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: Bart Van Assche <bart.vanassche@sandisk.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Hannes Reinecke <hare@suse.com> Signed-off-by: Jens Axboe <axboe@fb.com>
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@ -2111,6 +2111,8 @@ static void blk_mq_update_tag_set_depth(struct blk_mq_tag_set *set, bool shared)
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{
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{
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struct request_queue *q;
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struct request_queue *q;
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lockdep_assert_held(&set->tag_list_lock);
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list_for_each_entry(q, &set->tag_list, tag_set_list) {
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list_for_each_entry(q, &set->tag_list, tag_set_list) {
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blk_mq_freeze_queue(q);
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blk_mq_freeze_queue(q);
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queue_set_hctx_shared(q, shared);
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queue_set_hctx_shared(q, shared);
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@ -2123,7 +2125,8 @@ static void blk_mq_del_queue_tag_set(struct request_queue *q)
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struct blk_mq_tag_set *set = q->tag_set;
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struct blk_mq_tag_set *set = q->tag_set;
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mutex_lock(&set->tag_list_lock);
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mutex_lock(&set->tag_list_lock);
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list_del_init(&q->tag_set_list);
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list_del_rcu(&q->tag_set_list);
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INIT_LIST_HEAD(&q->tag_set_list);
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if (list_is_singular(&set->tag_list)) {
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if (list_is_singular(&set->tag_list)) {
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/* just transitioned to unshared */
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/* just transitioned to unshared */
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set->flags &= ~BLK_MQ_F_TAG_SHARED;
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set->flags &= ~BLK_MQ_F_TAG_SHARED;
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@ -2131,6 +2134,8 @@ static void blk_mq_del_queue_tag_set(struct request_queue *q)
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blk_mq_update_tag_set_depth(set, false);
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blk_mq_update_tag_set_depth(set, false);
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}
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}
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mutex_unlock(&set->tag_list_lock);
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mutex_unlock(&set->tag_list_lock);
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synchronize_rcu();
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}
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}
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static void blk_mq_add_queue_tag_set(struct blk_mq_tag_set *set,
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static void blk_mq_add_queue_tag_set(struct blk_mq_tag_set *set,
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@ -2148,7 +2153,7 @@ static void blk_mq_add_queue_tag_set(struct blk_mq_tag_set *set,
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}
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}
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if (set->flags & BLK_MQ_F_TAG_SHARED)
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if (set->flags & BLK_MQ_F_TAG_SHARED)
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queue_set_hctx_shared(q, true);
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queue_set_hctx_shared(q, true);
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list_add_tail(&q->tag_set_list, &set->tag_list);
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list_add_tail_rcu(&q->tag_set_list, &set->tag_list);
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mutex_unlock(&set->tag_list_lock);
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mutex_unlock(&set->tag_list_lock);
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}
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}
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@ -2639,6 +2644,8 @@ void blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, int nr_hw_queues)
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{
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{
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struct request_queue *q;
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struct request_queue *q;
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lockdep_assert_held(&set->tag_list_lock);
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if (nr_hw_queues > nr_cpu_ids)
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if (nr_hw_queues > nr_cpu_ids)
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nr_hw_queues = nr_cpu_ids;
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nr_hw_queues = nr_cpu_ids;
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if (nr_hw_queues < 1 || nr_hw_queues == set->nr_hw_queues)
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if (nr_hw_queues < 1 || nr_hw_queues == set->nr_hw_queues)
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