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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 redhat com    +1-801-349-2682
Libvirt virtualization library http://libvirt.org


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