2008-08-14 09:57:16

by Chris Lalancette

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Subject: [PATCH]: Expand Xen blkfront for > 16 xvd

Jeremy,
Until recently, the maximum number of xvd block devices you could attach to
a Xen domU was 16. This limitation turned out to be problematic for some users,
so it was expanded to handle a much larger number of disks. However, this
requires a couple of changes in the way that blkfront scans for disks. This
functionality is already present in the Xen linux-2.6.18-xen.hg tree; the
attached patch adds this functionality to the mainline xen-blkfront
implementation. I successfully tested it on a 2.6.25 tree. I build tested it
on 2.6.27-rc3, but couldn't get that tree to boot due to some other bug.

Signed-off-by: Chris Lalancette <[email protected]>


Attachments:
lkml-blkfront-expand-xvd.patch (3.65 kB)

2008-08-18 17:17:10

by Jeremy Fitzhardinge

[permalink] [raw]
Subject: Re: [PATCH]: Expand Xen blkfront for > 16 xvd

Chris Lalancette wrote:
> Jeremy,
> Until recently, the maximum number of xvd block devices you could attach to
> a Xen domU was 16. This limitation turned out to be problematic for some users,
> so it was expanded to handle a much larger number of disks. However, this
> requires a couple of changes in the way that blkfront scans for disks. This
> functionality is already present in the Xen linux-2.6.18-xen.hg tree; the
> attached patch adds this functionality to the mainline xen-blkfront
> implementation.

I haven't tested this yet. You have tested it OK with some pvops
kernel? If so, send it to Jens Axboe with my ack.

> I successfully tested it on a 2.6.25 tree. I build tested it
> on 2.6.27-rc3, but couldn't get that tree to boot due to some other bug.

What other bug?

J

2008-08-19 06:55:17

by Chris Lalancette

[permalink] [raw]
Subject: Re: [Xen-devel] Re: [PATCH]: Expand Xen blkfront for > 16 xvd

Jeremy Fitzhardinge wrote:
> Chris Lalancette wrote:
>> Jeremy,
>> Until recently, the maximum number of xvd block devices you could attach to
>> a Xen domU was 16. This limitation turned out to be problematic for some users,
>> so it was expanded to handle a much larger number of disks. However, this
>> requires a couple of changes in the way that blkfront scans for disks. This
>> functionality is already present in the Xen linux-2.6.18-xen.hg tree; the
>> attached patch adds this functionality to the mainline xen-blkfront
>> implementation.
>
> I haven't tested this yet. You have tested it OK with some pvops
> kernel? If so, send it to Jens Axboe with my ack.

Yes, I tested it with a 2.6.25-something Fedora 9 pv-ops kernel (i386). I'll
send it along to Jens.

>
>> I successfully tested it on a 2.6.25 tree. I build tested it
>> on 2.6.27-rc3, but couldn't get that tree to boot due to some other bug.
>
> What other bug?

This is http://bugzilla.redhat.com/show_bug.cgi?id=459067, that I think you've
already looked at. Basically any F-10 or upstream git kernel is crashing on an
i386 RHEL-5 HV. We were a little confused by your comment in that bug, however;
we were under the impression that the fix you mentioned was specifically a
32-on-64 fix, not for 32-on-32. If we were wrong, please point it out.

Thanks,
Chris Lalancette