// SPDX-License-Identifier: GPL-2.0

  /*

   * Copyright (c) 2000-2005 Silicon Graphics, Inc.
   * All Rights Reserved.

   */

  #include "xfs.h"

  #include "xfs_fs.h"

  #include "xfs_shared.h"

  #include "xfs_format.h"
  #include "xfs_log_format.h"
  #include "xfs_trans_resv.h"

  #include "xfs_bit.h"

  #include "xfs_mount.h"

  #include "xfs_inode.h"

  #include "xfs_bmap.h"

  #include "xfs_bmap_btree.h"

  #include "xfs_trans.h"

  #include "xfs_trans_space.h"

  #include "xfs_icache.h"

  #include "xfs_rtalloc.h"

  #include "xfs_sb.h"

  
  /*

   * 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

  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 */

  {

  	return xfs_rtmodify_summary_int(mp, tp, log, bbno, 0, rbpp, rsb, sum);

  }
  
  /*

   * 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 */

  	/* There are no extents at levels < m_rsum_cache[bbno]. */
  	if (mp->m_rsum_cache && low < mp->m_rsum_cache[bbno])
  		low = mp->m_rsum_cache[bbno];

  	/*

  	 * Loop over logs of extent sizes.

  	 */

  	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;

  			goto out;

  		}

  	}
  	/*

  	 * Found nothing, return failure.

  	 */

  	*stat = 0;

  out:
  	/* There were no extents at levels < log. */
  	if (mp->m_rsum_cache && log > mp->m_rsum_cache[bbno])
  		mp->m_rsum_cache[bbno] = log;

  	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;
  }
  /*
   * 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 = 0;	/* first block allocated > end */
  	xfs_rtblock_t	preblock = 0;	/* 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;
  }
  
  /*
   * 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++) {

  		/* Make sure we don't scan off the end of the rt volume. */
  		maxlen = min(mp->m_sb.sb_rextents, i + maxlen) - 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) {
  			div_u64_rem(bestlen, prod, &p);
  			if (p)
  				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;

  
  	/* Make sure we don't run off the end of the rt volume. */
  	maxlen = min(mp->m_sb.sb_rextents, bno + maxlen) - bno;
  	if (maxlen < minlen) {
  		*rtblock = NULLRTBLOCK;
  		return 0;
  	}

  	/*
  	 * 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;

  	ASSERT(minlen != 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);

  	ASSERT(maxlen != 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;
  	}
  	ASSERT(minlen != 0);
  	ASSERT(maxlen != 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;
  }
  
  /*

   * Allocate space to the bitmap or summary file, and zero it, for growfs.

   */

  STATIC int

  xfs_growfs_rt_alloc(

  	struct xfs_mount	*mp,		/* file system mount point */
  	xfs_extlen_t		oblocks,	/* old count of blocks */
  	xfs_extlen_t		nblocks,	/* new count of blocks */
  	struct xfs_inode	*ip)		/* inode (bitmap/summary) */

  {

  	xfs_fileoff_t		bno;		/* block number in file */
  	struct xfs_buf		*bp;	/* temporary buffer for zeroing */

  	xfs_daddr_t		d;		/* disk block address */
  	int			error;		/* error return value */

  	xfs_fsblock_t		fsbno;		/* filesystem block for bno */
  	struct xfs_bmbt_irec	map;		/* block map output */
  	int			nmap;		/* number of block maps */
  	int			resblks;	/* space reservation */

  	enum xfs_blft		buf_type;

  	struct xfs_trans	*tp;

  	if (ip == mp->m_rsumip)
  		buf_type = XFS_BLFT_RTSUMMARY_BUF;
  	else
  		buf_type = XFS_BLFT_RTBITMAP_BUF;

  	/*

  	 * Allocate space to the file, as necessary.

  	 */

  	while (oblocks < nblocks) {

  		resblks = XFS_GROWFSRT_SPACE_RES(mp, nblocks - oblocks);

  		/*

  		 * Reserve space & log for one extent added to the file.

  		 */

  		error = xfs_trans_alloc(mp, &M_RES(mp)->tr_growrtalloc, resblks,
  				0, 0, &tp);

  		if (error)

  			return error;

  		/*

  		 * Lock the inode.

  		 */

  		xfs_ilock(ip, XFS_ILOCK_EXCL);
  		xfs_trans_ijoin(tp, ip, XFS_ILOCK_EXCL);

  		/*
  		 * Allocate blocks to the bitmap file.
  		 */
  		nmap = 1;

  		error = xfs_bmapi_write(tp, ip, oblocks, nblocks - oblocks,

  					XFS_BMAPI_METADATA, 0, &map, &nmap);

  		if (!error && nmap < 1)

  			error = -ENOSPC;

  		if (error)

  			goto out_trans_cancel;

  		/*
  		 * Free any blocks freed up in the transaction, then commit.
  		 */

  		error = xfs_trans_commit(tp);

  		if (error)

  			return error;

  		/*
  		 * Now we need to clear the allocated blocks.
  		 * Do this one block per transaction, to keep it simple.
  		 */

  		for (bno = map.br_startoff, fsbno = map.br_startblock;
  		     bno < map.br_startoff + map.br_blockcount;
  		     bno++, fsbno++) {

  			/*
  			 * Reserve log for one block zeroing.
  			 */

  			error = xfs_trans_alloc(mp, &M_RES(mp)->tr_growrtzero,
  					0, 0, 0, &tp);

  			if (error)

  				return error;

  			/*
  			 * Lock the bitmap inode.
  			 */
  			xfs_ilock(ip, XFS_ILOCK_EXCL);
  			xfs_trans_ijoin(tp, ip, XFS_ILOCK_EXCL);
  			/*
  			 * Get a buffer for the block.
  			 */
  			d = XFS_FSB_TO_DADDR(mp, fsbno);

  			error = xfs_trans_get_buf(tp, mp->m_ddev_targp, d,
  					mp->m_bsize, 0, &bp);
  			if (error)

  				goto out_trans_cancel;

  
  			xfs_trans_buf_set_type(tp, bp, buf_type);

  			bp->b_ops = &xfs_rtbuf_ops;

  			memset(bp->b_addr, 0, mp->m_sb.sb_blocksize);
  			xfs_trans_log_buf(tp, bp, 0, mp->m_sb.sb_blocksize - 1);
  			/*
  			 * Commit the transaction.
  			 */

  			error = xfs_trans_commit(tp);

  			if (error)

  				return error;

  		}

  		/*
  		 * Go on to the next extent, if any.
  		 */
  		oblocks = map.br_startoff + map.br_blockcount;

  	}

  	return 0;

  out_trans_cancel:
  	xfs_trans_cancel(tp);

  	return error;

  }

  static void
  xfs_alloc_rsum_cache(
  	xfs_mount_t	*mp,		/* file system mount structure */
  	xfs_extlen_t	rbmblocks)	/* number of rt bitmap blocks */
  {
  	/*
  	 * The rsum cache is initialized to all zeroes, which is trivially a
  	 * lower bound on the minimum level with any free extents. We can
  	 * continue without the cache if it couldn't be allocated.
  	 */

  	mp->m_rsum_cache = kvzalloc(rbmblocks, GFP_KERNEL);

  	if (!mp->m_rsum_cache)
  		xfs_warn(mp, "could not allocate realtime summary cache");
  }

  /*
   * Visible (exported) functions.
   */
  
  /*
   * Grow the realtime area of the filesystem.
   */
  int
  xfs_growfs_rt(
  	xfs_mount_t	*mp,		/* mount point for filesystem */
  	xfs_growfs_rt_t	*in)		/* growfs rt input struct */
  {
  	xfs_rtblock_t	bmbno;		/* bitmap block number */
  	xfs_buf_t	*bp;		/* temporary buffer */

  	int		error;		/* error return value */

  	xfs_mount_t	*nmp;		/* new (fake) mount structure */

  	xfs_rfsblock_t	nrblocks;	/* new number of realtime blocks */

  	xfs_extlen_t	nrbmblocks;	/* new number of rt bitmap blocks */

  	xfs_rtblock_t	nrextents;	/* new number of realtime extents */

  	uint8_t		nrextslog;	/* new log2 of sb_rextents */
  	xfs_extlen_t	nrsumblocks;	/* new number of summary blocks */
  	uint		nrsumlevels;	/* new rt summary levels */
  	uint		nrsumsize;	/* new size of rt summary, bytes */
  	xfs_sb_t	*nsbp;		/* new superblock */
  	xfs_extlen_t	rbmblocks;	/* current number of rt bitmap blocks */
  	xfs_extlen_t	rsumblocks;	/* current number of rt summary blks */
  	xfs_sb_t	*sbp;		/* old superblock */
  	xfs_fsblock_t	sumbno;		/* summary block number */

  	uint8_t		*rsum_cache;	/* old summary cache */

  
  	sbp = &mp->m_sb;
  	/*
  	 * Initial error checking.
  	 */

  	if (!capable(CAP_SYS_ADMIN))

  		return -EPERM;

  	if (mp->m_rtdev_targp == NULL || mp->m_rbmip == NULL ||

  	    (nrblocks = in->newblocks) <= sbp->sb_rblocks ||
  	    (sbp->sb_rblocks && (in->extsize != sbp->sb_rextsize)))

  		return -EINVAL;

  	if ((error = xfs_sb_validate_fsb_count(sbp, nrblocks)))
  		return error;

  	/*
  	 * Read in the last block of the device, make sure it exists.
  	 */

  	error = xfs_buf_read_uncached(mp->m_rtdev_targp,

  				XFS_FSB_TO_BB(mp, nrblocks - 1),

  				XFS_FSB_TO_BB(mp, 1), 0, &bp, NULL);
  	if (error)

  		return error;

  	xfs_buf_relse(bp);

  	/*
  	 * Calculate new parameters.  These are the final values to be reached.
  	 */
  	nrextents = nrblocks;
  	do_div(nrextents, in->extsize);

  	nrbmblocks = howmany_64(nrextents, NBBY * sbp->sb_blocksize);

  	nrextslog = xfs_highbit32(nrextents);
  	nrsumlevels = nrextslog + 1;
  	nrsumsize = (uint)sizeof(xfs_suminfo_t) * nrsumlevels * nrbmblocks;
  	nrsumblocks = XFS_B_TO_FSB(mp, nrsumsize);
  	nrsumsize = XFS_FSB_TO_B(mp, nrsumblocks);
  	/*
  	 * New summary size can't be more than half the size of
  	 * the log.  This prevents us from getting a log overflow,
  	 * since we'll log basically the whole summary file at once.
  	 */
  	if (nrsumblocks > (mp->m_sb.sb_logblocks >> 1))

  		return -EINVAL;

  	/*
  	 * Get the old block counts for bitmap and summary inodes.
  	 * These can't change since other growfs callers are locked out.
  	 */
  	rbmblocks = XFS_B_TO_FSB(mp, mp->m_rbmip->i_d.di_size);
  	rsumblocks = XFS_B_TO_FSB(mp, mp->m_rsumip->i_d.di_size);
  	/*
  	 * Allocate space to the bitmap and summary files, as necessary.
  	 */

  	error = xfs_growfs_rt_alloc(mp, rbmblocks, nrbmblocks, mp->m_rbmip);
  	if (error)

  		return error;

  	error = xfs_growfs_rt_alloc(mp, rsumblocks, nrsumblocks, mp->m_rsumip);
  	if (error)

  		return error;

  
  	rsum_cache = mp->m_rsum_cache;
  	if (nrbmblocks != sbp->sb_rbmblocks)
  		xfs_alloc_rsum_cache(mp, nrbmblocks);

  	/*
  	 * Allocate a new (fake) mount/sb.
  	 */

  	nmp = kmem_alloc(sizeof(*nmp), 0);

  	/*
  	 * Loop over the bitmap blocks.
  	 * We will do everything one bitmap block at a time.
  	 * Skip the current block if it is exactly full.
  	 * This also deals with the case where there were no rtextents before.
  	 */
  	for (bmbno = sbp->sb_rbmblocks -
  		     ((sbp->sb_rextents & ((1 << mp->m_blkbit_log) - 1)) != 0);
  	     bmbno < nrbmblocks;
  	     bmbno++) {

  		xfs_trans_t	*tp;

  		*nmp = *mp;
  		nsbp = &nmp->m_sb;
  		/*
  		 * Calculate new sb and mount fields for this round.
  		 */
  		nsbp->sb_rextsize = in->extsize;
  		nsbp->sb_rbmblocks = bmbno + 1;
  		nsbp->sb_rblocks =
  			XFS_RTMIN(nrblocks,
  				  nsbp->sb_rbmblocks * NBBY *
  				  nsbp->sb_blocksize * nsbp->sb_rextsize);
  		nsbp->sb_rextents = nsbp->sb_rblocks;
  		do_div(nsbp->sb_rextents, nsbp->sb_rextsize);

  		ASSERT(nsbp->sb_rextents != 0);

  		nsbp->sb_rextslog = xfs_highbit32(nsbp->sb_rextents);
  		nrsumlevels = nmp->m_rsumlevels = nsbp->sb_rextslog + 1;
  		nrsumsize =
  			(uint)sizeof(xfs_suminfo_t) * nrsumlevels *
  			nsbp->sb_rbmblocks;
  		nrsumblocks = XFS_B_TO_FSB(mp, nrsumsize);
  		nmp->m_rsumsize = nrsumsize = XFS_FSB_TO_B(mp, nrsumblocks);
  		/*
  		 * Start a transaction, get the log reservation.
  		 */

  		error = xfs_trans_alloc(mp, &M_RES(mp)->tr_growrtfree, 0, 0, 0,
  				&tp);

  		if (error)

  			break;

  		/*
  		 * Lock out other callers by grabbing the bitmap inode lock.
  		 */

  		xfs_ilock(mp->m_rbmip, XFS_ILOCK_EXCL | XFS_ILOCK_RTBITMAP);

  		xfs_trans_ijoin(tp, mp->m_rbmip, XFS_ILOCK_EXCL);

  		/*

  		 * Update the bitmap inode's size ondisk and incore.  We need
  		 * to update the incore size so that inode inactivation won't
  		 * punch what it thinks are "posteof" blocks.

  		 */
  		mp->m_rbmip->i_d.di_size =
  			nsbp->sb_rbmblocks * nsbp->sb_blocksize;

  		i_size_write(VFS_I(mp->m_rbmip), mp->m_rbmip->i_d.di_size);

  		xfs_trans_log_inode(tp, mp->m_rbmip, XFS_ILOG_CORE);

  		/*
  		 * Get the summary inode into the transaction.
  		 */

  		xfs_ilock(mp->m_rsumip, XFS_ILOCK_EXCL | XFS_ILOCK_RTSUM);

  		xfs_trans_ijoin(tp, mp->m_rsumip, XFS_ILOCK_EXCL);

  		/*

  		 * Update the summary inode's size.  We need to update the
  		 * incore size so that inode inactivation won't punch what it
  		 * thinks are "posteof" blocks.

  		 */
  		mp->m_rsumip->i_d.di_size = nmp->m_rsumsize;

  		i_size_write(VFS_I(mp->m_rsumip), mp->m_rsumip->i_d.di_size);

  		xfs_trans_log_inode(tp, mp->m_rsumip, XFS_ILOG_CORE);
  		/*
  		 * Copy summary data from old to new sizes.
  		 * Do this when the real size (not block-aligned) changes.
  		 */
  		if (sbp->sb_rbmblocks != nsbp->sb_rbmblocks ||
  		    mp->m_rsumlevels != nmp->m_rsumlevels) {
  			error = xfs_rtcopy_summary(mp, nmp, tp);
  			if (error)

  				goto error_cancel;

  		}
  		/*
  		 * Update superblock fields.
  		 */
  		if (nsbp->sb_rextsize != sbp->sb_rextsize)
  			xfs_trans_mod_sb(tp, XFS_TRANS_SB_REXTSIZE,
  				nsbp->sb_rextsize - sbp->sb_rextsize);
  		if (nsbp->sb_rbmblocks != sbp->sb_rbmblocks)
  			xfs_trans_mod_sb(tp, XFS_TRANS_SB_RBMBLOCKS,
  				nsbp->sb_rbmblocks - sbp->sb_rbmblocks);
  		if (nsbp->sb_rblocks != sbp->sb_rblocks)
  			xfs_trans_mod_sb(tp, XFS_TRANS_SB_RBLOCKS,
  				nsbp->sb_rblocks - sbp->sb_rblocks);
  		if (nsbp->sb_rextents != sbp->sb_rextents)
  			xfs_trans_mod_sb(tp, XFS_TRANS_SB_REXTENTS,
  				nsbp->sb_rextents - sbp->sb_rextents);
  		if (nsbp->sb_rextslog != sbp->sb_rextslog)
  			xfs_trans_mod_sb(tp, XFS_TRANS_SB_REXTSLOG,
  				nsbp->sb_rextslog - sbp->sb_rextslog);
  		/*
  		 * Free new extent.
  		 */
  		bp = NULL;
  		error = xfs_rtfree_range(nmp, tp, sbp->sb_rextents,
  			nsbp->sb_rextents - sbp->sb_rextents, &bp, &sumbno);

  		if (error) {
  error_cancel:

  			xfs_trans_cancel(tp);

  			break;

  		}

  		/*
  		 * Mark more blocks free in the superblock.
  		 */
  		xfs_trans_mod_sb(tp, XFS_TRANS_SB_FREXTENTS,
  			nsbp->sb_rextents - sbp->sb_rextents);
  		/*

  		 * Update mp values into the real mp structure.
  		 */
  		mp->m_rsumlevels = nrsumlevels;
  		mp->m_rsumsize = nrsumsize;

  		error = xfs_trans_commit(tp);

  		if (error)

  			break;

  	}

  	if (error)
  		goto out_free;
  
  	/* Update secondary superblocks now the physical grow has completed */
  	error = xfs_update_secondary_sbs(mp);

  out_free:

  	/*

  	 * Free the fake mp structure.

  	 */

  	kmem_free(nmp);

  	/*
  	 * If we had to allocate a new rsum_cache, we either need to free the
  	 * old one (if we succeeded) or free the new one and restore the old one
  	 * (if there was an error).
  	 */
  	if (rsum_cache != mp->m_rsum_cache) {
  		if (error) {
  			kmem_free(mp->m_rsum_cache);
  			mp->m_rsum_cache = rsum_cache;
  		} else {
  			kmem_free(rsum_cache);
  		}
  	}

  	return error;
  }
  
  /*
   * Allocate an extent in the realtime subvolume, with the usual allocation
   * parameters.  The length units are all in realtime extents, as is the
   * result block number.
   */
  int					/* error */
  xfs_rtallocate_extent(
  	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 */

  	int		wasdel,		/* was a delayed allocation extent */
  	xfs_extlen_t	prod,		/* extent product factor */
  	xfs_rtblock_t	*rtblock)	/* out: start block allocated */
  {

  	xfs_mount_t	*mp = tp->t_mountp;

  	int		error;		/* error value */

  	xfs_rtblock_t	r;		/* result allocated block */
  	xfs_fsblock_t	sb;		/* summary file block number */
  	xfs_buf_t	*sumbp;		/* summary file block buffer */

  	ASSERT(xfs_isilocked(mp->m_rbmip, XFS_ILOCK_EXCL));

  	ASSERT(minlen > 0 && minlen <= maxlen);

  	/*
  	 * If prod is set then figure out what to do to minlen and maxlen.
  	 */
  	if (prod > 1) {
  		xfs_extlen_t	i;
  
  		if ((i = maxlen % prod))
  			maxlen -= i;
  		if ((i = minlen % prod))
  			minlen += prod - i;
  		if (maxlen < minlen) {
  			*rtblock = NULLRTBLOCK;
  			return 0;
  		}
  	}

  retry:

  	sumbp = NULL;

  	if (bno == 0) {

  		error = xfs_rtallocate_extent_size(mp, tp, minlen, maxlen, len,
  				&sumbp,	&sb, prod, &r);

  	} else {

  		error = xfs_rtallocate_extent_near(mp, tp, bno, minlen, maxlen,
  				len, &sumbp, &sb, prod, &r);

  	}

  	if (error)

  		return error;

  	/*
  	 * If it worked, update the superblock.
  	 */
  	if (r != NULLRTBLOCK) {
  		long	slen = (long)*len;
  
  		ASSERT(*len >= minlen && *len <= maxlen);
  		if (wasdel)
  			xfs_trans_mod_sb(tp, XFS_TRANS_SB_RES_FREXTENTS, -slen);
  		else
  			xfs_trans_mod_sb(tp, XFS_TRANS_SB_FREXTENTS, -slen);

  	} else if (prod > 1) {
  		prod = 1;
  		goto retry;

  	}

  	*rtblock = r;
  	return 0;
  }
  
  /*

   * Initialize realtime fields in the mount structure.
   */
  int				/* error */
  xfs_rtmount_init(

  	struct xfs_mount	*mp)	/* file system mount structure */

  {

  	struct xfs_buf		*bp;	/* buffer for last block of subvolume */
  	struct xfs_sb		*sbp;	/* filesystem superblock copy in mount */
  	xfs_daddr_t		d;	/* address of last block of subvolume */
  	int			error;

  
  	sbp = &mp->m_sb;
  	if (sbp->sb_rblocks == 0)
  		return 0;
  	if (mp->m_rtdev_targp == NULL) {

  		xfs_warn(mp,
  	"Filesystem has a realtime volume, use rtdev=device option");

  		return -ENODEV;

  	}
  	mp->m_rsumlevels = sbp->sb_rextslog + 1;
  	mp->m_rsumsize =
  		(uint)sizeof(xfs_suminfo_t) * mp->m_rsumlevels *
  		sbp->sb_rbmblocks;
  	mp->m_rsumsize = roundup(mp->m_rsumsize, sbp->sb_blocksize);
  	mp->m_rbmip = mp->m_rsumip = NULL;
  	/*
  	 * Check that the realtime section is an ok size.
  	 */
  	d = (xfs_daddr_t)XFS_FSB_TO_BB(mp, mp->m_sb.sb_rblocks);
  	if (XFS_BB_TO_FSB(mp, d) != mp->m_sb.sb_rblocks) {

  		xfs_warn(mp, "realtime mount -- %llu != %llu",

  			(unsigned long long) XFS_BB_TO_FSB(mp, d),
  			(unsigned long long) mp->m_sb.sb_rblocks);

  		return -EFBIG;

  	}

  	error = xfs_buf_read_uncached(mp->m_rtdev_targp,

  					d - XFS_FSB_TO_BB(mp, 1),

  					XFS_FSB_TO_BB(mp, 1), 0, &bp, NULL);
  	if (error) {

  		xfs_warn(mp, "realtime device size check failed");

  		return error;

  	}
  	xfs_buf_relse(bp);
  	return 0;
  }
  
  /*

   * Get the bitmap and summary inodes and the summary cache into the mount
   * structure at mount time.

   */
  int					/* error */
  xfs_rtmount_inodes(
  	xfs_mount_t	*mp)		/* file system mount structure */
  {
  	int		error;		/* error return value */
  	xfs_sb_t	*sbp;
  
  	sbp = &mp->m_sb;

  	error = xfs_iget(mp, NULL, sbp->sb_rbmino, 0, 0, &mp->m_rbmip);

  	if (error)
  		return error;
  	ASSERT(mp->m_rbmip != NULL);

  	error = xfs_iget(mp, NULL, sbp->sb_rsumino, 0, 0, &mp->m_rsumip);

  	if (error) {

  		xfs_irele(mp->m_rbmip);

  		return error;
  	}
  	ASSERT(mp->m_rsumip != NULL);

  	xfs_alloc_rsum_cache(mp, sbp->sb_rbmblocks);

  	return 0;
  }

  void
  xfs_rtunmount_inodes(
  	struct xfs_mount	*mp)
  {

  	kmem_free(mp->m_rsum_cache);

  	if (mp->m_rbmip)

  		xfs_irele(mp->m_rbmip);

  	if (mp->m_rsumip)

  		xfs_irele(mp->m_rsumip);

  }

  /*
   * Pick an extent for allocation at the start of a new realtime file.
   * Use the sequence number stored in the atime field of the bitmap inode.
   * Translate this to a fraction of the rtextents, and return the product
   * of rtextents and the fraction.
   * The fraction sequence is 0, 1/2, 1/4, 3/4, 1/8, ..., 7/8, 1/16, ...
   */
  int					/* error */
  xfs_rtpick_extent(
  	xfs_mount_t	*mp,		/* file system mount point */
  	xfs_trans_t	*tp,		/* transaction pointer */
  	xfs_extlen_t	len,		/* allocation length (rtextents) */
  	xfs_rtblock_t	*pick)		/* result rt extent */
  {
  	xfs_rtblock_t	b;		/* result block */

  	int		log2;		/* log of sequence number */

  	uint64_t	resid;		/* residual after log removed */
  	uint64_t	seq;		/* sequence number of file creation */
  	uint64_t	*seqp;		/* pointer to seqno in inode */

  	ASSERT(xfs_isilocked(mp->m_rbmip, XFS_ILOCK_EXCL));

  	seqp = (uint64_t *)&VFS_I(mp->m_rbmip)->i_atime;

  	if (!(mp->m_rbmip->i_d.di_flags & XFS_DIFLAG_NEWRTBM)) {
  		mp->m_rbmip->i_d.di_flags |= XFS_DIFLAG_NEWRTBM;

  		*seqp = 0;
  	}
  	seq = *seqp;
  	if ((log2 = xfs_highbit64(seq)) == -1)
  		b = 0;
  	else {
  		resid = seq - (1ULL << log2);
  		b = (mp->m_sb.sb_rextents * ((resid << 1) + 1ULL)) >>
  		    (log2 + 1);
  		if (b >= mp->m_sb.sb_rextents)

  			div64_u64_rem(b, mp->m_sb.sb_rextents, &b);

  		if (b + len > mp->m_sb.sb_rextents)
  			b = mp->m_sb.sb_rextents - len;
  	}
  	*seqp = seq + 1;

  	xfs_trans_log_inode(tp, mp->m_rbmip, XFS_ILOG_CORE);

  	*pick = b;
  	return 0;
  }