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-rw-r--r--fs/xfs/xfs_alloc.h16
-rw-r--r--fs/xfs/xfs_bmap.c18
2 files changed, 26 insertions, 8 deletions
diff --git a/fs/xfs/xfs_alloc.h b/fs/xfs/xfs_alloc.h
index 0ab56b32c7eb..d0b3bc72005b 100644
--- a/fs/xfs/xfs_alloc.h
+++ b/fs/xfs/xfs_alloc.h
@@ -75,6 +75,22 @@ typedef unsigned int xfs_alloctype_t;
#define XFS_ALLOC_SET_ASIDE(mp) (4 + ((mp)->m_sb.sb_agcount * 4))
/*
+ * When deciding how much space to allocate out of an AG, we limit the
+ * allocation maximum size to the size the AG. However, we cannot use all the
+ * blocks in the AG - some are permanently used by metadata. These
+ * blocks are generally:
+ * - the AG superblock, AGF, AGI and AGFL
+ * - the AGF (bno and cnt) and AGI btree root blocks
+ * - 4 blocks on the AGFL according to XFS_ALLOC_SET_ASIDE() limits
+ *
+ * The AG headers are sector sized, so the amount of space they take up is
+ * dependent on filesystem geometry. The others are all single blocks.
+ */
+#define XFS_ALLOC_AG_MAX_USABLE(mp) \
+ ((mp)->m_sb.sb_agblocks - XFS_BB_TO_FSB(mp, XFS_FSS_TO_BB(mp, 4)) - 7)
+
+
+/*
* Argument structure for xfs_alloc routines.
* This is turned into a structure to avoid having 20 arguments passed
* down several levels of the stack.
diff --git a/fs/xfs/xfs_bmap.c b/fs/xfs/xfs_bmap.c
index 4111cd3966c7..f3a3768189bb 100644
--- a/fs/xfs/xfs_bmap.c
+++ b/fs/xfs/xfs_bmap.c
@@ -2430,7 +2430,7 @@ xfs_bmap_btalloc_nullfb(
startag = ag = 0;
pag = xfs_perag_get(mp, ag);
- while (*blen < ap->alen) {
+ while (*blen < args->maxlen) {
if (!pag->pagf_init) {
error = xfs_alloc_pagf_init(mp, args->tp, ag,
XFS_ALLOC_FLAG_TRYLOCK);
@@ -2452,7 +2452,7 @@ xfs_bmap_btalloc_nullfb(
notinit = 1;
if (xfs_inode_is_filestream(ap->ip)) {
- if (*blen >= ap->alen)
+ if (*blen >= args->maxlen)
break;
if (ap->userdata) {
@@ -2498,14 +2498,14 @@ xfs_bmap_btalloc_nullfb(
* If the best seen length is less than the request
* length, use the best as the minimum.
*/
- else if (*blen < ap->alen)
+ else if (*blen < args->maxlen)
args->minlen = *blen;
/*
- * Otherwise we've seen an extent as big as alen,
+ * Otherwise we've seen an extent as big as maxlen,
* use that as the minimum.
*/
else
- args->minlen = ap->alen;
+ args->minlen = args->maxlen;
/*
* set the failure fallback case to look in the selected
@@ -2573,7 +2573,9 @@ xfs_bmap_btalloc(
args.tp = ap->tp;
args.mp = mp;
args.fsbno = ap->rval;
- args.maxlen = MIN(ap->alen, mp->m_sb.sb_agblocks);
+
+ /* Trim the allocation back to the maximum an AG can fit. */
+ args.maxlen = MIN(ap->alen, XFS_ALLOC_AG_MAX_USABLE(mp));
args.firstblock = ap->firstblock;
blen = 0;
if (nullfb) {
@@ -2621,7 +2623,7 @@ xfs_bmap_btalloc(
/*
* Adjust for alignment
*/
- if (blen > args.alignment && blen <= ap->alen)
+ if (blen > args.alignment && blen <= args.maxlen)
args.minlen = blen - args.alignment;
args.minalignslop = 0;
} else {
@@ -2640,7 +2642,7 @@ xfs_bmap_btalloc(
* of minlen+alignment+slop doesn't go up
* between the calls.
*/
- if (blen > mp->m_dalign && blen <= ap->alen)
+ if (blen > mp->m_dalign && blen <= args.maxlen)
nextminlen = blen - mp->m_dalign;
else
nextminlen = args.minlen;