linux-kernel - [PATCH] bfq: do try insert merge before bfq_init

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Date:   Thu, 13 Oct 2022 21:53:21 +0800
From:   Yuwei Guan <ssawgyw@...il.com>
To:     paolo.valente@...aro.org, axboe@...nel.dk, jack@...e.cz
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        Yuwei.Guan@...krlife.com
Subject: [PATCH] bfq: do try insert merge before bfq_init_rq() call

It's useless to do bfq_init_rq(rq), if the rq can do merge first.

In the patch 5f550ede5edf8, it moved to bfq_init_rq() before
blk_mq_sched_try_insert_merge(), but it's pointless,
as the fifo_time of next is not set yet,
and !list_empty(&next->queuelist) is 0, so it does not
need to reposition rq's fifo_time.

And for the "hash lookup, try again" situation, as follow,
bfq_requests_merged() call can work normally.

blk_mq_sched_try_insert_merge
  elv_attempt_insert_merge
    elv_rqhash_find

Signed-off-by: Yuwei Guan <Yuwei.Guan@...krlife.com>
---
 block/bfq-iosched.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 7ea427817f7f..9845370a701c 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -6147,7 +6147,7 @@ static void bfq_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
 		bfqg_stats_update_legacy_io(q, rq);
 #endif
 	spin_lock_irq(&bfqd->lock);
-	bfqq = bfq_init_rq(rq);
+
 	if (blk_mq_sched_try_insert_merge(q, rq, &free)) {
 		spin_unlock_irq(&bfqd->lock);
 		blk_mq_free_requests(&free);
@@ -6156,6 +6156,7 @@ static void bfq_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
 
 	trace_block_rq_insert(rq);
 
+	bfqq = bfq_init_rq(rq);
 	if (!bfqq || at_head) {
 		if (at_head)
 			list_add(&rq->queuelist, &bfqd->dispatch);
-- 
2.34.1