Am 14.11.2016 um 16:46 hat Eric Blake geschrieben:
> 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

Ah, yes, sorry. I didn't make the connection today because this one had
qcow2 in the subject line and the patch doesn't.

Are you going to add a qemu-iotests case then, or do you want us to
merge the patch as it is?

Kevin