From 011e1561518b471da799e052dee91c82e2f6e55a Mon Sep 17 00:00:00 2001
From: Tao Ma <tao.ma@oracle.com>
Date: Sat, 17 Jul 2010 21:45:49 +0800
Subject: [PATCH] --- yaml --- r: 210383 b: refs/heads/master c:
 f63afdb2c32db850fa1bfccf84643a8885cbeb61 h: refs/heads/master i:   210381:
 f0c58e2fb953f9f04ee1af3290b26dee8f730c81   210379:
 ddd070fc3374c123146ccf34e45db045a41543b8   210375:
 2917e0e5be41d732ab12be4871c66b5f38196fbb   210367:
 66b40c41df84fb34774cb68bc3fd8b4301a4516d v: v3

---
 [refs]                | 2 +-
 trunk/fs/ocfs2/mmap.c | 8 +++++---
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/[refs] b/[refs]
index 4b44f19c3993..af799c00b43c 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: f5ce5a08a40f2086435858ddc80cb40394b082eb
+refs/heads/master: f63afdb2c32db850fa1bfccf84643a8885cbeb61
diff --git a/trunk/fs/ocfs2/mmap.c b/trunk/fs/ocfs2/mmap.c
index af2b8fe1f139..4c18f4ad93b4 100644
--- a/trunk/fs/ocfs2/mmap.c
+++ b/trunk/fs/ocfs2/mmap.c
@@ -74,9 +74,11 @@ static int __ocfs2_page_mkwrite(struct inode *inode, struct buffer_head *di_bh,
 	/*
 	 * Another node might have truncated while we were waiting on
 	 * cluster locks.
+	 * We don't check size == 0 before the shift. This is borrowed
+	 * from do_generic_file_read.
 	 */
-	last_index = size >> PAGE_CACHE_SHIFT;
-	if (page->index > last_index) {
+	last_index = (size - 1) >> PAGE_CACHE_SHIFT;
+	if (unlikely(!size || page->index > last_index)) {
 		ret = -EINVAL;
 		goto out;
 	}
@@ -107,7 +109,7 @@ static int __ocfs2_page_mkwrite(struct inode *inode, struct buffer_head *di_bh,
 	 * because the "write" would invalidate their data.
 	 */
 	if (page->index == last_index)
-		len = size & ~PAGE_CACHE_MASK;
+		len = ((size - 1) & ~PAGE_CACHE_MASK) + 1;
 
 	ret = ocfs2_write_begin_nolock(mapping, pos, len, 0, &locked_page,
 				       &fsdata, di_bh, page);