/*
 * Copyright (c) 2000-2004 Silicon Graphics, Inc.  All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of version 2 of the GNU General Public License as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it would be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 *
 * Further, this software is distributed without any warranty that it is
 * free of the rightful claim of any third person regarding infringement
 * or the like.  Any license provided herein, whether implied or
 * otherwise, applies only to this software file.  Patent licenses, if
 * any, provided herein do not apply to combinations of this program with
 * other software, or any other product whatsoever.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write the Free Software Foundation, Inc., 59
 * Temple Place - Suite 330, Boston MA 02111-1307, USA.
 *
 * Contact information: Silicon Graphics, Inc., 1600 Amphitheatre Pkwy,
 * Mountain View, CA  94043, or:
 *
 * http://www.sgi.com
 *
 * For further information regarding this notice, see:
 *
 * http://oss.sgi.com/projects/GenInfo/SGIGPLNoticeExplan/
 */

/*
 * Free realtime space allocation for XFS.
 */

#include "xfs.h"
#include "xfs_macros.h"
#include "xfs_types.h"
#include "xfs_inum.h"
#include "xfs_log.h"
#include "xfs_trans.h"
#include "xfs_sb.h"
#include "xfs_ag.h"
#include "xfs_dir.h"
#include "xfs_dir2.h"
#include "xfs_dmapi.h"
#include "xfs_mount.h"
#include "xfs_alloc_btree.h"
#include "xfs_bmap_btree.h"
#include "xfs_ialloc_btree.h"
#include "xfs_btree.h"
#include "xfs_ialloc.h"
#include "xfs_attr_sf.h"
#include "xfs_dir_sf.h"
#include "xfs_dir2_sf.h"
#include "xfs_dinode.h"
#include "xfs_inode.h"
#include "xfs_alloc.h"
#include "xfs_bmap.h"
#include "xfs_bit.h"
#include "xfs_rtalloc.h"
#include "xfs_fsops.h"
#include "xfs_error.h"
#include "xfs_rw.h"
#include "xfs_inode_item.h"
#include "xfs_trans_space.h"


/*
 * Prototypes for internal functions.
 */


STATIC int xfs_rtallocate_range(xfs_mount_t *, xfs_trans_t *, xfs_rtblock_t,
		xfs_extlen_t, xfs_buf_t **, xfs_fsblock_t *);
STATIC int xfs_rtany_summary(xfs_mount_t *, xfs_trans_t *, int, int,
		xfs_rtblock_t, xfs_buf_t **, xfs_fsblock_t *, int *);
STATIC int xfs_rtcheck_range(xfs_mount_t *, xfs_trans_t *, xfs_rtblock_t,
		xfs_extlen_t, int, xfs_rtblock_t *, int *);
STATIC int xfs_rtfind_back(xfs_mount_t *, xfs_trans_t *, xfs_rtblock_t,
		xfs_rtblock_t, xfs_rtblock_t *);
STATIC int xfs_rtfind_forw(xfs_mount_t *, xfs_trans_t *, xfs_rtblock_t,
		xfs_rtblock_t, xfs_rtblock_t *);
STATIC int xfs_rtget_summary( xfs_mount_t *, xfs_trans_t *, int,
		xfs_rtblock_t, xfs_buf_t **, xfs_fsblock_t *, xfs_suminfo_t *);
STATIC int xfs_rtmodify_range(xfs_mount_t *, xfs_trans_t *, xfs_rtblock_t,
		xfs_extlen_t, int);
STATIC int xfs_rtmodify_summary(xfs_mount_t *, xfs_trans_t *, int,
		xfs_rtblock_t, int, xfs_buf_t **, xfs_fsblock_t *);

/*
 * Internal functions.
 */

/*
 * xfs_lowbit32: get low bit set out of 32-bit argument, -1 if none set.
 */
STATIC int
xfs_lowbit32(
	__uint32_t	v)
{
	if (v)
		return ffs(v) - 1;
	return -1;
}

/*
 * Allocate space to the bitmap or summary file, and zero it, for growfs.
 */
STATIC int				/* error */
xfs_growfs_rt_alloc(
	xfs_mount_t	*mp,		/* file system mount point */
	xfs_extlen_t	oblocks,	/* old count of blocks */
	xfs_extlen_t	nblocks,	/* new count of blocks */
	xfs_ino_t	ino)		/* inode number (bitmap/summary) */
{
	xfs_fileoff_t	bno;		/* block number in file */
	xfs_buf_t	*bp;		/* temporary buffer for zeroing */
	int		cancelflags;	/* flags for xfs_trans_cancel */
	int		committed;	/* transaction committed flag */
	xfs_daddr_t	d;		/* disk block address */
	int		error;		/* error return value */
	xfs_fsblock_t	firstblock;	/* first block allocated in xaction */
	xfs_bmap_free_t	flist;		/* list of freed blocks */
	xfs_fsblock_t	fsbno;		/* filesystem block for bno */
	xfs_inode_t	*ip;		/* pointer to incore inode */
	xfs_bmbt_irec_t	map;		/* block map output */
	int		nmap;		/* number of block maps */
	int		resblks;	/* space reservation */
	xfs_trans_t	*tp;		/* transaction pointer */

	/*
	 * Allocate space to the file, as necessary.
	 */
	while (oblocks < nblocks) {
		tp = xfs_trans_alloc(mp, XFS_TRANS_GROWFSRT_ALLOC);
		resblks = XFS_GROWFSRT_SPACE_RES(mp, nblocks - oblocks);
		cancelflags = 0;
		/*
		 * Reserve space & log for one extent added to the file.
		 */
		if ((error = xfs_trans_reserve(tp, resblks,
				XFS_GROWRTALLOC_LOG_RES(mp), 0,
				XFS_TRANS_PERM_LOG_RES,
				XFS_DEFAULT_PERM_LOG_COUNT)))
			goto error_exit;
		cancelflags = XFS_TRANS_RELEASE_LOG_RES;
		/*
		 * Lock the inode.
		 */
		if ((error = xfs_trans_iget(mp, tp, ino, 0, XFS_ILOCK_EXCL, &ip)))
			goto error_exit;
		XFS_BMAP_INIT(&flist, &firstblock);
		/*
		 * Allocate blocks to the bitmap file.
		 */
		nmap = 1;
		cancelflags |= XFS_TRANS_ABORT;
		error = xfs_bmapi(tp, ip, oblocks, nblocks - oblocks,
			XFS_BMAPI_WRITE | XFS_BMAPI_METADATA, &firstblock,
			resblks, &map, &nmap, &flist);
		if (!error && nmap < 1)
			error = XFS_ERROR(ENOSPC);
		if (error)
			goto error_exit;
		/*
		 * Free any blocks freed up in the transaction, then commit.
		 */
		error = xfs_bmap_finish(&tp, &flist, firstblock, &committed);
		if (error)
			goto error_exit;
		xfs_trans_commit(tp, XFS_TRANS_RELEASE_LOG_RES, NULL);
		/*
		 * Now we need to clear the allocated blocks.
		 * Do this one block per transaction, to keep it simple.
		 */
		cancelflags = 0;
		for (bno = map.br_startoff, fsbno = map.br_startblock;
		     bno < map.br_startoff + map.br_blockcount;
		     bno++, fsbno++) {
			tp = xfs_trans_alloc(mp, XFS_TRANS_GROWFSRT_ZERO);
			/*
			 * Reserve log for one block zeroing.
			 */
			if ((error = xfs_trans_reserve(tp, 0,
					XFS_GROWRTZERO_LOG_RES(mp), 0, 0, 0)))
				goto error_exit;
			/*
			 * Lock the bitmap inode.
			 */
			if ((error = xfs_trans_iget(mp, tp, ino, 0, XFS_ILOCK_EXCL,
					&ip)))
				goto error_exit;
			/*
			 * Get a buffer for the block.
			 */
			d = XFS_FSB_TO_DADDR(mp, fsbno);
			bp = xfs_trans_get_buf(tp, mp->m_ddev_targp, d,
				mp->m_bsize, 0);
			if (bp == NULL) {
				error = XFS_ERROR(EIO);
				goto error_exit;
			}
			memset(XFS_BUF_PTR(bp), 0, mp->m_sb.sb_blocksize);
			xfs_trans_log_buf(tp, bp, 0, mp->m_sb.sb_blocksize - 1);
			/*
			 * Commit the transaction.
			 */
			xfs_trans_commit(tp, 0, NULL);
		}
		/*
		 * Go on to the next extent, if any.
		 */
		oblocks = map.br_startoff + map.br_blockcount;
	}
	return 0;
error_exit:
	xfs_trans_cancel(tp, cancelflags);
	return error;
}

/*
 * Attempt to allocate an extent minlen<=len<=maxlen starting from
 * bitmap block bbno.  If we don't get maxlen then use prod to trim
 * the length, if given.  Returns error; returns starting block in *rtblock.
 * The lengths are all in rtextents.
 */
STATIC int				/* error */
xfs_rtallocate_extent_block(
	xfs_mount_t	*mp,		/* file system mount point */
	xfs_trans_t	*tp,		/* transaction pointer */
	xfs_rtblock_t	bbno,		/* bitmap block number */
	xfs_extlen_t	minlen,		/* minimum length to allocate */
	xfs_extlen_t	maxlen,		/* maximum length to allocate */
	xfs_extlen_t	*len,		/* out: actual length allocated */
	xfs_rtblock_t	*nextp,		/* out: next block to try */
	xfs_buf_t	**rbpp,		/* in/out: summary block buffer */
	xfs_fsblock_t	*rsb,		/* in/out: summary block number */
	xfs_extlen_t	prod,		/* extent product factor */
	xfs_rtblock_t	*rtblock)	/* out: start block allocated */
{
	xfs_rtblock_t	besti;		/* best rtblock found so far */
	xfs_rtblock_t	bestlen;	/* best length found so far */
	xfs_rtblock_t	end;		/* last rtblock in chunk */
	int		error;		/* error value */
	xfs_rtblock_t	i;		/* current rtblock trying */
	xfs_rtblock_t	next;		/* next rtblock to try */
	int		stat;		/* status from internal calls */

	/*
	 * Loop over all the extents starting in this bitmap block,
	 * looking for one that's long enough.
	 */
	for (i = XFS_BLOCKTOBIT(mp, bbno), besti = -1, bestlen = 0,
		end = XFS_BLOCKTOBIT(mp, bbno + 1) - 1;
	     i <= end;
	     i++) {
		/*
		 * See if there's a free extent of maxlen starting at i.
		 * If it's not so then next will contain the first non-free.
		 */
		error = xfs_rtcheck_range(mp, tp, i, maxlen, 1, &next, &stat);
		if (error) {
			return error;
		}
		if (stat) {
			/*
			 * i for maxlen is all free, allocate and return that.
			 */
			error = xfs_rtallocate_range(mp, tp, i, maxlen, rbpp,
				rsb);
			if (error) {
				return error;
			}
			*len = maxlen;
			*rtblock = i;
			return 0;
		}
		/*
		 * In the case where we have a variable-sized allocation
		 * request, figure out how big this free piece is,
		 * and if it's big enough for the minimum, and the best
		 * so far, remember it.
		 */
		if (minlen < maxlen) {
			xfs_rtblock_t	thislen;	/* this extent size */

			thislen = next - i;
			if (thislen >= minlen && thislen > bestlen) {
				besti = i;
				bestlen = thislen;
			}
		}
		/*
		 * If not done yet, find the start of the next free space.
		 */
		if (next < end) {
			error = xfs_rtfind_forw(mp, tp, next, end, &i);
			if (error) {
				return error;
			}
		} else
			break;
	}
	/*
	 * Searched the whole thing & didn't find a maxlen free extent.
	 */
	if (minlen < maxlen && besti != -1) {
		xfs_extlen_t	p;	/* amount to trim length by */

		/*
		 * If size should be a multiple of prod, make that so.
		 */
		if (prod > 1 && (p = do_mod(bestlen, prod)))
			bestlen -= p;
		/*
		 * Allocate besti for bestlen & return that.
		 */
		error = xfs_rtallocate_range(mp, tp, besti, bestlen, rbpp, rsb);
		if (error) {
			return error;
		}
		*len = bestlen;
		*rtblock = besti;
		return 0;
	}
	/*
	 * Allocation failed.  Set *nextp to the next block to try.
	 */
	*nextp = next;
	*rtblock = NULLRTBLOCK;
	return 0;
}

/*
 * Allocate an extent of length minlen<=len<=maxlen, starting at block
 * bno.  If we don't get maxlen then use prod to trim the length, if given.
 * Returns error; returns starting block in *rtblock.
 * The lengths are all in rtextents.
 */
STATIC int				/* error */
xfs_rtallocate_extent_exact(
	xfs_mount_t	*mp,		/* file system mount point */
	xfs_trans_t	*tp,		/* transaction pointer */
	xfs_rtblock_t	bno,		/* starting block number to allocate */
	xfs_extlen_t	minlen,		/* minimum length to allocate */
	xfs_extlen_t	maxlen,		/* maximum length to allocate */
	xfs_extlen_t	*len,		/* out: actual length allocated */
	xfs_buf_t	**rbpp,		/* in/out: summary block buffer */
	xfs_fsblock_t	*rsb,		/* in/out: summary block number */
	xfs_extlen_t	prod,		/* extent product factor */
	xfs_rtblock_t	*rtblock)	/* out: start block allocated */
{
	int		error;		/* error value */
	xfs_extlen_t	i;		/* extent length trimmed due to prod */
	int		isfree;		/* extent is free */
	xfs_rtblock_t	next;		/* next block to try (dummy) */

	ASSERT(minlen % prod == 0 && maxlen % prod == 0);
	/*
	 * Check if the range in question (for maxlen) is free.
	 */
	error = xfs_rtcheck_range(mp, tp, bno, maxlen, 1, &next, &isfree);
	if (error) {
		return error;
	}
	if (isfree) {
		/*
		 * If it is, allocate it and return success.
		 */
		error = xfs_rtallocate_range(mp, tp, bno, maxlen, rbpp, rsb);
		if (error) {
			return error;
		}
		*len = maxlen;
		*rtblock = bno;
		return 0;
	}
	/*
	 * If not, allocate what there is, if it's at least minlen.
	 */
	maxlen = next - bno;
	if (maxlen < minlen) {
		/*
		 * Failed, return failure status.
		 */
		*rtblock = NULLRTBLOCK;
		return 0;
	}
	/*
	 * Trim off tail of extent, if prod is specified.
	 */
	if (prod > 1 && (i = maxlen % prod)) {
		maxlen -= i;
		if (maxlen < minlen) {
			/*
			 * Now we can't do it, return failure status.
			 */
			*rtblock = NULLRTBLOCK;
			return 0;
		}
	}
	/*
	 * Allocate what we can and return it.
	 */
	error = xfs_rtallocate_range(mp, tp, bno, maxlen, rbpp, rsb);
	if (error) {
		return error;
	}
	*len = maxlen;
	*rtblock = bno;
	return 0;
}

/*
 * Allocate an extent of length minlen<=len<=maxlen, starting as near
 * to bno as possible.  If we don't get maxlen then use prod to trim
 * the length, if given.  The lengths are all in rtextents.
 */
STATIC int				/* error */
xfs_rtallocate_extent_near(
	xfs_mount_t	*mp,		/* file system mount point */
	xfs_trans_t	*tp,		/* transaction pointer */
	xfs_rtblock_t	bno,		/* starting block number to allocate */
	xfs_extlen_t	minlen,		/* minimum length to allocate */
	xfs_extlen_t	maxlen,		/* maximum length to allocate */
	xfs_extlen_t	*len,		/* out: actual length allocated */
	xfs_buf_t	**rbpp,		/* in/out: summary block buffer */
	xfs_fsblock_t	*rsb,		/* in/out: summary block number */
	xfs_extlen_t	prod,		/* extent product factor */
	xfs_rtblock_t	*rtblock)	/* out: start block allocated */
{
	int		any;		/* any useful extents from summary */
	xfs_rtblock_t	bbno;		/* bitmap block number */
	int		error;		/* error value */
	int		i;		/* bitmap block offset (loop control) */
	int		j;		/* secondary loop control */
	int		log2len;	/* log2 of minlen */
	xfs_rtblock_t	n;		/* next block to try */
	xfs_rtblock_t	r;		/* result block */

	ASSERT(minlen % prod == 0 && maxlen % prod == 0);
	/*
	 * If the block number given is off the end, silently set it to
	 * the last block.
	 */
	if (bno >= mp->m_sb.sb_rextents)
		bno = mp->m_sb.sb_rextents - 1;
	/*
	 * Try the exact allocation first.
	 */
	error = xfs_rtallocate_extent_exact(mp, tp, bno, minlen, maxlen, len,
		rbpp, rsb, prod, &r);
	if (error) {
		return error;
	}
	/*
	 * If the exact allocation worked, return that.
	 */
	if (r != NULLRTBLOCK) {
		*rtblock = r;
		return 0;
	}
	bbno = XFS_BITTOBLOCK(mp, bno);
	i = 0;
	log2len = xfs_highbit32(minlen);
	/*
	 * Loop over all bitmap blocks (bbno + i is current block).
	 */
	for (;;) {
		/*
		 * Get summary information of extents of all useful levels
		 * starting in this bitmap block.
		 */
		error = xfs_rtany_summary(mp, tp, log2len, mp->m_rsumlevels - 1,
			bbno + i, rbpp, rsb, &any);
		if (error) {
			return error;
		}
		/*
		 * If there are any useful extents starting here, try
		 * allocating one.
		 */
		if (any) {
			/*
			 * On the positive side of the starting location.
			 */
			if (i >= 0) {
				/*
				 * Try to allocate an extent starting in
				 * this block.
				 */
				error = xfs_rtallocate_extent_block(mp, tp,
					bbno + i, minlen, maxlen, len, &n, rbpp,
					rsb, prod, &r);
				if (error) {
					return error;
				}
				/*
				 * If it worked, return it.
				 */
				if (r != NULLRTBLOCK) {
					*rtblock = r;
					return 0;
				}
			}
			/*
			 * On the negative side of the starting location.
			 */
			else {		/* i < 0 */
				/*
				 * Loop backwards through the bitmap blocks from
				 * the starting point-1 up to where we are now.
				 * There should be an extent which ends in this
				 * bitmap block and is long enough.
				 */
				for (j = -1; j > i; j--) {
					/*
					 * Grab the summary information for
					 * this bitmap block.
					 */
					error = xfs_rtany_summary(mp, tp,
						log2len, mp->m_rsumlevels - 1,
						bbno + j, rbpp, rsb, &any);
					if (error) {
						return error;
					}
					/*
					 * If there's no extent given in the
					 * summary that means the extent we
					 * found must carry over from an
					 * earlier block.  If there is an
					 * extent given, we've already tried
					 * that allocation, don't do it again.
					 */
					if (any)
						continue;
					error = xfs_rtallocate_extent_block(mp,
						tp, bbno + j, minlen, maxlen,
						len, &n, rbpp, rsb, prod, &r);
					if (error) {
						return error;
					}
					/*
					 * If it works, return the extent.
					 */
					if (r != NULLRTBLOCK) {
						*rtblock = r;
						return 0;
					}
				}
				/*
				 * There weren't intervening bitmap blocks
				 * with a long enough extent, or the
				 * allocation didn't work for some reason
				 * (i.e. it's a little * too short).
				 * Try to allocate from the summary block
				 * that we found.
				 */
				error = xfs_rtallocate_extent_block(mp, tp,
					bbno + i, minlen, maxlen, len, &n, rbpp,
					rsb, prod, &r);
				if (error) {
					return error;
				}
				/*
				 * If it works, return the extent.
				 */
				if (r != NULLRTBLOCK) {
					*rtblock = r;
					return 0;
				}
			}
		}
		/*
		 * Loop control.  If we were on the positive side, and there's
		 * still more blocks on the negative side, go there.
		 */
		if (i > 0 && (int)bbno - i >= 0)
			i = -i;
		/*
		 * If positive, and no more negative, but there are more
		 * positive, go there.
		 */
		else if (i > 0 && (int)bbno + i < mp->m_sb.sb_rbmblocks - 1)
			i++;
		/*
		 * If negative or 0 (just started), and there are positive
		 * blocks to go, go there.  The 0 case moves to block 1.
		 */
		else if (i <= 0 && (int)bbno - i < mp->m_sb.sb_rbmblocks - 1)
			i = 1 - i;
		/*
		 * If negative or 0 and there are more negative blocks,
		 * go there.
		 */
		else if (i <= 0 && (int)bbno + i > 0)
			i--;
		/*
		 * Must be done.  Return failure.
		 */
		else
			break;
	}
	*rtblock = NULLRTBLOCK;
	return 0;
}

/*
 * Allocate an extent of length minlen<=len<=maxlen, with no position
 * specified.  If we don't get maxlen then use prod to trim
 * the length, if given.  The lengths are all in rtextents.
 */
STATIC int				/* error */
xfs_rtallocate_extent_size(
	xfs_mount_t	*mp,		/* file system mount point */
	xfs_trans_t	*tp,		/* transaction pointer */
	xfs_extlen_t	minlen,		/* minimum length to allocate */
	xfs_extlen_t	maxlen,		/* maximum length to allocate */
	xfs_extlen_t	*len,		/* out: actual length allocated */
	xfs_buf_t	**rbpp,		/* in/out: summary block buffer */
	xfs_fsblock_t	*rsb,		/* in/out: summary block number */
	xfs_extlen_t	prod,		/* extent product factor */
	xfs_rtblock_t	*rtblock)	/* out: start block allocated */
{
	int		error;		/* error value */
	int		i;		/* bitmap block number */
	int		l;		/* level number (loop control) */
	xfs_rtblock_t	n;		/* next block to be tried */
	xfs_rtblock_t	r;		/* result block number */
	xfs_suminfo_t	sum;		/* summary information for extents */

	ASSERT(minlen % prod == 0 && maxlen % prod == 0);
	/*
	 * Loop over all the levels starting with maxlen.
	 * At each level, look at all the bitmap blocks, to see if there
	 * are extents starting there that are long enough (>= maxlen).
	 * Note, only on the initial level can the allocation fail if
	 * the summary says there's an extent.
	 */
	for (l = xfs_highbit32(maxlen); l < mp->m_rsumlevels; l++) {
		/*
		 * Loop over all the bitmap blocks.
		 */
		for (i = 0; i < mp->m_sb.sb_rbmblocks; i++) {
			/*
			 * Get the summary for this level/block.
			 */
			error = xfs_rtget_summary(mp, tp, l, i, rbpp, rsb,
				&sum);
			if (error) {
				return error;
			}
			/*
			 * Nothing there, on to the next block.
			 */
			if (!sum)
				continue;
			/*
			 * Try allocating the extent.
			 */
			error = xfs_rtallocate_extent_block(mp, tp, i, maxlen,
				maxlen, len, &n, rbpp, rsb, prod, &r);
			if (error) {
				return error;
			}
			/*
			 * If it worked, return that.
			 */
			if (r != NULLRTBLOCK) {
				*rtblock = r;
				return 0;
			}
			/*
			 * If the "next block to try" returned from the
			 * allocator is beyond the next bitmap block,
			 * skip to that bitmap block.
			 */
			if (XFS_BITTOBLOCK(mp, n) > i + 1)
				i = XFS_BITTOBLOCK(mp, n) - 1;
		}
	}
	/*
	 * Didn't find any maxlen blocks.  Try smaller ones, unless
	 * we're asking for a fixed size extent.
	 */
	if (minlen > --maxlen) {
		*rtblock = NULLRTBLOCK;
		return 0;
	}
	/*
	 * Loop over sizes, from maxlen down to minlen.
	 * This time, when we do the allocations, allow smaller ones
	 * to succeed.
	 */
	for (l = xfs_highbit32(maxlen); l >= xfs_highbit32(minlen); l--) {
		/*
		 * Loop over all the bitmap blocks, try an allocation
		 * starting in that block.
		 */
		for (i = 0; i < mp->m_sb.sb_rbmblocks; i++) {
			/*
			 * Get the summary information for this level/block.
			 */
			error =	xfs_rtget_summary(mp, tp, l, i, rbpp, rsb,
						  &sum);
			if (error) {
				return error;
			}
			/*
			 * If nothing there, go on to next.
			 */
			if (!sum)
				continue;
			/*
			 * Try the allocation.  Make sure the specified
			 * minlen/maxlen are in the possible range for
			 * this summary level.
			 */
			error = xfs_rtallocate_extent_block(mp, tp, i,
					XFS_RTMAX(minlen, 1 << l),
					XFS_RTMIN(maxlen, (1 << (l + 1)) - 1),
					len, &n, rbpp, rsb, prod, &r);
			if (error) {
				return error;
			}
			/*
			 * If it worked, return that extent.
			 */
			if (r != NULLRTBLOCK) {
				*rtblock = r;
				return 0;
			}
			/*
			 * If the "next block to try" returned from the
			 * allocator is beyond the next bitmap block,
			 * skip to that bitmap block.
			 */
			if (XFS_BITTOBLOCK(mp, n) > i + 1)
				i = XFS_BITTOBLOCK(mp, n) - 1;
		}
	}
	/*
	 * Got nothing, return failure.
	 */
	*rtblock = NULLRTBLOCK;
	return 0;
}

/*
 * Mark an extent specified by start and len allocated.
 * Updates all the summary information as well as the bitmap.
 */
STATIC int				/* error */
xfs_rtallocate_range(
	xfs_mount_t	*mp,		/* file system mount point */
	xfs_trans_t	*tp,		/* transaction pointer */
	xfs_rtblock_t	start,		/* start block to allocate */
	xfs_extlen_t	len,		/* length to allocate */
	xfs_buf_t	**rbpp,		/* in/out: summary block buffer */
	xfs_fsblock_t	*rsb)		/* in/out: summary block number */
{
	xfs_rtblock_t	end;		/* end of the allocated extent */
	int		error;		/* error value */
	xfs_rtblock_t	postblock;	/* first block allocated > end */
	xfs_rtblock_t	preblock;	/* first block allocated < start */

	end = start + len - 1;
	/*
	 * Assume we're allocating out of the middle of a free extent.
	 * We need to find the beginning and end of the extent so we can
	 * properly update the summary.
	 */
	error = xfs_rtfind_back(mp, tp, start, 0, &preblock);
	if (error) {
		return error;
	}
	/*
	 * Find the next allocated block (end of free extent).
	 */
	error = xfs_rtfind_forw(mp, tp, end, mp->m_sb.sb_rextents - 1,
		&postblock);
	if (error) {
		return error;
	}
	/*
	 * Decrement the summary information corresponding to the entire
	 * (old) free extent.
	 */
	error = xfs_rtmodify_summary(mp, tp,
		XFS_RTBLOCKLOG(postblock + 1 - preblock),
		XFS_BITTOBLOCK(mp, preblock), -1, rbpp, rsb);
	if (error) {
		return error;
	}
	/*
	 * If there are blocks not being allocated at the front of the
	 * old extent, add summary data for them to be free.
	 */
	if (preblock < start) {
		error = xfs_rtmodify_summary(mp, tp,
			XFS_RTBLOCKLOG(start - preblock),
			XFS_BITTOBLOCK(mp, preblock), 1, rbpp, rsb);
		if (error) {
			return error;
		}
	}
	/*
	 * If there are blocks not being allocated at the end of the
	 * old extent, add summary data for them to be free.
	 */
	if (postblock > end) {
		error = xfs_rtmodify_summary(mp, tp,
			XFS_RTBLOCKLOG(postblock - end),
			XFS_BITTOBLOCK(mp, end + 1), 1, rbpp, rsb);
		if (error) {
			return error;
		}
	}
	/*
	 * Modify the bitmap to mark this extent allocated.
	 */
	error = xfs_rtmodify_range(mp, tp, start, len, 0);
	return error;
}

/*
 * Return whether there are any free extents in the size range given
 * by low and high, for the bitmap block bbno.
 */
STATIC int				/* error */
xfs_rtany_summary(
	xfs_mount_t	*mp,		/* file system mount structure */
	xfs_trans_t	*tp,		/* transaction pointer */
	int		low,		/* low log2 extent size */
	int		high,		/* high log2 extent size */
	xfs_rtblock_t	bbno,		/* bitmap block number */
	xfs_buf_t	**rbpp,		/* in/out: summary block buffer */
	xfs_fsblock_t	*rsb,		/* in/out: summary block number */
	int		*stat)		/* out: any good extents here? */
{
	int		error;		/* error value */
	int		log;		/* loop counter, log2 of ext. size */
	xfs_suminfo_t	sum;		/* summary data */

	/*
	 * Loop over logs of extent sizes.  Order is irrelevant.
	 */
	for (log = low; log <= high; log++) {
		/*
		 * Get one summary datum.
		 */
		error = xfs_rtget_summary(mp, tp, log, bbno, rbpp, rsb, &sum);
		if (error) {
			return error;
		}
		/*
		 * If there are any, return success.
		 */
		if (sum) {
			*stat = 1;
			return 0;
		}
	}
	/*
	 * Found nothing, return failure.
	 */
	*stat = 0;
	return 0;
}

/*
 * Get a buffer for the bitmap or summary file block specified.
 * The buffer is returned read and locked.
 */
STATIC int				/* error */
xfs_rtbuf_get(
	xfs_mount_t	*mp,		/* file system mount structure */
	xfs_trans_t	*tp,		/* transaction pointer */
	xfs_rtblock_t	block,		/* block number in bitmap or summary */
	int		issum,		/* is summary not bitmap */
	xfs_buf_t	**bpp)		/* output: buffer for the block */
{
	xfs_buf_t	*bp;		/* block buffer, result */
	xfs_daddr_t	d;		/* disk addr of block */
	int		error;		/* error value */
	xfs_fsblock_t	fsb;		/* fs block number for block */
	xfs_inode_t	*ip;		/* bitmap or summary inode */

	ip = issum ? mp->m_rsumip : mp->m_rbmip;
	/*
	 * Map from the file offset (block) and inode number to the
	 * file system block.
	 */
	error = xfs_bmapi_single(tp, ip, XFS_DATA_FORK, &fsb, block);
	if (error) {
		return error;
	}
	ASSERT(fsb != NULLFSBLOCK);
	/*
	 * Convert to disk address for buffer cache.
	 */
	d = XFS_FSB_TO_DADDR(mp, fsb);
	/*
	 * Read the buffer.
	 */
	error = xfs_trans_read_buf(mp, tp, mp->m_ddev_targp, d,
				   mp->m_bsize, 0, &bp);
	if (error) {
		return error;
	}
	ASSERT(bp && !XFS_BUF_GETERROR(bp));
	*bpp = bp;
	return 0;
}

#ifdef DEBUG
/*
 * Check that the given extent (block range) is allocated already.
 */
STATIC int				/* error */
xfs_rtcheck_alloc_range(
	xfs_mount_t	*mp,		/* file system mount point */
	xfs_trans_t	*tp,		/* transaction pointer */
	xfs_rtblock_t	bno,		/* starting block number of extent */
	xfs_extlen_t	len,		/* length of extent */
	int		*stat)		/* out: 1 for allocated, 0 for not */
{
	xfs_rtblock_t	new;		/* dummy for xfs_rtcheck_range */

	return xfs_rtcheck_range(mp, tp, bno, len, 0, &new, stat);
}
#endif

#ifdef DEBUG
/*
 * Check whether the given block in the bitmap has the given value.
 */
STATIC int				/* 1 for matches, 0 for not */
xfs_rtcheck_bit(
	xfs_mount_t	*mp,		/* file system mount structure */
	xfs_trans_t	*tp,		/* transaction pointer */
	xfs_rtblock_t	start,		/* bit (block) to check */
	int		val)		/* 1 for free, 0 for allocated */
{
	int		bit;		/* bit number in the word */
	xfs_rtblock_t	block;		/* bitmap block number */
	xfs_buf_t	*bp;		/* buf for the block */
	xfs_rtword_t	*bufp;		/* pointer into the buffer */
	/* REFERENCED */
	int		error;		/* error value */
	xfs_rtword_t	wdiff;		/* difference between bit & expected */
	int		word;		/* word number in the buffer */
	xfs_rtword_t	wval;		/* word value from buffer */

	block = XFS_BITTOBLOCK(mp, start);
	error = xfs_rtbuf_get(mp, tp, block, 0, &bp);
	bufp = (xfs_rtword_t *)XFS_BUF_PTR(bp);
	word = XFS_BITTOWORD(mp, start);
	bit = (int)(start & (XFS_NBWORD - 1));
	wval = bufp[word];
	xfs_trans_brelse(tp, bp);
	wdiff = (wval ^ -val) & ((xfs_rtword_t)1 << bit);
	return !wdiff;
}
#endif	/* DEBUG */

#if 0
/*
 * Check that the given extent (block range) is free already.
 */
STATIC int				/* error */
xfs_rtcheck_free_range(
	xfs_mount_t	*mp,		/* file system mount point */
	xfs_trans_t	*tp,		/* transaction pointer */
	xfs_rtblock_t	bno,		/* starting block number of extent */
	xfs_extlen_t	len,		/* length of extent */
	int		*stat)		/* out: 1 for free, 0 for not */
{
	xfs_rtblock_t	new;		/* dummy for xfs_rtcheck_range */

	return xfs_rtcheck_range(mp, tp, bno, len, 1, &new, stat);
}
#endif

/*
 * Check that the given range is either all allocated (val = 0) or
 * all free (val = 1).
 */
STATIC int				/* error */
xfs_rtcheck_range(
	xfs_mount_t	*mp,		/* file system mount point */
	xfs_trans_t	*tp,		/* transaction pointer */
	xfs_rtblock_t	start,		/* starting block number of extent */
	xfs_extlen_t	len,		/* length of extent */
	int		val,		/* 1 for free, 0 for allocated */
	xfs_rtblock_t	*new,		/* out: first block not matching */
	int		*stat)		/* out: 1 for matches, 0 for not */
{
	xfs_rtword_t	*b;		/* current word in buffer */
	int		bit;		/* bit number in the word */
	xfs_rtblock_t	block;		/* bitmap block number */
	xfs_buf_t	*bp;		/* buf for the block */
	xfs_rtword_t	*bufp;		/* starting word in buffer */
	int		error;		/* error value */
	xfs_rtblock_t	i;		/* current bit number rel. to start */
	xfs_rtblock_t	lastbit;	/* last useful bit in word */
	xfs_rtword_t	mask;		/* mask of relevant bits for value */
	xfs_rtword_t	wdiff;		/* difference from wanted value */
	int		word;		/* word number in the buffer */

	/*
	 * Compute starting bitmap block number
	 */
	block = XFS_BITTOBLOCK(mp, start);
	/*
	 * Read the bitmap block.
	 */
	error = xfs_rtbuf_get(mp, tp, block, 0, &bp);
	if (error) {
		return error;
	}
	bufp = (xfs_rtword_t *)XFS_BUF_PTR(bp);
	/*
	 * Compute the starting word's address, and starting bit.
	 */
	word = XFS_BITTOWORD(mp, start);
	b = &bufp[word];
	bit = (int)(start & (XFS_NBWORD - 1));
	/*
	 * 0 (allocated) => all zero's; 1 (free) => all one's.
	 */
	val = -val;
	/*
	 * If not starting on a word boundary, deal with the first
	 * (partial) word.
	 */
	if (bit) {
		/*
		 * Compute first bit not examined.
		 */
		lastbit = XFS_RTMIN(bit + len, XFS_NBWORD);
		/*
		 * Mask of relevant bits.
		 */
		mask = (((xfs_rtword_t)1 << (lastbit - bit)) - 1) << bit;
		/*
		 * Compute difference between actual and desired value.
		 */
		if ((wdiff = (*b ^ val) & mask)) {
			/*
			 * Different, compute first wrong bit and return.
			 */
			xfs_trans_brelse(tp, bp);
			i = XFS_RTLOBIT(wdiff) - bit;
			*new = start + i;
			*stat = 0;
			return 0;
		}
		i = lastbit - bit;
		/*
		 * Go on to next block if that's where the next word is
		 * and we need the next word.
		 */
		if (++word == XFS_BLOCKWSIZE(mp) && i < len) {
			/*
			 * If done with this block, get the next one.
			 */
			xfs_trans_brelse(tp, bp);
			error = xfs_rtbuf_get(mp, tp, ++block, 0, &bp);
			if (error) {
				return error;
			}
			b = bufp = (xfs_rtword_t *)XFS_BUF_PTR(bp);
			word = 0;
		} else {
			/*
			 * Go on to the next word in the buffer.
			 */
			b++;
		}
	} else {
		/*
		 * Starting on a word boundary, no partial word.
		 */
		i = 0;
	}
	/*
	 * Loop over whole words in buffers.  When we use up one buffer
	 * we move on to the next one.
	 */
	while (len - i >= XFS_NBWORD) {
		/*
		 * Compute difference between actual and desired value.
		 */
		if ((wdiff = *b ^ val)) {
			/*
			 * Different, compute first wrong bit and return.
			 */
			xfs_trans_brelse(tp, bp);
			i += XFS_RTLOBIT(wdiff);
			*new = start + i;
			*stat = 0;
			return 0;
		}
		i += XFS_NBWORD;
		/*
		 * Go on to next block if that's where the next word is
		 * and we need the next word.
		 */
		if (++word == XFS_BLOCKWSIZE(mp) && i < len) {
			/*
			 * If done with this block, get the next one.
			 */
			xfs_trans_brelse(tp, bp);
			error = xfs_rtbuf_get(mp, tp, ++block, 0, &bp);
			if (error) {
				return error;
			}
			b = bufp = (xfs_rtword_t *)XFS_BUF_PTR(bp);
			word = 0;
		} else {
			/*
			 * Go on to the next word in the buffer.
			 */
			b++;
		}
	}
	/*
	 * If not ending on a word boundary, deal with the last
	 * (partial) word.
	 */
	if ((lastbit = len - i)) {
		/*
		 * Mask of relevant bits.
		 */
		mask = ((xfs_rtword_t)1 << lastbit) - 1;
		/*
		 * Compute difference between actual and desired value.
		 */
		if ((wdiff = (*b ^ val) & mask)) {
			/*
			 * Different, compute first wrong bit and return.
			 */
			xfs_trans_brelse(tp, bp);
			i += XFS_RTLOBIT(wdiff);
			*new = start + i;
			*stat = 0;
			return 0;
		} else
			i = len;
	}
	/*
	 * Successful, return.
	 */
	xfs_trans_brelse(tp, bp);
	*new = start + i;
	*stat = 1;
	return 0;
}

/*
 * Copy and transform the summary file, given the old and new
 * parameters in the mount structures.
 */
STATIC int				/* error */
xfs_rtcopy_summary(
	xfs_mount_t	*omp,		/* old file system mount point */
	xfs_mount_t	*nmp,		/* new file system mount point */
	xfs_trans_t	*tp)		/* transaction pointer */
{
	xfs_rtblock_t	bbno;		/* bitmap block number */
	xfs_buf_t	*bp;		/* summary buffer */
	int		error;		/* error return value */
	int		log;		/* summary level number (log length) */
	xfs_suminfo_t	sum;		/* summary data */
	xfs_fsblock_t	sumbno;		/* summary block number */

	bp = NULL;
	for (log = omp->m_rsumlevels - 1; log >= 0; log--) {
		for (bbno = omp->m_sb.sb_rbmblocks - 1;
		     (xfs_srtblock_t)bbno >= 0;
		     bbno--) {
			error = xfs_rtget_summary(omp, tp, log, bbno, &bp,
				&sumbno, &sum);
			if (error)
				return error;
			if (sum == 0)
				continue;
			error = xfs_rtmodify_summary(omp, tp, log, bbno, -sum,
				&bp, &sumbno);
			if (error)
				return error;
			error = xfs_rtmodify_summary(nmp, tp, log, bbno, sum,
				&bp, &sumbno);
			if (error)
				return error;
			ASSERT(sum > 0);
		}
	}
	return 0;
}

/*
 * Searching backward from start to limit, find the first block whose
 * allocated/free state is different from start's.
 */
STATIC int				/* error */
xfs_rtfind_back(
	xfs_mount_t	*mp,		/* file system mount point */
	xfs_trans_t	*tp,		/* transaction pointer */
	xfs_rtblock_t	start,		/* starting block to look at */
	xfs_rtblock_t	limit,		/* last block to look at */
	xfs_rtblock_t	*rtblock)	/* out: start block found */
{
	xfs_rtword_t	*b;		/* current word in buffer */
	int		bit;		/* bit number in the word */
	xfs_rtblock_t	block;		/* bitmap block number */
	xfs_buf_t	*bp;		/* buf for the block */
	xfs_rtword_t	*bufp;		/* starting word in buffer */
	int		error;		/* error value */
	xfs_rtblock_t	firstbit;	/* first useful bit in the word */
	xfs_rtblock_t	i;		/* current bit number rel. to start */
	xfs_rtblock_t	len;		/* length of inspected area */
	xfs_rtword_t	mask;		/* mask of relevant bits for value */
	xfs_rtword_t	want;		/* mask for "good" values */
	xfs_rtword_t	wdiff;		/* difference from wanted value */
	int		word;		/* word number in the buffer */

	/*
	 * Compute and read in starting bitmap block for starting block.
	 */
	block = XFS_BITTOBLOCK(mp, start);
	error = xfs_rtbuf_get(mp, tp, block, 0, &bp);
	if (error) {
		return error;
	}
	bufp = (xfs_rtword_t *)XFS_BUF_PTR(bp);
	/*
	 * Get the first word's index & point to it.
	 */
	word = XFS_BITTOWORD(mp, start);
	b = &bufp[word];
	bit = (int)(start & (XFS_NBWORD - 1));
	len = start - limit + 1;
	/*
	 * Compute match value, based on the bit at start: if 1 (free)
	 * then all-ones, else all-zeroes.
	 */
	want = (*b & ((xfs_rtword_t)1 << bit)) ? -1 : 0;
	/*
	 * If the starting position is not word-aligned, deal with the
	 * partial word.
	 */
	if (bit < XFS_NBWORD - 1) {
		/*
		 * Calculate first (leftmost) bit number to look at,
		 * and mask for all the relevant bits in this word.
		 */
		firstbit = XFS_RTMAX((xfs_srtblock_t)(bit - len + 1), 0);
		mask = (((xfs_rtword_t)1 << (bit - firstbit + 1)) - 1) <<
			firstbit;
		/*
		 * Calculate the difference between the value there
		 * and what we're looking for.
		 */
		if ((wdiff = (*b ^ want) & mask)) {
			/*
			 * Different.  Mark where we are and return.
			 */
			xfs_trans_brelse(tp, bp);
			i = bit - XFS_RTHIBIT(wdiff);
			*rtblock = start - i + 1;
			return 0;
		}
		i = bit - firstbit + 1;
		/*
		 * Go on to previous block if that's where the previous word is
		 * and we need the previous word.
		 */
		if (--word == -1 && i < len) {
			/*
			 * If done with this block, get the previous one.
			 */
			xfs_trans_brelse(tp, bp);
			error = xfs_rtbuf_get(mp, tp, --block, 0, &bp);
			if (error) {
				return error;
			}
			bufp = (xfs_rtword_t *)XFS_BUF_PTR(bp);
			word = XFS_BLOCKWMASK(mp);
			b = &bufp[word];
		} else {
			/*
			 * Go on to the previous word in the buffer.
			 */
			b--;
		}
	} else {
		/*
		 * Starting on a word boundary, no partial word.
		 */
		i = 0;
	}
	/*
	 * Loop over whole words in buffers.  When we use up one buffer
	 * we move on to the previous one.
	 */
	while (len - i >= XFS_NBWORD) {
		/*
		 * Compute difference between actual and desired value.
		 */
		if ((wdiff = *b ^ want)) {
			/*
			 * Different, mark where we are and return.
			 */
			xfs_trans_brelse(tp, bp);
			i += XFS_NBWORD - 1 - XFS_RTHIBIT(wdiff);
			*rtblock = start - i + 1;
			return 0;
		}
		i += XFS_NBWORD;
		/*
		 * Go on to previous block if that's where the previous word is
		 * and we need the previous word.
		 */
		if (--word == -1 && i < len) {
			/*
			 * If done with this block, get the previous one.
			 */
			xfs_trans_brelse(tp, bp);
			error = xfs_rtbuf_get(mp, tp, --block, 0, &bp);
			if (error) {
				return error;
			}
			bufp = (xfs_rtword_t *)XFS_BUF_PTR(bp);
			word = XFS_BLOCKWMASK(mp);
			b = &bufp[word];
		} else {
			/*
			 * Go on to the previous word in the buffer.
			 */
			b--;
		}
	}
	/*
	 * If not ending on a word boundary, deal with the last
	 * (partial) word.
	 */
	if (len - i) {
		/*
		 * Calculate first (leftmost) bit number to look at,
		 * and mask for all the relevant bits in this word.
		 */
		firstbit = XFS_NBWORD - (len - i);
		mask = (((xfs_rtword_t)1 << (len - i)) - 1) << firstbit;
		/*
		 * Compute difference between actual and desired value.
		 */
		if ((wdiff = (*b ^ want) & mask)) {
			/*
			 * Different, mark where we are and return.
			 */
			xfs_trans_brelse(tp, bp);
			i += XFS_NBWORD - 1 - XFS_RTHIBIT(wdiff);
			*rtblock = start - i + 1;
			return 0;
		} else
			i = len;
	}
	/*
	 * No match, return that we scanned the whole area.
	 */
	xfs_trans_brelse(tp, bp);
	*rtblock = start - i + 1;
	return 0;
}

/*
 * Searching forward from start to limit, find the first block whose
 * allocated/free state is different from start's.
 */
STATIC int				/* error */
xfs_rtfind_forw(
	xfs_mount_t	*mp,		/* file system mount point */
	xfs_trans_t	*tp,		/* transaction pointer */
	xfs_rtblock_t	start,		/* starting block to look at */
	xfs_rtblock_t	limit,		/* last block to look at */
	xfs_rtblock_t	*rtblock)	/* out: start block found */
{
	xfs_rtword_t	*b;		/* current word in buffer */
	int		bit;		/* bit number in the word */
	xfs_rtblock_t	block;		/* bitmap block number */
	xfs_buf_t	*bp;		/* buf for the block */
	xfs_rtword_t	*bufp;		/* starting word in buffer */
	int		error;		/* error value */
	xfs_rtblock_t	i;		/* current bit number rel. to start */
	xfs_rtblock_t	lastbit;	/* last useful bit in the word */
	xfs_rtblock_t	len;		/* length of inspected area */
	xfs_rtword_t	mask;		/* mask of relevant bits for value */
	xfs_rtword_t	want;		/* mask for "good" values */
	xfs_rtword_t	wdiff;		/* difference from wanted value */
	int		word;		/* word number in the buffer */

	/*
	 * Compute and read in starting bitmap block for starting block.
	 */
	block = XFS_BITTOBLOCK(mp, start);
	error = xfs_rtbuf_get(mp, tp, block, 0, &bp);
	if (error) {
		return error;
	}
	bufp = (xfs_rtword_t *)XFS_BUF_PTR(bp);
	/*
	 * Get the first word's index & point to it.
	 */
	word = XFS_BITTOWORD(mp, start);
	b = &bufp[word];
	bit = (int)(start & (XFS_NBWORD - 1));
	len = limit - start + 1;
	/*
	 * Compute match value, based on the bit at start: if 1 (free)
	 * then all-ones, else all-zeroes.
	 */
	want = (*b & ((xfs_rtword_t)1 << bit)) ? -1 : 0;
	/*
	 * If the starting position is not word-aligned, deal with the
	 * partial word.
	 */
	if (bit) {
		/*
		 * Calculate last (rightmost) bit number to look at,
		 * and mask for all the relevant bits in this word.
		 */
		lastbit = XFS_RTMIN(bit + len, XFS_NBWORD);
		mask = (((xfs_rtword_t)1 << (lastbit - bit)) - 1) << bit;
		/*
		 * Calculate the difference between the value there
		 * and what we're looking for.
		 */
		if ((wdiff = (*b ^ want) & mask)) {
			/*
			 * Different.  Mark where we are and return.
			 */
			xfs_trans_brelse(tp, bp);
			i = XFS_RTLOBIT(wdiff) - bit;
			*rtblock = start + i - 1;
			return 0;
		}
		i = lastbit - bit;
		/*
		 * Go on to next block if that's where the next word is
		 * and we need the next word.
		 */
		if (++word == XFS_BLOCKWSIZE(mp) && i < len) {
			/*
			 * If done with this block, get the previous one.
			 */
			xfs_trans_brelse(tp, bp);
			error = xfs_rtbuf_get(mp, tp, ++block, 0, &bp);
			if (error) {
				return error;
			}
			b = bufp = (xfs_rtword_t *)XFS_BUF_PTR(bp);
			word = 0;
		} else {
			/*
			 * Go on to the previous word in the buffer.
			 */
			b++;
		}
	} else {
		/*
		 * Starting on a word boundary, no partial word.
		 */
		i = 0;
	}
	/*
	 * Loop over whole words in buffers.  When we use up one buffer
	 * we move on to the next one.
	 */
	while (len - i >= XFS_NBWORD) {
		/*
		 * Compute difference between actual and desired value.
		 */
		if ((wdiff = *b ^ want)) {
			/*
			 * Different, mark where we are and return.
			 */
			xfs_trans_brelse(tp, bp);
			i += XFS_RTLOBIT(wdiff);
			*rtblock = start + i - 1;
			return 0;
		}
		i += XFS_NBWORD;
		/*
		 * Go on to next block if that's where the next word is
		 * and we need the next word.
		 */
		if (++word == XFS_BLOCKWSIZE(mp) && i < len) {
			/*
			 * If done with this block, get the next one.
			 */
			xfs_trans_brelse(tp, bp);
			error = xfs_rtbuf_get(mp, tp, ++block, 0, &bp);
			if (error) {
				return error;
			}
			b = bufp = (xfs_rtword_t *)XFS_BUF_PTR(bp);
			word = 0;
		} else {
			/*
			 * Go on to the next word in the buffer.
			 */
			b++;
		}
	}
	/*
	 * If not ending on a word boundary, deal with the last
	 * (partial) word.
	 */
	if ((lastbit = len - i)) {
		/*
		 * Calculate mask for all the relevant bits in this word.
		 */
		mask = ((xfs_rtword_t)1 << lastbit) - 1;
		/*
		 * Compute difference between actual and desired value.
		 */
		if ((wdiff = (*b ^ want) & mask)) {
			/*
			 * Different, mark where we are and return.
			 */
			xfs_trans_brelse(tp, bp);
			i += XFS_RTLOBIT(wdiff);
			*rtblock = start + i - 1;
			return 0;
		} else
			i = len;
	}
	/*
	 * No match, return that we scanned the whole area.
	 */
	xfs_trans_brelse(tp, bp);
	*rtblock = start + i - 1;
	return 0;
}

/*
 * Mark an extent specified by start and len freed.
 * Updates all the summary information as well as the bitmap.
 */
STATIC int				/* error */
xfs_rtfree_range(
	xfs_mount_t	*mp,		/* file system mount point */
	xfs_trans_t	*tp,		/* transaction pointer */
	xfs_rtblock_t	start,		/* starting block to free */
	xfs_extlen_t	len,		/* length to free */
	xfs_buf_t	**rbpp,		/* in/out: summary block buffer */
	xfs_fsblock_t	*rsb)		/* in/out: summary block number */
{
	xfs_rtblock_t	end;		/* end of the freed extent */
	int		error;		/* error value */
	xfs_rtblock_t	postblock;	/* first block freed > end */
	xfs_rtblock_t	preblock;	/* first block freed < start */

	end = start + len - 1;
	/*
	 * Modify the bitmap to mark this extent freed.
	 */
	error = xfs_rtmodify_range(mp, tp, start, len, 1);
	if (error) {
		return error;
	}
	/*
	 * Assume we're freeing out of the middle of an allocated extent.
	 * We need to find the beginning and end of the extent so we can
	 * properly update the summary.
	 */
	error = xfs_rtfind_back(mp, tp, start, 0, &preblock);
	if (error) {
		return error;
	}
	/*
	 * Find the next allocated block (end of allocated extent).
	 */
	error = xfs_rtfind_forw(mp, tp, end, mp->m_sb.sb_rextents - 1,
		&postblock);
	/*
	 * If there are blocks not being freed at the front of the
	 * old extent, add summary data for them to be allocated.
	 */
	if (preblock < start) {
		error = xfs_rtmodify_summary(mp, tp,
			XFS_RTBLOCKLOG(start - preblock),
			XFS_BITTOBLOCK(mp, preblock), -1, rbpp, rsb);
		if (error) {
			return error;
		}
	}
	/*
	 * If there are blocks not being freed at the end of the
	 * old extent, add summary data for them to be allocated.
	 */
	if (postblock > end) {
		error = xfs_rtmodify_summary(mp, tp,
			XFS_RTBLOCKLOG(postblock - end),
			XFS_BITTOBLOCK(mp, end + 1), -1, rbpp, rsb);
		if (error) {
			return error;
		}
	}
	/*
	 * Increment the summary information corresponding to the entire
	 * (new) free extent.
	 */
	error = xfs_rtmodify_summary(mp, tp,
		XFS_RTBLOCKLOG(postblock + 1 - preblock),
		XFS_BITTOBLOCK(mp, preblock), 1, rbpp, rsb);
	return error;
}

/*
 * Read and return the summary information for a given extent size,
 * bitmap block combination.
 * Keeps track of a current summary block, so we don't keep reading
 * it from the buffer cache.
 */
STATIC int				/* error */
xfs_rtget_summary(
	xfs_mount_t	*mp,		/* file system mount structure */
	xfs_trans_t	*tp,		/* transaction pointer */
	int		log,		/* log2 of extent size */
	xfs_rtblock_t	bbno,		/* bitmap block number */
	xfs_buf_t	**rbpp,		/* in/out: summary block buffer */
	xfs_fsblock_t	*rsb,		/* in/out: summary block number */
	xfs_suminfo_t	*sum)		/* out: summary info for this block */
{
	xfs_buf_t	*bp;		/* buffer for summary block */
	int		error;		/* error value */
	xfs_fsblock_t	sb;		/* summary fsblock */
	int		so;		/* index into the summary file */
	xfs_suminfo_t	*sp;		/* pointer to returned data */

	/*
	 * Compute entry number in the summary file.
	 */
	so = XFS_SUMOFFS(mp, log, bbno);
	/*
	 * Compute the block number in the summary file.
	 */
	sb = XFS_SUMOFFSTOBLOCK(mp, so);
	/*
	 * If we have an old buffer, and the block number matches, use that.
	 */
	if (rbpp && *rbpp && *rsb == sb)
		bp = *rbpp;
	/*
	 * Otherwise we have to get the buffer.
	 */
	else {
		/*
		 * If there was an old one, get rid of it first.
		 */
		if (rbpp && *rbpp)
			xfs_trans_brelse(tp, *rbpp);
		error = xfs_rtbuf_get(mp, tp, sb, 1, &bp);
		if (error) {
			return error;
		}
		/*
		 * Remember this buffer and block for the next call.
		 */
		if (rbpp) {
			*rbpp = bp;
			*rsb = sb;
		}
	}
	/*
	 * Point to the summary information & copy it out.
	 */
	sp = XFS_SUMPTR(mp, bp, so);
	*sum = *sp;
	/*
	 * Drop the buffer if we're not asked to remember it.
	 */
	if (!rbpp)
		xfs_trans_brelse(tp, bp);
	return 0;
}

/*
 * Set the given range of bitmap bits to the given value.
 * Do whatever I/O and logging is required.
 */
STATIC int				/* error */
xfs_rtmodify_range(
	xfs_mount_t	*mp,		/* file system mount point */
	xfs_trans_t	*tp,		/* transaction pointer */
	xfs_rtblock_t	start,		/* starting block to modify */
	xfs_extlen_t	len,		/* length of extent to modify */
	int		val)		/* 1 for free, 0 for allocated */
{
	xfs_rtword_t	*b;		/* current word in buffer */
	int		bit;		/* bit number in the word */
	xfs_rtblock_t	block;		/* bitmap block number */
	xfs_buf_t	*bp;		/* buf for the block */
	xfs_rtword_t	*bufp;		/* starting word in buffer */
	int		error;		/* error value */
	xfs_rtword_t	*first;		/* first used word in the buffer */
	int		i;		/* current bit number rel. to start */
	int		lastbit;	/* last useful bit in word */
	xfs_rtword_t	mask;		/* mask o frelevant bits for value */
	int		word;		/* word number in the buffer */

	/*
	 * Compute starting bitmap block number.
	 */
	block = XFS_BITTOBLOCK(mp, start);
	/*
	 * Read the bitmap block, and point to its data.
	 */
	error = xfs_rtbuf_get(mp, tp, block, 0, &bp);
	if (error) {
		return error;
	}
	bufp = (xfs_rtword_t *)XFS_BUF_PTR(bp);
	/*
	 * Compute the starting word's address, and starting bit.
	 */
	word = XFS_BITTOWORD(mp, start);
	first = b = &bufp[word];
	bit = (int)(start & (XFS_NBWORD - 1));
	/*
	 * 0 (allocated) => all zeroes; 1 (free) => all ones.
	 */
	val = -val;
	/*
	 * If not starting on a word boundary, deal with the first
	 * (partial) word.
	 */
	if (bit) {
		/*
		 * Compute first bit not changed and mask of relevant bits.
		 */
		lastbit = XFS_RTMIN(bit + len, XFS_NBWORD);
		mask = (((xfs_rtword_t)1 << (lastbit - bit)) - 1) << bit;
		/*
		 * Set/clear the active bits.
		 */
		if (val)
			*b |= mask;
		else
			*b &= ~mask;
		i = lastbit - bit;
		/*
		 * Go on to the next block if that's where the next word is
		 * and we need the next word.
		 */
		if (++word == XFS_BLOCKWSIZE(mp) && i < len) {
			/*
			 * Log the changed part of this block.
			 * Get the next one.
			 */
			xfs_trans_log_buf(tp, bp,
				(uint)((char *)first - (char *)bufp),
				(uint)((char *)b - (char *)bufp));
			error = xfs_rtbuf_get(mp, tp, ++block, 0, &bp);
			if (error) {
				return error;
			}
			first = b = bufp = (xfs_rtword_t *)XFS_BUF_PTR(bp);
			word = 0;
		} else {
			/*
			 * Go on to the next word in the buffer
			 */
			b++;
		}
	} else {
		/*
		 * Starting on a word boundary, no partial word.
		 */
		i = 0;
	}
	/*
	 * Loop over whole words in buffers.  When we use up one buffer
	 * we move on to the next one.
	 */
	while (len - i >= XFS_NBWORD) {
		/*
		 * Set the word value correctly.
		 */
		*b = val;
		i += XFS_NBWORD;
		/*
		 * Go on to the next block if that's where the next word is
		 * and we need the next word.
		 */
		if (++word == XFS_BLOCKWSIZE(mp) && i < len) {
			/*
			 * Log the changed part of this block.
			 * Get the next one.
			 */
			xfs_trans_log_buf(tp, bp,
				(uint)((char *)first - (char *)bufp),
				(uint)((char *)b - (char *)bufp));
			error = xfs_rtbuf_get(mp, tp, ++block, 0, &bp);
			if (error) {
				return error;
			}
			first = b = bufp = (xfs_rtword_t *)XFS_BUF_PTR(bp);
			word = 0;
		} else {
			/*
			 * Go on to the next word in the buffer
			 */
			b++;
		}
	}
	/*
	 * If not ending on a word boundary, deal with the last
	 * (partial) word.
	 */
	if ((lastbit = len - i)) {
		/*
		 * Compute a mask of relevant bits.
		 */
		bit = 0;
		mask = ((xfs_rtword_t)1 << lastbit) - 1;
		/*
		 * Set/clear the active bits.
		 */
		if (val)
			*b |= mask;
		else
			*b &= ~mask;
		b++;
	}
	/*
	 * Log any remaining changed bytes.
	 */
	if (b > first)
		xfs_trans_log_buf(tp, bp, (uint)((char *)first - (char *)bufp),
			(uint)((char *)b - (char *)bufp - 1));
	return 0;
}

/*
 * Read and modify the summary information for a given extent size,
 * bitmap block combination.
 * Keeps track of a current summary block, so we don't keep reading
 * it from the buffer cache.
 */
STATIC int				/* error */
xfs_rtmodify_summary(
	xfs_mount_t	*mp,		/* file system mount point */
	xfs_trans_t	*tp,		/* transaction pointer */
	int		log,		/* log2 of extent size */
	xfs_rtblock_t	bbno,		/* bitmap block number */
	int		delta,		/* change to make to summary info */
	xfs_buf_t	**rbpp,		/* in/out: summary block buffer */
	xfs_fsblock_t	*rsb)…