[PATCH v4 08/11] block: mq-deadline: Reduce lock contention

[Bart Van Assche <bvanassche@xxxxxxx>]

blk_mq_free_requests() calls dd_finish_request() indirectly. Prevent
nested locking of dd->lock and dd->zone_lock by unlocking dd->lock
before calling blk_mq_free_requests().

Cc: Damien Le Moal <damien.lemoal@xxxxxxxxxxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Ming Lei <ming.lei@xxxxxxxxxx>
Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
---
 block/mq-deadline.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/block/mq-deadline.c b/block/mq-deadline.c
index dbc0feca963e..56cc29953e15 100644
--- a/block/mq-deadline.c
+++ b/block/mq-deadline.c
@@ -758,6 +758,7 @@ static bool dd_bio_merge(struct request_queue *q, struct bio *bio,
  */
 static void dd_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
 			      blk_insert_t flags)
+	__must_hold(dd->lock)
 {
 	struct request_queue *q = hctx->queue;
 	struct deadline_data *dd = q->elevator->elevator_data;
@@ -784,7 +785,9 @@ static void dd_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
 	}
 
 	if (blk_mq_sched_try_insert_merge(q, rq, &free)) {
+		spin_unlock(&dd->lock);
 		blk_mq_free_requests(&free);
+		spin_lock(&dd->lock);
 		return;
 	}