linux-kernel - [RFC V5 01/16] blk: make the whole blk_mq_submit_bio under q_usage

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Date:   Thu, 24 Feb 2022 17:06:39 +0800
From:   "Wang Jianchao (Kuaishou)" <jianchao.wan9@...il.com>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     Josef Bacik <jbacik@...com>, Tejun Heo <tj@...nel.org>,
        Bart Van Assche <bvanassche@....org>,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [RFC V5 01/16] blk: make the whole blk_mq_submit_bio under q_usage_counter

This is to protect the rqos list against the rqos open/close. We
need to drain all of the caller of blk_mq_submit_bio() before
we can operate the rqos list.

Signed-off-by: Wang Jianchao (Kuaishou) <jianchao.wan9@...il.com>
---
 block/blk-mq.c | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 1adfe4824ef5..3c1cd32c72fd 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2723,8 +2723,7 @@ static struct request *blk_mq_get_new_requests(struct request_queue *q,
 	};
 	struct request *rq;
 
-	if (unlikely(bio_queue_enter(bio)))
-		return NULL;
+	percpu_ref_get(&q->q_usage_counter);
 
 	if (plug) {
 		data.nr_tags = plug->nr_ios;
@@ -2789,15 +2788,18 @@ void blk_mq_submit_bio(struct bio *bio)
 	if (unlikely(!blk_crypto_bio_prep(&bio)))
 		return;
 
+	if (unlikely(bio_queue_enter(bio)))
+		return;
+
 	blk_queue_bounce(q, &bio);
 	if (blk_may_split(q, bio))
 		__blk_queue_split(q, &bio, &nr_segs);
 
 	if (!bio_integrity_prep(bio))
-		return;
+		goto exit;
 
 	if (blk_mq_attempt_bio_merge(q, bio, nr_segs))
-		return;
+		goto exit;
 
 	rq_qos_throttle(q, bio);
 
@@ -2805,7 +2807,7 @@ void blk_mq_submit_bio(struct bio *bio)
 	if (!rq) {
 		rq = blk_mq_get_new_requests(q, plug, bio);
 		if (unlikely(!rq))
-			return;
+			goto exit;
 	}
 
 	trace_block_getrq(bio);
@@ -2819,12 +2821,12 @@ void blk_mq_submit_bio(struct bio *bio)
 		bio->bi_status = ret;
 		bio_endio(bio);
 		blk_mq_free_request(rq);
-		return;
+		goto exit;
 	}
 
 	if (op_is_flush(bio->bi_opf)) {
 		blk_insert_flush(rq);
-		return;
+		goto exit;
 	}
 
 	if (plug)
@@ -2836,6 +2838,8 @@ void blk_mq_submit_bio(struct bio *bio)
 	else
 		blk_mq_run_dispatch_ops(rq->q,
 				blk_mq_try_issue_directly(rq->mq_hctx, rq));
+exit:
+	blk_queue_exit(q);
 }
 
 /**
-- 
2.17.1