1 files changed, 21 insertions, 91 deletions

diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
index 56c493c6cd90..cf9c66c6d35a 100644
--- a/block/blk-mq-sched.c
+++ b/block/blk-mq-sched.c
@@ -59,29 +59,16 @@ static void blk_mq_sched_mark_restart_hctx(struct blk_mq_hw_ctx *hctx)
 	if (test_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state))
 		return;
 
-	if (hctx->flags & BLK_MQ_F_TAG_SHARED) {
-		struct request_queue *q = hctx->queue;
-
-		if (!test_and_set_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state))
-			atomic_inc(&q->shared_hctx_restart);
-	} else
-		set_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state);
+	set_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state);
 }
 
-static bool blk_mq_sched_restart_hctx(struct blk_mq_hw_ctx *hctx)
+void blk_mq_sched_restart(struct blk_mq_hw_ctx *hctx)
 {
 	if (!test_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state))
-		return false;
-
-	if (hctx->flags & BLK_MQ_F_TAG_SHARED) {
-		struct request_queue *q = hctx->queue;
-
-		if (test_and_clear_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state))
-			atomic_dec(&q->shared_hctx_restart);
-	} else
-		clear_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state);
+		return;
+	clear_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state);
 
-	return blk_mq_run_hw_queue(hctx, true);
+	blk_mq_run_hw_queue(hctx, true);
 }
 
 /*
@@ -219,15 +206,8 @@ void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx)
 		}
 	} else if (has_sched_dispatch) {
 		blk_mq_do_dispatch_sched(hctx);
-	} else if (q->mq_ops->get_budget) {
-		/*
-		 * If we need to get budget before queuing request, we
-		 * dequeue request one by one from sw queue for avoiding
-		 * to mess up I/O merge when dispatch runs out of resource.
-		 *
-		 * TODO: get more budgets, and dequeue more requests in
-		 * one time.
-		 */
+	} else if (hctx->dispatch_busy) {
+		/* dequeue request one by one from sw queue if queue is busy */
 		blk_mq_do_dispatch_ctx(hctx);
 	} else {
 		blk_mq_flush_busy_ctxs(hctx, &rq_list);
@@ -339,7 +319,8 @@ bool __blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio)
 		return e->type->ops.mq.bio_merge(hctx, bio);
 	}
 
-	if (hctx->flags & BLK_MQ_F_SHOULD_MERGE) {
+	if ((hctx->flags & BLK_MQ_F_SHOULD_MERGE) &&
+			!list_empty_careful(&ctx->rq_list)) {
 		/* default per sw-queue merge */
 		spin_lock(&ctx->lock);
 		ret = blk_mq_attempt_merge(q, ctx, bio);
@@ -380,68 +361,6 @@ static bool blk_mq_sched_bypass_insert(struct blk_mq_hw_ctx *hctx,
 	return false;
 }
 
-/**
- * list_for_each_entry_rcu_rr - iterate in a round-robin fashion over rcu list
- * @pos:    loop cursor.
- * @skip:   the list element that will not be examined. Iteration starts at
- *          @skip->next.
- * @head:   head of the list to examine. This list must have at least one
- *          element, namely @skip.
- * @member: name of the list_head structure within typeof(*pos).
- */
-#define list_for_each_entry_rcu_rr(pos, skip, head, member)		\
-	for ((pos) = (skip);						\
-	     (pos = (pos)->member.next != (head) ? list_entry_rcu(	\
-			(pos)->member.next, typeof(*pos), member) :	\
-	      list_entry_rcu((pos)->member.next->next, typeof(*pos), member)), \
-	     (pos) != (skip); )
-
-/*
- * Called after a driver tag has been freed to check whether a hctx needs to
- * be restarted. Restarts @hctx if its tag set is not shared. Restarts hardware
- * queues in a round-robin fashion if the tag set of @hctx is shared with other
- * hardware queues.
- */
-void blk_mq_sched_restart(struct blk_mq_hw_ctx *const hctx)
-{
-	struct blk_mq_tags *const tags = hctx->tags;
-	struct blk_mq_tag_set *const set = hctx->queue->tag_set;
-	struct request_queue *const queue = hctx->queue, *q;
-	struct blk_mq_hw_ctx *hctx2;
-	unsigned int i, j;
-
-	if (set->flags & BLK_MQ_F_TAG_SHARED) {
-		/*
-		 * If this is 0, then we know that no hardware queues
-		 * have RESTART marked. We're done.
-		 */
-		if (!atomic_read(&queue->shared_hctx_restart))
-			return;
-
-		rcu_read_lock();
-		list_for_each_entry_rcu_rr(q, queue, &set->tag_list,
-					   tag_set_list) {
-			queue_for_each_hw_ctx(q, hctx2, i)
-				if (hctx2->tags == tags &&
-				    blk_mq_sched_restart_hctx(hctx2))
-					goto done;
-		}
-		j = hctx->queue_num + 1;
-		for (i = 0; i < queue->nr_hw_queues; i++, j++) {
-			if (j == queue->nr_hw_queues)
-				j = 0;
-			hctx2 = queue->queue_hw_ctx[j];
-			if (hctx2->tags == tags &&
-			    blk_mq_sched_restart_hctx(hctx2))
-				break;
-		}
-done:
-		rcu_read_unlock();
-	} else {
-		blk_mq_sched_restart_hctx(hctx);
-	}
-}
-
 void blk_mq_sched_insert_request(struct request *rq, bool at_head,
 				 bool run_queue, bool async)
 {
@@ -486,8 +405,19 @@ void blk_mq_sched_insert_requests(struct request_queue *q,
 
 	if (e && e->type->ops.mq.insert_requests)
 		e->type->ops.mq.insert_requests(hctx, list, false);
-	else
+	else {
+		/*
+		 * try to issue requests directly if the hw queue isn't
+		 * busy in case of 'none' scheduler, and this way may save
+		 * us one extra enqueue & dequeue to sw queue.
+		 */
+		if (!hctx->dispatch_busy && !e && !run_queue_async) {
+			blk_mq_try_issue_list_directly(hctx, list);
+			if (list_empty(list))
+				return;
+		}
 		blk_mq_insert_requests(hctx, ctx, list);
+	}
 
 	blk_mq_run_hw_queue(hctx, run_queue_async);
 }