blk-mq: factor out a few helpers from __blk_mq_try_issue_directly

No functional change.  Just makes code flow more logically.

In following commit, __blk_mq_try_issue_directly() will be used to
return the dispatch result (blk_status_t) to DM.  DM needs this
information to improve IO merging.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-mq.c b/block/blk-mq.c
index ec429be..ddc46f2 100644 (file)
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1738,9 +1738,9 @@ static blk_qc_t request_to_qc_t(struct blk_mq_hw_ctx *hctx, struct request *rq)
        return blk_tag_to_qc_t(rq->internal_tag, hctx->queue_num, true);
 }
 
-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_issue_directly(struct blk_mq_hw_ctx *hctx,
+                                           struct request *rq,
+                                           blk_qc_t *cookie)
 {
        struct request_queue *q = rq->q;
        struct blk_mq_queue_data bd = {
@@ -1749,6 +1749,43 @@ static void __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
        };
        blk_qc_t new_cookie;
        blk_status_t ret;
+
+       new_cookie = request_to_qc_t(hctx, rq);
+
+       /*
+        * For OK queue, we are done. For error, caller may kill it.
+        * Any other error (busy), just add it to our list as we
+        * previously would have done.
+        */
+       ret = q->mq_ops->queue_rq(hctx, &bd);
+       switch (ret) {
+       case BLK_STS_OK:
+               *cookie = new_cookie;
+               break;
+       case BLK_STS_RESOURCE:
+               __blk_mq_requeue_request(rq);
+               break;
+       default:
+               *cookie = BLK_QC_T_NONE;
+               break;
+       }
+
+       return ret;
+}
+
+static void __blk_mq_fallback_to_insert(struct blk_mq_hw_ctx *hctx,
+                                       struct request *rq,
+                                       bool run_queue)
+{
+       blk_mq_sched_insert_request(rq, false, run_queue, false,
+                                       hctx->flags & BLK_MQ_F_BLOCKING);
+}
+
+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;
        bool run_queue = true;
 
        /* RCU or SRCU read lock is needed before checking quiesced flag */
@@ -1768,41 +1805,29 @@ static void __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
                goto insert;
        }
 
-       new_cookie = request_to_qc_t(hctx, rq);
-
-       /*
-        * For OK queue, we are done. For error, kill it. Any other
-        * error (busy), just add it to our list as we previously
-        * would have done
-        */
-       ret = q->mq_ops->queue_rq(hctx, &bd);
-       switch (ret) {
-       case BLK_STS_OK:
-               *cookie = new_cookie;
-               return;
-       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 __blk_mq_issue_directly(hctx, rq, cookie);
 insert:
-       blk_mq_sched_insert_request(rq, false, run_queue, false,
-                                       hctx->flags & BLK_MQ_F_BLOCKING);
+       __blk_mq_fallback_to_insert(hctx, rq, run_queue);
+
+       return BLK_STS_OK;
 }
 
 static void blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
                struct request *rq, blk_qc_t *cookie)
 {
+       blk_status_t ret;
        int srcu_idx;
 
        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);
+       if (ret == BLK_STS_RESOURCE)
+               __blk_mq_fallback_to_insert(hctx, rq, true);
+       else if (ret != BLK_STS_OK)
+               blk_mq_end_request(rq, ret);
+
        hctx_unlock(hctx, srcu_idx);
 }