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Re: [dm-devel] hunt for 2.6.37 dm-crypt+ext4 corruption? (was: Re: dm-crypt barrier support is effective)



On Wed, Dec 1, 2010 at 10:23 PM, Mike Snitzer <snitzer redhat com> wrote:
> On Wed, Dec 01 2010 at  3:45pm -0500,
> Milan Broz <mbroz redhat com> wrote:
>
>>
>> On 12/01/2010 08:34 PM, Jon Nelson wrote:
>> > Perhaps this is useful: for myself, I found that when I started using
>> > 2.6.37rc3 that postgresql starting having a *lot* of problems with
>> > corruption. Specifically, I noted zeroed pages, corruption in headers,
>> > all sorts of stuff on /newly created/ tables, especially during index
>> > creation. I had a fairly high hit rate of failure. I backed off to
>> > 2.6.34.7 and have *zero* problems (in fact, prior to 2.6.37rc3, I had
>> > never had a corruption issue with postgresql). I ran on 2.6.36 for a
>> > few weeks as well, without issue.
>> >
>> > I am using kcrypt with lvm on top of that, and ext4 on top of that.
>>
>> With unpatched dmcrypt (IOW with Linus' git)? Then it must be ext4 or
>> dm-core problem because there were no patches for dm-crypt...
>
> Matt and Jon,
>
> If you'd be up to it: could you try testing your dm-crypt+ext4
> corruption reproducers against the following two 2.6.37-rc commits:
>
> 1) 1de3e3df917459422cb2aecac440febc8879d410
> then
> 2) bd2d0210cf22f2bd0cef72eb97cf94fc7d31d8cc
>
> Then, depending on results of no corruption for those commits, bonus
> points for testing the same commits but with Andi and Milan's latest
> dm-crypt cpu scalability patch applied too:
> https://patchwork.kernel.org/patch/365542/
>
> Thanks!
> Mike
>

Hi Mike,

it seems like there isn't even much testing to do:

I tested all 3 commits / checkouts by re-compiling gcc which was/is
the 2nd easy way to trigger this "corruption", compiling google's
chromium (v9) and looking at the output/existance of gcc, g++ and
eselect opengl list

so far everything went fine

After that I used the new patch (v6 or pre-v6), before that I had to

replace WQ_MEM_RECLAIM with WQ_RESCUER

and, re-compiled the kernels

shortly after I had booted up the system with the first kernel
(http://git.eu.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=5a87b7a5da250c9be6d757758425dfeaf8ed3179)
the output of 'eselect opengl list' did show no opengl backend
selected

so it seems to manifest itself even earlier (ext4: call
mpage_da_submit_io() from mpage_da_map_blocks()) even if only subtly
and over time -
I'm still currently running that kernel and posting from it & having tests run

I'm not sure if it's even a problem with ext4 - I haven't had the time
to test with XFS yet - maybe it's also happening with that so it more
likely would be dm-core, like Milan suspected
(http://marc.info/?l=linux-kernel&m=129123636223477&w=2) :(

@Jon,

you had time to do some tests meanwhile ? what did you find out ?

even though most of the time it's compiling I don't need to do much -
I need the box for work so if my time allows next tests would be next
weekend and I'm back to my other partition

I really do hope that this bugger can be nailed down ASAP - I like the
improvements made in 2.6.37 but without the dm-crypt multi-cpu patch
it's only half the "fun" ;)

Thanks & Regards

Matt


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