nvmet-rdma: occasionally flush ongoing controller teardown

If we are attacked with establishments/teradowns we need to
make sure we do not consume too much system memory. Thus
let ongoing controller teardowns complete before accepting
new controller establishments.
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Jens Axboe <axboe@fb.com>

drivers/nvme/target/rdma.c

@@ -1199,6 +1199,11 @@ static int nvmet_rdma_queue_connect(struct rdma_cm_id *cm_id,
 	}
 	queue->port = cm_id->context;
 
+	if (queue->host_qid == 0) {
+		/* Let inflight controller teardown complete */
+		flush_scheduled_work();
+	}
+
 	ret = nvmet_rdma_cm_accept(cm_id, queue, &event->param.conn);
 	if (ret)
 		goto release_queue;