xref: /src/sys/ufs/ffs/ffs_alloc.c

/*	$NetBSD: ffs_alloc.c,v 1.97 2007/01/04 16:55:29 elad Exp $	*/

/*
 * 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
 *
 * 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	8.19 (Berkeley) 7/13/95
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: ffs_alloc.c,v 1.97 2007/01/04 16:55:29 elad Exp $");

#if defined(_KERNEL_OPT)
#include "opt_ffs.h"
#include "opt_quota.h"
#endif

#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/kauth.h>

#include <miscfs/specfs/specdev.h>
#include <ufs/ufs/quota.h>
#include <ufs/ufs/ufsmount.h>
#include <ufs/ufs/inode.h>
#include <ufs/ufs/ufs_extern.h>
#include <ufs/ufs/ufs_bswap.h>

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

static daddr_t ffs_alloccg(struct inode *, int, daddr_t, int);
static daddr_t ffs_alloccgblk(struct inode *, struct buf *, daddr_t);
#ifdef XXXUBC
static daddr_t ffs_clusteralloc(struct inode *, int, daddr_t, int);
#endif
static ino_t ffs_dirpref(struct inode *);
static daddr_t ffs_fragextend(struct inode *, int, daddr_t, int, int);
static void ffs_fserr(struct fs *, u_int, const char *);
static daddr_t ffs_hashalloc(struct inode *, int, daddr_t, int,
    daddr_t (*)(struct inode *, int, daddr_t, int));
static daddr_t ffs_nodealloccg(struct inode *, int, daddr_t, int);
static int32_t ffs_mapsearch(struct fs *, struct cg *,
				      daddr_t, int);
#if defined(DIAGNOSTIC) || defined(DEBUG)
#ifdef XXXUBC
static int ffs_checkblk(struct inode *, daddr_t, long size);
#endif
#endif

/* if 1, changes in optimalization strategy are logged */
int ffs_log_changeopt = 0;

/* in ffs_tables.c */
extern const int inside[], around[];
extern const u_char * const fragtbl[];

/*
 * 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 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(struct inode *ip, daddr_t lbn, daddr_t bpref, int size,
    kauth_cred_t cred, daddr_t *bnp)
{
	struct fs *fs;
	daddr_t bno;
	int cg;
#ifdef QUOTA
	int error;
#endif

	fs = ip->i_fs;

#ifdef UVM_PAGE_TRKOWN
	if (ITOV(ip)->v_type == VREG &&
	    lblktosize(fs, (voff_t)lbn) < round_page(ITOV(ip)->v_size)) {
		struct vm_page *pg;
		struct uvm_object *uobj = &ITOV(ip)->v_uobj;
		voff_t off = trunc_page(lblktosize(fs, lbn));
		voff_t endoff = round_page(lblktosize(fs, lbn) + size);

		simple_lock(&uobj->vmobjlock);
		while (off < endoff) {
			pg = uvm_pagelookup(uobj, off);
			KASSERT(pg != NULL);
			KASSERT(pg->owner == curproc->p_pid);
			off += PAGE_SIZE;
		}
		simple_unlock(&uobj->vmobjlock);
	}
#endif

	*bnp = 0;
#ifdef 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");
#endif /* DIAGNOSTIC */
	if (size == fs->fs_bsize && fs->fs_cstotal.cs_nbfree == 0)
		goto nospace;
	if (kauth_authorize_generic(cred, KAUTH_GENERIC_ISSUSER, NULL) != 0 &&
	    freespace(fs, fs->fs_minfree) <= 0)
		goto nospace;
#ifdef QUOTA
	if ((error = chkdq(ip, btodb(size), cred, 0)) != 0)
		return (error);
#endif
	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, ffs_alloccg);
	if (bno > 0) {
		DIP_ADD(ip, blocks, btodb(size));
		ip->i_flag |= IN_CHANGE | IN_UPDATE;
		*bnp = bno;
		return (0);
	}
#ifdef QUOTA
	/*
	 * Restore user's disk quota because allocation failed.
	 */
	(void) chkdq(ip, -btodb(size), cred, FORCE);
#endif
nospace:
	ffs_fserr(fs, kauth_cred_geteuid(cred), "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.
 */
int
ffs_realloccg(struct inode *ip, daddr_t lbprev, daddr_t bpref, int osize,
    int nsize, kauth_cred_t cred, struct buf **bpp, daddr_t *blknop)
{
	struct fs *fs;
	struct buf *bp;
	int cg, request, error;
	daddr_t bprev, bno;

	fs = ip->i_fs;
#ifdef UVM_PAGE_TRKOWN
	if (ITOV(ip)->v_type == VREG) {
		struct vm_page *pg;
		struct uvm_object *uobj = &ITOV(ip)->v_uobj;
		voff_t off = trunc_page(lblktosize(fs, lbprev));
		voff_t endoff = round_page(lblktosize(fs, lbprev) + osize);

		simple_lock(&uobj->vmobjlock);
		while (off < endoff) {
			pg = uvm_pagelookup(uobj, off);
			KASSERT(pg != NULL);
			KASSERT(pg->owner == curproc->p_pid);
			KASSERT((pg->flags & PG_CLEAN) == 0);
			off += PAGE_SIZE;
		}
		simple_unlock(&uobj->vmobjlock);
	}
#endif

#ifdef 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");
#endif /* DIAGNOSTIC */
	if (kauth_authorize_generic(cred, KAUTH_GENERIC_ISSUSER, NULL) != 0 &&
	    freespace(fs, fs->fs_minfree) <= 0)
		goto nospace;
	if (fs->fs_magic == FS_UFS2_MAGIC)
		bprev = ufs_rw64(ip->i_ffs2_db[lbprev], UFS_FSNEEDSWAP(fs));
	else
		bprev = ufs_rw32(ip->i_ffs1_db[lbprev], UFS_FSNEEDSWAP(fs));

	if (bprev == 0) {
		printf("dev = 0x%x, bsize = %d, bprev = %" PRId64 ", 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 (bpp != NULL &&
	    (error = bread(ITOV(ip), lbprev, osize, NOCRED, &bp)) != 0) {
		brelse(bp);
		return (error);
	}
#ifdef QUOTA
	if ((error = chkdq(ip, btodb(nsize - osize), cred, 0)) != 0) {
		if (bpp != NULL) {
			brelse(bp);
		}
		return (error);
	}
#endif
	/*
	 * Check for extension in the existing location.
	 */
	cg = dtog(fs, bprev);
	if ((bno = ffs_fragextend(ip, cg, bprev, osize, nsize)) != 0) {
		DIP_ADD(ip, blocks, btodb(nsize - osize));
		ip->i_flag |= IN_CHANGE | IN_UPDATE;

		if (bpp != NULL) {
			if (bp->b_blkno != fsbtodb(fs, bno))
				panic("bad blockno");
			allocbuf(bp, nsize, 1);
			bp->b_flags |= B_DONE;
			memset(bp->b_data + osize, 0, nsize - osize);
			*bpp = bp;
		}
		if (blknop != NULL) {
			*blknop = bno;
		}
		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;

		if (ffs_log_changeopt) {
			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;

		if (ffs_log_changeopt) {
			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 = ffs_hashalloc(ip, cg, bpref, request, ffs_alloccg);
	if (bno > 0) {
		if (!DOINGSOFTDEP(ITOV(ip)))
			ffs_blkfree(fs, ip->i_devvp, bprev, (long)osize,
			    ip->i_number);
		if (nsize < request)
			ffs_blkfree(fs, ip->i_devvp, bno + numfrags(fs, nsize),
			    (long)(request - nsize), ip->i_number);
		DIP_ADD(ip, blocks, btodb(nsize - osize));
		ip->i_flag |= IN_CHANGE | IN_UPDATE;
		if (bpp != NULL) {
			bp->b_blkno = fsbtodb(fs, bno);
			allocbuf(bp, nsize, 1);
			bp->b_flags |= B_DONE;
			memset(bp->b_data + osize, 0, (u_int)nsize - osize);
			*bpp = bp;
		}
		if (blknop != NULL) {
			*blknop = bno;
		}
		return (0);
	}
#ifdef QUOTA
	/*
	 * Restore user's disk quota because allocation failed.
	 */
	(void) chkdq(ip, -btodb(nsize - osize), cred, FORCE);
#endif
	if (bpp != NULL) {
		brelse(bp);
	}

nospace:
	/*
	 * no space available
	 */
	ffs_fserr(fs, kauth_cred_geteuid(cred), "file system full");
	uprintf("\n%s: write failed, file system is full\n", fs->fs_fsmnt);
	return (ENOSPC);
}

#if 0
/*
 * 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.

 */
#ifdef XXXUBC
#ifdef DEBUG
#include <sys/sysctl.h>
int prtrealloc = 0;
struct ctldebug debug15 = { "prtrealloc", &prtrealloc };
#endif
#endif

/*
 * NOTE: when re-enabling this, it must be updated for UFS2.
 */

int doasyncfree = 1;

int
ffs_reallocblks(void *v)
{
#ifdef XXXUBC
	struct vop_reallocblks_args /* {
		struct vnode *a_vp;
		struct cluster_save *a_buflist;
	} */ *ap = v;
	struct fs *fs;
	struct inode *ip;
	struct vnode *vp;
	struct buf *sbp, *ebp;
	int32_t *bap, *ebap = NULL, *sbap;	/* XXX ondisk32 */
	struct cluster_save *buflist;
	daddr_t start_lbn, end_lbn, soff, newblk, blkno;
	struct indir start_ap[NIADDR + 1], end_ap[NIADDR + 1], *idp;
	int i, len, start_lvl, end_lvl, pref, ssize;
#endif /* XXXUBC */

	/* XXXUBC don't reallocblks for now */
	return ENOSPC;

#ifdef XXXUBC
	vp = ap->a_vp;
	ip = VTOI(vp);
	fs = ip->i_fs;
	if (fs->fs_contigsumsize <= 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 DIAGNOSTIC
	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 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_ffs1_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 = (int32_t *)sbp->b_data;
		soff = idp->in_off;
	}
	/*
	 * Find the preferred location for the cluster.
	 */
	pref = ffs_blkpref(ip, start_lbn, soff, sbap);
	/*
	 * If the block range spans two block maps, get the second map.
	 */
	if (end_lvl == 0 || (idp = &end_ap[end_lvl - 1])->in_off + 1 >= len) {
		ssize = len;
	} else {
#ifdef DIAGNOSTIC
		if (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 = (int32_t *)ebp->b_data;	/* XXX ondisk32 */
	}
	/*
	 * Search the block map looking for an allocation of the desired size.
	 */
	if ((newblk = (daddr_t)ffs_hashalloc(ip, dtog(fs, pref), (long)pref,
	    len, ffs_clusteralloc)) == 0)
		goto fail;
	/*
	 * We have found a new contiguous block.
	 *
	 * First we have to replace the old block pointers with the new
	 * block pointers in the inode and indirect blocks associated
	 * with the file.
	 */
#ifdef DEBUG
	if (prtrealloc)
		printf("realloc: ino %d, lbns %d-%d\n\told:", ip->i_number,
		    start_lbn, end_lbn);
#endif
	blkno = newblk;
	for (bap = &sbap[soff], i = 0; i < len; i++, blkno += fs->fs_frag) {
		daddr_t ba;

		if (i == ssize) {
			bap = ebap;
			soff = -i;
		}
		/* XXX ondisk32 */
		ba = ufs_rw32(*bap, UFS_FSNEEDSWAP(fs));
#ifdef DIAGNOSTIC
		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) != ba)
			panic("ffs_reallocblks: alloc mismatch");
#endif
#ifdef DEBUG
		if (prtrealloc)
			printf(" %d,", ba);
#endif
 		if (DOINGSOFTDEP(vp)) {
 			if (sbap == &ip->i_ffs1_db[0] && i < ssize)
 				softdep_setup_allocdirect(ip, start_lbn + i,
 				    blkno, ba, 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,
 				    ba, buflist->bs_children[i]);
 		}
		/* XXX ondisk32 */
		*bap++ = ufs_rw32((u_int32_t)blkno, UFS_FSNEEDSWAP(fs));
	}
	/*
	 * 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_ffs1_db[0]) {
		if (doasyncfree)
			bdwrite(sbp);
		else
			bwrite(sbp);
	} else {
		ip->i_flag |= IN_CHANGE | IN_UPDATE;
		if (!doasyncfree)
			ffs_update(vp, NULL, NULL, 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(fs, ip->i_devvp,
			    dbtofsb(fs, buflist->bs_children[i]->b_blkno),
			    fs->fs_bsize, ip->i_number);
		buflist->bs_children[i]->b_blkno = fsbtodb(fs, blkno);
#ifdef DEBUG
		if (!ffs_checkblk(ip,
		   dbtofsb(fs, buflist->bs_children[i]->b_blkno), fs->fs_bsize))
			panic("ffs_reallocblks: unallocated block 3");
		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_ffs1_db[0])
		brelse(sbp);
	return (ENOSPC);
#endif /* XXXUBC */
}
#endif /* 0 */

/*
 * 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 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(struct vnode *pvp, int mode, kauth_cred_t cred,
    struct vnode **vpp)
{
	struct inode *pip;
	struct fs *fs;
	struct inode *ip;
	struct timespec ts;
	ino_t ino, ipref;
	int cg, error;

	*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(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, ffs_nodealloccg);
	if (ino == 0)
		goto noinodes;
	error = VFS_VGET(pvp->v_mount, ino, vpp);
	if (error) {
		ffs_vfree(pvp, ino, mode);
		return (error);
	}
	KASSERT((*vpp)->v_type == VNON);
	ip = VTOI(*vpp);
	if (ip->i_mode) {
#if 0
		printf("mode = 0%o, inum = %d, fs = %s\n",
		    ip->i_mode, ip->i_number, fs->fs_fsmnt);
#else
		printf("dmode %x mode %x dgen %x gen %x\n",
		    DIP(ip, mode), ip->i_mode,
		    DIP(ip, gen), ip->i_gen);
		printf("size %llx blocks %llx\n",
		    (long long)DIP(ip, size), (long long)DIP(ip, blocks));
		printf("ino %llu ipref %llu\n", (unsigned long long)ino,
		    (unsigned long long)ipref);
#if 0
		error = bread(ump->um_devvp, fsbtodb(fs, ino_to_fsba(fs, ino)),
		    (int)fs->fs_bsize, NOCRED, &bp);
#endif

#endif
		panic("ffs_valloc: dup alloc");
	}
	if (DIP(ip, blocks)) {				/* XXX */
		printf("free inode %s/%llu had %" PRId64 " blocks\n",
		    fs->fs_fsmnt, (unsigned long long)ino, DIP(ip, blocks));
		DIP_ASSIGN(ip, blocks, 0);
	}
	ip->i_flag &= ~IN_SPACECOUNTED;
	ip->i_flags = 0;
	DIP_ASSIGN(ip, flags, 0);
	/*
	 * Set up a new generation number for this inode.
	 */
	ip->i_gen++;
	DIP_ASSIGN(ip, gen, ip->i_gen);
	if (fs->fs_magic == FS_UFS2_MAGIC) {
		vfs_timestamp(&ts);
		ip->i_ffs2_birthtime = ts.tv_sec;
		ip->i_ffs2_birthnsec = ts.tv_nsec;
	}
	return (0);
noinodes:
	ffs_fserr(fs, kauth_cred_geteuid(cred), "out of inodes");
	uprintf("\n%s: create/symlink failed, no inodes free\n", fs->fs_fsmnt);
	return (ENOSPC);
}

/*
 * Find a cylinder group in which 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(struct inode *pip)
{
	register struct fs *fs;
	int cg, prefcg;
	int64_t dirsize, cgsize, curdsz;
	int avgifree, avgbfree, avgndir;
	int minifree, minbfree, maxndir;
	int mincg, minndir;
	int maxcontigdirs;

	fs = pip->i_fs;

	avgifree = fs->fs_cstotal.cs_nifree / fs->fs_ncg;
	avgbfree = fs->fs_cstotal.cs_nbfree / fs->fs_ncg;
	avgndir = fs->fs_cstotal.cs_ndir / fs->fs_ncg;

	/*
	 * Force allocation in another cg if creating a first level dir.
	 */
	if (ITOV(pip)->v_flag & VROOT) {
		prefcg = random() % 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 - fs->fs_ipg / 4;
	if (minifree < 0)
		minifree = 0;
	minbfree = avgbfree - fragstoblks(fs, fs->fs_fpg) / 4;
	if (minbfree < 0)
		minbfree = 0;
	cgsize = (int64_t)fs->fs_fsize * fs->fs_fpg;
	dirsize = (int64_t)fs->fs_avgfilesize * fs->fs_avgfpdir;
	if (avgndir != 0) {
		curdsz = (cgsize - (int64_t)avgbfree * fs->fs_bsize) / avgndir;
		if (dirsize < curdsz)
			dirsize = curdsz;
	}
	if (cgsize < dirsize * 255)
		maxcontigdirs = cgsize / dirsize;
	else
		maxcontigdirs = 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.
	 */
	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 are deficient 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. 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 laid out
 * contigously if possible.
 */
daddr_t
ffs_blkpref_ufs1(struct inode *ip, daddr_t lbn, int indx,
    int32_t *bap /* XXX ondisk32 */)
{
	struct fs *fs;
	int cg;
	int avgbfree, startcg;

	fs = ip->i_fs;
	if (indx % fs->fs_maxbpg == 0 || bap[indx - 1] == 0) {
		if (lbn < NDADDR + NINDIR(fs)) {
			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 (indx == 0 || bap[indx - 1] == 0)
			startcg =
			    ino_to_cg(fs, ip->i_number) + lbn / fs->fs_maxbpg;
		else
			startcg = dtog(fs,
				ufs_rw32(bap[indx - 1], UFS_FSNEEDSWAP(fs)) + 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) {
				return (fs->fs_fpg * cg + fs->fs_frag);
			}
		for (cg = 0; cg < startcg; cg++)
			if (fs->fs_cs(fs, cg).cs_nbfree >= avgbfree) {
				return (fs->fs_fpg * cg + fs->fs_frag);
			}
		return (0);
	}
	/*
	 * We just always try to lay things out contiguously.
	 */
	return ufs_rw32(bap[indx - 1], UFS_FSNEEDSWAP(fs)) + fs->fs_frag;
}

daddr_t
ffs_blkpref_ufs2(struct inode *ip, daddr_t lbn, int indx, int64_t *bap)
{
	struct fs *fs;
	int cg;
	int avgbfree, startcg;

	fs = ip->i_fs;
	if (indx % fs->fs_maxbpg == 0 || bap[indx - 1] == 0) {
		if (lbn < NDADDR + NINDIR(fs)) {
			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 (indx == 0 || bap[indx - 1] == 0)
			startcg =
			    ino_to_cg(fs, ip->i_number) + lbn / fs->fs_maxbpg;
		else
			startcg = dtog(fs,
				ufs_rw64(bap[indx - 1], UFS_FSNEEDSWAP(fs)) + 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) {
				return (fs->fs_fpg * cg + fs->fs_frag);
			}
		for (cg = 0; cg < startcg; cg++)
			if (fs->fs_cs(fs, cg).cs_nbfree >= avgbfree) {
				return (fs->fs_fpg * cg + fs->fs_frag);
			}
		return (0);
	}
	/*
	 * We just always try to lay things out contiguously.
	 */
	return ufs_rw64(bap[indx - 1], UFS_FSNEEDSWAP(fs)) + 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.
 */
/*VARARGS5*/
static daddr_t
ffs_hashalloc(struct inode *ip, int cg, daddr_t pref,
    int size /* size for data blocks, mode for inodes */,
    daddr_t (*allocator)(struct inode *, int, daddr_t, int))
{
	struct fs *fs;
	daddr_t 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 (0);
}

/*
 * Determine whether a fragment can be extended.
 *
 * Check to see if the necessary fragments are available, and
 * if they are, allocate them.
 */
static daddr_t
ffs_fragextend(struct inode *ip, int cg, daddr_t bprev, int osize, int nsize)
{
	struct fs *fs;
	struct cg *cgp;
	struct buf *bp;
	daddr_t bno;
	int frags, bbase;
	int i, error;
	u_int8_t *blksfree;

	fs = ip->i_fs;
	if (fs->fs_cs(fs, cg).cs_nffree < numfrags(fs, nsize - osize))
		return (0);
	frags = numfrags(fs, nsize);
	bbase = fragnum(fs, bprev);
	if (bbase > fragnum(fs, (bprev + frags - 1))) {
		/* cannot extend across a block boundary */
		return (0);
	}
	error = bread(ip->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 (!cg_chkmagic(cgp, UFS_FSNEEDSWAP(fs))) {
		brelse(bp);
		return (0);
	}
	cgp->cg_old_time = ufs_rw32(time_second, UFS_FSNEEDSWAP(fs));
	if ((fs->fs_magic != FS_UFS1_MAGIC) ||
	    (fs->fs_old_flags & FS_FLAGS_UPDATED))
		cgp->cg_time = ufs_rw64(time_second, UFS_FSNEEDSWAP(fs));
	bno = dtogd(fs, bprev);
	blksfree = cg_blksfree(cgp, UFS_FSNEEDSWAP(fs));
	for (i = numfrags(fs, osize); i < frags; i++)
		if (isclr(blksfree, bno + i)) {
			brelse(bp);
			return (0);
		}
	/*
	 * 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;
	ufs_add32(cgp->cg_frsum[i - numfrags(fs, osize)], -1, UFS_FSNEEDSWAP(fs));
	if (i != frags)
		ufs_add32(cgp->cg_frsum[i - frags], 1, UFS_FSNEEDSWAP(fs));
	for (i = numfrags(fs, osize); i < frags; i++) {
		clrbit(blksfree, bno + i);
		ufs_add32(cgp->cg_cs.cs_nffree, -1, UFS_FSNEEDSWAP(fs));
		fs->fs_cstotal.cs_nffree--;
		fs->fs_cs(fs, cg).cs_nffree--;
	}
	fs->fs_fmod = 1;
	if (DOINGSOFTDEP(ITOV(ip)))
		softdep_setup_blkmapdep(bp, fs, bprev);
	ACTIVECG_CLR(fs, cg);
	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 daddr_t
ffs_alloccg(struct inode *ip, int cg, daddr_t bpref, int size)
{
	struct fs *fs = ip->i_fs;
	struct cg *cgp;
	struct buf *bp;
	int32_t bno;
	daddr_t blkno;
	int error, frags, allocsiz, i;
	u_int8_t *blksfree;
#ifdef FFS_EI
	const int needswap = UFS_FSNEEDSWAP(fs);
#endif

	if (fs->fs_cs(fs, cg).cs_nbfree == 0 && size == fs->fs_bsize)
		return (0);
	error = bread(ip->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 (!cg_chkmagic(cgp, needswap) ||
	    (cgp->cg_cs.cs_nbfree == 0 && size == fs->fs_bsize)) {
		brelse(bp);
		return (0);
	}
	cgp->cg_old_time = ufs_rw32(time_second, needswap);
	if ((fs->fs_magic != FS_UFS1_MAGIC) ||
	    (fs->fs_old_flags & FS_FLAGS_UPDATED))
		cgp->cg_time = ufs_rw64(time_second, needswap);
	if (size == fs->fs_bsize) {
		blkno = ffs_alloccgblk(ip, bp, bpref);
		ACTIVECG_CLR(fs, cg);
		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, needswap);
	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) {
			brelse(bp);
			return (0);
		}
		blkno = ffs_alloccgblk(ip, bp, bpref);
		bno = dtogd(fs, blkno);
		for (i = frags; i < fs->fs_frag; i++)
			setbit(blksfree, bno + i);
		i = fs->fs_frag - frags;
		ufs_add32(cgp->cg_cs.cs_nffree, i, needswap);
		fs->fs_cstotal.cs_nffree += i;
		fs->fs_cs(fs, cg).cs_nffree += i;
		fs->fs_fmod = 1;
		ufs_add32(cgp->cg_frsum[i], 1, needswap);
		ACTIVECG_CLR(fs, cg);
		bdwrite(bp);
		return (blkno);
	}
	bno = ffs_mapsearch(fs, cgp, bpref, allocsiz);
#if 0
	/*
	 * XXX fvdl mapsearch will panic, and never return -1
	 *          also: returning NULL as daddr_t ?
	 */
	if (bno < 0) {
		brelse(bp);
		return (0);
	}
#endif
	for (i = 0; i < frags; i++)
		clrbit(blksfree, bno + i);
	ufs_add32(cgp->cg_cs.cs_nffree, -frags, needswap);
	fs->fs_cstotal.cs_nffree -= frags;
	fs->fs_cs(fs, cg).cs_nffree -= frags;
	fs->fs_fmod = 1;
	ufs_add32(cgp->cg_frsum[allocsiz], -1, needswap);
	if (frags != allocsiz)
		ufs_add32(cgp->cg_frsum[allocsiz - frags], 1, needswap);
	blkno = cg * fs->fs_fpg + bno;
	if (DOINGSOFTDEP(ITOV(ip)))
		softdep_setup_blkmapdep(bp, fs, blkno);
	ACTIVECG_CLR(fs, cg);
	bdwrite(bp);
	return blkno;
}

/*
 * 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 daddr_t
ffs_alloccgblk(struct inode *ip, struct buf *bp, daddr_t bpref)
{
	struct fs *fs = ip->i_fs;
	struct cg *cgp;
	daddr_t blkno;
	int32_t bno;
	u_int8_t *blksfree;
#ifdef FFS_EI
	const int needswap = UFS_FSNEEDSWAP(fs);
#endif

	cgp = (struct cg *)bp->b_data;
	blksfree = cg_blksfree(cgp, needswap);
	if (bpref == 0 || dtog(fs, bpref) != ufs_rw32(cgp->cg_cgx, needswap)) {
		bpref = ufs_rw32(cgp->cg_rotor, needswap);
	} else {
		bpref = blknum(fs, bpref);
		bno = dtogd(fs, bpref);
		/*
		 * if the requested block is available, use it
		 */
		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);
	cgp->cg_rotor = ufs_rw32(bno, needswap);
gotit:
	blkno = fragstoblks(fs, bno);
	ffs_clrblock(fs, blksfree, blkno);
	ffs_clusteracct(fs, cgp, blkno, -1);
	ufs_add32(cgp->cg_cs.cs_nbfree, -1, needswap);
	fs->fs_cstotal.cs_nbfree--;
	fs->fs_cs(fs, ufs_rw32(cgp->cg_cgx, needswap)).cs_nbfree--;
	if ((fs->fs_magic == FS_UFS1_MAGIC) &&
	    ((fs->fs_old_flags & FS_FLAGS_UPDATED) == 0)) {
		int cylno;
		cylno = old_cbtocylno(fs, bno);
		KASSERT(cylno >= 0);
		KASSERT(cylno < fs->fs_old_ncyl);
		KASSERT(old_cbtorpos(fs, bno) >= 0);
		KASSERT(fs->fs_old_nrpos == 0 || old_cbtorpos(fs, bno) < fs->fs_old_nrpos);
		ufs_add16(old_cg_blks(fs, cgp, cylno, needswap)[old_cbtorpos(fs, bno)], -1,
		    needswap);
		ufs_add32(old_cg_blktot(cgp, needswap)[cylno], -1, needswap);
	}
	fs->fs_fmod = 1;
	blkno = ufs_rw32(cgp->cg_cgx, needswap) * fs->fs_fpg + bno;
	if (DOINGSOFTDEP(ITOV(ip)))
		softdep_setup_blkmapdep(bp, fs, blkno);
	return (blkno);
}

#ifdef XXXUBC
/*
 * 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.
 */

/*
 * This function must be fixed for UFS2 if re-enabled.
 */
static daddr_t
ffs_clusteralloc(struct inode *ip, int cg, daddr_t bpref, int len)
{
	struct fs *fs;
	struct cg *cgp;
	struct buf *bp;
	int i, got, run, bno, bit, map;
	u_char *mapp;
	int32_t *lp;

	fs = ip->i_fs;
	if (fs->fs_maxcluster[cg] < len)
		return (0);
	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 (!cg_chkmagic(cgp, UFS_FSNEEDSWAP(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, UFS_FSNEEDSWAP(fs))[len];
	for (i = len; i <= fs->fs_contigsumsize; i++)
		if (ufs_rw32(*lp++, UFS_FSNEEDSWAP(fs)) > 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, UFS_FSNEEDSWAP(fs))[len - 1];
		for (i = len - 1; i > 0; i--)
			if (ufs_rw32(*lp--, UFS_FSNEEDSWAP(fs)) > 0)
				break;
		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 = 0;
	else
		bpref = fragstoblks(fs, dtogd(fs, blknum(fs, bpref)));
	mapp = &cg_clustersfree(cgp, UFS_FSNEEDSWAP(fs))[bpref / NBBY];
	map = *mapp++;
	bit = 1 << (bpref % NBBY);
	for (run = 0, got = bpref;
		got < ufs_rw32(cgp->cg_nclusterblks, UFS_FSNEEDSWAP(fs)); 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 == ufs_rw32(cgp->cg_nclusterblks, UFS_FSNEEDSWAP(fs)))
		goto fail;
	/*
	 * Allocate the cluster that we have found.
	 */
#ifdef DIAGNOSTIC
	for (i = 1; i <= len; i++)
		if (!ffs_isblock(fs, cg_blksfree(cgp, UFS_FSNEEDSWAP(fs)),
		    got - run + i))
			panic("ffs_clusteralloc: map mismatch");
#endif
	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(ip, bp, bno + i)) != bno + i)
			panic("ffs_clusteralloc: lost block");
	ACTIVECG_CLR(fs, cg);
	bdwrite(bp);
	return (bno);

fail:
	brelse(bp);
	return (0);
}
#endif /* XXXUBC */

/*
 * 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 daddr_t
ffs_nodealloccg(struct inode *ip, int cg, daddr_t ipref, int mode)
{
	struct fs *fs = ip->i_fs;
	struct cg *cgp;
	struct buf *bp, *ibp;
	u_int8_t *inosused;
	int error, start, len, loc, map, i;
	int32_t initediblk;
	struct ufs2_dinode *dp2;
#ifdef FFS_EI
	const int needswap = UFS_FSNEEDSWAP(fs);
#endif

	if (fs->fs_cs(fs, cg).cs_nifree == 0)
		return (0);
	error = bread(ip->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 (!cg_chkmagic(cgp, needswap) || cgp->cg_cs.cs_nifree == 0) {
		brelse(bp);
		return (0);
	}
	cgp->cg_old_time = ufs_rw32(time_second, needswap);
	if ((fs->fs_magic != FS_UFS1_MAGIC) ||
	    (fs->fs_old_flags & FS_FLAGS_UPDATED))
		cgp->cg_time = ufs_rw64(time_second, needswap);
	inosused = cg_inosused(cgp, needswap);
	if (ipref) {
		ipref %= fs->fs_ipg;
		if (isclr(inosused, ipref))
			goto gotit;
	}
	start = ufs_rw32(cgp->cg_irotor, needswap) / NBBY;
	len = howmany(fs->fs_ipg - ufs_rw32(cgp->cg_irotor, needswap),
		NBBY);
	loc = skpc(0xff, len, &inosused[start]);
	if (loc == 0) {
		len = start + 1;
		start = 0;
		loc = skpc(0xff, len, &inosused[0]);
		if (loc == 0) {
			printf("cg = %d, irotor = %d, fs = %s\n",
			    cg, ufs_rw32(cgp->cg_irotor, needswap),
				fs->fs_fsmnt);
			panic("ffs_nodealloccg: map corrupted");
			/* NOTREACHED */
		}
	}
	i = start + len - loc;
	map = inosused[i];
	ipref = i * NBBY;
	for (i = 1; i < (1 << NBBY); i <<= 1, ipref++) {
		if ((map & i) == 0) {
			cgp->cg_irotor = ufs_rw32(ipref, needswap);
			goto gotit;
		}
	}
	printf("fs = %s\n", fs->fs_fsmnt);
	panic("ffs_nodealloccg: block not in map");
	/* NOTREACHED */
gotit:
	if (DOINGSOFTDEP(ITOV(ip)))
		softdep_setup_inomapdep(bp, ip, cg * fs->fs_ipg + ipref);
	setbit(inosused, ipref);
	ufs_add32(cgp->cg_cs.cs_nifree, -1, needswap);
	fs->fs_cstotal.cs_nifree--;
	fs->fs_cs(fs, cg).cs_nifree--;
	fs->fs_fmod = 1;
	if ((mode & IFMT) == IFDIR) {
		ufs_add32(cgp->cg_cs.cs_ndir, 1, needswap);
		fs->fs_cstotal.cs_ndir++;
		fs->fs_cs(fs, cg).cs_ndir++;
	}
	/*
	 * Check to see if we need to initialize more inodes.
	 */
	initediblk = ufs_rw32(cgp->cg_initediblk, needswap);
	if (fs->fs_magic == FS_UFS2_MAGIC &&
	    ipref + INOPB(fs) > initediblk &&
	    initediblk < ufs_rw32(cgp->cg_niblk, needswap)) {
		ibp = getblk(ip->i_devvp, fsbtodb(fs,
		    ino_to_fsba(fs, cg * fs->fs_ipg + initediblk)),
		    (int)fs->fs_bsize, 0, 0);
		    memset(ibp->b_data, 0, fs->fs_bsize);
		    dp2 = (struct ufs2_dinode *)(ibp->b_data);
		    for (i = 0; i < INOPB(fs); i++) {
			/*
			 * Don't bother to swap, it's supposed to be
			 * random, after all.
			 */
			dp2->di_gen = (arc4random() & INT32_MAX) / 2 + 1;
			dp2++;
		}
		bawrite(ibp);
		initediblk += INOPB(fs);
		cgp->cg_initediblk = ufs_rw32(initediblk, needswap);
	}

	ACTIVECG_CLR(fs, cg);
	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.
 */
void
ffs_blkfree(struct fs *fs, struct vnode *devvp, daddr_t bno, long size,
    ino_t inum)
{
	struct cg *cgp;
	struct buf *bp;
	struct ufsmount *ump;
	int32_t fragno, cgbno;
	daddr_t cgblkno;
	int i, error, cg, blk, frags, bbase;
	u_int8_t *blksfree;
	dev_t dev;
	const int needswap = UFS_FSNEEDSWAP(fs);

	cg = dtog(fs, bno);
	if (devvp->v_type != VBLK) {
		/* devvp is a snapshot */
		dev = VTOI(devvp)->i_devvp->v_rdev;
		cgblkno = fragstoblks(fs, cgtod(fs, cg));
	} else {
		dev = devvp->v_rdev;
		ump = VFSTOUFS(devvp->v_specmountpoint);
		cgblkno = fsbtodb(fs, cgtod(fs, cg));
		if (TAILQ_FIRST(&ump->um_snapshots) != NULL &&
		    ffs_snapblkfree(fs, devvp, bno, size, inum))
			return;
	}
	if ((u_int)size > fs->fs_bsize || fragoff(fs, size) != 0 ||
	    fragnum(fs, bno) + numfrags(fs, size) > fs->fs_frag) {
		printf("dev = 0x%x, bno = %" PRId64 " bsize = %d, "
		       "size = %ld, fs = %s\n",
		    dev, bno, fs->fs_bsize, size, fs->fs_fsmnt);
		panic("blkfree: bad size");
	}

	if (bno >= fs->fs_size) {
		printf("bad block %" PRId64 ", ino %llu\n", bno,
		    (unsigned long long)inum);
		ffs_fserr(fs, inum, "bad block");
		return;
	}
	error = bread(devvp, cgblkno, (int)fs->fs_cgsize, NOCRED, &bp);
	if (error) {
		brelse(bp);
		return;
	}
	cgp = (struct cg *)bp->b_data;
	if (!cg_chkmagic(cgp, needswap)) {
		brelse(bp);
		return;
	}
	cgp->cg_old_time = ufs_rw32(time_second, needswap);
	if ((fs->fs_magic != FS_UFS1_MAGIC) ||
	    (fs->fs_old_flags & FS_FLAGS_UPDATED))
		cgp->cg_time = ufs_rw64(time_second, needswap);
	cgbno = dtogd(fs, bno);
	blksfree = cg_blksfree(cgp, needswap);
	if (size == fs->fs_bsize) {
		fragno = fragstoblks(fs, cgbno);
		if (!ffs_isfreeblock(fs, blksfree, fragno)) {
			if (devvp->v_type != VBLK) {
				/* devvp is a snapshot */
				brelse(bp);
				return;
			}
			printf("dev = 0x%x, block = %" PRId64 ", fs = %s\n",
			    dev, bno, fs->fs_fsmnt);
			panic("blkfree: freeing free block");
		}
		ffs_setblock(fs, blksfree, fragno);
		ffs_clusteracct(fs, cgp, fragno, 1);
		ufs_add32(cgp->cg_cs.cs_nbfree, 1, needswap);
		fs->fs_cstotal.cs_nbfree++;
		fs->fs_cs(fs, cg).cs_nbfree++;
		if ((fs->fs_magic == FS_UFS1_MAGIC) &&
		    ((fs->fs_old_flags & FS_FLAGS_UPDATED) == 0)) {
			i = old_cbtocylno(fs, cgbno);
			KASSERT(i >= 0);
			KASSERT(i < fs->fs_old_ncyl);
			KASSERT(old_cbtorpos(fs, cgbno) >= 0);
			KASSERT(fs->fs_old_nrpos == 0 || old_cbtorpos(fs, cgbno) < fs->fs_old_nrpos);
			ufs_add16(old_cg_blks(fs, cgp, i, needswap)[old_cbtorpos(fs, cgbno)], 1,
			    needswap);
			ufs_add32(old_cg_blktot(cgp, needswap)[i], 1, needswap);
		}
	} 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, needswap);
		/*
		 * deallocate the fragment
		 */
		frags = numfrags(fs, size);
		for (i = 0; i < frags; i++) {
			if (isset(blksfree, cgbno + i)) {
				printf("dev = 0x%x, block = %" PRId64
				       ", fs = %s\n",
				    dev, bno + i, fs->fs_fsmnt);
				panic("blkfree: freeing free frag");
			}
			setbit(blksfree, cgbno + i);
		}
		ufs_add32(cgp->cg_cs.cs_nffree, i, needswap);
		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, needswap);
		/*
		 * if a complete block has been reassembled, account for it
		 */
		fragno = fragstoblks(fs, bbase);
		if (ffs_isblock(fs, blksfree, fragno)) {
			ufs_add32(cgp->cg_cs.cs_nffree, -fs->fs_frag, needswap);
			fs->fs_cstotal.cs_nffree -= fs->fs_frag;
			fs->fs_cs(fs, cg).cs_nffree -= fs->fs_frag;
			ffs_clusteracct(fs, cgp, fragno, 1);
			ufs_add32(cgp->cg_cs.cs_nbfree, 1, needswap);
			fs->fs_cstotal.cs_nbfree++;
			fs->fs_cs(fs, cg).cs_nbfree++;
			if ((fs->fs_magic == FS_UFS1_MAGIC) &&
			    ((fs->fs_old_flags & FS_FLAGS_UPDATED) == 0)) {
				i = old_cbtocylno(fs, bbase);
				KASSERT(i >= 0);
				KASSERT(i < fs->fs_old_ncyl);
				KASSERT(old_cbtorpos(fs, bbase) >= 0);
				KASSERT(fs->fs_old_nrpos == 0 || old_cbtorpos(fs, bbase) < fs->fs_old_nrpos);
				ufs_add16(old_cg_blks(fs, cgp, i, needswap)[old_cbtorpos(fs,
				    bbase)], 1, needswap);
				ufs_add32(old_cg_blktot(cgp, needswap)[i], 1, needswap);
			}
		}
	}
	fs->fs_fmod = 1;
	ACTIVECG_CLR(fs, cg);
	bdwrite(bp);
}

#if defined(DIAGNOSTIC) || defined(DEBUG)
#ifdef XXXUBC
/*
 * Verify allocation of a block or fragment. Returns true if block or
 * fragment is allocated, false if it is free.
 */
static int
ffs_checkblk(struct inode *ip, daddr_t bno, long size)
{
	struct fs *fs;
	struct cg *cgp;
	struct buf *bp;
	int i, error, frags, free;

	fs = ip->i_fs;
	if ((u_int)size > fs->fs_bsize || fragoff(fs, size) != 0) {
		printf("bsize = %d, size = %ld, fs = %s\n",
		    fs->fs_bsize, size, fs->fs_fsmnt);
		panic("checkblk: bad size");
	}
	if (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 0;
	}
	cgp = (struct cg *)bp->b_data;
	if (!cg_chkmagic(cgp, UFS_FSNEEDSWAP(fs))) {
		brelse(bp);
		return 0;
	}
	bno = dtogd(fs, bno);
	if (size == fs->fs_bsize) {
		free = ffs_isblock(fs, cg_blksfree(cgp, UFS_FSNEEDSWAP(fs)),
			fragstoblks(fs, bno));
	} else {
		frags = numfrags(fs, size);
		for (free = 0, i = 0; i < frags; i++)
			if (isset(cg_blksfree(cgp, UFS_FSNEEDSWAP(fs)), bno + i))
				free++;
		if (free != 0 && free != frags)
			panic("checkblk: partially free fragment");
	}
	brelse(bp);
	return (!free);
}
#endif /* XXXUBC */
#endif /* DIAGNOSTIC */

/*
 * Free an inode.
 */
int
ffs_vfree(struct vnode *vp, ino_t ino, int mode)
{

	if (DOINGSOFTDEP(vp)) {
		softdep_freefile(vp, ino, mode);
		return (0);
	}
	return ffs_freefile(VTOI(vp)->i_fs, VTOI(vp)->i_devvp, ino, mode);
}

/*
 * Do the actual free operation.
 * The specified inode is placed back in the free map.
 */
int
ffs_freefile(struct fs *fs, struct vnode *devvp, ino_t ino, int mode)
{
	struct cg *cgp;
	struct buf *bp;
	int error, cg;
	daddr_t cgbno;
	u_int8_t *inosused;
	dev_t dev;
#ifdef FFS_EI
	const int needswap = UFS_FSNEEDSWAP(fs);
#endif

	cg = ino_to_cg(fs, ino);
	if (devvp->v_type != VBLK) {
		/* devvp is a snapshot */
		dev = VTOI(devvp)->i_devvp->v_rdev;
		cgbno = fragstoblks(fs, cgtod(fs, cg));
	} else {
		dev = devvp->v_rdev;
		cgbno = fsbtodb(fs, cgtod(fs, cg));
	}
	if ((u_int)ino >= fs->fs_ipg * fs->fs_ncg)
		panic("ifree: range: dev = 0x%x, ino = %llu, fs = %s",
		    dev, (unsigned long long)ino, fs->fs_fsmnt);
	error = bread(devvp, cgbno, (int)fs->fs_cgsize, NOCRED, &bp);
	if (error) {
		brelse(bp);
		return (error);
	}
	cgp = (struct cg *)bp->b_data;
	if (!cg_chkmagic(cgp, needswap)) {
		brelse(bp);
		return (0);
	}
	cgp->cg_old_time = ufs_rw32(time_second, needswap);
	if ((fs->fs_magic != FS_UFS1_MAGIC) ||
	    (fs->fs_old_flags & FS_FLAGS_UPDATED))
		cgp->cg_time = ufs_rw64(time_second, needswap);
	inosused = cg_inosused(cgp, needswap);
	ino %= fs->fs_ipg;
	if (isclr(inosused, ino)) {
		printf("ifree: dev = 0x%x, ino = %llu, fs = %s\n",
		    dev, (unsigned long long)ino + cg * fs->fs_ipg,
		    fs->fs_fsmnt);
		if (fs->fs_ronly == 0)
			panic("ifree: freeing free inode");
	}
	clrbit(inosused, ino);
	if (ino < ufs_rw32(cgp->cg_irotor, needswap))
		cgp->cg_irotor = ufs_rw32(ino, needswap);
	ufs_add32(cgp->cg_cs.cs_nifree, 1, needswap);
	fs->fs_cstotal.cs_nifree++;
	fs->fs_cs(fs, cg).cs_nifree++;
	if ((mode & IFMT) == IFDIR) {
		ufs_add32(cgp->cg_cs.cs_ndir, -1, needswap);
		fs->fs_cstotal.cs_ndir--;
		fs->fs_cs(fs, cg).cs_ndir--;
	}
	fs->fs_fmod = 1;
	ACTIVECG_CLR(fs, cg);
	bdwrite(bp);
	return (0);
}

/*
 * Check to see if a file is free.
 */
int
ffs_checkfreefile(struct fs *fs, struct vnode *devvp, ino_t ino)
{
	struct cg *cgp;
	struct buf *bp;
	daddr_t cgbno;
	int ret, cg;
	u_int8_t *inosused;

	cg = ino_to_cg(fs, ino);
	if (devvp->v_type != VBLK) {
		/* devvp is a snapshot */
		cgbno = fragstoblks(fs, cgtod(fs, cg));
	} else
		cgbno = fsbtodb(fs, cgtod(fs, cg));
	if ((u_int)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, UFS_FSNEEDSWAP(fs))) {
		brelse(bp);
		return 1;
	}
	inosused = cg_inosused(cgp, UFS_FSNEEDSWAP(fs));
	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 int32_t
ffs_mapsearch(struct fs *fs, struct cg *cgp, daddr_t bpref, int allocsiz)
{
	int32_t bno;
	int start, len, loc, i;
	int blk, field, subfield, pos;
	int ostart, olen;
	u_int8_t *blksfree;
#ifdef FFS_EI
	const int needswap = UFS_FSNEEDSWAP(fs);
#endif

	/*
	 * find the fragment by searching through the free block
	 * map for an appropriate bit pattern
	 */
	if (bpref)
		start = dtogd(fs, bpref) / NBBY;
	else
		start = ufs_rw32(cgp->cg_frotor, needswap) / NBBY;
	blksfree = cg_blksfree(cgp, needswap);
	len = howmany(fs->fs_fpg, NBBY) - start;
	ostart = start;
	olen = len;
	loc = scanc((u_int)len,
		(const u_char *)&blksfree[start],
		(const u_char *)fragtbl[fs->fs_frag],
		(1 << (allocsiz - 1 + (fs->fs_frag & (NBBY - 1)))));
	if (loc == 0) {
		len = start + 1;
		start = 0;
		loc = scanc((u_int)len,
			(const u_char *)&blksfree[0],
			(const u_char *)fragtbl[fs->fs_frag],
			(1 << (allocsiz - 1 + (fs->fs_frag & (NBBY - 1)))));
		if (loc == 0) {
			printf("start = %d, len = %d, fs = %s\n",
			    ostart, olen, fs->fs_fsmnt);
			printf("offset=%d %ld\n",
				ufs_rw32(cgp->cg_freeoff, needswap),
				(long)blksfree - (long)cgp);
			printf("cg %d\n", cgp->cg_cgx);
			panic("ffs_alloccg: map corrupted");
			/* NOTREACHED */
		}
	}
	bno = (start + len - loc) * NBBY;
	cgp->cg_frotor = ufs_rw32(bno, needswap);
	/*
	 * 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 = %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.
 */
void
ffs_clusteracct(struct fs *fs, struct cg *cgp, int32_t blkno, int cnt)
{
	int32_t *sump;
	int32_t *lp;
	u_char *freemapp, *mapp;
	int i, start, end, forw, back, map, bit;
#ifdef FFS_EI
	const int needswap = UFS_FSNEEDSWAP(fs);
#endif

	if (fs->fs_contigsumsize <= 0)
		return;
	freemapp = cg_clustersfree(cgp, needswap);
	sump = cg_clustersum(cgp, needswap);
	/*
	 * 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 >= ufs_rw32(cgp->cg_nclusterblks, needswap))
		end = ufs_rw32(cgp->cg_nclusterblks, needswap);
	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;
	ufs_add32(sump[i], cnt, needswap);
	if (back > 0)
		ufs_add32(sump[back], -cnt, needswap);
	if (forw > 0)
		ufs_add32(sump[forw], -cnt, needswap);

	/*
	 * Update cluster summary information.
	 */
	lp = &sump[fs->fs_contigsumsize];
	for (i = fs->fs_contigsumsize; i > 0; i--)
		if (ufs_rw32(*lp--, needswap) > 0)
			break;
	fs->fs_maxcluster[ufs_rw32(cgp->cg_cgx, needswap)] = 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(struct fs *fs, u_int uid, const char *cp)
{

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