linux-kernel - [28/83] ext4: lock i_mutex when truncating orphan inodes

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Message-ID: <lsq.1371420097.220610690@decadent.org.uk>
Date:	Sun, 16 Jun 2013 23:01:37 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org,
	"Alexander Beregalov" <a.beregalov@...il.com>,
	"Theodore Ts'o" <tytso@....edu>,
	"Zheng Liu" <wenqing.lz@...bao.com>
Subject: [28/83] ext4: lock i_mutex when truncating orphan inodes

3.2.47-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Theodore Ts'o <tytso@....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@...il.com>
Signed-off-by: "Theodore Ts'o" <tytso@....edu>
Reviewed-by: Zheng Liu <wenqing.lz@...bao.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 fs/ext4/super.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -2260,7 +2260,9 @@ static void ext4_orphan_cleanup(struct s
 				__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,

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