block: add helper for checking if queue is registered

There are 4 users which check if queue is registered, so add one helper
to check it.

Cc: Christoph Hellwig <hch@infradead.org>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: Mike Snitzer <snitzer@redhat.com>
Cc: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-sysfs.c

@@ -942,7 +942,7 @@ int blk_register_queue(struct gendisk *disk)
 	if (WARN_ON(!q))
 		return -ENXIO;
 
-	WARN_ONCE(test_bit(QUEUE_FLAG_REGISTERED, &q->queue_flags),
+	WARN_ONCE(blk_queue_registered(q),
 		  "%s is registering an already registered queue\n",
 		  kobject_name(&dev->kobj));
 	blk_queue_flag_set(QUEUE_FLAG_REGISTERED, q);
@@ -1026,7 +1026,7 @@ void blk_unregister_queue(struct gendisk *disk)
 		return;
 
 	/* Return early if disk->queue was never registered. */
-	if (!test_bit(QUEUE_FLAG_REGISTERED, &q->queue_flags))
+	if (!blk_queue_registered(q))
 		return;
 
 	/*

block/blk-wbt.c

@@ -656,7 +656,7 @@ void wbt_enable_default(struct request_queue *q)
 		return;
 
 	/* Queue not registered? Maybe shutting down... */
-	if (!test_bit(QUEUE_FLAG_REGISTERED, &q->queue_flags))
+	if (!blk_queue_registered(q))
 		return;
 
 	if (queue_is_mq(q) && IS_ENABLED(CONFIG_BLK_WBT_MQ))

block/elevator.c

@@ -656,7 +656,7 @@ static int __elevator_change(struct request_queue *q, const char *name)
 	struct elevator_type *e;
 
 	/* Make sure queue is not in the middle of being removed */
-	if (!test_bit(QUEUE_FLAG_REGISTERED, &q->queue_flags))
+	if (!blk_queue_registered(q))
 		return -ENOENT;
 
 	/*

include/linux/blkdev.h

@@ -643,6 +643,7 @@ bool blk_queue_flag_test_and_set(unsigned int flag, struct request_queue *q);
 #define blk_queue_quiesced(q)	test_bit(QUEUE_FLAG_QUIESCED, &(q)->queue_flags)
 #define blk_queue_pm_only(q)	atomic_read(&(q)->pm_only)
 #define blk_queue_fua(q)	test_bit(QUEUE_FLAG_FUA, &(q)->queue_flags)
+#define blk_queue_registered(q)	test_bit(QUEUE_FLAG_REGISTERED, &(q)->queue_flags)
 
 extern void blk_set_pm_only(struct request_queue *q);
 extern void blk_clear_pm_only(struct request_queue *q);