block: skip QUEUE_FLAG_STATS and rq-qos for passthrough io

Write-back throttling (WBT) enables QUEUE_FLAG_STATS on the request
queue. But WBT does not make sense for passthrough io, so skip
QUEUE_FLAG_STATS processing.

Also skip rq_qos_issue/done for passthrough io.

Overall, the change gives ~11% hike in peak performance.

Signed-off-by: Kundan Kumar <[email protected]>
Signed-off-by: Kanchan Joshi <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>

Author: Kundan Kumar

block/blk-mq.c

@@ -1248,7 +1248,8 @@ void blk_mq_start_request(struct request *rq)
 
 	trace_block_rq_issue(rq);
 
-	if (test_bit(QUEUE_FLAG_STATS, &q->queue_flags)) {
+	if (test_bit(QUEUE_FLAG_STATS, &q->queue_flags) &&
+	    !blk_rq_is_passthrough(rq)) {
 		rq->io_start_time_ns = ktime_get_ns();
 		rq->stats_sectors = blk_rq_sectors(rq);
 		rq->rq_flags |= RQF_STATS;

block/blk-rq-qos.h

@@ -118,7 +118,7 @@ static inline void rq_qos_cleanup(struct request_queue *q, struct bio *bio)
 
 static inline void rq_qos_done(struct request_queue *q, struct request *rq)
 {
-	if (q->rq_qos)
+	if (q->rq_qos && !blk_rq_is_passthrough(rq))
 		__rq_qos_done(q->rq_qos, rq);
 }