qapi: Allow getting flat output from 'query-named-block-nodes'

When a management application manages node names there's no reason to
recurse into backing images in the output of query-named-block-nodes.

Add a parameter to the command which will return just the top level
structs.

Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Message-Id: <4470f8c779abc404dcf65e375db195cd91a80651.1579509782.git.pkrempa@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[mreitz: Fixed coding style]
Signed-off-by: Max Reitz <mreitz@redhat.com>

block.c

@@ -4807,14 +4807,15 @@ BlockDriverState *bdrv_find_node(const char *node_name)
 }
 
 /* Put this QMP function here so it can access the static graph_bdrv_states. */
-BlockDeviceInfoList *bdrv_named_nodes_list(Error **errp)
+BlockDeviceInfoList *bdrv_named_nodes_list(bool flat,
+                                           Error **errp)
 {
     BlockDeviceInfoList *list, *entry;
     BlockDriverState *bs;
 
     list = NULL;
     QTAILQ_FOREACH(bs, &graph_bdrv_states, node_list) {
-        BlockDeviceInfo *info = bdrv_block_device_info(NULL, bs, errp);
+        BlockDeviceInfo *info = bdrv_block_device_info(NULL, bs, flat, errp);
         if (!info) {
             qapi_free_BlockDeviceInfoList(list);
             return NULL;

block/qapi.c

@@ -42,7 +42,9 @@
 #include "qemu/cutils.h"
 
 BlockDeviceInfo *bdrv_block_device_info(BlockBackend *blk,
-                                        BlockDriverState *bs, Error **errp)
+                                        BlockDriverState *bs,
+                                        bool flat,
+                                        Error **errp)
 {
     ImageInfo **p_image_info;
     BlockDriverState *bs0;
@@ -156,6 +158,11 @@ BlockDeviceInfo *bdrv_block_device_info(BlockBackend *blk,
             return NULL;
         }
 
+        /* stop gathering data for flat output */
+        if (flat) {
+            break;
+        }
+
         if (bs0->drv && bs0->backing) {
             info->backing_file_depth++;
             bs0 = bs0->backing->bs;
@@ -389,7 +396,7 @@ static void bdrv_query_info(BlockBackend *blk, BlockInfo **p_info,
 
     if (bs && bs->drv) {
         info->has_inserted = true;
-        info->inserted = bdrv_block_device_info(blk, bs, errp);
+        info->inserted = bdrv_block_device_info(blk, bs, false, errp);
         if (info->inserted == NULL) {
             goto err;
         }

blockdev.c

@@ -3734,9 +3734,13 @@ void qmp_drive_backup(DriveBackup *backup, Error **errp)
     blockdev_do_action(&action, errp);
 }
 
-BlockDeviceInfoList *qmp_query_named_block_nodes(Error **errp)
+BlockDeviceInfoList *qmp_query_named_block_nodes(bool has_flat,
+                                                 bool flat,
+                                                 Error **errp)
 {
-    return bdrv_named_nodes_list(errp);
+    bool return_flat = has_flat && flat;
+
+    return bdrv_named_nodes_list(return_flat, errp);
 }
 
 XDbgBlockGraph *qmp_x_debug_query_block_graph(Error **errp)

include/block/block.h

@@ -454,7 +454,7 @@ void bdrv_lock_medium(BlockDriverState *bs, bool locked);
 void bdrv_eject(BlockDriverState *bs, bool eject_flag);
 const char *bdrv_get_format_name(BlockDriverState *bs);
 BlockDriverState *bdrv_find_node(const char *node_name);
-BlockDeviceInfoList *bdrv_named_nodes_list(Error **errp);
+BlockDeviceInfoList *bdrv_named_nodes_list(bool flat, Error **errp);
 XDbgBlockGraph *bdrv_get_xdbg_block_graph(Error **errp);
 BlockDriverState *bdrv_lookup_bs(const char *device,
                                  const char *node_name,

include/block/qapi.h

@@ -29,7 +29,9 @@
 #include "block/snapshot.h"
 
 BlockDeviceInfo *bdrv_block_device_info(BlockBackend *blk,
-                                        BlockDriverState *bs, Error **errp);
+                                        BlockDriverState *bs,
+                                        bool flat,
+                                        Error **errp);
 int bdrv_query_snapshot_info_list(BlockDriverState *bs,
                                   SnapshotInfoList **p_list,
                                   Error **errp);

monitor/hmp-cmds.c

@@ -620,7 +620,7 @@ void hmp_info_block(Monitor *mon, const QDict *qdict)
     }
 
     /* Print node information */
-    blockdev_list = qmp_query_named_block_nodes(NULL);
+    blockdev_list = qmp_query_named_block_nodes(false, false, NULL);
     for (blockdev = blockdev_list; blockdev; blockdev = blockdev->next) {
         assert(blockdev->value->has_node_name);
         if (device && strcmp(device, blockdev->value->node_name)) {

qapi/block-core.json

@@ -1758,6 +1758,9 @@
 #
 # Get the named block driver list
 #
+# @flat: Omit the nested data about backing image ("backing-image" key) if true.
+#        Default is false (Since 5.0)
+#
 # Returns: the list of BlockDeviceInfo
 #
 # Since: 2.0
@@ -1811,7 +1814,9 @@
 #                    } } ] }
 #
 ##
-{ 'command': 'query-named-block-nodes', 'returns': [ 'BlockDeviceInfo' ] }
+{ 'command': 'query-named-block-nodes',
+  'returns': [ 'BlockDeviceInfo' ],
+  'data': { '*flat': 'bool' } }
 
 ##
 # @XDbgBlockGraphNodeType: