block: move hctx cpuhp add/del out of queue freezing

Move hctx cpuhp add/del out of queue freezing for not connecting freeze
lock with cpuhp locks, then lockdep warning can be avoided.

This way is safe because both needn't queue to be frozen and scheduler
switch isn't allowed, with same reason for moving hctx debugfs/sysfs
register out of queue freeze.

Reviewed-by: Hannes Reinecke <[email protected]>
Reviewed-by: Nilay Shroff <[email protected]>
Signed-off-by: Ming Lei <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>

Author: Ming Lei

block/blk-mq.c

@@ -5008,7 +5008,7 @@ static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set,
 fallback:
 	blk_mq_update_queue_map(set);
 	list_for_each_entry(q, &set->tag_list, tag_set_list) {
-		blk_mq_realloc_hw_ctxs(set, q);
+		__blk_mq_realloc_hw_ctxs(set, q);
 
 		if (q->nr_hw_queues != set->nr_hw_queues) {
 			int i = prev_nr_hw_queues;
@@ -5032,6 +5032,9 @@ static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set,
 	list_for_each_entry(q, &set->tag_list, tag_set_list) {
 		blk_mq_sysfs_register_hctxs(q);
 		blk_mq_debugfs_register_hctxs(q);
+
+		blk_mq_remove_hw_queues_cpuhp(q);
+		blk_mq_add_hw_queues_cpuhp(q);
 	}
 	memalloc_noio_restore(memflags);