From ea2caed88755f36c1e1b80ff01b3577e9838a877 Mon Sep 17 00:00:00 2001
From: Dave Chinner <dchinner@redhat.com>
Date: Thu, 27 Jan 2011 12:14:12 +1100
Subject: [PATCH] --- yaml --- r: 232663 b: refs/heads/master c:
 b8fc82630ae289bb4e661567808afc59e3298dce h: refs/heads/master i:   232661:
 329bd7c492ae7a428f2fd798350ca700bb199cd7   232659:
 19a8e12db8283ef676b6dd4121ce6f8d8eb36778   232655:
 d51c4f2e62a86f68a0f3f2f0b41fbc4832851d93 v: v3

---
 [refs]                   | 2 +-
 trunk/fs/xfs/xfs_iomap.c | 7 ++++++-
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/[refs] b/[refs]
index 26489bf95752..38f664bb56f4 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: e34a314c5e49fe6b763568f6576b19f1299c33c2
+refs/heads/master: b8fc82630ae289bb4e661567808afc59e3298dce
diff --git a/trunk/fs/xfs/xfs_iomap.c b/trunk/fs/xfs/xfs_iomap.c
index 55582bd66659..8a0f044750c3 100644
--- a/trunk/fs/xfs/xfs_iomap.c
+++ b/trunk/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));