block: move blk_mq_add_queue_tag_set() after blk_mq_map_swqueue()

JIRA: https://issues.redhat.com/browse/RHEL-106845

commit f24d47e
Author: Ming Lei <ming.lei@redhat.com>
Date:   Mon May 5 22:17:39 2025 +0800

    block: move blk_mq_add_queue_tag_set() after blk_mq_map_swqueue()

    Move blk_mq_add_queue_tag_set() after blk_mq_map_swqueue(), and publish
    this request queue to tagset after everything is setup.

    This way is safe because BLK_MQ_F_TAG_QUEUE_SHARED isn't used by
    blk_mq_map_swqueue(), and this flag is mainly checked in fast IO code
    path.

    Prepare for removing ->elevator_lock from blk_mq_map_swqueue() which
    is supposed to be called when elevator switch can't be done.

    Reviewed-by: Nilay Shroff <nilay@linux.ibm.com>
    Reviewed-by: Christoph Hellwig <hch@lst.de>
    Reviewed-by: Hannes Reinecke <hare@suse.de>
    Reported-by: Nilay Shroff <nilay@linux.ibm.com>
    Closes: https://lore.kernel.org/linux-block/567cb7ab-23d6-4cee-a915-c8cdac903ddd@linux.ibm.com/
    Signed-off-by: Ming Lei <ming.lei@redhat.com>
    Link: https://lore.kernel.org/r/20250505141805.2751237-2-ming.lei@redhat.com
    Signed-off-by: Jens Axboe <axboe@kernel.dk>

Signed-off-by: Ming Lei <ming.lei@redhat.com>

Author: Ming Lei

block/blk-mq.c

@@ -4625,8 +4625,8 @@ int blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
 	q->nr_requests = set->queue_depth;
 
 	blk_mq_init_cpu_queues(q, set->nr_hw_queues);
-	blk_mq_add_queue_tag_set(set, q);
 	blk_mq_map_swqueue(q);
+	blk_mq_add_queue_tag_set(set, q);
 	return 0;
 
 err_hctxs: