[PATCH V4 2/3] blk-mq: return dispatch result to caller in blk_mq_try_issue_directly

[Ming Lei]

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....@redhat.com>
---
 block/blk-mq.c | 23 ++++++++++++++---------
 1 file changed, 14 insertions(+), 9 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index bf8d6651f40e..1654c9c284d8 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1722,13 +1722,13 @@ static blk_status_t __blk_mq_issue_req(struct 
blk_mq_hw_ctx *hctx,
        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)
 {
        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 */
@@ -1752,31 +1752,36 @@ 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,
                                        hctx->flags & BLK_MQ_F_BLOCKING);
+       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)
 {
        int srcu_idx;
+       blk_status_t ret;
 
        might_sleep_if(hctx->flags & BLK_MQ_F_BLOCKING);
 
        hctx_lock(hctx, &srcu_idx);
-       __blk_mq_try_issue_directly(hctx, rq, cookie);
+       ret = __blk_mq_try_issue_directly(hctx, rq, cookie);
        hctx_unlock(hctx, srcu_idx);
+
+       return ret;
 }
 
 static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio)
-- 
2.9.5