xnu-344.21.74.tar.gz

[apple/xnu.git] / bsd / ufs / ffs / ffs_alloc.c

/*
 * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 * 
 * Copyright (c) 1999-2003 Apple Computer, Inc.  All Rights Reserved.
 * 
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this
 * file.
 * 
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 * 
 * @APPLE_LICENSE_HEADER_END@
 */
/* Copyright (c) 1995 NeXT Computer, Inc. All Rights Reserved */
/*
 * Copyright (c) 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *      @(#)ffs_alloc.c 8.18 (Berkeley) 5/26/95
 */
#include <rev_endian_fs.h>
#include <vm/vm_pager.h>

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/buf.h>
#include <sys/proc.h>
#include <sys/vnode.h>
#include <sys/mount.h>
#include <sys/kernel.h>
#include <sys/syslog.h>
#include <sys/quota.h>

#include <sys/vm.h>

#include <ufs/ufs/quota.h>
#include <ufs/ufs/inode.h>

#include <ufs/ffs/fs.h>
#include <ufs/ffs/ffs_extern.h>

#if REV_ENDIAN_FS
#include <ufs/ufs/ufs_byte_order.h>
#include <architecture/byte_order.h>
#endif /* REV_ENDIAN_FS */

extern u_long nextgennumber;

static ufs_daddr_t ffs_alloccg __P((struct inode *, int, ufs_daddr_t, int));
static ufs_daddr_t ffs_alloccgblk __P((struct fs *, struct cg *, ufs_daddr_t));
static ufs_daddr_t ffs_clusteralloc __P((struct inode *, int, ufs_daddr_t,
            int));
static ino_t    ffs_dirpref __P((struct fs *));
static ufs_daddr_t ffs_fragextend __P((struct inode *, int, long, int, int));
static void     ffs_fserr __P((struct fs *, u_int, char *));
static u_long   ffs_hashalloc
                    __P((struct inode *, int, long, int, u_int32_t (*)()));
static ino_t    ffs_nodealloccg __P((struct inode *, int, ufs_daddr_t, int));
static ufs_daddr_t ffs_mapsearch __P((struct fs *, struct cg *, ufs_daddr_t,
            int));

/*
 * Allocate a block in the file system.
 * 
 * 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 heirarchy 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.
 */
ffs_alloc(ip, lbn, bpref, size, cred, bnp)
        register struct inode *ip;
        ufs_daddr_t lbn, bpref;
        int size;
        struct ucred *cred;
        ufs_daddr_t *bnp;
{
        register struct fs *fs;
        ufs_daddr_t bno;
        int cg, error;
        int devBlockSize=0;
        *bnp = 0;
        fs = ip->i_fs;
#if DIAGNOSTIC
        if ((u_int)size > fs->fs_bsize || fragoff(fs, size) != 0) {
                printf("dev = 0x%x, bsize = %d, size = %d, fs = %s\n",
                    ip->i_dev, fs->fs_bsize, size, fs->fs_fsmnt);
                panic("ffs_alloc: bad size");
        }
        if (cred == NOCRED)
                panic("ffs_alloc: missing credential\n");
#endif /* DIAGNOSTIC */
        if (size == fs->fs_bsize && fs->fs_cstotal.cs_nbfree == 0)
                goto nospace;
        if (cred->cr_uid != 0 && freespace(fs, fs->fs_minfree) <= 0)
                goto nospace;
        VOP_DEVBLOCKSIZE(ip->i_devvp,&devBlockSize);
#if QUOTA
        if (error = chkdq(ip, (int64_t)size, cred, 0))
                return (error);
#endif /* QUOTA */
        if (bpref >= fs->fs_size)
                bpref = 0;
        if (bpref == 0)
                cg = ino_to_cg(fs, ip->i_number);
        else
                cg = dtog(fs, bpref);
        bno = (ufs_daddr_t)ffs_hashalloc(ip, cg, (long)bpref, size,
            (u_int32_t (*)())ffs_alloccg);
        if (bno > 0) {
                ip->i_blocks += btodb(size, devBlockSize);
                ip->i_flag |= IN_CHANGE | IN_UPDATE;
                *bnp = bno;
                return (0);
        }
#if QUOTA
        /*
         * Restore user's disk quota because allocation failed.
         */
        (void) chkdq(ip, (int64_t)-size, cred, FORCE);
#endif /* QUOTA */
nospace:
        ffs_fserr(fs, cred->cr_uid, "file system full");
        uprintf("\n%s: write failed, file system 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.
 */
ffs_realloccg(ip, lbprev, bpref, osize, nsize, cred, bpp)
        register struct inode *ip;
        ufs_daddr_t lbprev;
        ufs_daddr_t bpref;
        int osize, nsize;
        struct ucred *cred;
        struct buf **bpp;
{
        register struct fs *fs;
        struct buf *bp;
        int cg, request, error;
        ufs_daddr_t bprev, bno;
        int devBlockSize=0;
        
        *bpp = 0;
        fs = ip->i_fs;
#if DIAGNOSTIC
        if ((u_int)osize > fs->fs_bsize || fragoff(fs, osize) != 0 ||
            (u_int)nsize > fs->fs_bsize || fragoff(fs, nsize) != 0) {
                printf(
                    "dev = 0x%x, bsize = %d, osize = %d, nsize = %d, fs = %s\n",
                    ip->i_dev, fs->fs_bsize, osize, nsize, fs->fs_fsmnt);
                panic("ffs_realloccg: bad size");
        }
        if (cred == NOCRED)
                panic("ffs_realloccg: missing credential\n");
#endif /* DIAGNOSTIC */
        if (cred->cr_uid != 0 && freespace(fs, fs->fs_minfree) <= 0)
                goto nospace;
        if ((bprev = ip->i_db[lbprev]) == 0) {
                printf("dev = 0x%x, bsize = %d, bprev = %d, fs = %s\n",
                    ip->i_dev, fs->fs_bsize, bprev, fs->fs_fsmnt);
                panic("ffs_realloccg: bad bprev");
        }
        /*
         * Allocate the extra space in the buffer.
         */
        if (error = bread(ITOV(ip), lbprev, osize, NOCRED, &bp)) {
                brelse(bp);
                return (error);
        }
        VOP_DEVBLOCKSIZE(ip->i_devvp,&devBlockSize);

#if QUOTA
        if (error = chkdq(ip, (int64_t)(nsize - osize), cred, 0))
        {
                brelse(bp);
                return (error);
        }
#endif /* QUOTA */
        /*
         * Check for extension in the existing location.
         */
        cg = dtog(fs, bprev);
        if (bno = ffs_fragextend(ip, cg, (long)bprev, osize, nsize)) {
                if (bp->b_blkno != fsbtodb(fs, bno))
                        panic("bad blockno");
                ip->i_blocks += btodb(nsize - osize, devBlockSize);
                ip->i_flag |= IN_CHANGE | IN_UPDATE;
                allocbuf(bp, nsize);
                bp->b_flags |= B_DONE;
                bzero((char *)bp->b_data + osize, (u_int)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 >
                    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 <
                    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 = 0x%x, optim = %d, fs = %s\n",
                    ip->i_dev, fs->fs_optim, fs->fs_fsmnt);
                panic("ffs_realloccg: bad optim");
                /* NOTREACHED */
        }
        bno = (ufs_daddr_t)ffs_hashalloc(ip, cg, (long)bpref, request,
            (u_int32_t (*)())ffs_alloccg);
        if (bno > 0) {
                bp->b_blkno = fsbtodb(fs, bno);
                ffs_blkfree(ip, bprev, (long)osize);
                if (nsize < request)
                        ffs_blkfree(ip, bno + numfrags(fs, nsize),
                            (long)(request - nsize));
                ip->i_blocks += btodb(nsize - osize, devBlockSize);
                ip->i_flag |= IN_CHANGE | IN_UPDATE;
                allocbuf(bp, nsize);
                bp->b_flags |= B_DONE;
                bzero((char *)bp->b_data + osize, (u_int)nsize - osize);
                *bpp = bp;
                return (0);
        }
#if QUOTA
        /*
         * Restore user's disk quota because allocation failed.
         */
        (void) chkdq(ip, (int64_t)-(nsize - osize), cred, FORCE);
#endif /* QUOTA */
        brelse(bp);
nospace:
        /*
         * no space available
         */
        ffs_fserr(fs, cred->cr_uid, "file system full");
        uprintf("\n%s: write failed, file system 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 to
 * an fs_rotdelay offset from the end of the allocation for the logical
 * block immediately preceeding 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.
 */
/* Note: This routine is unused in UBC cluster I/O */

int doasyncfree = 1;
int doreallocblks = 1;

int
ffs_reallocblks(ap)
        struct vop_reallocblks_args *ap;
{
        return (ENOSPC);
}

/*
 * Allocate an inode in the file system.
 * 
 * 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 heirarchy 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(ap)
        struct vop_valloc_args /* {
                struct vnode *a_pvp;
                int a_mode;
                struct ucred *a_cred;
                struct vnode **a_vpp;
        } */ *ap;
{
        register struct vnode *pvp = ap->a_pvp;
        register struct inode *pip;
        register struct fs *fs;
        register struct inode *ip;
        mode_t mode = ap->a_mode;
        ino_t ino, ipref;
        int cg, error;
        
        *ap->a_vpp = NULL;
        pip = VTOI(pvp);
        fs = pip->i_fs;
        if (fs->fs_cstotal.cs_nifree == 0)
                goto noinodes;

        if ((mode & IFMT) == IFDIR)
                ipref = ffs_dirpref(fs);
        else
                ipref = pip->i_number;
        if (ipref >= fs->fs_ncg * fs->fs_ipg)
                ipref = 0;
        cg = ino_to_cg(fs, ipref);
        ino = (ino_t)ffs_hashalloc(pip, cg, (long)ipref, mode, ffs_nodealloccg);
        if (ino == 0)
                goto noinodes;
        error = VFS_VGET(pvp->v_mount, ino, ap->a_vpp);
        if (error) {
                VOP_VFREE(pvp, ino, mode);
                return (error);
        }
        ip = VTOI(*ap->a_vpp);
        if (ip->i_mode) {
                printf("mode = 0%o, inum = %d, fs = %s\n",
                    ip->i_mode, ip->i_number, fs->fs_fsmnt);
                panic("ffs_valloc: dup alloc");
        }
        if (ip->i_blocks) {                             /* XXX */
                printf("free inode %s/%d had %d blocks\n",
                    fs->fs_fsmnt, ino, ip->i_blocks);
                ip->i_blocks = 0;
        }
        ip->i_flags = 0;
        /*
         * Set up a new generation number for this inode.
         */
        if (++nextgennumber < (u_long)time.tv_sec)
                nextgennumber = time.tv_sec;
        ip->i_gen = nextgennumber;
        return (0);
noinodes:
        ffs_fserr(fs, ap->a_cred->cr_uid, "out of inodes");
        uprintf("\n%s: create/symlink failed, no inodes free\n", fs->fs_fsmnt);
        return (ENOSPC);
}

/*
 * Find a cylinder to place a directory.
 *
 * The policy implemented by this algorithm is to select from
 * among those cylinder groups with above the average number of
 * free inodes, the one with the smallest number of directories.
 */
static ino_t
ffs_dirpref(fs)
        register struct fs *fs;
{
        int cg, minndir, mincg, avgifree;

        avgifree = fs->fs_cstotal.cs_nifree / fs->fs_ncg;
        minndir = fs->fs_ipg;
        mincg = 0;
        for (cg = 0; cg < fs->fs_ncg; cg++)
                if (fs->fs_cs(fs, cg).cs_ndir < minndir &&
                    fs->fs_cs(fs, cg).cs_nifree >= avgifree) {
                        mincg = cg;
                        minndir = fs->fs_cs(fs, cg).cs_ndir;
                }
        return ((ino_t)(fs->fs_ipg * mincg));
}

/*
 * 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. 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. If no blocks have been allocated in any other section, the
 * policy is to place the section 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, the information on the previous allocation is unavailable;
 * here a best guess is made based upon the logical block number being
 * allocated.
 * 
 * If a section is already partially allocated, the policy is to
 * contiguously allocate fs_maxcontig blocks.  The end of one of these
 * contiguous blocks and the beginning of the next is physically separated
 * so that the disk head will be in transit between them for at least
 * fs_rotdelay milliseconds.  This is to allow time for the processor to
 * schedule another I/O transfer.
 */
ufs_daddr_t
ffs_blkpref(ip, lbn, indx, bap)
        struct inode *ip;
        ufs_daddr_t lbn;
        int indx;
        ufs_daddr_t *bap;
{
        register struct fs *fs;
        register int cg;
        int avgbfree, startcg;
        ufs_daddr_t nextblk;
#if     REV_ENDIAN_FS
        daddr_t prev=0;
        struct vnode *vp=ITOV(ip);
        struct mount *mp=vp->v_mount;
        int rev_endian=(mp->mnt_flag & MNT_REVEND);
#endif  /* REV_ENDIAN_FS */

        fs = ip->i_fs;
#if     REV_ENDIAN_FS
        if (indx && bap) {
        if (rev_endian) {
                if (bap != &ip->i_db[0])
                        prev = NXSwapLong(bap[indx - 1]);
                else
                        prev = bap[indx - 1];
        } else prev = bap[indx - 1];
        }
        if (indx % fs->fs_maxbpg == 0 || prev == 0)
#else   /* REV_ENDIAN_FS */
        if (indx % fs->fs_maxbpg == 0 || bap[indx - 1] == 0) 
#endif /* REV_ENDIAN_FS */
        {
                if (lbn < NDADDR) {
                        cg = ino_to_cg(fs, ip->i_number);
                        return (fs->fs_fpg * cg + fs->fs_frag);
                }
                /*
                 * Find a cylinder with greater than average number of
                 * unused data blocks.
                 */
#if     REV_ENDIAN_FS
                if (indx == 0 || prev == 0)
#else   /* REV_ENDIAN_FS */
                if (indx == 0 || bap[indx - 1] == 0)
#endif /* REV_ENDIAN_FS */
                        startcg =
                            ino_to_cg(fs, ip->i_number) + lbn / fs->fs_maxbpg;
                else
#if     REV_ENDIAN_FS
                        startcg = dtog(fs, prev) + 1;
#else   /* REV_ENDIAN_FS */
                        startcg = dtog(fs, bap[indx - 1]) + 1;
#endif  /* REV_ENDIAN_FS */
                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 (fs->fs_fpg * cg + fs->fs_frag);
                        }
                for (cg = 0; cg <= startcg; cg++)
                        if (fs->fs_cs(fs, cg).cs_nbfree >= avgbfree) {
                                fs->fs_cgrotor = cg;
                                return (fs->fs_fpg * cg + fs->fs_frag);
                        }
                return (NULL);
        }
        /*
         * One or more previous blocks have been laid out. If less
         * than fs_maxcontig previous blocks are contiguous, the
         * next block is requested contiguously, otherwise it is
         * requested rotationally delayed by fs_rotdelay milliseconds.
         */
#if     REV_ENDIAN_FS
        if (rev_endian) {
                nextblk = prev + fs->fs_frag;
                if (indx < fs->fs_maxcontig) {
                        return (nextblk);
                }
                if (bap != &ip->i_db[0])
                        prev = NXSwapLong(bap[indx - fs->fs_maxcontig]);
                else
                        prev = bap[indx - fs->fs_maxcontig];
                if (prev + blkstofrags(fs, fs->fs_maxcontig) != nextblk)
                        return (nextblk);
        } else {
#endif  /* REV_ENDIAN_FS */
        nextblk = bap[indx - 1] + fs->fs_frag;
        if (indx < fs->fs_maxcontig || bap[indx - fs->fs_maxcontig] +
            blkstofrags(fs, fs->fs_maxcontig) != nextblk)
                return (nextblk);
#if REV_ENDIAN_FS
        }
#endif  /* REV_ENDIAN_FS */
        if (fs->fs_rotdelay != 0)
                /*
                 * Here we convert ms of delay to frags as:
                 * (frags) = (ms) * (rev/sec) * (sect/rev) /
                 *      ((sect/frag) * (ms/sec))
                 * then round up to the next block.
                 */
                nextblk += roundup(fs->fs_rotdelay * fs->fs_rps * fs->fs_nsect /
                    (NSPF(fs) * 1000), fs->fs_frag);
        return (nextblk);
}

/*
 * 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.
 */
/*VARARGS5*/
static u_long
ffs_hashalloc(ip, cg, pref, size, allocator)
        struct inode *ip;
        int cg;
        long pref;
        int size;       /* size for data blocks, mode for inodes */
        u_int32_t (*allocator)();
{
        register struct fs *fs;
        long result;
        int i, icg = cg;

        fs = ip->i_fs;
        /*
         * 1: preferred cylinder group
         */
        result = (*allocator)(ip, cg, pref, size);
        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);
                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);
                if (result)
                        return (result);
                cg++;
                if (cg == fs->fs_ncg)
                        cg = 0;
        }
        return (NULL);
}

/*
 * Determine whether a fragment can be extended.
 *
 * Check to see if the necessary fragments are available, and 
 * if they are, allocate them.
 */
static ufs_daddr_t
ffs_fragextend(ip, cg, bprev, osize, nsize)
        struct inode *ip;
        int cg;
        long bprev;
        int osize, nsize;
{
        register struct fs *fs;
        register struct cg *cgp;
        struct buf *bp;
        long bno;
        int frags, bbase;
        int i, error;
#if REV_ENDIAN_FS
        struct vnode *vp=ITOV(ip);
        struct mount *mp=vp->v_mount;
        int rev_endian=(mp->mnt_flag & MNT_REVEND);
#endif /* REV_ENDIAN_FS */

        fs = ip->i_fs;
        if (fs->fs_cs(fs, cg).cs_nffree < numfrags(fs, nsize - osize))
                return (NULL);
        frags = numfrags(fs, nsize); /* number of fragments needed */
        bbase = fragnum(fs, bprev); /*  offset in a frag (it is mod fragsize */
        if (bbase > fragnum(fs, (bprev + frags - 1))) {
                /* cannot extend across a block boundary */
                return (NULL);
        }
        /* read corresponding cylinder group info */
        error = bread(ip->i_devvp, fsbtodb(fs, cgtod(fs, cg)),
                (int)fs->fs_cgsize, NOCRED, &bp);
        if (error) {
                brelse(bp);
                return (NULL);
        }
        cgp = (struct cg *)bp->b_data;
#if REV_ENDIAN_FS
        if (rev_endian) {
                byte_swap_cgin(cgp, fs);
        }
#endif /* REV_ENDIAN_FS */

        if (!cg_chkmagic(cgp)) {
#if REV_ENDIAN_FS
                if (rev_endian)
                        byte_swap_cgout(cgp,fs);
#endif /* REV_ENDIAN_FS */
                brelse(bp);
                return (NULL);
        }
        cgp->cg_time = time.tv_sec;
        bno = dtogd(fs, bprev);
        for (i = numfrags(fs, osize); i < frags; i++)
                if (isclr(cg_blksfree(cgp), bno + i)) {
#if REV_ENDIAN_FS
                        if (rev_endian)
                                byte_swap_cgout(cgp,fs);
#endif /* REV_ENDIAN_FS */
                        brelse(bp);
                        return (NULL);
                }
        /*
         * 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(cg_blksfree(cgp), bno + i))
                        break;
        cgp->cg_frsum[i - numfrags(fs, osize)]--;
        if (i != frags)
                cgp->cg_frsum[i - frags]++;
        for (i = numfrags(fs, osize); i < frags; i++) {
                clrbit(cg_blksfree(cgp), bno + i);
                cgp->cg_cs.cs_nffree--;
                fs->fs_cstotal.cs_nffree--;
                fs->fs_cs(fs, cg).cs_nffree--;
        }
        fs->fs_fmod = 1;
#if REV_ENDIAN_FS
        if (rev_endian)
                byte_swap_cgout(cgp,fs);
#endif /* REV_ENDIAN_FS */
        bdwrite(bp);
        return (bprev);
}

/*
 * 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 ufs_daddr_t
ffs_alloccg(ip, cg, bpref, size)
        struct inode *ip;
        int cg;
        ufs_daddr_t bpref;
        int size;
{
        register struct fs *fs;
        register struct cg *cgp;
        struct buf *bp;
        register int i;
        int error, bno, frags, allocsiz;
#if REV_ENDIAN_FS
        struct vnode *vp=ITOV(ip);
        struct mount *mp=vp->v_mount;
        int rev_endian=(mp->mnt_flag & MNT_REVEND);
#endif /* REV_ENDIAN_FS */

        fs = ip->i_fs;
        if (fs->fs_cs(fs, cg).cs_nbfree == 0 && size == fs->fs_bsize)
                return (NULL);
        error = bread(ip->i_devvp, fsbtodb(fs, cgtod(fs, cg)),
                (int)fs->fs_cgsize, NOCRED, &bp);
        if (error) {
                brelse(bp);
                return (NULL);
        }
        cgp = (struct cg *)bp->b_data;
#if REV_ENDIAN_FS
        if (rev_endian)
                byte_swap_cgin(cgp,fs);
#endif /* REV_ENDIAN_FS */
        if (!cg_chkmagic(cgp) ||
            (cgp->cg_cs.cs_nbfree == 0 && size == fs->fs_bsize)) {
#if REV_ENDIAN_FS
                if (rev_endian)
                        byte_swap_cgout(cgp,fs);
#endif /* REV_ENDIAN_FS */
                brelse(bp);
                return (NULL);
        }
        cgp->cg_time = time.tv_sec;
        if (size == fs->fs_bsize) {
                bno = ffs_alloccgblk(fs, cgp, bpref);
#if REV_ENDIAN_FS
                if (rev_endian)
                        byte_swap_cgout(cgp,fs);
#endif /* REV_ENDIAN_FS */
                bdwrite(bp);
                return (bno);
        }
        /*
         * 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
         */
        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) {
#if     REV_ENDIAN_FS
                        if (rev_endian)
                                byte_swap_cgout(cgp,fs);
#endif  /* REV_ENDIAN_FS */
                        brelse(bp);
                        return (NULL);
                }
                bno = ffs_alloccgblk(fs, cgp, bpref);
                bpref = dtogd(fs, bno);
                for (i = frags; i < fs->fs_frag; i++)
                        setbit(cg_blksfree(cgp), bpref + i);
                i = fs->fs_frag - frags;
                cgp->cg_cs.cs_nffree += i;
                fs->fs_cstotal.cs_nffree += i;
                fs->fs_cs(fs, cg).cs_nffree += i;
                fs->fs_fmod = 1;
                cgp->cg_frsum[i]++;
#if     REV_ENDIAN_FS
                if (rev_endian)
                        byte_swap_cgout(cgp,fs);
#endif  /* REV_ENDIAN_FS */
                bdwrite(bp);
                return (bno);
        }
        bno = ffs_mapsearch(fs, cgp, bpref, allocsiz);
        if (bno < 0) {
#if     REV_ENDIAN_FS
                if (rev_endian)
                        byte_swap_cgout(cgp,fs);
#endif  /* REV_ENDIAN_FS */
                brelse(bp);
                return (NULL);
        }
        for (i = 0; i < frags; i++)
                clrbit(cg_blksfree(cgp), bno + i);
        cgp->cg_cs.cs_nffree -= frags;
        fs->fs_cstotal.cs_nffree -= frags;
        fs->fs_cs(fs, cg).cs_nffree -= frags;
        fs->fs_fmod = 1;
        cgp->cg_frsum[allocsiz]--;
        if (frags != allocsiz)
                cgp->cg_frsum[allocsiz - frags]++;
#if     REV_ENDIAN_FS
        if (rev_endian)
                byte_swap_cgout(cgp,fs);
#endif  /* REV_ENDIAN_FS */
        bdwrite(bp);
        return (cg * fs->fs_fpg + bno);
}

/*
 * 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 ufs_daddr_t
ffs_alloccgblk(fs, cgp, bpref)
        register struct fs *fs;
        register struct cg *cgp;
        ufs_daddr_t bpref;
{
        ufs_daddr_t bno, blkno;
        int cylno, pos, delta;
        short *cylbp;
        register int i;

        if (bpref == 0 || dtog(fs, bpref) != cgp->cg_cgx) {
                bpref = cgp->cg_rotor;
                goto norot;
        }
        bpref = blknum(fs, bpref);
        bpref = dtogd(fs, bpref);
        /*
         * if the requested block is available, use it
         */
        if (ffs_isblock(fs, cg_blksfree(cgp), fragstoblks(fs, bpref))) {
                bno = bpref;
                goto gotit;
        }
        if (fs->fs_nrpos <= 1 || fs->fs_cpc == 0) {
                /*
                 * Block layout information is not available.
                 * Leaving bpref unchanged means we take the
                 * next available free block following the one 
                 * we just allocated. Hopefully this will at
                 * least hit a track cache on drives of unknown
                 * geometry (e.g. SCSI).
                 */
                goto norot;
        }
        /*
         * check for a block available on the same cylinder
         */
        cylno = cbtocylno(fs, bpref);
        if (cg_blktot(cgp)[cylno] == 0)
                goto norot;
        /*
         * check the summary information to see if a block is 
         * available in the requested cylinder starting at the
         * requested rotational position and proceeding around.
         */
        cylbp = cg_blks(fs, cgp, cylno);
        pos = cbtorpos(fs, bpref);
        for (i = pos; i < fs->fs_nrpos; i++)
                if (cylbp[i] > 0)
                        break;
        if (i == fs->fs_nrpos)
                for (i = 0; i < pos; i++)
                        if (cylbp[i] > 0)
                                break;
        if (cylbp[i] > 0) {
                /*
                 * found a rotational position, now find the actual
                 * block. A panic if none is actually there.
                 */
                pos = cylno % fs->fs_cpc;
                bno = (cylno - pos) * fs->fs_spc / NSPB(fs);
                if (fs_postbl(fs, pos)[i] == -1) {
                        printf("pos = %d, i = %d, fs = %s\n",
                            pos, i, fs->fs_fsmnt);
                        panic("ffs_alloccgblk: cyl groups corrupted");
                }
                for (i = fs_postbl(fs, pos)[i];; ) {
                        if (ffs_isblock(fs, cg_blksfree(cgp), bno + i)) {
                                bno = blkstofrags(fs, (bno + i));
                                goto gotit;
                        }
                        delta = fs_rotbl(fs)[i];
                        if (delta <= 0 ||
                            delta + i > fragstoblks(fs, fs->fs_fpg))
                                break;
                        i += delta;
                }
                printf("pos = %d, i = %d, fs = %s\n", pos, i, fs->fs_fsmnt);
                panic("ffs_alloccgblk: can't find blk in cyl");
        }
norot:
        /*
         * no blocks in the requested cylinder, so take next
         * available one in this cylinder group.
         */
        bno = ffs_mapsearch(fs, cgp, bpref, (int)fs->fs_frag);
        if (bno < 0)
                return (NULL);
        cgp->cg_rotor = bno;
gotit:
        blkno = fragstoblks(fs, bno);
        ffs_clrblock(fs, cg_blksfree(cgp), (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--;
        cylno = cbtocylno(fs, bno);
        cg_blks(fs, cgp, cylno)[cbtorpos(fs, bno)]--;
        cg_blktot(cgp)[cylno]--;
        fs->fs_fmod = 1;
        return (cgp->cg_cgx * fs->fs_fpg + bno);
}

/*
 * 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 ufs_daddr_t
ffs_clusteralloc(ip, cg, bpref, len)
        struct inode *ip;
        int cg;
        ufs_daddr_t bpref;
        int len;
{
        register struct fs *fs;
        register struct cg *cgp;
        struct buf *bp;
        int i, got, run, bno, bit, map;
        u_char *mapp;
        int32_t *lp;
#if REV_ENDIAN_FS
        struct vnode *vp=ITOV(ip);
        struct mount *mp=vp->v_mount;
        int rev_endian=(mp->mnt_flag & MNT_REVEND);
#endif /* REV_ENDIAN_FS */

        fs = ip->i_fs;
        if (fs->fs_maxcluster[cg] < len)
                return (NULL);
        if (bread(ip->i_devvp, fsbtodb(fs, cgtod(fs, cg)), (int)fs->fs_cgsize,
            NOCRED, &bp))
                goto fail;
        cgp = (struct cg *)bp->b_data;
#if     REV_ENDIAN_FS
        if (rev_endian)
                byte_swap_cgin(cgp,fs);
#endif  /* REV_ENDIAN_FS */
        if (!cg_chkmagic(cgp)) {
#if     REV_ENDIAN_FS
                if (rev_endian)
                        byte_swap_cgout(cgp,fs);
#endif  /* REV_ENDIAN_FS */
                goto fail;
        }
        /*
         * 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;
                fs->fs_maxcluster[cg] = i;
#if     REV_ENDIAN_FS
                if (rev_endian)
                        byte_swap_cgout(cgp,fs);
#endif  /* REV_ENDIAN_FS */
                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 = 0;
        else
                bpref = fragstoblks(fs, dtogd(fs, blknum(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) {
#if     REV_ENDIAN_FS
                if (rev_endian)
                        byte_swap_cgout(cgp,fs);
#endif  /* REV_ENDIAN_FS */
                goto fail;
        }
        /*
         * Allocate the cluster that we have found.
         */
        for (i = 1; i <= len; i++)
                if (!ffs_isblock(fs, cg_blksfree(cgp), got - run + i))
                        panic("ffs_clusteralloc: map mismatch");
        bno = cg * fs->fs_fpg + blkstofrags(fs, got - run + 1);
        if (dtog(fs, bno) != cg)
                panic("ffs_clusteralloc: allocated out of group");
        len = blkstofrags(fs, len);
        for (i = 0; i < len; i += fs->fs_frag)
                if ((got = ffs_alloccgblk(fs, cgp, bno + i)) != bno + i)
                        panic("ffs_clusteralloc: lost block");
#if     REV_ENDIAN_FS
        if (rev_endian)
                byte_swap_cgout(cgp,fs);
#endif  /* REV_ENDIAN_FS */
        bdwrite(bp);
        return (bno);

fail:
        brelse(bp);
        return (0);
}

/*
 * 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 ino_t
ffs_nodealloccg(ip, cg, ipref, mode)
        struct inode *ip;
        int cg;
        ufs_daddr_t ipref;
        int mode;
{
        register struct fs *fs;
        register struct cg *cgp;
        struct buf *bp;
        int error, start, len, loc, map, i;
#if REV_ENDIAN_FS
        struct vnode *vp=ITOV(ip);
        struct mount *mp=vp->v_mount;
        int rev_endian=(mp->mnt_flag & MNT_REVEND);
#endif /* REV_ENDIAN_FS */

        fs = ip->i_fs;
        if (fs->fs_cs(fs, cg).cs_nifree == 0)
                return (NULL);
        error = bread(ip->i_devvp, fsbtodb(fs, cgtod(fs, cg)),
                (int)fs->fs_cgsize, NOCRED, &bp);
        if (error) {
                brelse(bp);
                return (NULL);
        }
        cgp = (struct cg *)bp->b_data;
#if REV_ENDIAN_FS
        if (rev_endian)
                byte_swap_cgin(cgp,fs);
#endif /* REV_ENDIAN_FS */
        if (!cg_chkmagic(cgp) || cgp->cg_cs.cs_nifree == 0) {
#if REV_ENDIAN_FS
                if (rev_endian)
                        byte_swap_cgout(cgp,fs);
#endif /* REV_ENDIAN_FS */
                brelse(bp);
                return (NULL);
        }

        cgp->cg_time = time.tv_sec;
        if (ipref) {
                ipref %= fs->fs_ipg;
                if (isclr(cg_inosused(cgp), ipref))
                        goto gotit;
        }
        start = cgp->cg_irotor / NBBY;
        len = howmany(fs->fs_ipg - cgp->cg_irotor, NBBY);
        loc = skpc(0xff, len, &cg_inosused(cgp)[start]);
        if (loc == 0) {
                len = start + 1;
                start = 0;
                loc = skpc(0xff, len, &cg_inosused(cgp)[0]);
                if (loc == 0) {
                        printf("cg = %d, irotor = %d, fs = %s\n",
                            cg, cgp->cg_irotor, fs->fs_fsmnt);
                        panic("ffs_nodealloccg: map corrupted");
                        /* NOTREACHED */
                }
        }
        i = start + len - loc;
        map = cg_inosused(cgp)[i];
        ipref = i * NBBY;
        for (i = 1; i < (1 << NBBY); i <<= 1, ipref++) {
                if ((map & i) == 0) {
                        cgp->cg_irotor = ipref;
                        goto gotit;
                }
        }
        printf("fs = %s\n", fs->fs_fsmnt);
        panic("ffs_nodealloccg: block not in map");
        /* NOTREACHED */
gotit:
        setbit(cg_inosused(cgp), 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++;
        }
#if REV_ENDIAN_FS
        if (rev_endian)
                byte_swap_cgout(cgp,fs);
#endif /* REV_ENDIAN_FS */
        bdwrite(bp);
        return (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.
 */
ffs_blkfree(ip, bno, size)
        register struct inode *ip;
        ufs_daddr_t bno;
        long size;
{
        register struct fs *fs;
        register struct cg *cgp;
        struct buf *bp;
        ufs_daddr_t blkno;
        int i, error, cg, blk, frags, bbase;
#if REV_ENDIAN_FS
        struct vnode *vp=ITOV(ip);
        struct mount *mp=vp->v_mount;
        int rev_endian=(mp->mnt_flag & MNT_REVEND);
#endif /* REV_ENDIAN_FS */
        fs = ip->i_fs;
        if ((u_int)size > fs->fs_bsize || fragoff(fs, size) != 0) {
                printf("dev = 0x%x, bsize = %d, size = %d, fs = %s\n",
                    ip->i_dev, fs->fs_bsize, size, fs->fs_fsmnt);
                panic("blkfree: bad size");
        }
        cg = dtog(fs, bno);
        if ((u_int)bno >= fs->fs_size) {
                printf("bad block %d, ino %d\n", bno, ip->i_number);
                ffs_fserr(fs, ip->i_uid, "bad block");
                return;
        }
        error = bread(ip->i_devvp, fsbtodb(fs, cgtod(fs, cg)),
                (int)fs->fs_cgsize, NOCRED, &bp);
        if (error) {
                brelse(bp);
                return;
        }
        cgp = (struct cg *)bp->b_data;
#if REV_ENDIAN_FS
        if (rev_endian)
                byte_swap_cgin(cgp,fs);
#endif /* REV_ENDIAN_FS */
        if (!cg_chkmagic(cgp)) {
#if REV_ENDIAN_FS
                if (rev_endian)
                        byte_swap_cgout(cgp,fs);
#endif /* REV_ENDIAN_FS */
                brelse(bp);
                return;
        }
        cgp->cg_time = time.tv_sec;
        bno = dtogd(fs, bno);
        if (size == fs->fs_bsize) {
                blkno = fragstoblks(fs, bno);
                if (ffs_isblock(fs, cg_blksfree(cgp), blkno)) {
                        printf("dev = 0x%x, block = %d, fs = %s\n",
                            ip->i_dev, bno, fs->fs_fsmnt);
                        panic("blkfree: freeing free block");
                }
                ffs_setblock(fs, cg_blksfree(cgp), blkno);
                ffs_clusteracct(fs, cgp, blkno, 1);
                cgp->cg_cs.cs_nbfree++;
                fs->fs_cstotal.cs_nbfree++;
                fs->fs_cs(fs, cg).cs_nbfree++;
                i = cbtocylno(fs, bno);
                cg_blks(fs, cgp, i)[cbtorpos(fs, bno)]++;
                cg_blktot(cgp)[i]++;
        } else {
                bbase = bno - fragnum(fs, bno);
                /*
                 * decrement the counts associated with the old frags
                 */
                blk = blkmap(fs, cg_blksfree(cgp), bbase);
                ffs_fragacct(fs, blk, cgp->cg_frsum, -1);
                /*
                 * deallocate the fragment
                 */
                frags = numfrags(fs, size);
                for (i = 0; i < frags; i++) {
                        if (isset(cg_blksfree(cgp), bno + i)) {
                                printf("dev = 0x%x, block = %d, fs = %s\n",
                                    ip->i_dev, bno + i, fs->fs_fsmnt);
                                panic("blkfree: freeing free frag");
                        }
                        setbit(cg_blksfree(cgp), bno + 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, cg_blksfree(cgp), bbase);
                ffs_fragacct(fs, blk, cgp->cg_frsum, 1);
                /*
                 * if a complete block has been reassembled, account for it
                 */
                blkno = fragstoblks(fs, bbase);
                if (ffs_isblock(fs, cg_blksfree(cgp), blkno)) {
                        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, blkno, 1);
                        cgp->cg_cs.cs_nbfree++;
                        fs->fs_cstotal.cs_nbfree++;
                        fs->fs_cs(fs, cg).cs_nbfree++;
                        i = cbtocylno(fs, bbase);
                        cg_blks(fs, cgp, i)[cbtorpos(fs, bbase)]++;
                        cg_blktot(cgp)[i]++;
                }
        }
        fs->fs_fmod = 1;
#if REV_ENDIAN_FS
        if (rev_endian)
                byte_swap_cgout(cgp,fs);
#endif /* REV_ENDIAN_FS */
        bdwrite(bp);
}

#if DIAGNOSTIC
/*
 * Verify allocation of a block or fragment. Returns true if block or
 * fragment is allocated, false if it is free.
 */
ffs_checkblk(ip, bno, size)
        struct inode *ip;
        ufs_daddr_t bno;
        long size;
{
        struct fs *fs;
        struct cg *cgp;
        struct buf *bp;
        int i, error, frags, free;
#if REV_ENDIAN_FS
        struct vnode *vp=ITOV(ip);
        struct mount *mp=vp->v_mount;
        int rev_endian=(mp->mnt_flag & MNT_REVEND);
#endif /* REV_ENDIAN_FS */

        fs = ip->i_fs;
        if ((u_int)size > fs->fs_bsize || fragoff(fs, size) != 0) {
                printf("bsize = %d, size = %d, fs = %s\n",
                    fs->fs_bsize, size, fs->fs_fsmnt);
                panic("checkblk: bad size");
        }
        if ((u_int)bno >= fs->fs_size)
                panic("checkblk: bad block %d", bno);
        error = bread(ip->i_devvp, fsbtodb(fs, cgtod(fs, dtog(fs, bno))),
                (int)fs->fs_cgsize, NOCRED, &bp);
        if (error) {
                brelse(bp);
                return;
        }
        cgp = (struct cg *)bp->b_data;
#if REV_ENDIAN_FS
        if (rev_endian)
                byte_swap_cgin(cgp,fs);
#endif /* REV_ENDIAN_FS */
        if (!cg_chkmagic(cgp)) {
#if REV_ENDIAN_FS
                if (rev_endian)
                        byte_swap_cgout(cgp,fs);
#endif /* REV_ENDIAN_FS */
                brelse(bp);
                return;
        }
        bno = dtogd(fs, bno);
        if (size == fs->fs_bsize) {
                free = ffs_isblock(fs, cg_blksfree(cgp), fragstoblks(fs, bno));
        } else {
                frags = numfrags(fs, size);
                for (free = 0, i = 0; i < frags; i++)
                        if (isset(cg_blksfree(cgp), bno + i))
                                free++;
                if (free != 0 && free != frags)
                        panic("checkblk: partially free fragment");
        }
#if REV_ENDIAN_FS
        if (rev_endian)
                byte_swap_cgout(cgp,fs);
#endif /* REV_ENDIAN_FS */
        brelse(bp);
        return (!free);
}
#endif /* DIAGNOSTIC */

/*
 * Free an inode.
 *
 * The specified inode is placed back in the free map.
 */
int
ffs_vfree(ap)
        struct vop_vfree_args /* {
                struct vnode *a_pvp;
                ino_t a_ino;
                int a_mode;
        } */ *ap;
{
        register struct fs *fs;
        register struct cg *cgp;
        register struct inode *pip;
        ino_t ino = ap->a_ino;
        struct buf *bp;
        int error, cg;
#if REV_ENDIAN_FS
        struct vnode *vp=ap->a_pvp;
        struct mount *mp=vp->v_mount;
        int rev_endian=(mp->mnt_flag & MNT_REVEND);
#endif /* REV_ENDIAN_FS */

        pip = VTOI(ap->a_pvp);
        fs = pip->i_fs;
        if ((u_int)ino >= fs->fs_ipg * fs->fs_ncg)
                panic("ifree: range: dev = 0x%x, ino = %d, fs = %s\n",
                    pip->i_dev, ino, fs->fs_fsmnt);
        cg = ino_to_cg(fs, ino);
        error = bread(pip->i_devvp, fsbtodb(fs, cgtod(fs, cg)),
                (int)fs->fs_cgsize, NOCRED, &bp);
        if (error) {
                brelse(bp);
                return (0);
        }
        cgp = (struct cg *)bp->b_data;
#if REV_ENDIAN_FS
        if (rev_endian)
                byte_swap_cgin(cgp,fs);
#endif /* REV_ENDIAN_FS */
        if (!cg_chkmagic(cgp)) {
#if REV_ENDIAN_FS
                if (rev_endian)
                        byte_swap_cgout(cgp,fs);
#endif /* REV_ENDIAN_FS */
                brelse(bp);
                return (0);
        }
        cgp->cg_time = time.tv_sec;
        ino %= fs->fs_ipg;
        if (isclr(cg_inosused(cgp), ino)) {
                printf("dev = 0x%x, ino = %d, fs = %s\n",
                    pip->i_dev, ino, fs->fs_fsmnt);
                if (fs->fs_ronly == 0)
                        panic("ifree: freeing free inode");
        }
        clrbit(cg_inosused(cgp), ino);
        if (ino < cgp->cg_irotor)
                cgp->cg_irotor = ino;
        cgp->cg_cs.cs_nifree++;
        fs->fs_cstotal.cs_nifree++;
        fs->fs_cs(fs, cg).cs_nifree++;
        if ((ap->a_mode & IFMT) == IFDIR) {
                cgp->cg_cs.cs_ndir--;
                fs->fs_cstotal.cs_ndir--;
                fs->fs_cs(fs, cg).cs_ndir--;
        }
        fs->fs_fmod = 1;
#if REV_ENDIAN_FS
        if (rev_endian)
                byte_swap_cgout(cgp,fs);
#endif /* REV_ENDIAN_FS */
        bdwrite(bp);
        return (0);
}

/*
 * 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 ufs_daddr_t
ffs_mapsearch(fs, cgp, bpref, allocsiz)
        register struct fs *fs;
        register struct cg *cgp;
        ufs_daddr_t bpref;
        int allocsiz;
{
        ufs_daddr_t bno;
        int start, len, loc, i;
        int blk, field, subfield, pos;

        /*
         * 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;
        len = howmany(fs->fs_fpg, NBBY) - start;
        loc = scanc((u_int)len, (u_char *)&cg_blksfree(cgp)[start],
                (u_char *)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 *)&cg_blksfree(cgp)[0],
                        (u_char *)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, cg_blksfree(cgp), 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 = %d, fs = %s\n", bno, fs->fs_fsmnt);
        panic("ffs_alloccg: block not in map");
        return (-1);
}

/*
 * Update the cluster map because of an allocation or free.
 *
 * Cnt == 1 means free; cnt == -1 means allocating.
 */
ffs_clusteracct(fs, cgp, blkno, cnt)
        struct fs *fs;
        struct cg *cgp;
        ufs_daddr_t blkno;
        int cnt;
{
        int32_t *sump;
        int32_t *lp;
        u_char *freemapp, *mapp;
        int i, start, end, forw, back, map, bit;

        if (fs->fs_contigsumsize <= 0)
                return;
        freemapp = cg_clustersfree(cgp);
        sump = cg_clustersum(cgp);
        /*
         * Allocate or clear the actual block.
         */
        if (cnt > 0)
                setbit(freemapp, blkno);
        else
                clrbit(freemapp, blkno);
        /*
         * Find the size of the cluster going forward.
         */
        start = blkno + 1;
        end = start + fs->fs_contigsumsize;
        if (end >= cgp->cg_nclusterblks)
                end = cgp->cg_nclusterblks;
        mapp = &freemapp[start / NBBY];
        map = *mapp++;
        bit = 1 << (start % NBBY);
        for (i = start; i < end; i++) {
                if ((map & bit) == 0)
                        break;
                if ((i & (NBBY - 1)) != (NBBY - 1)) {
                        bit <<= 1;
                } else {
                        map = *mapp++;
                        bit = 1;
                }
        }
        forw = i - start;
        /*
         * Find the size of the cluster going backward.
         */
        start = blkno - 1;
        end = start - fs->fs_contigsumsize;
        if (end < 0)
                end = -1;
        mapp = &freemapp[start / NBBY];
        map = *mapp--;
        bit = 1 << (start % NBBY);
        for (i = start; i > end; i--) {
                if ((map & bit) == 0)
                        break;
                if ((i & (NBBY - 1)) != 0) {
                        bit >>= 1;
                } else {
                        map = *mapp--;
                        bit = 1 << (NBBY - 1);
                }
        }
        back = start - i;
        /*
         * Account for old cluster and the possibly new forward and
         * back clusters.
         */
        i = back + forw + 1;
        if (i > fs->fs_contigsumsize)
                i = fs->fs_contigsumsize;
        sump[i] += cnt;
        if (back > 0)
                sump[back] -= cnt;
        if (forw > 0)
                sump[forw] -= cnt;
        /*
         * Update cluster summary information.
         */
        lp = &sump[fs->fs_contigsumsize];
        for (i = fs->fs_contigsumsize; i > 0; i--)
                if (*lp-- > 0)
                        break;
        fs->fs_maxcluster[cgp->cg_cgx] = i;
}

/*
 * Fserr prints the name of a file system with an error diagnostic.
 * 
 * The form of the error message is:
 *      fs: error message
 */
static void
ffs_fserr(fs, uid, cp)
        struct fs *fs;
        u_int uid;
        char *cp;
{

        log(LOG_ERR, "uid %d on %s: %s\n", uid, fs->fs_fsmnt, cp);
}