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authorDave Chinner <dchinner@redhat.com>2011-01-27 12:14:12 +1100
committerAlex Elder <aelder@sgi.com>2011-01-28 09:05:35 -0600
commitb8fc82630ae289bb4e661567808afc59e3298dce (patch)
tree70e319ec3d804992c1dd11e5123547d0901a40a0
parente34a314c5e49fe6b763568f6576b19f1299c33c2 (diff)
xfs: speculative delayed allocation uses rounddown_power_of_2 badly
rounddown_power_of_2() returns an undefined result when passed a value of zero. The specualtive delayed allocation code is doing this when the inode is zero length. Hence occasionally the preallocation is much, much larger than is necessary (e.g. 8GB for a 270 _byte_ file). Ensure we don't even pass a zero value to this function so the result of preallocation is always the desired size. Signed-off-by: Dave Chinner <dchinner@redhat.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Alex Elder <aelder@sgi.com>
-rw-r--r--fs/xfs/xfs_iomap.c7
1 files changed, 6 insertions, 1 deletions
diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index 55582bd66659..8a0f044750c3 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -337,7 +337,12 @@ xfs_iomap_prealloc_size(
int shift = 0;
int64_t freesp;
- alloc_blocks = XFS_B_TO_FSB(mp, ip->i_size);
+ /*
+ * rounddown_pow_of_two() returns an undefined result
+ * if we pass in alloc_blocks = 0. Hence the "+ 1" to
+ * ensure we always pass in a non-zero value.
+ */
+ alloc_blocks = XFS_B_TO_FSB(mp, ip->i_size) + 1;
alloc_blocks = XFS_FILEOFF_MIN(MAXEXTLEN,
rounddown_pow_of_two(alloc_blocks));