * fs->fs_ipg + cginoblk)), (int)fs->fs_bsize, 0, 0,
              gbflags));
  }
  
  /*
   * Determine whether an inode can be allocated.
   *
   * Check to see if an inode is available, and if it is,
   * allocate it using the following policy:
   *   1) allocate the requested inode.
   *   2) allocate the next available inode after the requested
   *      inode in the specified cylinder group.
   */
  static ufs2_daddr_t
  ffs_nodealloccg(ip, cg, ipref, mode, unused)
          struct inode *ip;
          u_int cg;
          ufs2_daddr_t ipref;
          int mode;
          int unused;
  {
          struct fs *fs;
          struct cg *cgp;
          struct buf *bp, *ibp;
          struct ufsmount *ump;
          u_int8_t *inosused, *loc;
          struct ufs2_dinode *dp2;
          int error, start, len, i;
          u_int32_t old_initediblk;
  
          fs = ip->i_fs;
          ump = ip->i_ump;
  check_nifree:
          if (fs->fs_cs(fs, cg).cs_nifree == 0)
                  return (0);
          UFS_UNLOCK(ump);
          error = bread(ip->i_devvp, fsbtodb(fs, cgtod(fs, cg)),
                  (int)fs->fs_cgsize, NOCRED, &bp);
          if (error) {
                  brelse(bp);
                  UFS_LOCK(ump);
                  return (0);
          }
          cgp = (struct cg *)bp->b_data;
  restart:
          if (!cg_chkmagic(cgp) || cgp->cg_cs.cs_nifree == 0) {
                  brelse(bp);
                  UFS_LOCK(ump);
                  return (0);
          }
          bp->b_xflags |= BX_BKGRDWRITE;
          inosused = cg_inosused(cgp);
          if (ipref) {
                  ipref %= fs->fs_ipg;
                  if (isclr(inosused, ipref))
                          goto gotit;
          }
          start = cgp->cg_irotor / NBBY;
          len = howmany(fs->fs_ipg - cgp->cg_irotor, NBBY);
          loc = memcchr(&inosused[start], 0xff, len);
          if (loc == NULL) {
                  len = start + 1;
                  start = 0;
                  loc = memcchr(&inosused[start], 0xff, len);
                  if (loc == NULL) {
                          printf("cg = %d, irotor = %ld, fs = %s\n",
                              cg, (long)cgp->cg_irotor, fs->fs_fsmnt);
                          panic("ffs_nodealloccg: map corrupted");
                          /* NOTREACHED */
                  }
          }
          ipref = (loc - inosused) * NBBY + ffs(~*loc) - 1;
  gotit:
          /*
           * Check to see if we need to initialize more inodes.
           */
          if (fs->fs_magic == FS_UFS2_MAGIC &&
              ipref + INOPB(fs) > cgp->cg_initediblk &&
              cgp->cg_initediblk < cgp->cg_niblk) {
                  old_initediblk = cgp->cg_initediblk;
  
                  /*
                   * Free the cylinder group lock before writing the
                   * initialized inode block.  Entering the
                   * babarrierwrite() with the cylinder group lock
                   * causes lock order violation between the lock and
                   * snaplk.
                   *
                   * Another thread can decide to initialize the same
                   * inode block, but whichever thread first gets the
                   * cylinder group lock after writing the newly
                   * allocated inode block will update it and the other
                   * will realize that it has lost and leave the
                   * cylinder group unchanged.
                   */
                  ibp = getinobuf(ip, cg, old_initediblk, GB_LOCK_NOWAIT);
                  brelse(bp);
                  if (ibp == NULL) {
                          /*
                           * The inode block buffer is already owned by
                           * another thread, which must initialize it.
                           * Wait on the buffer to allow another thread
                           * to finish the updates, with dropped cg
                           * buffer lock, then retry.
                           */
                          ibp = getinobuf(ip, cg, old_initediblk, 0);
                          brelse(ibp);
                          UFS_LOCK(ump);
                          goto check_nifree;
                  }
                  bzero(ibp->b_data, (int)fs->fs_bsize);
                  dp2 = (struct ufs2_dinode *)(ibp->b_data);
                  for (i = 0; i < INOPB(fs); i++) {
                          dp2->di_gen = arc4random() / 2 + 1;
                          dp2++;
                  }
                  /*
                   * Rather than adding a soft updates dependency to ensure
                   * that the new inode block is written before it is claimed
                   * by the cylinder group map, we just do a barrier write
                   * here. The barrier write will ensure that the inode block
                   * gets written before the updated cylinder group map can be
                   * written. The barrier write should only slow down bulk
                   * loading of newly created filesystems.
                   */
                  babarrierwrite(ibp);
  
                  /*
                   * After the inode block is written, try to update the
                   * cg initediblk pointer.  If another thread beat us
                   * to it, then leave it unchanged as the other thread
                   * has already set it correctly.
                   */
                  error = bread(ip->i_devvp, fsbtodb(fs, cgtod(fs, cg)),
                      (int)fs->fs_cgsize, NOCRED, &bp);
                  UFS_LOCK(ump);
                  ACTIVECLEAR(fs, cg);
                  UFS_UNLOCK(ump);
                  if (error != 0) {
                          brelse(bp);
                          return (error);
                  }
                  cgp = (struct cg *)bp->b_data;
                  if (cgp->cg_initediblk == old_initediblk)
                          cgp->cg_initediblk += INOPB(fs);
                  goto restart;
          }
          cgp->cg_old_time = cgp->cg_time = time_second;
          cgp->cg_irotor = ipref;
          UFS_LOCK(ump);
          ACTIVECLEAR(fs, cg);
          setbit(inosused, ipref);
          cgp->cg_cs.cs_nifree--;
          fs->fs_cstotal.cs_nifree--;
          fs->fs_cs(fs, cg).cs_nifree--;
          fs->fs_fmod = 1;
          if ((mode & IFMT) == IFDIR) {
                  cgp->cg_cs.cs_ndir++;
                  fs->fs_cstotal.cs_ndir++;
                  fs->fs_cs(fs, cg).cs_ndir++;
          }
          UFS_UNLOCK(ump);
          if (DOINGSOFTDEP(ITOV(ip)))
                  softdep_setup_inomapdep(bp, ip, cg * fs->fs_ipg + ipref, mode);
          bdwrite(bp);
          return ((ino_t)(cg * fs->fs_ipg + ipref));
  }
  
  /*
   * Free a block or fragment.
   *
   * The specified block or fragment is placed back in the
   * free map. If a fragment is deallocated, a possible
   * block reassembly is checked.
   */
  static void
  ffs_blkfree_cg(ump, fs, devvp, bno, size, inum, dephd)
          struct ufsmount *ump;
          struct fs *fs;
          struct vnode *devvp;
          ufs2_daddr_t bno;
          long size;
          ino_t inum;
          struct workhead *dephd;
  {
          struct mount *mp;
          struct cg *cgp;
          struct buf *bp;
          ufs1_daddr_t fragno, cgbno;
          ufs2_daddr_t cgblkno;
          int i, blk, frags, bbase;
          u_int cg;
          u_int8_t *blksfree;
          struct cdev *dev;
  
          cg = dtog(fs, bno);
          if (devvp->v_type == VREG) {
                  /* devvp is a snapshot */
                  dev = VTOI(devvp)->i_devvp->v_rdev;
                  cgblkno = fragstoblks(fs, cgtod(fs, cg));
          } else {
                  /* devvp is a normal disk device */
                  dev = devvp->v_rdev;
                  cgblkno = fsbtodb(fs, cgtod(fs, cg));
                  ASSERT_VOP_LOCKED(devvp, "ffs_blkfree_cg");
          }
  #ifdef INVARIANTS
          if ((u_int)size > fs->fs_bsize || fragoff(fs, size) != 0 ||
              fragnum(fs, bno) + numfrags(fs, size) > fs->fs_frag) {
                  printf("dev=%s, bno = %jd, bsize = %ld, size = %ld, fs = %s\n",
                      devtoname(dev), (intmax_t)bno, (long)fs->fs_bsize,
                      size, fs->fs_fsmnt);
                  panic("ffs_blkfree_cg: bad size");
          }
  #endif
          if ((u_int)bno >= fs->fs_size) {
                  printf("bad block %jd, ino %lu\n", (intmax_t)bno,
                      (u_long)inum);
                  ffs_fserr(fs, inum, "bad block");
                  return;
          }
          if (bread(devvp, cgblkno, (int)fs->fs_cgsize, NOCRED, &bp)) {
                  brelse(bp);
                  return;
          }
          cgp = (struct cg *)bp->b_data;
          if (!cg_chkmagic(cgp)) {
                  brelse(bp);
                  return;
          }
          bp->b_xflags |= BX_BKGRDWRITE;
          cgp->cg_old_time = cgp->cg_time = time_second;
          cgbno = dtogd(fs, bno);
          blksfree = cg_blksfree(cgp);
          UFS_LOCK(ump);
          if (size == fs->fs_bsize) {
                  fragno = fragstoblks(fs, cgbno);
                  if (!ffs_isfreeblock(fs, blksfree, fragno)) {
                          if (devvp->v_type == VREG) {
                                  UFS_UNLOCK(ump);
                                  /* devvp is a snapshot */
                                  brelse(bp);
                                  return;
                          }
                          printf("dev = %s, block = %jd, fs = %s\n",
                              devtoname(dev), (intmax_t)bno, fs->fs_fsmnt);
                          panic("ffs_blkfree_cg: freeing free block");
                  }
                  ffs_setblock(fs, blksfree, fragno);
                  ffs_clusteracct(fs, cgp, fragno, 1);
                  cgp->cg_cs.cs_nbfree++;
                  fs->fs_cstotal.cs_nbfree++;
                  fs->fs_cs(fs, cg).cs_nbfree++;
          } else {
                  bbase = cgbno - fragnum(fs, cgbno);
                  /*
                   * decrement the counts associated with the old frags
                   */
                  blk = blkmap(fs, blksfree, bbase);
                  ffs_fragacct(fs, blk, cgp->cg_frsum, -1);
                  /*
                   * deallocate the fragment
                   */
                  frags = numfrags(fs, size);
                  for (i = 0; i < frags; i++) {
                          if (isset(blksfree, cgbno + i)) {
                                  printf("dev = %s, block = %jd, fs = %s\n",
                                      devtoname(dev), (intmax_t)(bno + i),
                                      fs->fs_fsmnt);
                                  panic("ffs_blkfree_cg: freeing free frag");
                          }
                          setbit(blksfree, cgbno + i);
                  }
                  cgp->cg_cs.cs_nffree += i;
                  fs->fs_cstotal.cs_nffree += i;
                  fs->fs_cs(fs, cg).cs_nffree += i;
                  /*
                   * add back in counts associated with the new frags
                   */
                  blk = blkmap(fs, blksfree, bbase);
                  ffs_fragacct(fs, blk, cgp->cg_frsum, 1);
                  /*
                   * if a complete block has been reassembled, account for it
                   */
                  fragno = fragstoblks(fs, bbase);
                  if (ffs_isblock(fs, blksfree, fragno)) {
                          cgp->cg_cs.cs_nffree -= fs->fs_frag;
                          fs->fs_cstotal.cs_nffree -= fs->fs_frag;
                          fs->fs_cs(fs, cg).cs_nffree -= fs->fs_frag;
                          ffs_clusteracct(fs, cgp, fragno, 1);
                          cgp->cg_cs.cs_nbfree++;
                          fs->fs_cstotal.cs_nbfree++;
                          fs->fs_cs(fs, cg).cs_nbfree++;
                  }
          }
          fs->fs_fmod = 1;
          ACTIVECLEAR(fs, cg);
          UFS_UNLOCK(ump);
          mp = UFSTOVFS(ump);
          if (MOUNTEDSOFTDEP(mp) && devvp->v_type != VREG)
                  softdep_setup_blkfree(UFSTOVFS(ump), bp, bno,
                      numfrags(fs, size), dephd);
          bdwrite(bp);
  }
  
  TASKQUEUE_DEFINE_THREAD(ffs_trim);
  
  struct ffs_blkfree_trim_params {
          struct task task;
          struct ufsmount *ump;
          struct vnode *devvp;
          ufs2_daddr_t bno;
          long size;
          ino_t inum;
          struct workhead *pdephd;
          struct workhead dephd;
  };
  
  static void
  ffs_blkfree_trim_task(ctx, pending)
          void *ctx;
          int pending;
  {
          struct ffs_blkfree_trim_params *tp;
  
          tp = ctx;
          ffs_blkfree_cg(tp->ump, tp->ump->um_fs, tp->devvp, tp->bno, tp->size,
              tp->inum, tp->pdephd);
          vn_finished_secondary_write(UFSTOVFS(tp->ump));
          free(tp, M_TEMP);
  }
  
  static void
  ffs_blkfree_trim_completed(bip)
          struct bio *bip;
  {
          struct ffs_blkfree_trim_params *tp;
  
          tp = bip->bio_caller2;
          g_destroy_bio(bip);
          TASK_INIT(&tp->task, 0, ffs_blkfree_trim_task, tp);
          taskqueue_enqueue(taskqueue_ffs_trim, &tp->task);
  }
  
  void
  ffs_blkfree(ump, fs, devvp, bno, size, inum, vtype, dephd)
          struct ufsmount *ump;
          struct fs *fs;
          struct vnode *devvp;
          ufs2_daddr_t bno;
          long size;
          ino_t inum;
          enum vtype vtype;
          struct workhead *dephd;
  {
          struct mount *mp;
          struct bio *bip;
          struct ffs_blkfree_trim_params *tp;
  
          /*
           * Check to see if a snapshot wants to claim the block.
           * Check that devvp is a normal disk device, not a snapshot,
           * it has a snapshot(s) associated with it, and one of the
           * snapshots wants to claim the block.
           */
          if (devvp->v_type != VREG &&
              (devvp->v_vflag & VV_COPYONWRITE) &&
              ffs_snapblkfree(fs, devvp, bno, size, inum, vtype, dephd)) {
                  return;
          }
          /*
           * Nothing to delay if TRIM is disabled, or the operation is
           * performed on the snapshot.
           */
          if (!ump->um_candelete || devvp->v_type == VREG) {
                  ffs_blkfree_cg(ump, fs, devvp, bno, size, inum, dephd);
                  return;
          }
  
          /*
           * Postpone the set of the free bit in the cg bitmap until the
           * BIO_DELETE is completed.  Otherwise, due to disk queue
           * reordering, TRIM might be issued after we reuse the block
           * and write some new data into it.
           */
          tp = malloc(sizeof(struct ffs_blkfree_trim_params), M_TEMP, M_WAITOK);
          tp->ump = ump;
          tp->devvp = devvp;
          tp->bno = bno;
          tp->size = size;
          tp->inum = inum;
          if (dephd != NULL) {
                  LIST_INIT(&tp->dephd);
                  LIST_SWAP(dephd, &tp->dephd, worklist, wk_list);
                  tp->pdephd = &tp->dephd;
          } else
                  tp->pdephd = NULL;
  
          bip = g_alloc_bio();
          bip->bio_cmd = BIO_DELETE;
          bip->bio_offset = dbtob(fsbtodb(fs, bno));
          bip->bio_done = ffs_blkfree_trim_completed;
          bip->bio_length = size;
          bip->bio_caller2 = tp;
  
          mp = UFSTOVFS(ump);
          vn_start_secondary_write(NULL, &mp, 0);
          g_io_request(bip, (struct g_consumer *)devvp->v_bufobj.bo_private);
  }
  
  #ifdef INVARIANTS
  /*
   * Verify allocation of a block or fragment. Returns true if block or
   * fragment is allocated, false if it is free.
   */
  static int
  ffs_checkblk(ip, bno, size)
          struct inode *ip;
          ufs2_daddr_t bno;
          long size;
  {
          struct fs *fs;
          struct cg *cgp;
          struct buf *bp;
          ufs1_daddr_t cgbno;
          int i, error, frags, free;
          u_int8_t *blksfree;
  
          fs = ip->i_fs;
          if ((u_int)size > fs->fs_bsize || fragoff(fs, size) != 0) {
                  printf("bsize = %ld, size = %ld, fs = %s\n",
                      (long)fs->fs_bsize, size, fs->fs_fsmnt);
                  panic("ffs_checkblk: bad size");
          }
          if ((u_int)bno >= fs->fs_size)
                  panic("ffs_checkblk: bad block %jd", (intmax_t)bno);
          error = bread(ip->i_devvp, fsbtodb(fs, cgtod(fs, dtog(fs, bno))),
                  (int)fs->fs_cgsize, NOCRED, &bp);
          if (error)
                  panic("ffs_checkblk: cg bread failed");
          cgp = (struct cg *)bp->b_data;
          if (!cg_chkmagic(cgp))
                  panic("ffs_checkblk: cg magic mismatch");
          bp->b_xflags |= BX_BKGRDWRITE;
          blksfree = cg_blksfree(cgp);
          cgbno = dtogd(fs, bno);
          if (size == fs->fs_bsize) {
                  free = ffs_isblock(fs, blksfree, fragstoblks(fs, cgbno));
          } else {
                  frags = numfrags(fs, size);
                  for (free = 0, i = 0; i < frags; i++)
                          if (isset(blksfree, cgbno + i))
                                  free++;
                  if (free != 0 && free != frags)
                          panic("ffs_checkblk: partially free fragment");
          }
          brelse(bp);
          return (!free);
  }
  #endif /* INVARIANTS */
  
  /*
   * Free an inode.
   */
  int
  ffs_vfree(pvp, ino, mode)
          struct vnode *pvp;
          ino_t ino;
          int mode;
  {
          struct inode *ip;
  
          if (DOINGSOFTDEP(pvp)) {
                  softdep_freefile(pvp, ino, mode);
                  return (0);
          }
          ip = VTOI(pvp);
          return (ffs_freefile(ip->i_ump, ip->i_fs, ip->i_devvp, ino, mode,
              NULL));
  }
  
  /*
   * Do the actual free operation.
   * The specified inode is placed back in the free map.
   */
  int
  ffs_freefile(ump, fs, devvp, ino, mode, wkhd)
          struct ufsmount *ump;
          struct fs *fs;
          struct vnode *devvp;
          ino_t ino;
          int mode;
          struct workhead *wkhd;
  {
          struct cg *cgp;
          struct buf *bp;
          ufs2_daddr_t cgbno;
          int error;
          u_int cg;
          u_int8_t *inosused;
          struct cdev *dev;
  
          cg = ino_to_cg(fs, ino);
          if (devvp->v_type == VREG) {
                  /* devvp is a snapshot */
                  dev = VTOI(devvp)->i_devvp->v_rdev;
                  cgbno = fragstoblks(fs, cgtod(fs, cg));
          } else {
                  /* devvp is a normal disk device */
                  dev = devvp->v_rdev;
                  cgbno = fsbtodb(fs, cgtod(fs, cg));
          }
          if (ino >= fs->fs_ipg * fs->fs_ncg)
                  panic("ffs_freefile: range: dev = %s, ino = %ju, fs = %s",
                      devtoname(dev), (uintmax_t)ino, fs->fs_fsmnt);
          if ((error = bread(devvp, cgbno, (int)fs->fs_cgsize, NOCRED, &bp))) {
                  brelse(bp);
                  return (error);
          }
          cgp = (struct cg *)bp->b_data;
          if (!cg_chkmagic(cgp)) {
                  brelse(bp);
                  return (0);
          }
          bp->b_xflags |= BX_BKGRDWRITE;
          cgp->cg_old_time = cgp->cg_time = time_second;
          inosused = cg_inosused(cgp);
          ino %= fs->fs_ipg;
          if (isclr(inosused, ino)) {
                  printf("dev = %s, ino = %ju, fs = %s\n", devtoname(dev),
                      (uintmax_t)(ino + cg * fs->fs_ipg), fs->fs_fsmnt);
                  if (fs->fs_ronly == 0)
                          panic("ffs_freefile: freeing free inode");
          }
          clrbit(inosused, ino);
          if (ino < cgp->cg_irotor)
                  cgp->cg_irotor = ino;
          cgp->cg_cs.cs_nifree++;
          UFS_LOCK(ump);
          fs->fs_cstotal.cs_nifree++;
          fs->fs_cs(fs, cg).cs_nifree++;
          if ((mode & IFMT) == IFDIR) {
                  cgp->cg_cs.cs_ndir--;
                  fs->fs_cstotal.cs_ndir--;
                  fs->fs_cs(fs, cg).cs_ndir--;
          }
          fs->fs_fmod = 1;
          ACTIVECLEAR(fs, cg);
          UFS_UNLOCK(ump);
          if (MOUNTEDSOFTDEP(UFSTOVFS(ump)) && devvp->v_type != VREG)
                  softdep_setup_inofree(UFSTOVFS(ump), bp,
                      ino + cg * fs->fs_ipg, wkhd);
          bdwrite(bp);
          return (0);
  }
  
  /*
   * Check to see if a file is free.
   */
  int
  ffs_checkfreefile(fs, devvp, ino)
          struct fs *fs;
          struct vnode *devvp;
          ino_t ino;
  {
          struct cg *cgp;
          struct buf *bp;
          ufs2_daddr_t cgbno;
          int ret;
          u_int cg;
          u_int8_t *inosused;
  
          cg = ino_to_cg(fs, ino);
          if (devvp->v_type == VREG) {
                  /* devvp is a snapshot */
                  cgbno = fragstoblks(fs, cgtod(fs, cg));
          } else {
                  /* devvp is a normal disk device */
                  cgbno = fsbtodb(fs, cgtod(fs, cg));
          }
          if (ino >= fs->fs_ipg * fs->fs_ncg)
                  return (1);
          if (bread(devvp, cgbno, (int)fs->fs_cgsize, NOCRED, &bp)) {
                  brelse(bp);
                  return (1);
          }
          cgp = (struct cg *)bp->b_data;
          if (!cg_chkmagic(cgp)) {
                  brelse(bp);
                  return (1);
          }
          inosused = cg_inosused(cgp);
          ino %= fs->fs_ipg;
          ret = isclr(inosused, ino);
          brelse(bp);
          return (ret);
  }
  
  /*
   * Find a block of the specified size in the specified cylinder group.
   *
   * It is a panic if a request is made to find a block if none are
   * available.
   */
  static ufs1_daddr_t
  ffs_mapsearch(fs, cgp, bpref, allocsiz)
          struct fs *fs;
          struct cg *cgp;
          ufs2_daddr_t bpref;
          int allocsiz;
  {
          ufs1_daddr_t bno;
          int start, len, loc, i;
          int blk, field, subfield, pos;
          u_int8_t *blksfree;
  
          /*
           * find the fragment by searching through the free block
           * map for an appropriate bit pattern
           */
          if (bpref)
                  start = dtogd(fs, bpref) / NBBY;
          else
                  start = cgp->cg_frotor / NBBY;
          blksfree = cg_blksfree(cgp);
          len = howmany(fs->fs_fpg, NBBY) - start;
          loc = scanc((u_int)len, (u_char *)&blksfree[start],
                  fragtbl[fs->fs_frag],
                  (u_char)(1 << (allocsiz - 1 + (fs->fs_frag % NBBY))));
          if (loc == 0) {
                  len = start + 1;
                  start = 0;
                  loc = scanc((u_int)len, (u_char *)&blksfree[0],
                          fragtbl[fs->fs_frag],
                          (u_char)(1 << (allocsiz - 1 + (fs->fs_frag % NBBY))));
                  if (loc == 0) {
                          printf("start = %d, len = %d, fs = %s\n",
                              start, len, fs->fs_fsmnt);
                          panic("ffs_alloccg: map corrupted");
                          /* NOTREACHED */
                  }
          }
          bno = (start + len - loc) * NBBY;
          cgp->cg_frotor = bno;
          /*
           * found the byte in the map
           * sift through the bits to find the selected frag
           */
          for (i = bno + NBBY; bno < i; bno += fs->fs_frag) {
                  blk = blkmap(fs, blksfree, bno);
                  blk <<= 1;
                  field = around[allocsiz];
                  subfield = inside[allocsiz];
                  for (pos = 0; pos <= fs->fs_frag - allocsiz; pos++) {
                          if ((blk & field) == subfield)
                                  return (bno + pos);
                          field <<= 1;
                          subfield <<= 1;
                  }
          }
          printf("bno = %lu, fs = %s\n", (u_long)bno, fs->fs_fsmnt);
          panic("ffs_alloccg: block not in map");
          return (-1);
  }
  
  /*
   * Fserr prints the name of a filesystem with an error diagnostic.
   *
   * The form of the error message is:
   *      fs: error message
   */
  void
  ffs_fserr(fs, inum, cp)
          struct fs *fs;
          ino_t inum;
          char *cp;
  {
          struct thread *td = curthread;  /* XXX */
          struct proc *p = td->td_proc;
  
          log(LOG_ERR, "pid %d (%s), uid %d inumber %ju on %s: %s\n",
              p->p_pid, p->p_comm, td->td_ucred->cr_uid, (uintmax_t)inum,
              fs->fs_fsmnt, cp);
  }
  
  /*
   * This function provides the capability for the fsck program to
   * update an active filesystem. Fourteen operations are provided:
   *
   * adjrefcnt(inode, amt) - adjusts the reference count on the
   *      specified inode by the specified amount. Under normal
   *      operation the count should always go down. Decrementing
   *      the count to zero will cause the inode to be freed.
   * adjblkcnt(inode, amt) - adjust the number of blocks used by the
   *      inode by the specified amount.
   * adjndir, adjbfree, adjifree, adjffree, adjnumclusters(amt) -
   *      adjust the superblock summary.
   * freedirs(inode, count) - directory inodes [inode..inode + count - 1]
   *      are marked as free. Inodes should never have to be marked
   *      as in use.
   * freefiles(inode, count) - file inodes [inode..inode + count - 1]
   *      are marked as free. Inodes should never have to be marked
   *      as in use.
   * freeblks(blockno, size) - blocks [blockno..blockno + size - 1]
   *      are marked as free. Blocks should never have to be marked
   *      as in use.
   * setflags(flags, set/clear) - the fs_flags field has the specified
   *      flags set (second parameter +1) or cleared (second parameter -1).
   * setcwd(dirinode) - set the current directory to dirinode in the
   *      filesystem associated with the snapshot.
   * setdotdot(oldvalue, newvalue) - Verify that the inode number for ".."
   *      in the current directory is oldvalue then change it to newvalue.
   * unlink(nameptr, oldvalue) - Verify that the inode number associated
   *      with nameptr in the current directory is oldvalue then unlink it.
   *
   * The following functions may only be used on a quiescent filesystem
   * by the soft updates journal. They are not safe to be run on an active
   * filesystem.
   *
   * setinode(inode, dip) - the specified disk inode is replaced with the
   *      contents pointed to by dip.
   * setbufoutput(fd, flags) - output associated with the specified file
   *      descriptor (which must reference the character device supporting
   *      the filesystem) switches from using physio to running through the
   *      buffer cache when flags is set to 1. The descriptor reverts to
   *      physio for output when flags is set to zero.
   */
  
  static int sysctl_ffs_fsck(SYSCTL_HANDLER_ARGS);
  
  SYSCTL_PROC(_vfs_ffs, FFS_ADJ_REFCNT, adjrefcnt, CTLFLAG_WR|CTLTYPE_STRUCT,
          0, 0, sysctl_ffs_fsck, "S,fsck", "Adjust Inode Reference Count");
  
  static SYSCTL_NODE(_vfs_ffs, FFS_ADJ_BLKCNT, adjblkcnt, CTLFLAG_WR,
          sysctl_ffs_fsck, "Adjust Inode Used Blocks Count");
  
  static SYSCTL_NODE(_vfs_ffs, FFS_ADJ_NDIR, adjndir, CTLFLAG_WR,
          sysctl_ffs_fsck, "Adjust number of directories");
  
  static SYSCTL_NODE(_vfs_ffs, FFS_ADJ_NBFREE, adjnbfree, CTLFLAG_WR,
          sysctl_ffs_fsck, "Adjust number of free blocks");
  
  static SYSCTL_NODE(_vfs_ffs, FFS_ADJ_NIFREE, adjnifree, CTLFLAG_WR,
          sysctl_ffs_fsck, "Adjust number of free inodes");
  
  static SYSCTL_NODE(_vfs_ffs, FFS_ADJ_NFFREE, adjnffree, CTLFLAG_WR,
          sysctl_ffs_fsck, "Adjust number of free frags");
  
  static SYSCTL_NODE(_vfs_ffs, FFS_ADJ_NUMCLUSTERS, adjnumclusters, CTLFLAG_WR,
          sysctl_ffs_fsck, "Adjust number of free clusters");
  
  static SYSCTL_NODE(_vfs_ffs, FFS_DIR_FREE, freedirs, CTLFLAG_WR,
          sysctl_ffs_fsck, "Free Range of Directory Inodes");
  
  static SYSCTL_NODE(_vfs_ffs, FFS_FILE_FREE, freefiles, CTLFLAG_WR,
          sysctl_ffs_fsck, "Free Range of File Inodes");
  
  static SYSCTL_NODE(_vfs_ffs, FFS_BLK_FREE, freeblks, CTLFLAG_WR,
          sysctl_ffs_fsck, "Free Range of Blocks");
  
  static SYSCTL_NODE(_vfs_ffs, FFS_SET_FLAGS, setflags, CTLFLAG_WR,
          sysctl_ffs_fsck, "Change Filesystem Flags");
  
  static SYSCTL_NODE(_vfs_ffs, FFS_SET_CWD, setcwd, CTLFLAG_WR,
          sysctl_ffs_fsck, "Set Current Working Directory");
  
  static SYSCTL_NODE(_vfs_ffs, FFS_SET_DOTDOT, setdotdot, CTLFLAG_WR,
          sysctl_ffs_fsck, "Change Value of .. Entry");
  
  static SYSCTL_NODE(_vfs_ffs, FFS_UNLINK, unlink, CTLFLAG_WR,
          sysctl_ffs_fsck, "Unlink a Duplicate Name");
  
  static SYSCTL_NODE(_vfs_ffs, FFS_SET_INODE, setinode, CTLFLAG_WR,
          sysctl_ffs_fsck, "Update an On-Disk Inode");
  
  static SYSCTL_NODE(_vfs_ffs, FFS_SET_BUFOUTPUT, setbufoutput, CTLFLAG_WR,
          sysctl_ffs_fsck, "Set Buffered Writing for Descriptor");
  
  #define DEBUG 1
  #ifdef DEBUG
  static int fsckcmds = 0;
  SYSCTL_INT(_debug, OID_AUTO, fsckcmds, CTLFLAG_RW, &fsckcmds, 0, "");
  #endif /* DEBUG */
  
  static int buffered_write(struct file *, struct uio *, struct ucred *,
          int, struct thread *);
  
  static int
  sysctl_ffs_fsck(SYSCTL_HANDLER_ARGS)
  {
          struct thread *td = curthread;
          struct fsck_cmd cmd;
          struct ufsmount *ump;
          struct vnode *vp, *vpold, *dvp, *fdvp;
          struct inode *ip, *dp;
          struct mount *mp;
          struct fs *fs;
          ufs2_daddr_t blkno;
          long blkcnt, blksize;
          struct filedesc *fdp;
          struct file *fp, *vfp;
          cap_rights_t rights;
          int filetype, error;
          static struct fileops *origops, bufferedops;
  
          if (req->newlen > sizeof cmd)
                  return (EBADRPC);
          if ((error = SYSCTL_IN(req, &cmd, sizeof cmd)) != 0)
                  return (error);
          if (cmd.version != FFS_CMD_VERSION)
                  return (ERPCMISMATCH);
          if ((error = getvnode(td->td_proc->p_fd, cmd.handle,
              cap_rights_init(&rights, CAP_FSCK), &fp)) != 0)
                  return (error);
          vp = fp->f_data;
          if (vp->v_type != VREG && vp->v_type != VDIR) {
                  fdrop(fp, td);
                  return (EINVAL);
          }
          vn_start_write(vp, &mp, V_WAIT);
          if (mp == 0 || strncmp(mp->mnt_stat.f_fstypename, "ufs", MFSNAMELEN)) {
                  vn_finished_write(mp);
                  fdrop(fp, td);
                  return (EINVAL);
          }
          ump = VFSTOUFS(mp);
          if ((mp->mnt_flag & MNT_RDONLY) &&
              ump->um_fsckpid != td->td_proc->p_pid) {
                  vn_finished_write(mp);
                  fdrop(fp, td);
                  return (EROFS);
          }
          fs = ump->um_fs;
          filetype = IFREG;
  
          switch (oidp->oid_number) {
  
          case FFS_SET_FLAGS:
  #ifdef DEBUG
                  if (fsckcmds)
                          printf("%s: %s flags\n", mp->mnt_stat.f_mntonname,
                              cmd.size > 0 ? "set" : "clear");
  #endif /* DEBUG */
                  if (cmd.size > 0)
                          fs->fs_flags |= (long)cmd.value;
                  else
                          fs->fs_flags &= ~(long)cmd.value;
                  break;
  
          case FFS_ADJ_REFCNT:
  #ifdef DEBUG
                  if (fsckcmds) {
                          printf("%s: adjust inode %jd link count by %jd\n",
                              mp->mnt_stat.f_mntonname, (intmax_t)cmd.value,
                              (intmax_t)cmd.size);
                  }
  #endif /* DEBUG */
                  if ((error = ffs_vget(mp, (ino_t)cmd.value, LK_EXCLUSIVE, &vp)))
                          break;
                  ip = VTOI(vp);
                  ip->i_nlink += cmd.size;
                  DIP_SET(ip, i_nlink, ip->i_nlink);
                  ip->i_effnlink += cmd.size;
                  ip->i_flag |= IN_CHANGE | IN_MODIFIED;
                  error = ffs_update(vp, 1);
                  if (DOINGSOFTDEP(vp))
                          softdep_change_linkcnt(ip);
                  vput(vp);
                  break;
  
          case FFS_ADJ_BLKCNT:
  #ifdef DEBUG
                  if (fsckcmds) {
                          printf("%s: adjust inode %jd block count by %jd\n",
                              mp->mnt_stat.f_mntonname, (intmax_t)cmd.value,
                              (intmax_t)cmd.size);
                  }
  #endif /* DEBUG */
                  if ((error = ffs_vget(mp, (ino_t)cmd.value, LK_EXCLUSIVE, &vp)))
                          break;
                  ip = VTOI(vp);
                  DIP_SET(ip, i_blocks, DIP(ip, i_blocks) + cmd.size);
                  ip->i_flag |= IN_CHANGE | IN_MODIFIED;
                  error = ffs_update(vp, 1);
                  vput(vp);
                  break;
  
          case FFS_DIR_FREE:
                  filetype = IFDIR;
                  /* fall through */
  
          case FFS_FILE_FREE:
  #ifdef DEBUG
                  if (fsckcmds) {
                          if (cmd.size == 1)
                                  printf("%s: free %s inode %ju\n",
                                      mp->mnt_stat.f_mntonname,
                                      filetype == IFDIR ? "directory" : "file",
                                      (uintmax_t)cmd.value);
                          else
                                  printf("%s: free %s inodes %ju-%ju\n",
                                      mp->mnt_stat.f_mntonname,
                                      filetype == IFDIR ? "directory" : "file",
                                      (uintmax_t)cmd.value,
                                      (uintmax_t)(cmd.value + cmd.size - 1));
                  }
  #endif /* DEBUG */
                  while (cmd.size > 0) {
                          if ((error = ffs_freefile(ump, fs, ump->um_devvp,
                              cmd.value, filetype, NULL)))
                                  break;
                          cmd.size -= 1;
                          cmd.value += 1;
                  }
                  break;
  
          case FFS_BLK_FREE:
  #ifdef DEBUG
                  if (fsckcmds) {
                          if (cmd.size == 1)
                                  printf("%s: free block %jd\n",
                                      mp->mnt_stat.f_mntonname,
                                      (intmax_t)cmd.value);
                          else
                                  printf("%s: free blocks %jd-%jd\n",
                                      mp->mnt_stat.f_mntonname, 
                                      (intmax_t)cmd.value,
                                      (intmax_t)cmd.value + cmd.size - 1);
                  }
  #endif /* DEBUG */
                  blkno = cmd.value;
                  blkcnt = cmd.size;
                  blksize = fs->fs_frag - (blkno % fs->fs_frag);
                  while (blkcnt > 0) {
                          if (blksize > blkcnt)
                                  blksize = blkcnt;
                          ffs_blkfree(ump, fs, ump->um_devvp, blkno,
                              blksize * fs->fs_fsize, ROOTINO, VDIR, NULL);
                          blkno += blksize;
                          blkcnt -= blksize;
                          blksize = fs->fs_frag;
                  }
                  break;
  
          /*
           * Adjust superblock summaries.  fsck(8) is expected to
           * submit deltas when necessary.
           */
          case FFS_ADJ_NDIR:
  #ifdef DEBUG
                  if (fsckcmds) {
                          printf("%s: adjust number of directories by %jd\n",
                              mp->mnt_stat.f_mntonname, (intmax_t)cmd.value);
                  }
  #endif /* DEBUG */
                  fs->fs_cstotal.cs_ndir += cmd.value;
                  break;
  
          case FFS_ADJ_NBFREE:
  #ifdef DEBUG
                  if (fsckcmds) {
                          printf("%s: adjust number of free blocks by %+jd\n",
                              mp->mnt_stat.f_mntonname, (intmax_t)cmd.value);
                  }
  #endif /* DEBUG */
                  fs->fs_cstotal.cs_nbfree += cmd.value;
                  break;
  
          case FFS_ADJ_NIFREE:
  #ifdef DEBUG
                  if (fsckcmds) {
                          printf("%s: adjust number of free inodes by %+jd\n",
                              mp->mnt_stat.f_mntonname, (intmax_t)cmd.value);
                  }
  #endif /* DEBUG */
                  fs->fs_cstotal.cs_nifree += cmd.value;
                  break;
  
          case FFS_ADJ_NFFREE:
  #ifdef DEBUG
                  if (fsckcmds) {
                          printf("%s: adjust number of free frags by %+jd\n",
                              mp->mnt_stat.f_mntonname, (intmax_t)cmd.value);
                  }
  #endif /* DEBUG */
                  fs->fs_cstotal.cs_nffree += cmd.value;
                  break;
  
          case FFS_ADJ_NUMCLUSTERS:
  #ifdef DEBUG
                  if (fsckcmds) {
                          printf("%s: adjust number of free clusters by %+jd\n",
                              mp->mnt_stat.f_mntonname, (intmax_t)cmd.value);
                  }
  #endif /* DEBUG */
                  fs->fs_cstotal.cs_numclusters += cmd.value;
                  break;
  
          case FFS_SET_CWD:
  #ifdef DEBUG
                  if (fsckcmds) {
                          printf("%s: set current directory to inode %jd\n",
                              mp->mnt_stat.f_mntonname, (intmax_t)cmd.value);
                  }
  #endif /* DEBUG */
                  if ((error = ffs_vget(mp, (ino_t)cmd.value, LK_SHARED, &vp)))
                          break;
                  AUDIT_ARG_VNODE1(vp);
                  if ((error = change_dir(vp, td)) != 0) {
                          vput(vp);
                          break;
                  }
                  VOP_UNLOCK(vp, 0);
                  fdp = td->td_proc->p_fd;
                  FILEDESC_XLOCK(fdp);
                  vpold = fdp->fd_cdir;
                  fdp->fd_cdir = vp;
                  FILEDESC_XUNLOCK(fdp);
                  vrele(vpold);
                  break;
  
          case FFS_SET_DOTDOT:
  #ifdef DEBUG
                  if (fsckcmds) {
                          printf("%s: change .. in cwd from %jd to %jd\n",
                              mp->mnt_stat.f_mntonname, (intmax_t)cmd.value,
                              (intmax_t)cmd.size);
                  }
  #endif /* DEBUG */
                  /*
                   * First we have to get and lock the parent directory
                   * to which ".." points.
                   */
                  error = ffs_vget(mp, (ino_t)cmd.value, LK_EXCLUSIVE, &fdvp);
                  if (error)
                          break;
                  /*
                   * Now we get and lock the child directory containing "..".
                   */
                  FILEDESC_SLOCK(td->td_proc->p_fd);
                  dvp = td->td_proc->p_fd->fd_cdir;
                  FILEDESC_SUNLOCK(td->td_proc->p_fd);
                  if ((error = vget(dvp, LK_EXCLUSIVE, td)) != 0) {
                          vput(fdvp);
                          break;
                  }
                  dp = VTOI(dvp);
                  dp->i_offset = 12;      /* XXX mastertemplate.dot_reclen */
                  error = ufs_dirrewrite(dp, VTOI(fdvp), (ino_t)cmd.size,
                      DT_DIR, 0);
                  cache_purge(fdvp);
                  cache_purge(dvp);
                  vput(dvp);
                  vput(fdvp);
                  break;
  
          case FFS_UNLINK:
  #ifdef DEBUG
                  if (fsckcmds) {
                          char buf[32];
  
                          if (copyinstr((char *)(intptr_t)cmd.value, buf,32,NULL))
                                  strncpy(buf, "Name_too_long", 32);
                          printf("%s: unlink %s (inode %jd)\n",
                              mp->mnt_stat.f_mntonname, buf, (intmax_t)cmd.size);
                  }
  #endif /* DEBUG */
                  /*
                   * kern_unlinkat will do its own start/finish writes and
                   * they do not nest, so drop ours here. Setting mp == NULL
                   * indicates that vn_finished_write is not needed down below.
                   */
                  vn_finished_write(mp);
                  mp = NULL;
                  error = kern_unlinkat(td, AT_FDCWD, (char *)(intptr_t)cmd.value,
                      UIO_USERSPACE, (ino_t)cmd.size);
                  break;
  
          case FFS_SET_INODE:
                  if (ump->um_fsckpid != td->td_proc->p_pid) {
                          error = EPERM;
                          break;
                  }
  #ifdef DEBUG
                  if (fsckcmds) {
                          printf("%s: update inode %jd\n",
                              mp->mnt_stat.f_mntonname, (intmax_t)cmd.value);
                  }
  #endif /* DEBUG */
                  if ((error = ffs_vget(mp, (ino_t)cmd.value, LK_EXCLUSIVE, &vp)))
                          break;
                  AUDIT_ARG_VNODE1(vp);
                  ip = VTOI(vp);
                  if (ip->i_ump->um_fstype == UFS1)
                          error = copyin((void *)(intptr_t)cmd.size, ip->i_din1,
                              sizeof(struct ufs1_dinode));
                  else
                          error = copyin((void *)(intptr_t)cmd.size, ip->i_din2,
                              sizeof(struct ufs2_dinode));
                  if (error) {
                          vput(vp);
                          break;
                  }
                  ip->i_flag |= IN_CHANGE | IN_MODIFIED;
                  error = ffs_update(vp, 1);
                  vput(vp);
                  break;
  
          case FFS_SET_BUFOUTPUT:
                  if (ump->um_fsckpid != td->td_proc->p_pid) {
                          error = EPERM;
                          break;
                  }
                  if (VTOI(vp)->i_ump != ump) {
                          error = EINVAL;
                          break;
                  }
  #ifdef DEBUG
                  if (fsckcmds) {
                          printf("%s: %s buffered output for descriptor %jd\n",
                              mp->mnt_stat.f_mntonname,
                              cmd.size == 1 ? "enable" : "disable",
                              (intmax_t)cmd.value);
                  }
  #endif /* DEBUG */
                  if ((error = getvnode(td->td_proc->p_fd, cmd.value,
                      cap_rights_init(&rights, CAP_FSCK), &vfp)) != 0)
                          break;
                  if (vfp->f_vnode->v_type != VCHR) {
                          fdrop(vfp, td);
                          error = EINVAL;
                          break;
                  }
                  if (origops == NULL) {
                          origops = vfp->f_ops;
                          bcopy((void *)origops, (void *)&bufferedops,
                              sizeof(bufferedops));
                          bufferedops.fo_write = buffered_write;
                  }
                  if (cmd.size == 1)
                          atomic_store_rel_ptr((volatile uintptr_t *)&vfp->f_ops,
                              (uintptr_t)&bufferedops);
                  else
                          atomic_store_rel_ptr((volatile uintptr_t *)&vfp->f_ops,
                              (uintptr_t)origops);
                  fdrop(vfp, td);
                  break;
  
          default:
  #ifdef DEBUG
                  if (fsckcmds) {
                          printf("Invalid request %d from fsck\n",
                              oidp->oid_number);
                  }
  #endif /* DEBUG */
                  error = EINVAL;
                  break;
  
          }
          fdrop(fp, td);
          vn_finished_write(mp);
          return (error);
  }
  
  /*
   * Function to switch a descriptor to use the buffer cache to stage
   * its I/O. This is needed so that writes to the filesystem device
   * will give snapshots a chance to copy modified blocks for which it
   * needs to retain copies.
   */
  static int
  buffered_write(fp, uio, active_cred, flags, td)
          struct file *fp;
          struct uio *uio;
          struct ucred *active_cred;
          int flags;
          struct thread *td;
  {
          struct vnode *devvp, *vp;
          struct inode *ip;
          struct buf *bp;
          struct fs *fs;
          struct filedesc *fdp;
          int error;
          daddr_t lbn;
  
          /*
           * The devvp is associated with the /dev filesystem. To discover
           * the filesystem with which the device is associated, we depend
           * on the application setting the current directory to a location
           * within the filesystem being written. Yes, this is an ugly hack.
           */
          devvp = fp->f_vnode;
          if (!vn_isdisk(devvp, NULL))
                  return (EINVAL);
          fdp = td->td_proc->p_fd;
          FILEDESC_SLOCK(fdp);
          vp = fdp->fd_cdir;
          vref(vp);
          FILEDESC_SUNLOCK(fdp);
          vn_lock(vp, LK_SHARED | LK_RETRY);
          /*
           * Check that the current directory vnode indeed belongs to
           * UFS before trying to dereference UFS-specific v_data fields.
           */
          if (vp->v_op != &ffs_vnodeops1 && vp->v_op != &ffs_vnodeops2) {
                  vput(vp);
                  return (EINVAL);
          }
          ip = VTOI(vp);
          if (ip->i_devvp != devvp) {
                  vput(vp);
                  return (EINVAL);
          }
          fs = ip->i_fs;
          vput(vp);
          foffset_lock_uio(fp, uio, flags);
          vn_lock(devvp, LK_EXCLUSIVE | LK_RETRY);
  #ifdef DEBUG
          if (fsckcmds) {
                  printf("%s: buffered write for block %jd\n",
                      fs->fs_fsmnt, (intmax_t)btodb(uio->uio_offset));
          }
  #endif /* DEBUG */
          /*
           * All I/O must be contained within a filesystem block, start on
           * a fragment boundary, and be a multiple of fragments in length.
           */
          if (uio->uio_resid > fs->fs_bsize - (uio->uio_offset % fs->fs_bsize) ||
              fragoff(fs, uio->uio_offset) != 0 ||
              fragoff(fs, uio->uio_resid) != 0) {
                  error = EINVAL;
                  goto out;
          }
          lbn = numfrags(fs, uio->uio_offset);
          bp = getblk(devvp, lbn, uio->uio_resid, 0, 0, 0);
          bp->b_flags |= B_RELBUF;
          if ((error = uiomove((char *)bp->b_data, uio->uio_resid, uio)) != 0) {
                  brelse(bp);
                  goto out;
          }
          error = bwrite(bp);
  out:
          VOP_UNLOCK(devvp, 0);
          foffset_unlock_uio(fp, uio, flags | FOF_NEXTOFF);
          return (error);
  }