linux-ext4 - Re: Re: Re: EXT4 panic at jbd2_journal_put_journal

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Date:	Mon, 13 May 2013 19:26:34 +0800
From:	Zheng Liu <gnehzuil.liu@...il.com>
To:	EUNBONG SONG <eunb.song@...sung.com>
Cc:	Tony Luck <tony.luck@...il.com>,
	Dmitry Monakhov <dmonakhov@...nvz.org>,
	Theodore Ts'o <tytso@....edu>,
	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: Re: Re: EXT4 panic at jbd2_journal_put_journal_head() in 3.9+

On Mon, May 13, 2013 at 09:53:25AM +0000, EUNBONG SONG wrote:
> 
> 
> > Hi all,
> 
> > First of all I couldn't reproduce this regression in my sand box.  So
> > the following speculation is only my guess.  I suspect that the commit
> > (ae4647fb) isn't root cause.  It just uncover a potential bug that has
> > been there for a long time.  I look at the code, and found two
> > suspicious stuff in jbd2.  The first one is in do_get_write_access().
> > In this function we forgot to lock bh state when we check b_jlist ==
> > BJ_Shadow.  I generate a patch to fix it, and I really think it is the
> > root cause.  Further, in __journal_remove_journal_head() we check
> > b_jlist == BJ_None.  But, when this function is called, bh state won't
> > be locked sometimes.  So I suspect this is why we hit a BUG in
> > jbd2_journal_put_journal_head().  But I don't have a good solution to
> > fix this until now because I don't know whether we need to lock bh state
> > here, or maybe we should remove this assertation.
> >
> > So, generally, Tony, Eunbong, could you please try the following patch?
> >
> > Thanks in advance,
> >                                                 - Zheng
> 
> 
> Hi, I tested your patch. Unfortunately, the same problem was reproduced.
> Thanks.

Thanks for trying this patch.  Could you please repost the dmesg log for
me?  I want to make sure whether the second suspicious stuff causes this
regression or not.  Further, that would be great if you could try to
comment this line as the following?

diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index 886ec2f..a9e3779 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -2453,7 +2453,7 @@ static void __journal_remove_journal_head(struct
buffer_head *bh)
        J_ASSERT_JH(jh, jh->b_transaction == NULL);
        J_ASSERT_JH(jh, jh->b_next_transaction == NULL);
        J_ASSERT_JH(jh, jh->b_cp_transaction == NULL);
-       J_ASSERT_JH(jh, jh->b_jlist == BJ_None);
+       /*J_ASSERT_JH(jh, jh->b_jlist == BJ_None);*/
        J_ASSERT_BH(bh, buffer_jbd(bh));
        J_ASSERT_BH(bh, jh2bh(jh) == bh);
        BUFFER_TRACE(bh, "remove journal_head");

Really thanks,
                                                - Zheng
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