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Re: [Xen-API] XCP 1.0-beta: md on dom0 kernel causes kernel oops

To: Daniel Stodden <daniel.stodden@xxxxxxxxxx>
Subject: Re: [Xen-API] XCP 1.0-beta: md on dom0 kernel causes kernel oops
From: Tomoe Sugihara <sugihara@xxxxxxxxxxxxx>
Date: Wed, 15 Dec 2010 19:58:48 +0900
Cc: "xen-api@xxxxxxxxxxxxxxxxxxx" <xen-api@xxxxxxxxxxxxxxxxxxx>, Simon Rowe <Simon.Rowe@xxxxxxxxxxxxx>, Jonathan Ludlam <Jonathan.Ludlam@xxxxxxxxxxxxx>
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On 12/08/2010 07:53 AM, Tomoe Sugihara wrote:
On 12/07/2010 11:51 PM, Daniel Stodden wrote:
On Mon, 2010-12-06 at 07:40 -0500, Tomoe Sugihara wrote:
On 12/03/2010 08:03 AM, Tomoe Sugihara wrote:
On 12/02/2010 05:50 PM, Simon Rowe wrote:
On Wednesday 01 Dec 2010 23:03:48 Tomoe Sugihara wrote:

I tried the following two and both ended up with Oops.

1. just two regular HDDs --- /dev/sdc and /dev/sde or whatever.

        Here's how I reproduced just now.Very soon after dd, kernel panics.

         $ mdadm --create /dev/md0 --level=mirror --raid-devices=2 /dev/sdc
/dev/sde mdadm: /dev/sdc appears to be part of a raid array:
             level=raid1 devices=2 ctime=Mon Nov 29 15:52:53 2010
         mdadm: /dev/sde appears to be part of a raid array:
             level=raid1 devices=2 ctime=Mon Nov 29 09:34:34 2010
         Continue creating array? y
         mdadm: array /dev/md0 started.
         $ dd if=/dev/zero of=/dev/md0 bs=1M



2. dm linear devices which are on top of iscsi

       mdadm --create /dev/mirror/000008bc --auto=md --bitmap=internal
--metadata=0 --run --bitmap-chunk=65536 --delay=5   --level=1
--assume-clean --raid-devices=3 /dev/mapper/00000001-00000003
/dev/mapper/00000002-000002d7 /dev/mapper/00000003-0000050a

        Interestingly, his doesn't cause kernel panic; similar stack trace
shows up in dmsg and mdadm stalls.

We don't support (and therefore test) software RAID in XenServer. I'll some of
our kernel guys if there's anything obvious.

        Simon


Could you see the email that I reported the issue? Here's a link to the post:
http://www.mail-archive.com/xen-api@xxxxxxxxxxxxxxxxxxx/msg02151.html

As I said, the issue is introduced by dom0 custom patch, which I put a link to 
the repository below,
therefor it is not there in vanilla kernel.

http://xenbits.xen.org/XCP/linux-2.6.32.pq.hg?diff/2d68a42120cf/blktap2-ioc.diff

I would really want it to be addressed not only for our SM backend plugin but 
also for the sake
of removing the vulnerability.

Hi,

We would really like this to be addressed so we can test
XCP 1.0 beta with our SM backend driver.

I found the author and the log for the patch that introduces the oops from the 
following link.
http://xenbits.xen.org/XCP/linux-2.6.32.pq.hg?annotate/2d68a42120cf/blktap2-ioc.diff

I didn't get what it is for, but I hope the author may be able to help this 
fixed.

Yeah, looks like this queue got tagged for XCP on a quite unfortunate
edge, indeed. The patch series has long been fixed since then, but
merged a little further on trunk, so I can't just offer you a
replacement for the -ioc diff.


Thanks for following this up, Daniel.
I'll wait for a fixed kernel.

Hi,
I'm still looking forward to a fixed kernel.

One could replace the entire blktap2-series, or maybe there's a bigger
update already in the make (?).

Any update on this? I hope someone is working on the issue.

Daniel,
Thanks for sending me a set of patches off line.
Sorry, I haven't had a chance to try, though.

Best,
Tomoe

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