block/mq-deadline: Improve request accounting further

The scheduler .insert_requests() callback is called when a request is
queued for the first time and also when it is requeued. Only count a
request the first time it is queued. Additionally, since the mq-deadline
scheduler only performs zone locking for requests that have been
inserted, skip the zone unlock code for requests that have not been
inserted into the mq-deadline scheduler.

Fixes: 38ba64d1 ("block/mq-deadline: Track I/O statistics")
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: Niklas Cassel <Niklas.Cassel@wdc.com>
Cc: Hannes Reinecke <hare@suse.de>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Link: https://lore.kernel.org/r/20210927220328.1410161-2-bvanassche@acm.orgSigned-off-by: Jens Axboe <axboe@kernel.dk>

block/mq-deadline.c

@@ -677,8 +677,10 @@ static void dd_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
 	blk_req_zone_write_unlock(rq);
 
 	prio = ioprio_class_to_prio[ioprio_class];
+	if (!rq->elv.priv[0]) {
 		dd_count(dd, inserted, prio);
 		rq->elv.priv[0] = (void *)(uintptr_t)1;
+	}
 
 	if (blk_mq_sched_try_insert_merge(q, rq, &free)) {
 		blk_mq_free_requests(&free);
@@ -759,11 +761,12 @@ static void dd_finish_request(struct request *rq)
 
 	/*
 	 * The block layer core may call dd_finish_request() without having
-	 * called dd_insert_requests(). Hence only update statistics for
-	 * requests for which dd_insert_requests() has been called. See also
-	 * blk_mq_request_bypass_insert().
+	 * called dd_insert_requests(). Skip requests that bypassed I/O
+	 * scheduling. See also blk_mq_request_bypass_insert().
 	 */
-	if (rq->elv.priv[0])
+	if (!rq->elv.priv[0])
+		return;
+
 	dd_count(dd, completed, prio);
 
 	if (blk_queue_is_zoned(q)) {