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

[Kevin Wolf <kwolf@redhat.com>]

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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?

Kevin

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