Re: [Qemu-devel] [Qemu-stable] Patch Round-up for stable 1.4.2, freeze on Monday

[Josh Durgin <josh.durgin@inktank.com>]

On 05/17/2013 12:08 PM, mdroth wrote:
> On Fri, May 17, 2013 at 10:46:15AM -0500, Doug Goldstein wrote:
>> On Tue, May 14, 2013 at 4:52 PM, Michael Roth <mdroth@linux.vnet.ibm.com>wrote:
>>
>>> Hi everyone,
>>>
>>> The following new patches are queued for QEMU stable v1.4.2:
>>>
>>> https://github.com/mdroth/qemu/commits/stable-1.4-staging
>>>
>>> The release is planned for 05-24-2013:
>>>
>>> http://wiki.qemu.org/Planning/1.4
>>>
>>> Please CC qemu-stable@nongnu.org on any patches you think should be
>>> included in the release. The cut-off date is 05-20-2013 for new patches.
>>>
>>> Testing/feedback is greatly appreciated.
>>>
>>> Thanks!
>>>
>>>
>> Michael,
>>
>> I have one patch in my 1.4 stable queue.
>>
>> From: Paolo Bonzini <pbonzini@redhat.com>
>> Date: Wed, 13 Mar 2013 14:58:13 +0000 (+0100)
>> Subject: qemu-iotests: add tests for rebasing zero clusters
>> X-Git-Url: http://git.qemu.org/?p=qemu.git;a=commitdiff_plain;h=acbf30ec601b1f817febc4500025b7c4181312c4
>>
>> qemu-iotests: add tests for rebasing zero clusters
>>
>> If zero clusters are erroneously treated as unallocated, "qemu-img rebase"
>> will copy the backing file's contents onto the cluster.
>>
>> The bug existed also in image streaming, but since the root cause was in
>> qcow2's is_allocated implementation it is enough to test it with qemu-img.
>>
>> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
>> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
>>
>> ---
>>
>>
>> It only adds a test for something that was fixed in 1.4.1 (maybe was fixed
>> by the final 1.4.0 release I can't recall).
>
> Thanks, pushed this to staging along with what should be all outstanding
> patches noted so far.

Could you add the patch:

commit dc7588c1eb3008bda53dde1d6b890cd299758155
Author: Josh Durgin <josh.durgin@inktank.com>
Date:   Fri Mar 29 13:03:23 2013 -0700

rbd: add an asynchronous flush

The existing bdrv_co_flush_to_disk implementation uses rbd_flush(),
which is sychronous and causes the main qemu thread to block until it
is complete. This results in unresponsiveness and extra latency for
the guest.

Fix this by using an asynchronous version of flush.  This was added to
librbd with a special #define to indicate its presence, since it will
be backported to stable versions. Thus, there is no need to check the
version of librbd.

Implement this as bdrv_aio_flush, since it matches other aio functions
in the rbd block driver, and leave out bdrv_co_flush_to_disk when the
asynchronous version is available.

Reported-by: Oliver Francke <oliver@filoo.de>
Signed-off-by: Josh Durgin <josh.durgin@inktank.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

I sent a cherry-pick of it to qemu-stable a couple days ago, although
it applies to the stable-1.4 branch cleanly. It fixes a significant
interactivity and performance problem when rbd is used with caching
enabled.

Thanks,
Josh