blk-mq: cleanup __blk_mq_sched_dispatch_requests

__blk_mq_sched_dispatch_requests currently has duplicated logic
for the cases where requests are on the hctx dispatch list or not.
Merge the two with a new need_dispatch variable and remove a few
pointless local variables.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Link: https://lore.kernel.org/r/20230413060651.694656-2-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: Christoph Hellwig

block/blk-mq-sched.c

@@ -269,9 +269,7 @@ static int blk_mq_do_dispatch_ctx(struct blk_mq_hw_ctx *hctx)
 
 static int __blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx)
 {
-	struct request_queue *q = hctx->queue;
-	const bool has_sched = q->elevator;
-	int ret = 0;
+	bool need_dispatch = false;
 	LIST_HEAD(rq_list);
 
 	/*
@@ -300,23 +298,22 @@ static int __blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx)
 	 */
 	if (!list_empty(&rq_list)) {
 		blk_mq_sched_mark_restart_hctx(hctx);
-		if (blk_mq_dispatch_rq_list(hctx, &rq_list, 0)) {
-			if (has_sched)
-				ret = blk_mq_do_dispatch_sched(hctx);
-			else
-				ret = blk_mq_do_dispatch_ctx(hctx);
-		}
-	} else if (has_sched) {
-		ret = blk_mq_do_dispatch_sched(hctx);
-	} else if (hctx->dispatch_busy) {
-		/* dequeue request one by one from sw queue if queue is busy */
-		ret = blk_mq_do_dispatch_ctx(hctx);
+		if (!blk_mq_dispatch_rq_list(hctx, &rq_list, 0))
+			return 0;
+		need_dispatch = true;
 	} else {
-		blk_mq_flush_busy_ctxs(hctx, &rq_list);
-		blk_mq_dispatch_rq_list(hctx, &rq_list, 0);
+		need_dispatch = hctx->dispatch_busy;
 	}
 
-	return ret;
+	if (hctx->queue->elevator)
+		return blk_mq_do_dispatch_sched(hctx);
+
+	/* dequeue request one by one from sw queue if queue is busy */
+	if (need_dispatch)
+		return blk_mq_do_dispatch_ctx(hctx);
+	blk_mq_flush_busy_ctxs(hctx, &rq_list);
+	blk_mq_dispatch_rq_list(hctx, &rq_list, 0);
+	return 0;
 }
 
 void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx)