linux-kernel - Re: hunt for 2.6.37 dm-crypt+ext4 corruption? (was: Re: dm-crypt barrier support is effective)

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Date:	Fri, 10 Dec 2010 10:54:40 -0600
From:	Jon Nelson <jnelson@...poni.net>
To:	"Ted Ts'o" <tytso@....edu>, Matt <jackdachef@...il.com>,
	Chris Mason <chris.mason@...cle.com>,
	Andi Kleen <andi@...stfloor.org>,
	Jon Nelson <jnelson@...poni.net>,
	Mike Snitzer <snitzer@...hat.com>,
	Milan Broz <mbroz@...hat.com>,
	linux-btrfs <linux-btrfs@...r.kernel.org>,
	dm-devel <dm-devel@...hat.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	htd <htd@...cy-poultry.org>, htejun <htejun@...il.com>,
	linux-ext4 <linux-ext4@...r.kernel.org>
Subject: Re: hunt for 2.6.37 dm-crypt+ext4 corruption? (was: Re: dm-crypt
 barrier support is effective)

On Fri, Dec 10, 2010 at 8:58 AM, Jon Nelson <jnelson@...poni.net> wrote:
> On Fri, Dec 10, 2010 at 12:52 AM, Jon Nelson <jnelson@...poni.net> wrote:
>> On Thu, Dec 9, 2010 at 8:38 PM, Ted Ts'o <tytso@....edu> wrote:
>>> On Fri, Dec 10, 2010 at 02:53:30AM +0100, Matt wrote:
>>>>
>>>> Try a kernel before 5a87b7a5da250c9be6d757758425dfeaf8ed3179
>>>>
>>>> from the tests I've done that one showed the least or no corruption if
>>>> you count the empty /etc/env.d/03opengl as an artefact
>>>
>>> Yes, that's a good test.  Also try commit bd2d0210cf.  The patch
>>> series that is most likely to be at fault if there is a regression in
>>> between 5a87b7a5d and bd2d0210cf inclusive.
>>>
>>> I did a lot of testing before submitting it, but that wa a tricky
>>> rewrite.  If you can reproduce the problem reliably, it might be good
>>> to try commit 16828088f9 (the commit before 5a87b7a5d) and commit
>>> bd2d0210cf.  If it reliably reproduces on bd2d0210cf, but is clean on
>>> 16828088f9, then it's my ext4 block i/o submission patches, and we'll
>>> need to either figure out what's going on or back out that set of
>>> changes.
>>>
>>> If that's the case, a bisect of those changes (it's only 6 commits, so
>>> it shouldn't take long) would be most appreciated.
>>
>> I observed the behavior on bd2d0210cf in a qemu-kvm install of
>> openSUSE 11.3 (x86_64) on *totally* different host - an AMD quad-core.
>>
>> I did /not/ observe the behavior on 16828088f9 (yet). I'll run the
>> test a few more times on 1682..
>>
>> Additionally, I am building a bisected kernel now (
>> cb20d5188366f04d96d2e07b1240cc92170ade40 ), but won't be able to get
>> back at it for a while.
>
> cb20d5188366f04d96d2e07b1240cc92170ade40 seems OK so far. I'm going to
> try 1de3e3df917459422cb2aecac440febc8879d410 soon.

Barring false negatives, bd2d0210cf22f2bd0cef72eb97cf94fc7d31d8cc
appears to be the culprit (according to git bisect).
I will test bd2d0210cf22f2bd0cef72eb97cf94fc7d31d8cc again, confirm
the behavior, and work backwards to try to reduce the possibility of
false negatives.

-- 
Jon
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