blk-mq-sched: move actual dispatching into one helper

So that it becomes easy to support to dispatch from sw queue in the
following patch.

No functional change.

Reviewed-by: Bart Van Assche <bart.vanassche@wdc.com>
Reviewed-by: Omar Sandoval <osandov@fb.com>
Suggested-by: Christoph Hellwig <hch@lst.de> # for simplifying dispatch logic
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
index eca011fdfa0ede407443c2de9c1e7d45787f4313..be29ba84940852503cf78b855b8da0d2adf6bfa0 100644 (file)
--- a/block/blk-mq-sched.c
+++ b/block/blk-mq-sched.c
@@ -89,12 +89,26 @@ static bool blk_mq_sched_restart_hctx(struct blk_mq_hw_ctx *hctx)
        return false;
 }
 
+static void blk_mq_do_dispatch_sched(struct blk_mq_hw_ctx *hctx)
+{
+       struct request_queue *q = hctx->queue;
+       struct elevator_queue *e = q->elevator;
+       LIST_HEAD(rq_list);
+
+       do {
+               struct request *rq = e->type->ops.mq.dispatch_request(hctx);
+
+               if (!rq)
+                       break;
+               list_add(&rq->queuelist, &rq_list);
+       } while (blk_mq_dispatch_rq_list(q, &rq_list));
+}
+
 void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx)
 {
        struct request_queue *q = hctx->queue;
        struct elevator_queue *e = q->elevator;
        const bool has_sched_dispatch = e && e->type->ops.mq.dispatch_request;
-       bool do_sched_dispatch = true;
        LIST_HEAD(rq_list);
 
        /* RCU or SRCU read lock is needed before checking quiesced flag */
@@ -122,30 +136,21 @@ void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx)
         * scheduler, we can no longer merge or sort them. So it's best to
         * leave them there for as long as we can. Mark the hw queue as
         * needing a restart in that case.
+        *
+        * We want to dispatch from the scheduler if there was nothing
+        * on the dispatch list or we were able to dispatch from the
+        * dispatch list.
         */
        if (!list_empty(&rq_list)) {
                blk_mq_sched_mark_restart_hctx(hctx);
-               do_sched_dispatch = blk_mq_dispatch_rq_list(q, &rq_list);
-       } else if (!has_sched_dispatch) {
+               if (blk_mq_dispatch_rq_list(q, &rq_list) && has_sched_dispatch)
+                       blk_mq_do_dispatch_sched(hctx);
+       } else if (has_sched_dispatch) {
+               blk_mq_do_dispatch_sched(hctx);
+       } else {
                blk_mq_flush_busy_ctxs(hctx, &rq_list);
                blk_mq_dispatch_rq_list(q, &rq_list);
        }
-
-       /*
-        * We want to dispatch from the scheduler if there was nothing
-        * on the dispatch list or we were able to dispatch from the
-        * dispatch list.
-        */
-       if (do_sched_dispatch && has_sched_dispatch) {
-               do {
-                       struct request *rq;
-
-                       rq = e->type->ops.mq.dispatch_request(hctx);
-                       if (!rq)
-                               break;
-                       list_add(&rq->queuelist, &rq_list);
-               } while (blk_mq_dispatch_rq_list(q, &rq_list));
-       }
 }
 
 bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio,