RDMA/rtrs-clt: Check if the queue_depth has changed during a reconnection

The queue_depth is a module parameter for rtrs_server. It is used on the
client side to determing the queue_depth of the request queue for the RNBD
virtual block device.

During a reconnection event for an already mapped device, in case the
rtrs_server module queue_depth has changed, fail the reconnect attempt.

Also stop further auto reconnection attempts. A manual reconnect via
sysfs has to be triggerred.

Fixes: 6a98d71d ("RDMA/rtrs: client: main functionality")
Link: https://lore.kernel.org/r/20210528113018.52290-20-jinpu.wang@ionos.comSigned-off-by: Md Haris Iqbal <haris.iqbal@ionos.com>
Signed-off-by: Gioh Kim <gi-oh.kim@ionos.com>
Signed-off-by: Jack Wang <jinpu.wang@ionos.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/infiniband/ulp/rtrs/rtrs-clt.c

@@ -1780,7 +1780,19 @@ static int rtrs_rdma_conn_established(struct rtrs_clt_con *con,
 				  queue_depth);
 			return -ECONNRESET;
 		}
-		if (!sess->rbufs || sess->queue_depth < queue_depth) {
+		if (sess->queue_depth > 0 && queue_depth != sess->queue_depth) {
+			rtrs_err(clt, "Error: queue depth changed\n");
+
+			/*
+			 * Stop any more reconnection attempts
+			 */
+			sess->reconnect_attempts = -1;
+			rtrs_err(clt,
+				"Disabling auto-reconnect. Trigger a manual reconnect after issue is resolved\n");
+			return -ECONNRESET;
+		}
+
+		if (!sess->rbufs) {
 			kfree(sess->rbufs);
 			sess->rbufs = kcalloc(queue_depth, sizeof(*sess->rbufs),
 					      GFP_KERNEL);
@@ -1794,7 +1806,7 @@ static int rtrs_rdma_conn_established(struct rtrs_clt_con *con,
 		sess->chunk_size = sess->max_io_size + sess->max_hdr_size;
 
 		/*
-		 * Global queue depth and IO size is always a minimum.
+		 * Global IO size is always a minimum.
 		 * If while a reconnection server sends us a value a bit
 		 * higher - client does not care and uses cached minimum.
 		 *
@@ -1802,8 +1814,7 @@ static int rtrs_rdma_conn_established(struct rtrs_clt_con *con,
 		 * connections in parallel, use lock.
 		 */
 		mutex_lock(&clt->paths_mutex);
-		clt->queue_depth = min_not_zero(sess->queue_depth,
-						clt->queue_depth);
+		clt->queue_depth = sess->queue_depth;
 		clt->max_io_size = min_not_zero(sess->max_io_size,
 						clt->max_io_size);
 		mutex_unlock(&clt->paths_mutex);