blk-wbt: don't enable throttling if default elevator is bfq

mainline inclusion
from mainline-v6.2-rc1
commit 671fae5e
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I6HOKY
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?h=v6.2&id=671fae5e51297fc76b3758ca2edd514858734a6a

--------------------------------

Commit b5dc5d4d ("block,bfq: Disable writeback throttling") tries to
disable wbt for bfq, it's done by calling wbt_disable_default() in
bfq_init_queue(). However, wbt is still enabled if default elevator is
bfq:

device_add_disk
 elevator_init_mq
  bfq_init_queue
   wbt_disable_default -> done nothing

 blk_register_queue
  wbt_enable_default -> wbt is enabled

Fix the problem by adding a new flag ELEVATOR_FLAG_DISBALE_WBT, bfq
will set the flag in bfq_init_queue, and following wbt_enable_default()
won't enable wbt while the flag is set.
Signed-off-by: NYu Kuai <yukuai3@huawei.com>
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20221019121518.3865235-7-yukuai1@huaweicloud.comSigned-off-by: NJens Axboe <axboe@kernel.dk>

Conflict:
  block/bfq-iosched.c
  block/blk-wbt.c
  block/elevator.h
Signed-off-by: NLi Lingfeng <lilingfeng3@huawei.com>
Reviewed-by: NHou Tao <houtao1@huawei.com>
Signed-off-by: NYongqiang Liu <liuyongqiang13@huawei.com>

block/blk-wbt.c

@@ -711,11 +711,15 @@ void wbt_set_write_cache(struct request_queue *q, bool write_cache_on)
  */
 void wbt_enable_default(struct request_queue *q)
 {
-	struct rq_qos *rqos = wbt_rq_qos(q);
+	struct rq_qos *rqos;
+	bool disable_flag = q->elevator &&
+			    !strcmp(q->elevator->type->elevator_name, "cfq");
 
 	/* Throttling already enabled? */
+	rqos = wbt_rq_qos(q);
 	if (rqos) {
-		if (RQWB(rqos)->enable_state == WBT_STATE_OFF_DEFAULT)
+		if (!disable_flag &&
+		    RQWB(rqos)->enable_state == WBT_STATE_OFF_DEFAULT)
 			RQWB(rqos)->enable_state = WBT_STATE_ON_DEFAULT;
 		return;
 	}
@@ -724,8 +728,9 @@ void wbt_enable_default(struct request_queue *q)
 	if (!test_bit(QUEUE_FLAG_REGISTERED, &q->queue_flags))
 		return;
 
-	if ((q->mq_ops && IS_ENABLED(CONFIG_BLK_WBT_MQ)) ||
-	    (q->request_fn && IS_ENABLED(CONFIG_BLK_WBT_SQ)))
+	if (((q->mq_ops && IS_ENABLED(CONFIG_BLK_WBT_MQ)) ||
+	    (q->request_fn && IS_ENABLED(CONFIG_BLK_WBT_SQ))) &&
+	    !disable_flag)
 		wbt_init(q);
 }
 EXPORT_SYMBOL_GPL(wbt_enable_default);