Merge ACPICA 20170531.

[FreeBSD/FreeBSD.git] / 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.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *      @(#)ffs_alloc.c 8.18 (Berkeley) 5/26/95
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

#include "opt_quota.h"

#include <sys/param.h>
#include <sys/capsicum.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);
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;
        ump = ITOUMP(ip);
        fs = ump->um_fs;
        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(ump->um_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;

        vp = ITOV(ip);
        ump = ITOUMP(ip);
        fs = ump->um_fs;
        bp = NULL;
        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(ump->um_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(ump->um_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 >= UFS_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.
         */
        *bpp = NULL;
        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(ump->um_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, ump->um_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,
"do not force synchronous writes when blocks are reallocated");

static int doreallocblks = 1;
SYSCTL_INT(_vfs_ffs, OID_AUTO, doreallocblks, CTLFLAG_RW, &doreallocblks, 0,
"enable block reallocation");

static int maxclustersearch = 10;
SYSCTL_INT(_vfs_ffs, OID_AUTO, maxclustersearch, CTLFLAG_RW, &maxclustersearch,
0, "max number of cylinder group to search for contigous blocks");

#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;
{
        struct ufsmount *ump;

        /*
         * If the underlying device can do deletes, then skip reallocating
         * the blocks of this file into contiguous sequences. Devices that
         * benefit from BIO_DELETE also benefit from not moving the data.
         * These devices are flash and therefore work less well with this
         * optimization. Also skip if reallocblks has been disabled globally.
         */
        ump = ap->a_vp->v_mount->mnt_data;
        if (ump->um_candelete || 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 (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;
        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[UFS_NIADDR + 1], end_ap[UFS_NIADDR + 1], *idp;
        int i, cg, len, start_lvl, end_lvl, ssize;

        vp = ap->a_vp;
        ip = VTOI(vp);
        ump = ITOUMP(ip);
        fs = ump->um_fs;
        /*
         * If we are not tracking block clusters or if we have less than 4%
         * 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, 4) < 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 < UFS_NDADDR && end_lbn >= UFS_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.
         */
        ebap = NULL;
        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. If we have not
         * previously failed at this endeavor, then follow our standard
         * preference calculation. If we have failed at it, then pick up
         * where we last ended our search.
         */
        UFS_LOCK(ump);
        if (ip->i_nextclustercg == -1)
                pref = ffs_blkpref_ufs1(ip, start_lbn, soff, sbap);
        else
                pref = cgdata(fs, ip->i_nextclustercg);
        /*
         * Search the block map looking for an allocation of the desired size.
         * To avoid wasting too much time, we limit the number of cylinder
         * groups that we will search.
         */
        cg = dtog(fs, pref);
        for (i = min(maxclustersearch, fs->fs_ncg); i > 0; i--) {
                if ((newblk = ffs_clusteralloc(ip, cg, pref, len)) != 0)
                        break;
                cg += 1;
                if (cg >= fs->fs_ncg)
                        cg = 0;
        }
        /*
         * If we have failed in our search, record where we gave up for
         * next time. Otherwise, fall back to our usual search citerion.
         */
        if (newblk == 0) {
                ip->i_nextclustercg = cg;
                UFS_UNLOCK(ump);
                goto fail;
        }
        ip->i_nextclustercg = -1;
        /*
         * 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, ump->um_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;
        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[UFS_NIADDR + 1], end_ap[UFS_NIADDR + 1], *idp;
        int i, cg, len, start_lvl, end_lvl, ssize;

        vp = ap->a_vp;
        ip = VTOI(vp);
        ump = ITOUMP(ip);
        fs = ump->um_fs;
        /*
         * If we are not tracking block clusters or if we have less than 4%
         * 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, 4) < 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 < UFS_NDADDR && end_lbn >= UFS_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.
         */
        ebap = NULL;
        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. If we have not
         * previously failed at this endeavor, then follow our standard
         * preference calculation. If we have failed at it, then pick up
         * where we last ended our search.
         */
        UFS_LOCK(ump);
        if (ip->i_nextclustercg == -1)
                pref = ffs_blkpref_ufs2(ip, start_lbn, soff, sbap);
        else
                pref = cgdata(fs, ip->i_nextclustercg);
        /*
         * Search the block map looking for an allocation of the desired size.
         * To avoid wasting too much time, we limit the number of cylinder
         * groups that we will search.
         */
        cg = dtog(fs, pref);
        for (i = min(maxclustersearch, fs->fs_ncg); i > 0; i--) {
                if ((newblk = ffs_clusteralloc(ip, cg, pref, len)) != 0)
                        break;
                cg += 1;
                if (cg >= fs->fs_ncg)
                        cg = 0;
        }
        /*
         * If we have failed in our search, record where we gave up for
         * next time. Otherwise, fall back to our usual search citerion.
         */
        if (newblk == 0) {
                ip->i_nextclustercg = cg;
                UFS_UNLOCK(ump);
                goto fail;
        }
        ip->i_nextclustercg = -1;
        /*
         * 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(" %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, ump->um_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);
        ump = ITOUMP(pip);
        fs = ump->um_fs;

        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 = %ju, fs = %s\n",
                    ip->i_mode, (uintmax_t)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.
         */
        while (ip->i_gen == 0 || ++ip->i_gen == 0)
                ip->i_gen = arc4random();
        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;
                ip->i_flag |= IN_UFS2;
        } 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(ITOUMP(pip)), MA_OWNED);
        fs = ITOFS(pip);

        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 forwards from the beginning of the
         * filesystem. While it might seem sensible to start scanning
         * backwards or even to alternate looking forward and backward,
         * this approach fails badly when the filesystem is nearly full.
         * Specifically, we first search all the areas that have no space
         * and finally try the one preceding that. We repeat this on
         * every request and in the case of the final block end up
         * searching the entire filesystem. By jumping to the front
         * of the filesystem, our future forward searches always look
         * in new cylinder groups so finds every possible block after
         * one pass over 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(ITOUMP(ip)), MA_OWNED);
        fs = ITOFS(ip);
        /*
         * 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 < UFS_NDADDR + NINDIR(fs) &&
                    ip->i_din1->di_db[UFS_NDADDR - 1] != 0)
                        pref = ip->i_din1->di_db[UFS_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 == UFS_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 preceding 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 < UFS_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(ITOUMP(ip)), MA_OWNED);
        fs = ITOFS(ip);
        /*
         * 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 < UFS_NDADDR + NINDIR(fs) &&
                    ip->i_din2->di_db[UFS_NDADDR - 1] != 0)
                        pref = ip->i_din2->di_db[UFS_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 == UFS_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 preceding 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 < UFS_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(ITOUMP(ip)), MA_OWNED);
#ifdef INVARIANTS
        if (ITOV(ip)->v_mount->mnt_kern_flag & MNTK_SUSPENDED)
                panic("ffs_hashalloc: allocation on suspended filesystem");
#endif
        fs = ITOFS(ip);
        /*
         * 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 = ITOUMP(ip);
        fs = ump->um_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(ump->um_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 = ITOUMP(ip);
        fs = ump->um_fs;
        if (fs->fs_cs(fs, cg).cs_nbfree == 0 && size == fs->fs_bsize)
                return (0);
        UFS_UNLOCK(ump);
        error = bread(ump->um_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;

        ump = ITOUMP(ip);
        fs = ump->um_fs;
        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)
        struct inode *ip;
        u_int cg;
        ufs2_daddr_t bpref;
        int len;
{
        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;

        ump = ITOUMP(ip);
        fs = ump->um_fs;
        if (fs->fs_maxcluster[cg] < len)
                return (0);
        UFS_UNLOCK(ump);
        if (bread(ump->um_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 = ITOFS(ip);
        return (getblk(ITODEVVP(ip), 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;

        ump = ITOUMP(ip);
        fs = ump->um_fs;
check_nifree:
        if (fs->fs_cs(fs, cg).cs_nifree == 0)
                return (0);
        UFS_UNLOCK(ump);
        error = bread(ump->um_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++) {
                        while (dp2->di_gen == 0)
                                dp2->di_gen = arc4random();
                        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(ump->um_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 */
                MPASS(devvp->v_mount->mnt_data == ump);
                dev = ump->um_devvp->v_rdev;
                cgblkno = fragstoblks(fs, cgtod(fs, cg));
        } else if (devvp->v_type == VCHR) {
                /* devvp is a normal disk device */
                dev = devvp->v_rdev;
                cgblkno = fsbtodb(fs, cgtod(fs, cg));
                ASSERT_VOP_LOCKED(devvp, "ffs_blkfree_cg");
        } else
                return;
#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 == VCHR)
                softdep_setup_blkfree(UFSTOVFS(ump), bp, bno,
                    numfrags(fs, size), dephd);
        bdwrite(bp);
}

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));
        atomic_add_int(&tp->ump->um_trim_inflight, -1);
        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(tp->ump->um_trim_tq, &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 == VCHR &&
            (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.
         */
        atomic_add_int(&ump->um_trim_inflight, 1);
        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 = ITOFS(ip);
        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(ITODEVVP(ip), 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 ufsmount *ump;
        struct inode *ip;

        if (DOINGSOFTDEP(pvp)) {
                softdep_freefile(pvp, ino, mode);
                return (0);
        }
        ip = VTOI(pvp);
        ump = VFSTOUFS(pvp->v_mount);
        return (ffs_freefile(ump, ump->um_fs, ump->um_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 */
                MPASS(devvp->v_mount->mnt_data == ump);
                dev = ump->um_devvp->v_rdev;
                cgbno = fragstoblks(fs, cgtod(fs, cg));
        } else if (devvp->v_type == VCHR) {
                /* devvp is a normal disk device */
                dev = devvp->v_rdev;
                cgbno = fsbtodb(fs, cgtod(fs, cg));
        } else {
                bp = NULL;
                return (0);
        }
        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 == VCHR)
                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 if (devvp->v_type == VCHR) {
                /* devvp is a normal disk device */
                cgbno = fsbtodb(fs, cgtod(fs, cg));
        } else {
                return (1);
        }
        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, *dvp, *fdvp;
        struct inode *ip, *dp;
        struct mount *mp;
        struct fs *fs;
        ufs2_daddr_t blkno;
        long blkcnt, blksize;
        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, 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 == NULL ||
            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, UFS_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);
                pwd_chdir(td, vp);
                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 (I_IS_UFS1(ip))
                        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 (ITOUMP(VTOI(vp)) != 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, 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 (ITODEVVP(ip) != devvp) {
                vput(vp);
                return (EINVAL);
        }
        fs = ITOFS(ip);
        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);
}