Comment 22 for bug 1846427

I finally got an image with which I can reproduce the problem. I think I may have had the wrong image size before because both tmpfs and my spare LVM volume are rather limited in size.

Anyway, so far locking around qcow2_get_refcount() seems to do the trick. I'll try to investigate the details a bit more, but this is something that would actually feel reasonable as a fix.