Xen devel - Aug 2008 - [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 <clalance@redhat.com>


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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

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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

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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 <clalance@redhat.com>
Acked-by: Jeremy Fitzhardinge <jeremy@goop.org>


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