block: protect debugfs attrs using elevator_lock instead of sysfs_lock

Currently, the block debugfs attributes (tags, tags_bitmap, sched_tags,
and sched_tags_bitmap) are protected using q->sysfs_lock. However, these
attributes are updated in multiple scenarios:
- During driver probe method
- During an elevator switch/update
- During an nr_hw_queues update
- When writing to the sysfs attribute nr_requests

All these update paths (except driver probe method, which doesn't
require any protection) are already protected using q->elevator_lock. To
ensure consistency and proper synchronization, replace q->sysfs_lock
with q->elevator_lock for protecting these debugfs attributes.

Signed-off-by: Nilay Shroff <nilay@linux.ibm.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20250313115235.3707600-2-nilay@linux.ibm.com
[axboe: some commit message rewording/fixes]
Signed-off-by: Jens Axboe <axboe@kernel.dk>

include/linux/blkdev.h

@@ -566,9 +566,9 @@ struct request_queue {
 	 * nr_requests and wbt latency, this lock also protects the sysfs attrs
 	 * nr_requests and wbt_lat_usec. Additionally the nr_hw_queues update
 	 * may modify hctx tags, reserved-tags and cpumask, so this lock also
-	 * helps protect the hctx attrs. To ensure proper locking order during
-	 * an elevator or nr_hw_queue update, first freeze the queue, then
-	 * acquire ->elevator_lock.
+	 * helps protect the hctx sysfs/debugfs attrs. To ensure proper locking
+	 * order during an elevator or nr_hw_queue update, first freeze the
+	 * queue, then acquire ->elevator_lock.
 	 */
 	struct mutex		elevator_lock;