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));