[PATCH] xfs: fix potential infinite loop in xfs_iomap_prealloc_size()

[Brian Foster]

If freesp == 0, we could end up in an infinite loop while squashing
the preallocation. Break the loop when we've killed the prealloc
entirely.

Signed-off-by: Brian Foster <bfoster at redhat.com>
---
Hi all,

Mark caught this while reviewing the quota throttling patchset. I figured
it better that my set depend on this rather than vice versa, so I'll plan on a
v5 for at least a rebase, but I'll wait a bit for further comments on v4.

Brian

 fs/xfs/xfs_iomap.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index 912d83d..b0b0f44 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -413,7 +413,7 @@ xfs_iomap_prealloc_size(
 		 * have a large file on a small filesystem and the above
 		 * lowspace thresholds are smaller than MAXEXTLEN.
 		 */
-		while (alloc_blocks >= freesp)
+		while (alloc_blocks && alloc_blocks >= freesp)
 			alloc_blocks >>= 4;
 	}
 
-- 
1.7.7.6