linux-ext4 - Re: [PATCH V3] fix bb_prealloc_list corruption due to wrong group locking

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Date:	Wed, 18 Mar 2009 09:11:34 -0700
From:	Frank Mayhar <fmayhar@...gle.com>
To:	Eric Sandeen <sandeen@...hat.com>
Cc:	ext4 development <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH V3] fix bb_prealloc_list corruption due to wrong group
	locking

On Mon, 2009-03-16 at 10:53 -0700, Frank Mayhar wrote: 
> On Mon, 2009-03-16 at 12:48 -0500, Eric Sandeen wrote:
> > Hi Frank - I don't *think* so just because deleted items are poisoned
> > and I would expect that we'd trip over a bad pointer in the corrupted
> > list item as the first indicator of trouble... but I could be wrong.
> > 
> > I think you said you could reproduce it, right?  So certainly worth
> > testing with this fix I suppose.
> 
> Yeah, we're working on doing that now.  We're not running with a lot of
> debugging turned on so we may or may not actually fall over if we try to
> traverse freed (or just wrong) list entries.  If it isn't the same race,
> though, then there's still one lurking in this code and that would be a
> hell of a coincidence.

FYI we're running now with this patch in both a test and a production
environment and haven't (yet) seen the bitmap inconsistency we were
encountering regularly.  So far we have over 18 hours of runtime.  So,
despite the enormous coincidence, our problem appears to be due to the
same cause.

Thanks for the fix, Eric!
-- 
Frank Mayhar <fmayhar@...gle.com>
Google, Inc.

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