Re: [libvirt] [Qemu-devel] live snapshot wiki updated
On 07/20/2011 07:25 AM, Jes Sorensen wrote:
> I think if libvirt wants qemu to use an fd instead of a file
name, it
> shouldn't pass a file name but an fd in the first place. Which means
> that the two that we need are support for an fd: protocol (patches on
> the list, need review), and a way for libvirt to override the backing
> file of an image.
The problem is that QEMU will find backing file file names inside the
images which it will be unable to open. How do you suggest we get around
that?
We've already told you - qemu must have a way to be passed fds which are
associated with names, and when a file refers to another backing file by
name, then qemu falls back on its fd/name mapping to use the
already-passed fd instead. Which implies that someone else, either
libvirt or a qemu-maintained libblockformat.so, needs to have a stable
interface for parsing the backing file name out of an arbitrary qcow2
file, and that this interface must work no matter how many other
extensions are added to qcow2.
--
Eric Blake eblake(a)redhat.com +1-801-349-2682
Libvirt virtualization library http://libvirt.org