block: move ELEVATOR_FLAG_DISABLE_WBT a request queue flag

ELEVATOR_FLAG_DISABLE_WBT is only used by BFQ to disallow wbt when BFQ is
in use. The flag is set in BFQ's init(), and cleared in BFQ's exit().

Making it as request queue flag, so that we can avoid to deal with elevator
switch race. Also it isn't graceful to checking one scheduler flag in
wbt_enable_default().

Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Nilay Shroff <nilay@linux.ibm.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20250505141805.2751237-3-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: Ming Lei

block/bfq-iosched.c

@@ -7210,7 +7210,7 @@ static void bfq_exit_queue(struct elevator_queue *e)
 #endif
 
 	blk_stat_disable_accounting(bfqd->queue);
-	clear_bit(ELEVATOR_FLAG_DISABLE_WBT, &e->flags);
+	blk_queue_flag_clear(QUEUE_FLAG_DISABLE_WBT_DEF, bfqd->queue);
 	wbt_enable_default(bfqd->queue->disk);
 
 	kfree(bfqd);
@@ -7397,7 +7397,7 @@ static int bfq_init_queue(struct request_queue *q, struct elevator_type *e)
 	/* We dispatch from request queue wide instead of hw queue */
 	blk_queue_flag_set(QUEUE_FLAG_SQ_SCHED, q);
 
-	set_bit(ELEVATOR_FLAG_DISABLE_WBT, &eq->flags);
+	blk_queue_flag_set(QUEUE_FLAG_DISABLE_WBT_DEF, q);
 	wbt_disable_default(q->disk);
 	blk_stat_enable_accounting(q);
 

block/blk-mq-debugfs.c

@@ -93,6 +93,7 @@ static const char *const blk_queue_flag_name[] = {
 	QUEUE_FLAG_NAME(RQ_ALLOC_TIME),
 	QUEUE_FLAG_NAME(HCTX_ACTIVE),
 	QUEUE_FLAG_NAME(SQ_SCHED),
+	QUEUE_FLAG_NAME(DISABLE_WBT_DEF),
 };
 #undef QUEUE_FLAG_NAME
 

block/blk-wbt.c

@@ -704,8 +704,7 @@ void wbt_enable_default(struct gendisk *disk)
 	struct rq_qos *rqos;
 	bool enable = IS_ENABLED(CONFIG_BLK_WBT_MQ);
 
-	if (q->elevator &&
-	    test_bit(ELEVATOR_FLAG_DISABLE_WBT, &q->elevator->flags))
+	if (blk_queue_disable_wbt(q))
 		enable = false;
 
 	/* Throttling already enabled? */

block/elevator.h

@@ -121,7 +121,6 @@ struct elevator_queue
 };
 
 #define ELEVATOR_FLAG_REGISTERED	0
-#define ELEVATOR_FLAG_DISABLE_WBT	1
 
 /*
  * block elevator interface

include/linux/blkdev.h

@@ -641,6 +641,7 @@ enum {
 	QUEUE_FLAG_RQ_ALLOC_TIME,	/* record rq->alloc_time_ns */
 	QUEUE_FLAG_HCTX_ACTIVE,		/* at least one blk-mq hctx is active */
 	QUEUE_FLAG_SQ_SCHED,		/* single queue style io dispatch */
+	QUEUE_FLAG_DISABLE_WBT_DEF,	/* for sched to disable/enable wbt */
 	QUEUE_FLAG_MAX
 };
 
@@ -676,6 +677,8 @@ void blk_queue_flag_clear(unsigned int flag, struct request_queue *q);
 #define blk_queue_sq_sched(q)	test_bit(QUEUE_FLAG_SQ_SCHED, &(q)->queue_flags)
 #define blk_queue_skip_tagset_quiesce(q) \
 	((q)->limits.features & BLK_FEAT_SKIP_TAGSET_QUIESCE)
+#define blk_queue_disable_wbt(q)	\
+	test_bit(QUEUE_FLAG_DISABLE_WBT_DEF, &(q)->queue_flags)
 
 extern void blk_set_pm_only(struct request_queue *q);
 extern void blk_clear_pm_only(struct request_queue *q);