This looks reasonable to me, but a little question below:

quoted

@@ -1442,7 +1491,8 @@ static void nvmet_rdma_remove_port(struct nvmet_port *port)
 {
 	struct rdma_cm_id *cm_id = port->priv;

-	rdma_destroy_id(cm_id);
+	if (cm_id)
+		rdma_destroy_id(cm_id);
 }

How is ->remove_port synchronized vs the RDMA/CM even handler?

Easy, it isn't :)

So we have three choices here:
1. Add a lock in nvmet_port that only rdma will use for now (don't like
it)
or
2. Add nvmet_rdma_port as nvmet_port->priv with a lock (don't like it)
or
3. take the global nvmet_config_sem (hate it)

Any preferences?