block: Mark bdrv_get_parent_name() and callers GRAPH_RDLOCK

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

For some places, we know that they will hold the lock, but we don't have
the GRAPH_RDLOCK annotations yet. In this case, add assume_graph_lock()
with a FIXME comment. These places will be removed once everything is
properly annotated.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-ID: <20230929145157.45443-13-kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

blockjob.c

@@ -485,6 +485,7 @@ void *block_job_create(const char *job_id, const BlockJobDriver *driver,
     BlockJob *job;
     int ret;
     GLOBAL_STATE_CODE();
+    GRAPH_RDLOCK_GUARD_MAINLOOP();
 
     if (job_id == NULL && !(flags & JOB_INTERNAL)) {
         job_id = bdrv_get_device_name(bs);