blk-mq: pass obtained budget count to blk_mq_dispatch_rq_list

Pass obtained budget count to blk_mq_dispatch_rq_list(), and prepare
for supporting fully batching submission.

With the obtained budget count, it is easier to put extra budgets
in case of .queue_rq failure.

Meantime remove the old 'got_budget' parameter.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
Tested-by: Baolin Wang <baolin.wang7@gmail.com>
Reviewed-by: Christoph Hellwig <hch@infradead.org>
Cc: Sagi Grimberg <sagi@grimberg.me>
Cc: Baolin Wang <baolin.wang7@gmail.com>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-mq-sched.c

@@ -130,7 +130,7 @@ static int blk_mq_do_dispatch_sched(struct blk_mq_hw_ctx *hctx)
 		 * in blk_mq_dispatch_rq_list().
 		 */
 		list_add(&rq->queuelist, &rq_list);
-	} while (blk_mq_dispatch_rq_list(rq->mq_hctx, &rq_list, true));
+	} while (blk_mq_dispatch_rq_list(rq->mq_hctx, &rq_list, 1));
 
 	return ret;
 }
@@ -198,7 +198,7 @@ static int blk_mq_do_dispatch_ctx(struct blk_mq_hw_ctx *hctx)
 		/* round robin for fair dispatch */
 		ctx = blk_mq_next_ctx(hctx, rq->mq_ctx);
 
-	} while (blk_mq_dispatch_rq_list(rq->mq_hctx, &rq_list, true));
+	} while (blk_mq_dispatch_rq_list(rq->mq_hctx, &rq_list, 1));
 
 	WRITE_ONCE(hctx->dispatch_from, ctx);
 	return ret;
@@ -238,7 +238,7 @@ 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, false)) {
+		if (blk_mq_dispatch_rq_list(hctx, &rq_list, 0)) {
 			if (has_sched_dispatch)
 				ret = blk_mq_do_dispatch_sched(hctx);
 			else
@@ -251,7 +251,7 @@ static int __blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx)
 		ret = blk_mq_do_dispatch_ctx(hctx);
 	} else {
 		blk_mq_flush_busy_ctxs(hctx, &rq_list);
-		blk_mq_dispatch_rq_list(hctx, &rq_list, false);
+		blk_mq_dispatch_rq_list(hctx, &rq_list, 0);
 	}
 
 	return ret;

block/blk-mq.c

@@ -1280,19 +1280,34 @@ static enum prep_dispatch blk_mq_prep_dispatch_rq(struct request *rq,
 		 * we'll re-run it below.
 		 */
 		if (!blk_mq_mark_tag_wait(hctx, rq)) {
-			blk_mq_put_dispatch_budget(rq->q);
+			/*
+			 * All budgets not got from this function will be put
+			 * together during handling partial dispatch
+			 */
+			if (need_budget)
+				blk_mq_put_dispatch_budget(rq->q);
 			return PREP_DISPATCH_NO_TAG;
 		}
 	}
 
 	return PREP_DISPATCH_OK;
 }
 
+/* release all allocated budgets before calling to blk_mq_dispatch_rq_list */
+static void blk_mq_release_budgets(struct request_queue *q,
+		unsigned int nr_budgets)
+{
+	int i;
+
+	for (i = 0; i < nr_budgets; i++)
+		blk_mq_put_dispatch_budget(q);
+}
+
 /*
  * Returns true if we did some work AND can potentially do more.
  */
 bool blk_mq_dispatch_rq_list(struct blk_mq_hw_ctx *hctx, struct list_head *list,
-			     bool got_budget)
+			     unsigned int nr_budgets)
 {
 	enum prep_dispatch prep;
 	struct request_queue *q = hctx->queue;
@@ -1304,7 +1319,7 @@ bool blk_mq_dispatch_rq_list(struct blk_mq_hw_ctx *hctx, struct list_head *list,
 	if (list_empty(list))
 		return false;
 
-	WARN_ON(!list_is_singular(list) && got_budget);
+	WARN_ON(!list_is_singular(list) && nr_budgets);
 
 	/*
 	 * Now process all the entries, sending them to the driver.
@@ -1316,7 +1331,7 @@ bool blk_mq_dispatch_rq_list(struct blk_mq_hw_ctx *hctx, struct list_head *list,
 		rq = list_first_entry(list, struct request, queuelist);
 
 		WARN_ON_ONCE(hctx != rq->mq_hctx);
-		prep = blk_mq_prep_dispatch_rq(rq, !got_budget);
+		prep = blk_mq_prep_dispatch_rq(rq, !nr_budgets);
 		if (prep != PREP_DISPATCH_OK)
 			break;
 
@@ -1335,6 +1350,12 @@ bool blk_mq_dispatch_rq_list(struct blk_mq_hw_ctx *hctx, struct list_head *list,
 			bd.last = !blk_mq_get_driver_tag(nxt);
 		}
 
+		/*
+		 * once the request is queued to lld, no need to cover the
+		 * budget any more
+		 */
+		if (nr_budgets)
+			nr_budgets--;
 		ret = q->mq_ops->queue_rq(hctx, &bd);
 		if (ret == BLK_STS_RESOURCE || ret == BLK_STS_DEV_RESOURCE) {
 			blk_mq_handle_dev_resource(rq, list);
@@ -1376,6 +1397,8 @@ bool blk_mq_dispatch_rq_list(struct blk_mq_hw_ctx *hctx, struct list_head *list,
                         (hctx->flags & BLK_MQ_F_TAG_SHARED);
 		bool no_budget_avail = prep == PREP_DISPATCH_NO_BUDGET;
 
+		blk_mq_release_budgets(q, nr_budgets);
+
 		/*
 		 * If we didn't flush the entire list, we could have told
 		 * the driver there was more coming, but that turned out to

block/blk-mq.h

@@ -40,7 +40,8 @@ struct blk_mq_ctx {
 void blk_mq_exit_queue(struct request_queue *q);
 int blk_mq_update_nr_requests(struct request_queue *q, unsigned int nr);
 void blk_mq_wake_waiters(struct request_queue *q);
-bool blk_mq_dispatch_rq_list(struct blk_mq_hw_ctx *hctx, struct list_head *, bool);
+bool blk_mq_dispatch_rq_list(struct blk_mq_hw_ctx *hctx, struct list_head *,
+			     unsigned int);
 void blk_mq_add_to_requeue_list(struct request *rq, bool at_head,
 				bool kick_requeue_list);
 void blk_mq_flush_busy_ctxs(struct blk_mq_hw_ctx *hctx, struct list_head *list);