Re: Plans to bring QMP 'x-blockdev-reopen' out of experimental?

[Kevin Wolf <kwolf@redhat.com>]

Am 19.10.2020 um 18:46 hat Alberto Garcia geschrieben:
> On Mon 19 Oct 2020 05:56:56 PM CEST, Alberto Garcia wrote:
> > And this one in particular:
> >
> >    https://lists.gnu.org/archive/html/qemu-block/2020-02/msg00601.html
> 
> I forgot to add, we still don't support changing bs->file with this
> command, so I guess that would be one blocker?
> 
> There's no other way of inserting filter nodes, or is there?

Not that I'm aware of.

So yes, changing bs->file is the one thing I had in mind for
implementing before we mark it stable.

I'm not entirely sure if we should make some restrictions or allow
arbitrary changes. If it's only about filters, we could check that the
node returned by bdrv_skip_filters() stays the same. This would be
almost certainly safe (if the chain is not frozen, of course).

If people want to dynamically insert non-filters (maybe quorum?), it
might be more restrictive than necessary, though.

Other cases like inserting a qcow2 file in the chain where the old child
becomes the backing file of the newly inserted node should in theory
already be covered by blockdev-snapshot.

Kevin