Am 22.04.2017 um 19:56 hat Max Reitz geschrieben:
> On 21.04.2017 23:09, Eric Blake wrote:
> > And meanwhile, it looks like I have some patches to propose (and
> > qemu-iotests to write) if I can help fix the bugs I've pointed out.
> 
> You mean these?
> https://github.com/XanClic/qemu/commits/random-qcow2-stuff-v1
> 
> ;-)
> 
> I'll send them once I've written tests.

You were quicker with writing the patches than I could reply that I
already started a patch to reuse preallocated zero clusters, but never
got around to finish it:

http://repo.or.cz/qemu/kevin.git/commitdiff/60b9f813bb258978455944b4ace1ab5d93b5e7d4

I seem to remember that it still had a problem (and probably also the
refcount > 0 bug that Eric mentioned), but maybe you can reuse at least
the test case from there.

Kevin