Re: [PATCH RFC v2 5/5] block: Deprecate transaction type drive-backup

[Markus Armbruster <armbru@redhat.com>]

Kevin Wolf <kwolf@redhat.com> writes:

> Am 11.10.2021 um 20:58 hat Eric Blake geschrieben:
>> On Sat, Oct 09, 2021 at 02:09:44PM +0200, Markus Armbruster wrote:
>> > Several moons ago, Vladimir posted
>> > 
>> >     Subject: [PATCH v2 3/3] qapi: deprecate drive-backup
>> >     Date: Wed,  5 May 2021 16:58:03 +0300
>> >     Message-Id: <20210505135803.67896-4-vsementsov@virtuozzo.com>
>> >     https://lists.gnu.org/archive/html/qemu-devel/2021-05/msg01394.html
>> > 
>> > with this
>> > 
>> >     TODO: We also need to deprecate drive-backup transaction action..
>> >     But union members in QAPI doesn't support 'deprecated' feature. I tried
>> >     to dig a bit, but failed :/ Markus, could you please help with it? At
>> >     least by advice?
>> > 
>> > This is one way to resolve it.  Sorry it took so long.
>> > 
>> > John explored another way, namely adding feature flags to union
>> > branches.  Could also be useful, say to add different features to
>> > branches in multiple unions sharing the same tag enum.
>> > 
>> > Signed-off-by: Markus Armbruster <armbru@redhat.com>
>> > ---
>> >  qapi/transaction.json | 5 ++++-
>> >  1 file changed, 4 insertions(+), 1 deletion(-)
>> > 
>> > diff --git a/qapi/transaction.json b/qapi/transaction.json
>> > index d175b5f863..0564a893b3 100644
>> > --- a/qapi/transaction.json
>> > +++ b/qapi/transaction.json
>> > @@ -54,6 +54,9 @@
>> >  # @blockdev-snapshot-sync: since 1.1
>> >  # @drive-backup: Since 1.6
>> >  #
>> > +# Features:
>> > +# @deprecated: Member @drive-backup is deprecated.  Use FIXME instead.
>> 
>> Obviously, we'd need to flesh this out ("'blockdev-backup' with proper
>> node names"? something else?) before dropping RFC on this patch.
>
> What does 'blockdev-backup' with improper node names look like?
>
> I think it's sufficient to say "Use @blockdev-backup instead", which is
> already documented to take a node/device name instead of a file name.

Sold!

>> And we'd want to edit docs/about/deprecated.rst to match.
>
> Yes.

My patch makes sense only together with Vladimir's patch to deprecate
the drive-backup command.  That one updates deprecated.rst.  The
combination of the two might need further tweaking, but let's not worry
about that now.