[PATCH 1/8] Revert "blk-mq: Fix races between blk_mq_update_nr_hw_queues() and iterating over tags"

[Ming Lei <ming.lei@redhat.com>]

This reverts commit ac81d1ffd022b432d24fe79adf2d31f81a4acdc3.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 block/blk-mq-tag.c | 39 ---------------------------------------
 1 file changed, 39 deletions(-)

diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index b0e0f074a864..39d5c9190a6b 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -376,31 +376,6 @@ void blk_mq_all_tag_iter_atomic(struct blk_mq_tags *tags, busy_tag_iter_fn *fn,
 	__blk_mq_all_tag_iter(tags, fn, priv, BT_TAG_ITER_STATIC_RQS);
 }
 
-/*
- * Iterate over all request queues in a tag set, find the first queue with a
- * non-zero usage count, increment its usage count and return the pointer to
- * that request queue. This prevents that blk_mq_update_nr_hw_queues() will
- * modify @set->nr_hw_queues while iterating over tags since
- * blk_mq_update_nr_hw_queues() only modifies @set->nr_hw_queues while the
- * usage count of all queues associated with a tag set is zero.
- */
-static struct request_queue *
-blk_mq_get_any_tagset_queue(struct blk_mq_tag_set *set)
-{
-	struct request_queue *q;
-
-	rcu_read_lock();
-	list_for_each_entry_rcu(q, &set->tag_list, tag_set_list) {
-		if (percpu_ref_tryget(&q->q_usage_counter)) {
-			rcu_read_unlock();
-			return q;
-		}
-	}
-	rcu_read_unlock();
-
-	return NULL;
-}
-
 /**
  * blk_mq_tagset_busy_iter - iterate over all started requests in a tag set
  * @tagset:	Tag set to iterate over.
@@ -416,22 +391,15 @@ blk_mq_get_any_tagset_queue(struct blk_mq_tag_set *set)
 void blk_mq_tagset_busy_iter(struct blk_mq_tag_set *tagset,
 		busy_tag_iter_fn *fn, void *priv)
 {
-	struct request_queue *q;
 	int i;
 
 	might_sleep();
 
-	q = blk_mq_get_any_tagset_queue(tagset);
-	if (!q)
-		return;
-
 	for (i = 0; i < tagset->nr_hw_queues; i++) {
 		if (tagset->tags && tagset->tags[i])
 			__blk_mq_all_tag_iter(tagset->tags[i], fn, priv,
 				BT_TAG_ITER_STARTED | BT_TAG_ITER_MAY_SLEEP);
 	}
-
-	blk_queue_exit(q);
 }
 EXPORT_SYMBOL(blk_mq_tagset_busy_iter);
 
@@ -450,20 +418,13 @@ EXPORT_SYMBOL(blk_mq_tagset_busy_iter);
 void blk_mq_tagset_busy_iter_atomic(struct blk_mq_tag_set *tagset,
 		busy_tag_iter_fn *fn, void *priv)
 {
-	struct request_queue *q;
 	int i;
 
-	q = blk_mq_get_any_tagset_queue(tagset);
-	if (!q)
-		return;
-
 	for (i = 0; i < tagset->nr_hw_queues; i++) {
 		if (tagset->tags && tagset->tags[i])
 			__blk_mq_all_tag_iter(tagset->tags[i], fn, priv,
 					      BT_TAG_ITER_STARTED);
 	}
-
-	blk_queue_exit(q);
 }
 EXPORT_SYMBOL(blk_mq_tagset_busy_iter_atomic);
 
-- 
2.29.2