linux-ext4 - [PATCH stable 3.3 thru 3.8] ext3: fix data=journal fast mount/umount hang

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Message-ID: <20130703213436.GA16960@kvack.org>
Date:	Wed, 3 Jul 2013 17:34:36 -0400
From:	Benjamin LaHaise <bcrl@...ck.org>
To:	stable@...r.kernel.org
Cc:	Jan Kara <jack@...e.cz>, Theodore Ts'o <tytso@....edu>,
	linux-ext4@...r.kernel.org
Subject: [PATCH stable 3.3 thru 3.8] ext3: fix data=journal fast mount/umount hang

This patch appears to have been missed for ext3, while the ext4 version was 
merged back in March -- see 1363783057-3874-1-git-send-email-tytso@....edu.  
A customer of mine has been running into this bug on their production 
servers on 3.4-stable.  It applies cleanly to the 3.3 through 3.8 trees.

		-ben

commit e643692138cfa33528f054b071ba2583509bb217
Author: Jan Kara <jack@...e.cz>
Date:   Wed Mar 20 14:39:05 2013 +0100

ext3: fix data=journal fast mount/umount hang

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>
Signed-off-by: Benjamin LaHaise <bcrl@...ck.org>

diff --git a/fs/ext3/inode.c b/fs/ext3/inode.c
index d512c4b..d706dbf 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;

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