block/qapi: Add 'qdev' field to query-blockstats result

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

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);
 

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'} }
@@ -941,7 +944,8 @@
 #                "idle_time_ns":2953431879,
 #                "account_invalid":true,
 #                "account_failed":false
-#             }
+#             },
+#             "qdev": "/machine/unattached/device[23]"
 #          },
 #          {
 #             "device":"ide1-cd0",
@@ -959,7 +963,8 @@
 #                "wr_merged":0,
 #                "account_invalid":false,
 #                "account_failed":false
-#             }
+#             },
+#             "qdev": "/machine/unattached/device[24]"
 #          },
 #          {
 #             "device":"floppy0",
@@ -977,7 +982,8 @@
 #                "wr_merged":0,
 #                "account_invalid":false,
 #                "account_failed":false
-#             }
+#             },
+#             "qdev": "/machine/unattached/device[16]"
 #          },
 #          {
 #             "device":"sd0",