Re: [PATCH v4 07/30] qcow2: Document the Extended L2 Entries feature

[Eric Blake]

On 4/14/20 1:16 PM, Alberto Garcia wrote:
> On Thu 09 Apr 2020 05:12:16 PM CEST, Eric Blake <address@hidden> wrote:
> > Hmm - raw external files are incompatible with backing files.
>
> Pre-existing, but I just realized that we are not checking that in
> qcow2_do_open(), only on _create().
>
> I suppose that if we find such an image we should either
>
>     a) Show an error message and abort.
>     b) Clear the 'raw data file' bit and proceed as if it was unset.

I would favor a).  Such an image was (hopefully) created externally, and 
not by qemu; therefore refusing to open it will call attention to the 
image (and it's creation process) being broken, rather than risking 
silent corruption of whatever the external process thought it was 
accomplishing by creating an image like that.

--
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org