block: pass elevator_queue to elv_register_queue & unregister_queue

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

commit a3dc627
Author: Ming Lei <ming.lei@redhat.com>
Date:   Mon May 5 22:17:55 2025 +0800

    block: pass elevator_queue to elv_register_queue & unregister_queue

    Pass elevator_queue reference to elv_register_queue() & elv_unregister_queue().

    No functional change, and prepare for moving the two out of elevator
    lock & freezing queue, when we need to store the old & new elevator
    queue in `struct elv_change_ctx` instance, then both two can co-exist
    for short while, so we have to pass the exact elevator_queue instance
    to elv_register_queue & unregister_queue.

    Reviewed-by: Christoph Hellwig <hch@lst.de>
    Reviewed-by: Hannes Reinecke <hare@suse.de>
    Reviewed-by: Nilay Shroff <nilay@linux.ibm.com>
    Signed-off-by: Ming Lei <ming.lei@redhat.com>
    Link: https://lore.kernel.org/r/20250505141805.2751237-18-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/elevator.c

@@ -458,9 +458,10 @@ static const struct kobj_type elv_ktype = {
 	.release	= elevator_release,
 };
 
-static int elv_register_queue(struct request_queue *q, bool uevent)
+static int elv_register_queue(struct request_queue *q,
+			      struct elevator_queue *e,
+			      bool uevent)
 {
-	struct elevator_queue *e = q->elevator;
 	int error;
 
 	lockdep_assert_held(&q->elevator_lock);
@@ -488,10 +489,9 @@ static int elv_register_queue(struct request_queue *q, bool uevent)
 	return error;
 }
 
-static void elv_unregister_queue(struct request_queue *q)
+static void elv_unregister_queue(struct request_queue *q,
+				 struct elevator_queue *e)
 {
-	struct elevator_queue *e = q->elevator;
-
 	lockdep_assert_held(&q->elevator_lock);
 
 	if (e && test_and_clear_bit(ELEVATOR_FLAG_REGISTERED, &e->flags)) {
@@ -584,15 +584,15 @@ static int elevator_switch(struct request_queue *q, struct elv_change_ctx *ctx)
 	blk_mq_quiesce_queue(q);
 
 	if (q->elevator) {
-		elv_unregister_queue(q);
+		elv_unregister_queue(q, q->elevator);
 		elevator_exit(q);
 	}
 
 	if (new_e) {
 		ret = blk_mq_init_sched(q, new_e);
 		if (ret)
 			goto out_unfreeze;
-		ret = elv_register_queue(q, !ctx->no_uevent);
+		ret = elv_register_queue(q, q->elevator, !ctx->no_uevent);
 		if (ret) {
 			elevator_exit(q);
 			goto out_unfreeze;