Re: [Xen-devel] BUG: ext3 corruption in domU

[Anthony Sheetz <sheetzam@xxxxxxxxxxx>]

I realize folks are pretty busy, but we're still interested in getting
this problem solved, and I want to be sure it's not lost in the
shuffle.
Any chance of getting some attention for it?

On Wed, Apr 17, 2013 at 9:00 AM, Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:
> On Tue, 2013-04-16 at 18:39 +0100, Anthony Sheetz wrote:
>> (re-sending, first message seems to have gotten lost)
>>
>> I was referred here by Ian Campbell ijc@xxxxxxxxxxxxxx from bugs.debian.org.
>
> I'm here too (different hat ;-)), thanks for posting it here. I've added
> some people who know about the block stuff to the CC.
>
> Guys, my suspicion is that the issue is that barriers issued by ext3
> inside the guest aren't making it all the way down the
> ext3->blkfront->blkback->lvm->dm-crypt->disk chain leading the
> filesystem to eventually corrupt itself.
>
> The issue seems to relate to the use of dm-crypt since
> ext3->blkfront->blkback->lvm->disk is reported work fine.
>
> However there is no problem with the local dom0 ext3 root filesystem
> which is also in the same lvm VG on the crypt device (i.e.
> ext3->lvm->dm-crypt->disk), so its not purely a dm-crypt issue. I figure
> something is up at the blkfront->back link which causes the barriers
> which blkback is injecting into the block subsystem either don't make it
> to the dm-crypt layer or do not DTRT once they arrive.
>
> I'm not really sure with how to proceed (or how to ask Anthony to
> proceed) with verifying any part of that hypothesis though.
>
> ISTR issues with old vs new style barriers or barriers with no data in
> them or something, could this be related to that? (or am I thinking of
> DISCARD?)
>
> The issue was initially reported with Squeeze (Jeremy 2.6.32 tree) domU
> on a Wheezy (mainline 3.2) dom0 but IIRC has also been repeated with
> Wheezy on Wheezy now so this isn't cross version confusion about barrier
> semantics AFAICT.
>
> Ian.
>
>> First, I'm happy to provide more information about this bug as
>> requsted. I recognize not all relevant data has
>> been collected yet.
>>
>> Detailed information about this bug can be found at
>> http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=705124.
>>
>> The executive summary is: Using Debian Testing (7.0, wheezy) dom0 with
>> LVM and full disk encryption with
>> Debian Stable (6.0, Squeeze) domU, transferring large files via scp or
>> rsync over openswan results in data corruption, with
>> eventual file system corruption. The culprit appears to be full disk
>> encryption, however that evidence may not be conclusive.
>>
>> While I don't mind providing additional information, I'd hate to have
>> to repeat the information I've provided to the Debian bug hunting
>> folks.
>>
>> Thanks in advance for any help you can provide.
>>
>> _______________________________________________
>> Xen-devel mailing list
>> Xen-devel@xxxxxxxxxxxxx
>> http://lists.xen.org/xen-devel
>
>

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