Commit b8fc8263 authored Jan 27, 2011 by Dave Chinner Committed by Alex Elder Jan 28, 2011

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>

parent e34a314c

fs/xfs/xfs_iomap.c

+6 −1

Original line number	Diff line number	Diff line
		@@ -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));

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