Like for query-block, the client needs to identify which BlockBackend
the returned data is for. Anonymous BlockBackends are identified by the
device model they are attached to. Add a 'qdev' field that contains the
qdev ID or QOM path of the attached device model.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 qapi/block-core.json |  5 ++++-
 block/qapi.c         | 10 ++++++++++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/qapi/block-core.json b/qapi/block-core.json
index d40d5ecc3b..3f09f62fa1 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -866,6 +866,9 @@
 #
 # @node-name: The node name of the device. (Since 2.3)
 #
+# @qdev: The qdev ID, or if no ID is assigned, the QOM path of the block
+#        device. (since 3.0)
+#
 # @stats:  A @BlockDeviceStats for the device.
 #
 # @parent: This describes the file block device if it has one.
@@ -879,7 +882,7 @@
 # Since: 0.14.0
 ##
 { 'struct': 'BlockStats',
-  'data': {'*device': 'str', '*node-name': 'str',
+  'data': {'*device': 'str', '*qdev': 'str', '*node-name': 'str',
            'stats': 'BlockDeviceStats',
            '*parent': 'BlockStats',
            '*backing': 'BlockStats'} }
diff --git a/block/qapi.c b/block/qapi.c
index e12968fec8..50f867d634 100644
--- a/block/qapi.c
+++ b/block/qapi.c
@@ -597,11 +597,21 @@ BlockStatsList *qmp_query_blockstats(bool has_query_nodes,
             BlockStatsList *info = g_malloc0(sizeof(*info));
             AioContext *ctx = blk_get_aio_context(blk);
             BlockStats *s;
+            char *qdev;
 
             aio_context_acquire(ctx);
             s = bdrv_query_bds_stats(blk_bs(blk), true);
             s->has_device = true;
             s->device = g_strdup(blk_name(blk));
+
+            qdev = blk_get_attached_dev_id(blk);
+            if (qdev && *qdev) {
+                s->has_qdev = true;
+                s->qdev = qdev;
+            } else {
+                g_free(qdev);
+            }
+
             bdrv_query_blk_stats(s->stats, blk);
             aio_context_release(ctx);
 
-- 
2.13.6

On 07/27/2018 09:15 AM, Kevin Wolf wrote:
> Like for query-block, the client needs to identify which BlockBackend
> the returned data is for. Anonymous BlockBackends are identified by the
> device model they are attached to. Add a 'qdev' field that contains the
> qdev ID or QOM path of the attached device model.
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---

> @@ -879,7 +882,7 @@
>   # Since: 0.14.0
>   ##
>   { 'struct': 'BlockStats',
> -  'data': {'*device': 'str', '*node-name': 'str',
> +  'data': {'*device': 'str', '*qdev': 'str', '*node-name': 'str',
>              'stats': 'BlockDeviceStats',
>              '*parent': 'BlockStats',
>              '*backing': 'BlockStats'} }

Can we also update the example under query-blockstats a few lines later 
to show the added field?

At any rate, it looks helpful. Although this is borderline new feature, 
it resolves a need identified in libvirt using -blockdev, and so I can 
live with it as a 3.0 bugfix.

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

Am 27.07.2018 um 17:07 hat Eric Blake geschrieben:
> On 07/27/2018 09:15 AM, Kevin Wolf wrote:
> > Like for query-block, the client needs to identify which BlockBackend
> > the returned data is for. Anonymous BlockBackends are identified by the
> > device model they are attached to. Add a 'qdev' field that contains the
> > qdev ID or QOM path of the attached device model.
> > 
> > Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> > ---
> 
> > @@ -879,7 +882,7 @@
> >   # Since: 0.14.0
> >   ##
> >   { 'struct': 'BlockStats',
> > -  'data': {'*device': 'str', '*node-name': 'str',
> > +  'data': {'*device': 'str', '*qdev': 'str', '*node-name': 'str',
> >              'stats': 'BlockDeviceStats',
> >              '*parent': 'BlockStats',
> >              '*backing': 'BlockStats'} }
> 
> Can we also update the example under query-blockstats a few lines later to
> show the added field?

I'll add the qdev field, but the example is hopelessly outdated anyway.
Sounds like something for another patch.

> At any rate, it looks helpful. Although this is borderline new feature, it
> resolves a need identified in libvirt using -blockdev, and so I can live
> with it as a 3.0 bugfix.
> 
> Reviewed-by: Eric Blake <eblake@redhat.com>

Thanks.

Kevin

On Fri, Jul 27, 2018 at 17:58:54 +0200, Kevin Wolf wrote:
> Am 27.07.2018 um 17:07 hat Eric Blake geschrieben:
> > On 07/27/2018 09:15 AM, Kevin Wolf wrote:
> > > Like for query-block, the client needs to identify which BlockBackend
> > > the returned data is for. Anonymous BlockBackends are identified by the
> > > device model they are attached to. Add a 'qdev' field that contains the
> > > qdev ID or QOM path of the attached device model.
> > > 
> > > Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> > > ---
> > 
> > > @@ -879,7 +882,7 @@
> > >   # Since: 0.14.0
> > >   ##
> > >   { 'struct': 'BlockStats',
> > > -  'data': {'*device': 'str', '*node-name': 'str',
> > > +  'data': {'*device': 'str', '*qdev': 'str', '*node-name': 'str',
> > >              'stats': 'BlockDeviceStats',
> > >              '*parent': 'BlockStats',
> > >              '*backing': 'BlockStats'} }
> > 
> > Can we also update the example under query-blockstats a few lines later to
> > show the added field?
> 
> I'll add the qdev field, but the example is hopelessly outdated anyway.
> Sounds like something for another patch.

When doing further cleanups it would be worth also noting that the
'query-nodes' argument of 'query-blockstats' does not return correct
information.

Right now it creates a false impression that it just changes the output
from nested to linear and includes filter nodes, but in fact the data is
not correct in that mode.