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Date:	Fri, 10 Dec 2010 20:14:56 -0600
From:	Jon Nelson <>
To:	"Ted Ts'o" <>, Matt <>,
	Chris Mason <>,
	Andi Kleen <>,
	Jon Nelson <>,
	Mike Snitzer <>,
	Milan Broz <>,
	linux-btrfs <>,
	dm-devel <>,
	Linux Kernel <>,
	htd <>, htejun <>,
	linux-ext4 <>
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 10:54 AM, Jon Nelson <> wrote:
> On Fri, Dec 10, 2010 at 8:58 AM, Jon Nelson <> wrote:
>> On Fri, Dec 10, 2010 at 12:52 AM, Jon Nelson <> wrote:
>>> On Thu, Dec 9, 2010 at 8:38 PM, Ted Ts'o <> 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.

A few additional notes, in no particular order:

- For me, triggering the problem is fairly easy when encryption is involved.
- I'm now 81 iterations into testing
bd2d0210cf22f2bd0cef72eb97cf94fc7d31d8cc *without* encryption.  Out of
81 iterations, I have 4 failures: #16, 40, 62, and 64.

I will now try 1de3e3df917459422cb2aecac440febc8879d410 much more extensively.

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