block: Mark bdrv_get_xdbg_block_graph() and callers GRAPH_RDLOCK

This adds GRAPH_RDLOCK annotations to declare that callers of
bdrv_get_xdbg_block_graph() need to hold a reader lock for the graph
because it accesses the children list of a node.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-ID: <20230929145157.45443-10-kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

blockdev.c

@@ -2846,6 +2846,8 @@ BlockDeviceInfoList *qmp_query_named_block_nodes(bool has_flat,
 
 XDbgBlockGraph *qmp_x_debug_query_block_graph(Error **errp)
 {
+    GRAPH_RDLOCK_GUARD_MAINLOOP();
+
     return bdrv_get_xdbg_block_graph(errp);
 }
 

include/block/block-global-state.h

@@ -192,7 +192,7 @@ int bdrv_has_zero_init_1(BlockDriverState *bs);
 int bdrv_has_zero_init(BlockDriverState *bs);
 BlockDriverState *bdrv_find_node(const char *node_name);
 BlockDeviceInfoList *bdrv_named_nodes_list(bool flat, Error **errp);
-XDbgBlockGraph *bdrv_get_xdbg_block_graph(Error **errp);
+XDbgBlockGraph * GRAPH_RDLOCK bdrv_get_xdbg_block_graph(Error **errp);
 BlockDriverState *bdrv_lookup_bs(const char *device,
                                  const char *node_name,
                                  Error **errp);