linux-kernel - [PATCH 66/98] ext3: fix data=journal fast mount/umount hang

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Message-Id: <1373552708-15235-67-git-send-email-luis.henriques@canonical.com>
Date:	Thu, 11 Jul 2013 15:24:36 +0100
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Jan Kara <jack@...e.cz>, Benjamin LaHaise <bcrl@...ck.org>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 66/98] ext3: fix data=journal fast mount/umount hang

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

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

From: Jan Kara <jack@...e.cz>

commit e643692138cfa33528f054b071ba2583509bb217 upstream.

In data=journal mode, if we unmount the file system before a
transaction has a chance to complete, when the journal inode is being
evicted, we can end up calling into log_wait_commit() for the
last transaction, after the journalling machinery has been shut down.
That triggers the WARN_ONCE in __log_start_commit().

Arguably we should adjust ext3_should_journal_data() to return FALSE
for the journal inode, but the only place it matters is
ext3_evict_inode(), and so it's to save a bit of CPU time, and to make
the patch much more obviously correct by inspection(tm), we'll fix it
by explicitly not trying to waiting for a journal commit when we are
evicting the journal inode, since it's guaranteed to never succeed in
this case.

This can be easily replicated via:

     mount -t ext3 -o data=journal /dev/vdb /vdb ; umount /vdb

This is a port of ext4 fix from Ted Ts'o.

Signed-off-by: Jan Kara <jack@...e.cz>
Cc: Benjamin LaHaise <bcrl@...ck.org>
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
 fs/ext3/inode.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/ext3/inode.c b/fs/ext3/inode.c
index 4a84e75..7da1b7e 100644
--- a/fs/ext3/inode.c
+++ b/fs/ext3/inode.c
@@ -218,7 +218,8 @@ void ext3_evict_inode (struct inode *inode)
 	 */
 	if (inode->i_nlink && ext3_should_journal_data(inode) &&
 	    EXT3_SB(inode->i_sb)->s_journal &&
-	    (S_ISLNK(inode->i_mode) || S_ISREG(inode->i_mode))) {
+	    (S_ISLNK(inode->i_mode) || S_ISREG(inode->i_mode)) &&
+	    inode->i_ino != EXT3_JOURNAL_INO) {
 		tid_t commit_tid = atomic_read(&ei->i_datasync_tid);
 		journal_t *journal = EXT3_SB(inode->i_sb)->s_journal;

-- 
1.8.1.2

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