xfs: fix potential infinite loop in xfs_iomap_prealloc_size()

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@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index 912d83d8860a..b0b0f448e843 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;
         }