[Qemu-devel] Re: [RFC] Allow 'qemu-img convert' to preserve the backing file

[Marc Bevand <m.bevand@gmail.com>]

Ian Jackson <Ian.Jackson <at> eu.citrix.com> writes:
> 
> If there were a generic way to ask a block driver for a cow format
> what the backing image filename was, then the block driver core could
> do the opening itself.  That would make everything a bit simpler as it
> would move code out of the invididual drivers.

I am done. I implemented this feature in a generic way as you suggested. I am
going to send the patch in a separate email. I am confident in its robustness,
so far I have successfully converted more than 20 copy-on-write qcow1 images to
the qcow2 format. Different sizes, different "ages" (between 0 and 90% of the
sectors rewritten in the COW copies), different guest filesystems, etc. I have
verified no corruption occured by making sure a final conversion to the raw
format led to the expected MD5 checksum.

-marc