On Mon, Jan 26, 2026 at 13:27:33 -0600, Eric Blake wrote:
> On Tue, Jan 20, 2026 at 03:45:56PM +0100, Peter Krempa wrote:
> > From: Peter Krempa <[email protected]>
> >
> > Some time ago (commit facda5443f5a8) I've added 'flat' mode (which
> > omits 'backing-image' key in reply) to 'query-named-block-nodes' to
> > minimize the size of the returned JSON for deeper backing chains.
> >
> > While 'query-block' behaved slightly better it turns out that in libvirt
> > we do call 'query-block' to figure out some information about the
> > block device (e.g. throttling info) but we don't look at the backing
> > chain itself.
> >
> > Wire up 'flat' for 'query-block' so that libvirt can ask for an
> > abbreviated output. The implementation is much simpler as the internals
> > are shared with 'query-named-block-nodes'.
> >
> > Signed-off-by: Peter Krempa <[email protected]>
> > Acked-by: Markus Armbruster <[email protected]>
> > ---
> > block/monitor/block-hmp-cmds.c | 4 ++--
> > block/qapi.c | 9 +++++----
> > qapi/block-core.json | 7 +++++++
> > ui/cocoa.m | 2 +-
> > 4 files changed, 15 insertions(+), 7 deletions(-)
> > +++ b/qapi/block-core.json
> > @@ -855,6 +855,12 @@
> > #
> > # Get a list of `BlockInfo` for all virtual block devices.
> > #
> > +# @flat: Omit the nested data about backing image (Omitted are
> > +# contents of 'backing-image' key of the 'ImageInfo' struct
> > +# which is returned as 'image' key of 'BlockDeviceInfo' struct
> > +# returned as 'inserted' key in 'BlockInfo' struct returned
>
> Extra space.
>
> > +# by this command). Default is false (Since 11.0)
>
> Still hard to parse. Maybe:
>
> @flat: Omit nested data about the backing image (ie. the contents at
> 'inserted.image.backing-image' are trimmed to avoid duplicate
> data about that backing image). Default is false (Since 11.0)
In this case the 'backing-image' data is not duplicate as it was the
case with 'query-named-block-nodes', as it is not repeated on top level.
Here using 'flat' decreases the amount of returned information, but in
case of libvirt we don't use anything from the 'backing-image', just
stuff that is related to the frontend device which is not queryable via
'query-named-block-nodes'.
So then perhaps just shorten it to:
@flat: Omit nested data about the backing image (ie. the contents at
'inserted.image.backing-image' are trimmed).
Default is false (Since 11.0)
> The idea makes sense to me, but I will defer to Markus on whether the
> wording still needs a tweak.
Should I post a v3?
