[libvirt] [Qemu-devel] live snapshot wiki updated
Eric Blake
eblake at redhat.com
Wed Jul 20 13:46:58 UTC 2011
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 at redhat.com +1-801-349-2682
Libvirt virtualization library http://libvirt.org
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