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authorYingping Lu <yingping@sgi.com>2006-06-09 14:55:18 +1000
committerNathan Scott <nathans@sgi.com>2006-06-09 14:55:18 +1000
commitd210a28cd851082cec9b282443f8cc0e6fc09830 (patch)
tree77b8c843d4cb7e6095b607570c5fd16702e50592 /fs/xfs/xfs_alloc.c
parentd3446eac3f50dade2f09ed212b112609ee78fb33 (diff)
[XFS] In actual allocation of file system blocks and freeing extents, the
transaction within each such operation may involve multiple locking of AGF buffer. While the freeing extent function has sorted the extents based on AGF number before entering into transaction, however, when the file system space is very limited, the allocation of space would try every AGF to get space allocated, this could potentially cause out-of-order locking, thus deadlock could happen. This fix mitigates the scarce space for allocation by setting aside a few blocks without reservation, and avoid deadlock by maintaining ascending order of AGF locking. SGI-PV: 947395 SGI-Modid: xfs-linux-melb:xfs-kern:210801a Signed-off-by: Yingping Lu <yingping@sgi.com> Signed-off-by: Nathan Scott <nathans@sgi.com>
Diffstat (limited to 'fs/xfs/xfs_alloc.c')
-rw-r--r--fs/xfs/xfs_alloc.c29
1 files changed, 23 insertions, 6 deletions
diff --git a/fs/xfs/xfs_alloc.c b/fs/xfs/xfs_alloc.c
index 8558226281c..22af489d3f3 100644
--- a/fs/xfs/xfs_alloc.c
+++ b/fs/xfs/xfs_alloc.c
@@ -1862,7 +1862,7 @@ xfs_alloc_fix_freelist(
(pag->pagf_longest - delta) :
(pag->pagf_flcount > 0 || pag->pagf_longest > 0);
if (args->minlen + args->alignment + args->minalignslop - 1 > longest ||
- (args->minleft &&
+ (!(flags & XFS_ALLOC_FLAG_FREEING) &&
(int)(pag->pagf_freeblks + pag->pagf_flcount -
need - args->total) <
(int)args->minleft)) {
@@ -1898,7 +1898,7 @@ xfs_alloc_fix_freelist(
longest = (longest > delta) ? (longest - delta) :
(be32_to_cpu(agf->agf_flcount) > 0 || longest > 0);
if (args->minlen + args->alignment + args->minalignslop - 1 > longest ||
- (args->minleft &&
+ (!(flags & XFS_ALLOC_FLAG_FREEING) &&
(int)(be32_to_cpu(agf->agf_freeblks) +
be32_to_cpu(agf->agf_flcount) - need - args->total) <
(int)args->minleft)) {
@@ -1951,8 +1951,14 @@ xfs_alloc_fix_freelist(
* the restrictions correctly. Can happen for free calls
* on a completely full ag.
*/
- if (targs.agbno == NULLAGBLOCK)
+ if (targs.agbno == NULLAGBLOCK) {
+ if (!(flags & XFS_ALLOC_FLAG_FREEING)) {
+ xfs_trans_brelse(tp, agflbp);
+ args->agbp = NULL;
+ return 0;
+ }
break;
+ }
/*
* Put each allocated block on the list.
*/
@@ -2360,8 +2366,19 @@ xfs_alloc_vextent(
if (args->agno == sagno &&
type == XFS_ALLOCTYPE_START_BNO)
args->type = XFS_ALLOCTYPE_THIS_AG;
- if (++(args->agno) == mp->m_sb.sb_agcount)
- args->agno = 0;
+ /*
+ * For the first allocation, we can try any AG to get
+ * space. However, if we already have allocated a
+ * block, we don't want to try AGs whose number is below
+ * sagno. Otherwise, we may end up with out-of-order
+ * locking of AGF, which might cause deadlock.
+ */
+ if (++(args->agno) == mp->m_sb.sb_agcount) {
+ if (args->firstblock != NULLFSBLOCK)
+ args->agno = sagno;
+ else
+ args->agno = 0;
+ }
/*
* Reached the starting a.g., must either be done
* or switch to non-trylock mode.
@@ -2443,7 +2460,7 @@ xfs_free_extent(
args.minlen = args.minleft = args.minalignslop = 0;
down_read(&args.mp->m_peraglock);
args.pag = &args.mp->m_perag[args.agno];
- if ((error = xfs_alloc_fix_freelist(&args, 0)))
+ if ((error = xfs_alloc_fix_freelist(&args, XFS_ALLOC_FLAG_FREEING)))
goto error0;
#ifdef DEBUG
ASSERT(args.agbp != NULL);