From 200e86b3372b51e136a382e007b6b904b1dac7e4 Mon Sep 17 00:00:00 2001
From: Jens Axboe <axboe@fb.com>
Date: Wed, 25 Jan 2017 08:11:38 -0700
Subject: [PATCH] blk-mq: only apply active queue tag throttling for driver
 tags

If we have a scheduler attached, we have two sets of tags. We don't
want to apply our active queue throttling for the scheduler side
of tags, that only applies to driver tags since that's the resource
we need to dispatch an IO.

Signed-off-by: Jens Axboe <axboe@fb.com>
---
 block/blk-mq-tag.c | 12 +++++++-----
 block/blk-mq.c     | 13 ++++++++-----
 2 files changed, 15 insertions(+), 10 deletions(-)

diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index a49ec77c415a..1b156ca79af6 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -90,9 +90,11 @@ static inline bool hctx_may_queue(struct blk_mq_hw_ctx *hctx,
 	return atomic_read(&hctx->nr_active) < depth;
 }
 
-static int __blk_mq_get_tag(struct blk_mq_hw_ctx *hctx, struct sbitmap_queue *bt)
+static int __blk_mq_get_tag(struct blk_mq_alloc_data *data,
+			    struct sbitmap_queue *bt)
 {
-	if (!hctx_may_queue(hctx, bt))
+	if (!(data->flags & BLK_MQ_REQ_INTERNAL) &&
+	    !hctx_may_queue(data->hctx, bt))
 		return -1;
 	return __sbitmap_queue_get(bt);
 }
@@ -118,7 +120,7 @@ unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data)
 		tag_offset = tags->nr_reserved_tags;
 	}
 
-	tag = __blk_mq_get_tag(data->hctx, bt);
+	tag = __blk_mq_get_tag(data, bt);
 	if (tag != -1)
 		goto found_tag;
 
@@ -129,7 +131,7 @@ unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data)
 	do {
 		prepare_to_wait(&ws->wait, &wait, TASK_UNINTERRUPTIBLE);
 
-		tag = __blk_mq_get_tag(data->hctx, bt);
+		tag = __blk_mq_get_tag(data, bt);
 		if (tag != -1)
 			break;
 
@@ -144,7 +146,7 @@ unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data)
 		 * Retry tag allocation after running the hardware queue,
 		 * as running the queue may also have found completions.
 		 */
-		tag = __blk_mq_get_tag(data->hctx, bt);
+		tag = __blk_mq_get_tag(data, bt);
 		if (tag != -1)
 			break;
 
diff --git a/block/blk-mq.c b/block/blk-mq.c
index ee69e5e89769..dcb567642db7 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -230,15 +230,14 @@ struct request *__blk_mq_alloc_request(struct blk_mq_alloc_data *data,
 
 		rq = tags->static_rqs[tag];
 
-		if (blk_mq_tag_busy(data->hctx)) {
-			rq->rq_flags = RQF_MQ_INFLIGHT;
-			atomic_inc(&data->hctx->nr_active);
-		}
-
 		if (data->flags & BLK_MQ_REQ_INTERNAL) {
 			rq->tag = -1;
 			rq->internal_tag = tag;
 		} else {
+			if (blk_mq_tag_busy(data->hctx)) {
+				rq->rq_flags = RQF_MQ_INFLIGHT;
+				atomic_inc(&data->hctx->nr_active);
+			}
 			rq->tag = tag;
 			rq->internal_tag = -1;
 		}
@@ -869,6 +868,10 @@ static bool blk_mq_get_driver_tag(struct request *rq,
 
 	rq->tag = blk_mq_get_tag(&data);
 	if (rq->tag >= 0) {
+		if (blk_mq_tag_busy(data.hctx)) {
+			rq->rq_flags |= RQF_MQ_INFLIGHT;
+			atomic_inc(&data.hctx->nr_active);
+		}
 		data.hctx->tags->rqs[rq->tag] = rq;
 		goto done;
 	}
-- 
GitLab