From b8fc82630ae289bb4e661567808afc59e3298dce Mon Sep 17 00:00:00 2001 From: Dave Chinner Date: Thu, 27 Jan 2011 12:14:12 +1100 Subject: [PATCH] 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 Reviewed-by: Christoph Hellwig Reviewed-by: Alex Elder --- fs/xfs/xfs_iomap.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) 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)); -- GitLab