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Commit 705cda97 authored by Bart Van Assche's avatar Bart Van Assche Committed by Jens Axboe
Browse files

blk-mq: Make it safe to use RCU to iterate over blk_mq_tag_set.tag_list 



Since the next patch in this series will use RCU to iterate over
tag_list, make this safe. Add lockdep_assert_held() statements
in functions that iterate over tag_list to make clear that using
list_for_each_entry() instead of list_for_each_entry_rcu() is
fine in these functions.

Signed-off-by: default avatarBart Van Assche <bart.vanassche@sandisk.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.com>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent d945a365

block/blk-mq.c

+9 −2
Original line number Diff line number Diff line
@@ -2111,6 +2111,8 @@ static void blk_mq_update_tag_set_depth(struct blk_mq_tag_set *set, bool shared) 
{

	struct request_queue *q;



	lockdep_assert_held(&set->tag_list_lock);



	list_for_each_entry(q, &set->tag_list, tag_set_list) {

		blk_mq_freeze_queue(q);

		queue_set_hctx_shared(q, shared);
@@ -2123,7 +2125,8 @@ static void blk_mq_del_queue_tag_set(struct request_queue *q) 
	struct blk_mq_tag_set *set = q->tag_set;



	mutex_lock(&set->tag_list_lock);

	list_del_init(&q->tag_set_list);

	list_del_rcu(&q->tag_set_list);

	INIT_LIST_HEAD(&q->tag_set_list);

	if (list_is_singular(&set->tag_list)) {

		/* just transitioned to unshared */

		set->flags &= ~BLK_MQ_F_TAG_SHARED;
@@ -2131,6 +2134,8 @@ static void blk_mq_del_queue_tag_set(struct request_queue *q) 
		blk_mq_update_tag_set_depth(set, false);

	}

	mutex_unlock(&set->tag_list_lock);



	synchronize_rcu();

}



static void blk_mq_add_queue_tag_set(struct blk_mq_tag_set *set,
@@ -2148,7 +2153,7 @@ static void blk_mq_add_queue_tag_set(struct blk_mq_tag_set *set, 
	}

	if (set->flags & BLK_MQ_F_TAG_SHARED)

		queue_set_hctx_shared(q, true);

	list_add_tail(&q->tag_set_list, &set->tag_list);

	list_add_tail_rcu(&q->tag_set_list, &set->tag_list);



	mutex_unlock(&set->tag_list_lock);

}
@@ -2639,6 +2644,8 @@ void blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, int nr_hw_queues) 
{

	struct request_queue *q;



	lockdep_assert_held(&set->tag_list_lock);



	if (nr_hw_queues > nr_cpu_ids)

		nr_hw_queues = nr_cpu_ids;

	if (nr_hw_queues < 1 || nr_hw_queues == set->nr_hw_queues)