Re: [PATCH v2 1/2] block: Wire up 'flat' mode also for 'query-block'

[Eric Blake <eblake@redhat.com>]

On Tue, Jan 20, 2026 at 03:45:56PM +0100, Peter Krempa wrote:
> From: Peter Krempa <pkrempa@redhat.com>
> 
> 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 <pkrempa@redhat.com>
> Acked-by: Markus Armbruster <armbru@redhat.com>
> ---
>  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)

The idea makes sense to me, but I will defer to Markus on whether the
wording still needs a tweak.


-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.
Virtualization:  qemu.org | libguestfs.org