[Qemu-devel] New option for snapshot_blkdev to avoid image creation

[Federico Simoncelli]

In some situations might be useful to let qemu use an image that was
prepared for a live snapshot.
The advantage is that creating the snapshot file outside of the qemu
process we can use the whole range of options provided by the format
(eg for qcow2: encryption, cluster_size and preallocation).
It is also possible to pre-set a relative path to the backing file
(now it is created by default as absolute path).
In the long run it can also avoid the danger of reimplementing qemu-img
inside qemu (if we wanted to expose such options when a snapshot is
requested).

-- 
Federico.