linux-kernel - [PATCH V2 4/5] blk-mq: return dispatch result to caller in blk_mq_try_issue

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Date:   Mon, 27 Nov 2017 13:07:20 +0800
From:   Ming Lei <ming.lei@...hat.com>
To:     Jens Axboe <axboe@...com>, linux-block@...r.kernel.org,
        Mike Snitzer <snitzer@...hat.com>, dm-devel@...hat.com
Cc:     Christoph Hellwig <hch@...radead.org>,
        Bart Van Assche <bart.vanassche@...disk.com>,
        linux-kernel@...r.kernel.org, Hannes Reinecke <hare@...e.com>,
        Omar Sandoval <osandov@...com>, Ming Lei <ming.lei@...hat.com>
Subject: [PATCH V2 4/5] blk-mq: return dispatch result to caller in blk_mq_try_issue_directly

In the following patch, we will use blk_mq_try_issue_directly() for DM
to return the dispatch result, and DM need this informatin to improve
IO merge.

Signed-off-by: Ming Lei <ming.lei@...hat.com>
---
 block/blk-mq.c | 27 +++++++++++++++++----------
 1 file changed, 17 insertions(+), 10 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index fe82d7a47b35..fd4fb6316ea1 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1620,13 +1620,14 @@ static bool __blk_mq_issue_req(struct blk_mq_hw_ctx *hctx,
 	return false;
 }
 
-static void __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
-					struct request *rq,
-					blk_qc_t *cookie, bool may_sleep)
+static blk_status_t __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
+						struct request *rq,
+						blk_qc_t *cookie,
+						bool may_sleep)
 {
 	struct request_queue *q = rq->q;
 	blk_qc_t new_cookie;
-	blk_status_t ret;
+	blk_status_t ret = BLK_STS_OK;
 	bool run_queue = true;
 
 	/* RCU or SRCU read lock is needed before checking quiesced flag */
@@ -1649,26 +1650,30 @@ static void __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
 	switch (ret) {
 	case BLK_STS_OK:
 		*cookie = new_cookie;
-		return;
+		return ret;
 	case BLK_STS_RESOURCE:
 		__blk_mq_requeue_request(rq);
 		goto insert;
 	default:
 		*cookie = BLK_QC_T_NONE;
 		blk_mq_end_request(rq, ret);
-		return;
+		return ret;
 	}
 
 insert:
 	blk_mq_sched_insert_request(rq, false, run_queue, false, may_sleep);
+	return ret;
 }
 
-static void blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
-		struct request *rq, blk_qc_t *cookie)
+static blk_status_t blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
+					      struct request *rq,
+					      blk_qc_t *cookie)
 {
+	blk_status_t ret;
+
 	if (!(hctx->flags & BLK_MQ_F_BLOCKING)) {
 		rcu_read_lock();
-		__blk_mq_try_issue_directly(hctx, rq, cookie, false);
+		ret = __blk_mq_try_issue_directly(hctx, rq, cookie, false);
 		rcu_read_unlock();
 	} else {
 		unsigned int srcu_idx;
@@ -1676,9 +1681,11 @@ static void blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
 		might_sleep();
 
 		srcu_idx = srcu_read_lock(hctx->queue_rq_srcu);
-		__blk_mq_try_issue_directly(hctx, rq, cookie, true);
+		ret = __blk_mq_try_issue_directly(hctx, rq, cookie, true);
 		srcu_read_unlock(hctx->queue_rq_srcu, srcu_idx);
 	}
+
+	return ret;
 }
 
 static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
-- 
2.9.5