On 07/18/2013 11:27 AM, Eric Blake wrote:
>> if (!has_format) {
>> - format = mode == NEW_IMAGE_MODE_EXISTING ? NULL :
>> bs->drv->format_name;
>> + format = mode == NEW_IMAGE_MODE_EXISTING ? NULL : "qcow2";
>
> Is this the right thing to do? Or should we do:
>
> if (!has_format) {
> if (mode == NEW_IMAGE_MODE_EXISTING) {
> format = NULL;
> } else {
> format = bs->drv->format_name ?: "qcow2";
> }
> }
>
> That is, I think we should default to doing a backup in the format given
> by the original (what if the original is qed, which also supports
> backing files), and only use qcow2 when there is no guidance whatsoever.
>
> But in practice, I don't careWell, I _DO_ care about one thing - make sure that the qapi-schema.json page accurately documents how this variable is defaulted for callers that don't care about the implications of omitting a format. Or we could simplify life by making 'format' mandatory for drive-backup; it was optional for 'drive-mirror' due to incremental implementation, but for 'drive-backup', we still have the opportunity to do things right from the first release. -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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