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

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

Konrad is on vacation this week, so it'll probably be next week before
this gets looked at by him.

Ian.

On Mon, 2013-04-22 at 13:22 +0100, Anthony Sheetz wrote:
> 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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