Adding upstream version 4.19.249.upstream/4.19.249upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1285 insertions, 0 deletions

diff --git a/fs/xfs/xfs_rtalloc.c b/fs/xfs/xfs_rtalloc.c
new file mode 100644
index 000000000..280965fc9
--- /dev/null
+++ b/fs/xfs/xfs_rtalloc.c
@@ -0,0 +1,1285 @@
+// 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_defer.h"
+#include "xfs_inode.h"
+#include "xfs_bmap.h"
+#include "xfs_bmap_util.h"
+#include "xfs_bmap_btree.h"
+#include "xfs_alloc.h"
+#include "xfs_error.h"
+#include "xfs_trans.h"
+#include "xfs_trans_space.h"
+#include "xfs_trace.h"
+#include "xfs_buf.h"
+#include "xfs_icache.h"
+#include "xfs_rtalloc.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 */
+
+	/*
+	 * 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;
+}
+
+
+/*
+ * 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 */
+	struct xfs_trans	*tp;
+
+	/*
+	 * 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, resblks, &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);
+			bp = xfs_trans_get_buf(tp, mp->m_ddev_targp, d,
+				mp->m_bsize, 0);
+			if (bp == NULL) {
+				error = -EIO;
+				goto out_trans_cancel;
+			}
+			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;
+}
+
+/*
+ * 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 */
+
+	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;
+	/*
+	 * Allocate a new (fake) mount/sb.
+	 */
+	nmp = kmem_alloc(sizeof(*nmp), KM_SLEEP);
+	/*
+	 * 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_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_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;
+	}
+
+	/*
+	 * Free the fake mp structure.
+	 */
+	kmem_free(nmp);
+
+	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 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);
+	return 0;
+}
+
+void
+xfs_rtunmount_inodes(
+	struct xfs_mount	*mp)
+{
+	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;
+}