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

[Ian Jackson]

I wrote:
> The best way to do this will probably involve a certain amount of
> restructuring of the interface to the block drivers.  So definitely
> something to discuss with upstream.

Ignore all that.

I thought I was replying to a message on the xen-devel list.
Sorry, I'm very thickheaded today.

Right, changing context:

> Marc Bevand <address@hidden>:
> > In order to preserve the backing file (to save disk space),
> > qemu-img should offer a command line option to enable the
> > feature. For this it needs to be made aware of BlockDrivers
> > supporting backing files.

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.

Ian.