block: move blk_queue_registered() check into elv_iosched_store()

Move blk_queue_registered() check into elv_iosched_store() and prepare
for using elevator_change() for covering any kind of elevator change in
adding/deleting disk and updating nr_hw_queue.

Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Nilay Shroff <nilay@linux.ibm.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20250505141805.2751237-13-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/elevator.c

@@ -676,10 +676,6 @@ int elevator_switch(struct request_queue *q, const char *name)
  */
 static int elevator_change(struct request_queue *q, const char *elevator_name)
 {
-	/* Make sure queue is not in the middle of being removed */
-	if (!blk_queue_registered(q))
-		return -ENOENT;
-
 	if (q->elevator && elevator_match(q->elevator->type, elevator_name))
 		return 0;
 
@@ -708,6 +704,10 @@ ssize_t elv_iosched_store(struct gendisk *disk, const char *buf,
 	struct request_queue *q = disk->queue;
 	struct blk_mq_tag_set *set = q->tag_set;
 
+	/* Make sure queue is not in the middle of being removed */
+	if (!blk_queue_registered(q))
+		return -ENOENT;
+
 	/*
 	 * If the attribute needs to load a module, do it before freezing the
 	 * queue to ensure that the module file can be read when the request