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authorBrian Foster <bfoster@redhat.com>2013-03-18 10:51:44 -0400
committerBen Myers <bpm@sgi.com>2013-03-22 16:05:00 -0500
commitc9bdbdc0741d90908f492415c890b630f43f17f8 (patch)
treecf8bf3498ad3b724adcd3b609947e8d88cfed0f7 /fs/xfs/xfs_iomap.c
parent3c58b5f809eda8ae8d891b7a87d0a235ab0f9bf5 (diff)
xfs: push rounddown_pow_of_two() to after prealloc throttle
The round down occurs towards the beginning of the function. Push it down after throttling has occurred. This is to support adding further transformations to 'alloc_blocks' that might not preserve power-of-two alignment (and thus could lead to rounding down multiple times). Signed-off-by: Brian Foster <bfoster@redhat.com> Reviewed-by: Ben Myers <bpm@sgi.com> Reviewed-by: Mark Tinguely <tinguely@sgi.com> Signed-off-by: Ben Myers <bpm@sgi.com>
Diffstat (limited to 'fs/xfs/xfs_iomap.c')
-rw-r--r--fs/xfs/xfs_iomap.c19
1 files changed, 17 insertions, 2 deletions
diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index 344557eef92..9072794e3a4 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -389,8 +389,15 @@ xfs_iomap_prealloc_size(
if (!alloc_blocks)
goto check_writeio;
- alloc_blocks = XFS_FILEOFF_MIN(MAXEXTLEN,
- rounddown_pow_of_two(alloc_blocks));
+ /*
+ * MAXEXTLEN is not a power of two value but we round the prealloc down
+ * to the nearest power of two value after throttling. To prevent the
+ * round down from unconditionally reducing the maximum supported prealloc
+ * size, we round up first, apply appropriate throttling, round down and
+ * cap the value to MAXEXTLEN.
+ */
+ alloc_blocks = XFS_FILEOFF_MIN(roundup_pow_of_two(MAXEXTLEN),
+ alloc_blocks);
xfs_icsb_sync_counters(mp, XFS_ICSB_LAZY_COUNT);
freesp = mp->m_sb.sb_fdblocks;
@@ -407,6 +414,14 @@ xfs_iomap_prealloc_size(
}
if (shift)
alloc_blocks >>= shift;
+ /*
+ * rounddown_pow_of_two() returns an undefined result if we pass in
+ * alloc_blocks = 0.
+ */
+ if (alloc_blocks)
+ alloc_blocks = rounddown_pow_of_two(alloc_blocks);
+ if (alloc_blocks > MAXEXTLEN)
+ alloc_blocks = MAXEXTLEN;
/*
* If we are still trying to allocate more space than is