Re: [PATCH v3 1/2] block: Wire up 'flat' mode also for 'query-block'

[Markus Armbruster <armbru@redhat.com>]

Peter Krempa <pkrempa@redhat.com> writes:

> 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>

[...]

> diff --git a/block/qapi.c b/block/qapi.c
> index 27e0ac6a32..3688d0e713 100644
> --- a/block/qapi.c
> +++ b/block/qapi.c

[...]

> @@ -698,11 +698,12 @@ bdrv_query_bds_stats(BlockDriverState *bs, bool blk_level)
>      return s;
>  }
>
> -BlockInfoList *qmp_query_block(Error **errp)
> +BlockInfoList *qmp_query_block(bool has_flat, bool flat, Error **errp)
>  {
>      BlockInfoList *head = NULL, **p_next = &head;
>      BlockBackend *blk;
>      Error *local_err = NULL;
> +    bool return_flat = has_flat && flat;

This is fine.  Just flat would also be fine: flat implies has_flat.

>
>      GRAPH_RDLOCK_GUARD_MAINLOOP();
>
> @@ -714,7 +715,7 @@ BlockInfoList *qmp_query_block(Error **errp)
>          }
>
>          info = g_malloc0(sizeof(*info));
> -        bdrv_query_info(blk, &info->value, &local_err);
> +        bdrv_query_info(blk, return_flat, &info->value, &local_err);
>          if (local_err) {
>              error_propagate(errp, local_err);
>              g_free(info);
> diff --git a/qapi/block-core.json b/qapi/block-core.json
> index b82af74256..a701f6bbee 100644
> --- a/qapi/block-core.json
> +++ b/qapi/block-core.json
> @@ -855,6 +855,10 @@
>  #
>  # Get a list of `BlockInfo` for all virtual block devices.
>  #
> +# @flat: Omit nested data about the backing image (ie. the contents at
> +#        'inserted.image.backing-image' are trimmed).
> +#        Default is false (Since 11.0)
> +#

s/ie./i.e./

Remind me: true suppresses member inserted.image.backing-image, i.e. it
is absent then.  Correct?

>  # Returns: a list describing each virtual block device.  Filter nodes
>  #     that were created implicitly are skipped over.
>  #
> @@ -945,6 +949,7 @@
>  #        }
>  ##
>  { 'command': 'query-block', 'returns': ['BlockInfo'],
> +  'data': { '*flat': 'bool' },
>    'allow-preconfig': true }
>
>  ##

[...]