block: avoid setting none scheduler if it's already none

There's no reason to freeze queue and remove scheduler if there's no scheduler already. Signed-off-by: Aleksei Zakharov <[email protected]> Signed-off-by: Jens Axboe <[email protected]>
niw · Feb 11, 2019 · fbd7212 · fbd7212
1 parent b7143fe
commit fbd7212
Showing 1 changed file with 4 additions and 1 deletion.
diff --git a/block/elevator.c b/block/elevator.c
@@ -667,8 +667,11 @@ static int __elevator_change(struct request_queue *q, const char *name)
 	/*
 	 * Special case for mq, turn off scheduling
 	 */
-	if (!strncmp(name, "none", 4))
+	if (!strncmp(name, "none", 4)) {
+		if (!q->elevator)
+			return 0;
 		return elevator_switch(q, NULL);
+	}
 
 	strlcpy(elevator_name, name, sizeof(elevator_name));
 	e = elevator_get(q, strstrip(elevator_name), true);