nvmet-rdma: Avoid o(n^2) loop in delete_ctrl

When deleting a nvmet-rdma ctrl, we essentially loop over all
queues that belong to the controller and schedule a removal of
each. Instead of restarting the loop every time a queue is found,
do a simple safe list traversal.

This addresses an unneeded time spent scheduling queue removal in
cases there a lot of queues.

Signed-off-by: Sagi Grimberg <sagi.grimberg@vastdata.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Keith Busch <kbusch@kernel.org>

Author: Sagi Grimberg

drivers/nvme/target/rdma.c

@@ -1814,18 +1814,14 @@ static int nvmet_rdma_cm_handler(struct rdma_cm_id *cm_id,
 
 static void nvmet_rdma_delete_ctrl(struct nvmet_ctrl *ctrl)
 {
-	struct nvmet_rdma_queue *queue;
+	struct nvmet_rdma_queue *queue, *n;
 
-restart:
 	mutex_lock(&nvmet_rdma_queue_mutex);
-	list_for_each_entry(queue, &nvmet_rdma_queue_list, queue_list) {
-		if (queue->nvme_sq.ctrl == ctrl) {
-			list_del_init(&queue->queue_list);
-			mutex_unlock(&nvmet_rdma_queue_mutex);
-
-			__nvmet_rdma_queue_disconnect(queue);
-			goto restart;
-		}
+	list_for_each_entry_safe(queue, n, &nvmet_rdma_queue_list, queue_list) {
+		if (queue->nvme_sq.ctrl != ctrl)
+			continue;
+		list_del_init(&queue->queue_list);
+		__nvmet_rdma_queue_disconnect(queue);
 	}
 	mutex_unlock(&nvmet_rdma_queue_mutex);
 }