From: Aleksei Zakharov <zakharov.a.g@yandex.ru>
Date: Mon, 11 Feb 2019 10:50:37 +0000 (+0300)
Subject: block: avoid setting none scheduler if it's already none
X-Git-Url: http://git.cdn.openwrt.org/?a=commitdiff_plain;h=fbd72127c975dc8e532ecc73d52f3b1b00935bec;p=openwrt%2Fstaging%2Fblogic.git

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 <zakharov.a.g@yandex.ru>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---

diff --git a/block/elevator.c b/block/elevator.c
index f05e90d4e695..d6d835a08de6 100644
--- 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);