linux-kernel - Re: 2.6.18 ext3 panic.

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Message-ID: <4533B9AB.8040403@redhat.com>
Date:	Mon, 16 Oct 2006 11:56:11 -0500
From:	Eric Sandeen <esandeen@...hat.com>
To:	Jan Kara <jack@...e.cz>
CC:	Badari Pulavarty <pbadari@...ibm.com>,
	Andrew Morton <akpm@...l.org>,
	Eric Sandeen <sandeen@...deen.net>,
	Dave Jones <davej@...hat.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: 2.6.18 ext3 panic.

Jan Kara wrote:

>>>   I think Eric's patch may be a part of it. But we still need to check whether
>>> the buffer is not after EOF before submitting it (or better said just
>>> after we manage to lock the buffer). Because while we are waiting for
>>> the buffer lock, journal_unmap_buffer() can still come and steal the
>>> buffer - at least the write-out in journal_dirty_data() definitely needs
>>> the check if I haven't overlooked something.
>> Ok, let me think on that today.  My first reaction is that if we have
>> the bh state lock and pay attention to mapped in journal_dirty_data(),
>> then any blocks past EOF which have gotten unmapped by
>> journal_unmap_buffer will be recognized as such (because they are now
>> unmapped... without needing to check for past EOF...) and we'll be fine.
>   Hmm, yes, you're right. If we do the test in journal_dirty_data() we
> should not file unmapped buffer into transaction's list and hence we
> should be safe. Fine. In case we eventually hit the assertion, we can
> think further ;).

Awww no way that can possibly happen right?  :)

>> As a datapoint, davej's stresstest (several fsx's and fsstresses)
>> survived an overnight run on his box, which used to panic in < 2 hrs.
>> Survived about 6 hours on my box until I intentionally stopped it; my
>> box had added a write/truncate test in a loop, with a bunch of periodic
>> syncs as well....
>   Perfect :).

Ok, thanks Jan!

I'll send a patch for -mm as a new thread, this one has gotten buried
pretty deep.

-Eric
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