Re: [Qemu-devel] Assertion failure on qcow2 disk with cluster_size != 64k

[Eric Blake <eblake@redhat.com>]

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On 11/14/2016 03:50 AM, Kevin Wolf wrote:
> Am 24.10.2016 um 22:32 hat Eric Blake geschrieben:
>> On 10/21/2016 08:14 AM, Ed Swierk wrote:
>>> On Thu, Oct 20, 2016 at 6:38 PM, Eric Blake <eblake@redhat.com> wrote:
>>>> On 10/20/2016 07:24 PM, Ed Swierk wrote:
>>>>> Changing max_transfer in the normal write case to
>>>>> MIN_NON_ZERO(alignment, MAX_WRITE_ZEROES_BOUNCE_BUFFER) appears to fix
>>>>> the problem, but I don't pretend to understand all the subtleties
>>>>> here.
>>>>
>>>> That actually sounds like the right fix.  But since the bug was probably
>>>> caused by my code, I'll formalize it into a patch and see if I can
>>>> modify the testsuite to give it coverage.
>>>
>>> If alignment > MAX_WRITE_ZEROES_BOUNCE_BUFFER (however unlikely) we
>>> have the same problem, so maybe this would be better?
>>
>> Our qcow2 support is currently limited to a maximum of 2M clusters;
>> while MAX_WRITE_ZEROES_BOUNCE_BUFFER is 32k * 512, or 16M.  The
>> maximum-size bounce buffer should not be the problem here; but for some
>> reason, it looks like alignment is larger than max_transfer which should
>> not normally be possible.  I'm still playing with what should be the
>> right patch, but hope to have something posted soon.
> 
> Are you still playing with it?

Patch was posted here:

https://lists.gnu.org/archive/html/qemu-devel/2016-11/msg01603.html

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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