linux-kernel - Re: kernel BUG at fs/buffer.c:3205 (stable 3.5.3)

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Message-ID: <20120927200342.GB12553@quack.suse.cz>
Date:	Thu, 27 Sep 2012 22:03:42 +0200
From:	Jan Kara <jack@...e.cz>
To:	Alexander Holler <holler@...oftware.de>
Cc:	Jan Kara <jack@...e.cz>, Dan Carpenter <dan.carpenter@...cle.com>,
	linux-kernel@...r.kernel.org
Subject: Re: kernel BUG at fs/buffer.c:3205 (stable 3.5.3)

On Thu 27-09-12 17:46:48, Alexander Holler wrote:
> Hello,
> 
> Am 27.09.2012 17:12, schrieb Jan Kara:
> >   Just some thoughts about your oops:
> >The assertion which fails is:
> >BUG_ON(!list_empty(&bh->b_assoc_buffers));
> >
> >Now b_assoc_buffers isn't used very much. In particular ext4 which you seem
> >to be using doesn't use this list at all (except when mounted in nojournal
> >mode but that doesn't seem to be your case). That would point rather
> >strongly at a memory corruption issue.
> >
> >So if you can reproduce the oops, it might be interesting to print
> >bh->b_assoc_buffers.next and &bh->b_assoc_buffers.next if the list is found
> >to be non-empty.
> 
> Hmm, a loose pointer would explain it all too. Especially the cases
> when I just have seen wrong content in the archive without having
> any oops. I try to reproduce it with
> 
> pr_info("AHO: %p %p\n", bh->b_assoc_buffers.next,
> &bh->b_assoc_buffers.next);
> after the BUG_ON().
  It should have been:
	if (!list_empty(&bh->b_assoc_buffers))
		pr_info("AHO: %p %p\n", bh->b_assoc_buffers.next,
			&bh->b_assoc_buffers.next);
  *before* BUG_ON().

  What you saw in the logs were just pointers showing the list is empty
(naturally as otherwise we'd see the BUG_ON trigger).

								Honza
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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