From: Maciej Żenczykowski <zenczykowski@gmail.com>
Date: Sun, 26 Sep 2010 12:38:28 +0000 (+0000)
Subject: ext3: don't update sb journal_devnum when RO dev
X-Git-Tag: v2.6.38-rc1~410^2~18
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=31d710a7bd42f0d89e30d53bdaad427c5f191d0d;p=profile%2Fivi%2Fkernel-x86-ivi.git

ext3: don't update sb journal_devnum when RO dev

An ext3 filesystem on a read-only device, with an external journal
which is at a different device number then recorded in the superblock
will fail to honor the read-only setting of the device and trigger
a superblock update (write).

For example:
  - ext3 on a software raid which is in read-only mode
  - external journal on a read-write device which has changed device num
  - attempt to mount with -o journal_dev=<new_number>
  - hits BUG_ON(mddev->ro = 1) in md.c

Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Maciej Żenczykowski <zenczykowski@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
---

diff --git a/fs/ext3/super.c b/fs/ext3/super.c
index acf8695..0416931 100644
--- a/fs/ext3/super.c
+++ b/fs/ext3/super.c
@@ -2290,7 +2290,7 @@ static int ext3_load_journal(struct super_block *sb,
 	EXT3_SB(sb)->s_journal = journal;
 	ext3_clear_journal_err(sb, es);
 
-	if (journal_devnum &&
+	if (!really_read_only && journal_devnum &&
 	    journal_devnum != le32_to_cpu(es->s_journal_dev)) {
 		es->s_journal_dev = cpu_to_le32(journal_devnum);