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

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Message-ID: <87ip0l45x2.fsf@canonical.com>
Date:	Mon, 08 Jul 2013 13:01:13 +0100
From:	Luis Henriques <luis.henriques@...onical.com>
To:	Benjamin LaHaise <bcrl@...ck.org>
Cc:	stable@...r.kernel.org, Jan Kara <jack@...e.cz>,
	"Theodore Ts'o" <tytso@....edu>, linux-ext4@...r.kernel.org
Subject: Re: [PATCH stable 3.3 thru 3.8] ext3: fix data=journal fast mount/umount hang

Benjamin LaHaise <bcrl@...ck.org> writes:

> 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

Thanks Ben, I'm queuing it for the 3.5 kernel.

Cheers,
-- 
Luis


>
> 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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