[libvirt PATCH v2 23/24] qemu_snapshot: add checks for external snapshot deletion

[Peter Krempa]

On Tue, Jun 27, 2023 at 17:07:26 +0200, Pavel Hrdina wrote:
> With the introduction of external snapshot revert support we need to
> error out in some cases when trying to delete some snapshots.
> 
> If users reverts to non-leaf snapshots and would try to delete it after
> the revert is done it would not work currently as this operation would
> require using block-stream which is not implemented for now as in this
> case the snapshot has two children so the disk files have multiple
> overlays.
> 
> Similarly if user reverts to non-leaf snapshot and would try to delete
> snapshot that is non-leaf but not in currently active snapshot chain we
> would still need to use block-commit operation. The issue here is that
> in order to do that we would have to start new qemu process with
> different domain definition than what is currently used by the domain.
> If the current domain would be running it would complicate things even
> more so this operation is not yet supported.
> 
> If user creates new snapshot after reverting to non-leaf snapshot it
> creates a new branch. Deleting snapshot with multiple children will
> require block-stream which is not implemented for now.
> 
> Signed-off-by: Pavel Hrdina <phrdina at redhat.com>
> ---
>  src/qemu/qemu_snapshot.c | 21 +++++++++++++++++++++

Reviewed-by: Peter Krempa <pkrempa at redhat.com>