linux-kernel - Re: 2.6.18 ext3 panic.

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Message-ID: <452E7100.2010102@redhat.com>
Date:	Thu, 12 Oct 2006 11:44:48 -0500
From:	Eric Sandeen <esandeen@...hat.com>
To:	Andrew Morton <akpm@...l.org>
CC:	Jan Kara <jack@...e.cz>, Badari Pulavarty <pbadari@...ibm.com>,
	Eric Sandeen <sandeen@...deen.net>,
	Dave Jones <davej@...hat.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: 2.6.18 ext3 panic.

Andrew Morton wrote:
> On Thu, 12 Oct 2006 14:28:20 +0200
> Jan Kara <jack@...e.cz> wrote:
> 
>> Where can we call
>> journal_dirty_data() without PageLock?
> 
> block_write_full_page() will unlock the page, so ext3_writepage()
> will run journal_dirty_data_fn() against an unlocked page.
> 
> I haven't looked into the exact details of the race, but it should
> be addressable via jbd_lock_bh_state() or j_list_lock coverage.

Yep, that's what I've been hashing out with Stephen today...

In one of my cases journal_dirty_data has dropped & re-acquired the
bh_state lock and j_list_lock, and journal_unmap_buffer has come along
in the meantime.

So it looks like we are missing some state tests, i.e. buffer_mapped(),
at a couple points after we acquire jbd_lock_bh_state().

-Eric
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