[PATCH 92/93] ext4: lock i_mutex when truncating orphan inodes

[Luis Henriques]

3.5.7.15 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Theodore Ts'o <tytso at mit.edu>

commit 721e3eba21e43532e438652dd8f1fcdfce3187e7 upstream.

Commit c278531d39 added a warning when ext4_flush_unwritten_io() is
called without i_mutex being taken.  It had previously not been taken
during orphan cleanup since races weren't possible at that point in
the mount process, but as a result of this c278531d39, we will now see
a kernel WARN_ON in this case.  Take the i_mutex in
ext4_orphan_cleanup() to suppress this warning.

Reported-by: Alexander Beregalov <a.beregalov at gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso at mit.edu>
Reviewed-by: Zheng Liu <wenqing.lz at taobao.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 fs/ext4/super.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index df4b8db..89abdd7 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -2208,7 +2208,9 @@ static void ext4_orphan_cleanup(struct super_block *sb,
 				__func__, inode->i_ino, inode->i_size);
 			jbd_debug(2, "truncating inode %lu to %lld bytes\n",
 				  inode->i_ino, inode->i_size);
+			mutex_lock(&inode->i_mutex);
 			ext4_truncate(inode);
+			mutex_unlock(&inode->i_mutex);
 			nr_truncates++;
 		} else {
 			ext4_msg(sb, KERN_DEBUG,
-- 
1.8.1.2