[PATCH v2 1/5] blk-mq: account active requests when get driver tag

chengming.zhou
2023-09-13T15:16:56Z

From: Chengming Zhou <zhouchengming@bytedance.com>

There is a limit that batched queue_rqs() can't work on shared tags
queue, since the account of active requests can't be done there.

Now we account the active requests only in blk_mq_get_driver_tag(),
which is not the time we get driver tag actually (with none elevator).

To support batched queue_rqs() on shared tags queue, we move the
account of active requests to where we get the driver tag:

1. none elevator: blk_mq_get_tags() and blk_mq_get_tag()
2. other elevator: __blk_mq_alloc_driver_tag()

This is clearer and match with the unaccount side, which just happen
when we put the driver tag.

The other good point is that we don't need RQF_MQ_INFLIGHT trick
anymore, which used to avoid double account of flush request.
Now we only account when actually get the driver tag, so all is good.
We will remove RQF_MQ_INFLIGHT in the next patch.

Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
---
block/blk-mq.c | 33 +++++++++++------------------
block/blk-mq.h | 56 ++++++++++++++++++++++++++++++++++++--------------
2 files changed, 53 insertions(+), 36 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 1fafd54dce3c..e776388decc3 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -426,6 +426,8 @@ __blk_mq_alloc_requests_batch(struct blk_mq_alloc_data *data)
rq_list_add(data->cached_rq, rq);
nr++;
}
+ if (!(data->rq_flags & RQF_SCHED_TAGS))
+ blk_mq_add_active_requests(data->hctx, nr);
/* caller already holds a reference, add for remainder */
percpu_ref_get_many(&data->q->q_usage_counter, nr - 1);
data->nr_tags -= nr;
@@ -510,6 +512,8 @@ static struct request *__blk_mq_alloc_requests(struct blk_mq_alloc_data *data)
goto retry;
}

+ if (!(data->rq_flags & RQF_SCHED_TAGS))
+ blk_mq_inc_active_requests(data->hctx);
rq = blk_mq_rq_ctx_init(data, blk_mq_tags_from_data(data), tag);
blk_mq_rq_time_init(rq, alloc_time_ns);
return rq;
@@ -669,6 +673,8 @@ struct request *blk_mq_alloc_request_hctx(struct request_queue *q,
tag = blk_mq_get_tag(&data);
if (tag == BLK_MQ_NO_TAG)
goto out_queue_exit;
+ if (!(data.rq_flags & RQF_SCHED_TAGS))
+ blk_mq_inc_active_requests(data.hctx);
rq = blk_mq_rq_ctx_init(&data, blk_mq_tags_from_data(&data), tag);
blk_mq_rq_time_init(rq, alloc_time_ns);
rq->__data_len = 0;
@@ -708,11 +714,10 @@ static void __blk_mq_free_request(struct request *rq)
blk_pm_mark_last_busy(rq);
rq->mq_hctx = NULL;

- if (rq->rq_flags & RQF_MQ_INFLIGHT)
- __blk_mq_dec_active_requests(hctx);
-
- if (rq->tag != BLK_MQ_NO_TAG)
+ if (rq->tag != BLK_MQ_NO_TAG) {
+ blk_mq_dec_active_requests(hctx);
blk_mq_put_tag(hctx->tags, ctx, rq->tag);
+ }
if (sched_tag != BLK_MQ_NO_TAG)
blk_mq_put_tag(hctx->sched_tags, ctx, sched_tag);
blk_mq_sched_restart(hctx);
@@ -1065,8 +1070,7 @@ static inline void blk_mq_flush_tag_batch(struct blk_mq_hw_ctx *hctx,
* All requests should have been marked as RQF_MQ_INFLIGHT, so
* update hctx->nr_active in batch
*/
- if (hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED)
- __blk_mq_sub_active_requests(hctx, nr_tags);
+ blk_mq_sub_active_requests(hctx, nr_tags);

blk_mq_put_tags(hctx->tags, tag_array, nr_tags);
percpu_ref_put_many(&q->q_usage_counter, nr_tags);
@@ -1748,7 +1752,7 @@ struct request *blk_mq_dequeue_from_ctx(struct blk_mq_hw_ctx *hctx,
return data.rq;
}

-static bool __blk_mq_alloc_driver_tag(struct request *rq)
+bool __blk_mq_alloc_driver_tag(struct request *rq)
{
struct sbitmap_queue *bt = &rq->mq_hctx->tags->bitmap_tags;
unsigned int tag_offset = rq->mq_hctx->tags->nr_reserved_tags;
@@ -1769,20 +1773,7 @@ static bool __blk_mq_alloc_driver_tag(struct request *rq)
return false;

rq->tag = tag + tag_offset;
- return true;
-}
-
-bool __blk_mq_get_driver_tag(struct blk_mq_hw_ctx *hctx, struct request *rq)
-{
- if (rq->tag == BLK_MQ_NO_TAG && !__blk_mq_alloc_driver_tag(rq))
- return false;
-
- if ((hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED) &&
- !(rq->rq_flags & RQF_MQ_INFLIGHT)) {
- rq->rq_flags |= RQF_MQ_INFLIGHT;
- __blk_mq_inc_active_requests(hctx);
- }
- hctx->tags->rqs[rq->tag] = rq;
+ blk_mq_inc_active_requests(rq->mq_hctx);
return true;
}

diff --git a/block/blk-mq.h b/block/blk-mq.h
index 1743857e0b01..560a76df290a 100644
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -271,12 +271,18 @@ static inline int blk_mq_get_rq_budget_token(struct request *rq)
return -1;
}

-static inline void __blk_mq_inc_active_requests(struct blk_mq_hw_ctx *hctx)
+static inline void __blk_mq_add_active_requests(struct blk_mq_hw_ctx *hctx,
+ int val)
{
if (blk_mq_is_shared_tags(hctx->flags))
- atomic_inc(&hctx->queue->nr_active_requests_shared_tags);
+ atomic_add(val, &hctx->queue->nr_active_requests_shared_tags);
else
- atomic_inc(&hctx->nr_active);
+ atomic_add(val, &hctx->nr_active);
+}
+
+static inline void __blk_mq_inc_active_requests(struct blk_mq_hw_ctx *hctx)
+{
+ __blk_mq_add_active_requests(hctx, 1);
}

static inline void __blk_mq_sub_active_requests(struct blk_mq_hw_ctx *hctx,
@@ -293,6 +299,32 @@ static inline void __blk_mq_dec_active_requests(struct blk_mq_hw_ctx *hctx)
__blk_mq_sub_active_requests(hctx, 1);
}

+static inline void blk_mq_add_active_requests(struct blk_mq_hw_ctx *hctx,
+ int val)
+{
+ if (hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED)
+ __blk_mq_add_active_requests(hctx, val);
+}
+
+static inline void blk_mq_inc_active_requests(struct blk_mq_hw_ctx *hctx)
+{
+ if (hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED)
+ __blk_mq_inc_active_requests(hctx);
+}
+
+static inline void blk_mq_sub_active_requests(struct blk_mq_hw_ctx *hctx,
+ int val)
+{
+ if (hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED)
+ __blk_mq_sub_active_requests(hctx, val);
+}
+
+static inline void blk_mq_dec_active_requests(struct blk_mq_hw_ctx *hctx)
+{
+ if (hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED)
+ __blk_mq_dec_active_requests(hctx);
+}
+
static inline int __blk_mq_active_requests(struct blk_mq_hw_ctx *hctx)
{
if (blk_mq_is_shared_tags(hctx->flags))
@@ -302,13 +334,9 @@ static inline int __blk_mq_active_requests(struct blk_mq_hw_ctx *hctx)
static inline void __blk_mq_put_driver_tag(struct blk_mq_hw_ctx *hctx,
struct request *rq)
{
+ blk_mq_dec_active_requests(hctx);
blk_mq_put_tag(hctx->tags, rq->mq_ctx, rq->tag);
rq->tag = BLK_MQ_NO_TAG;
-
- if (rq->rq_flags & RQF_MQ_INFLIGHT) {
- rq->rq_flags &= ~RQF_MQ_INFLIGHT;
- __blk_mq_dec_active_requests(hctx);
- }
}

static inline void blk_mq_put_driver_tag(struct request *rq)
@@ -319,19 +347,17 @@ static inline void blk_mq_put_driver_tag(struct request *rq)
__blk_mq_put_driver_tag(rq->mq_hctx, rq);
}

-bool __blk_mq_get_driver_tag(struct blk_mq_hw_ctx *hctx, struct request *rq);
+bool __blk_mq_alloc_driver_tag(struct request *rq);

static inline bool blk_mq_get_driver_tag(struct request *rq)
{
struct blk_mq_hw_ctx *hctx = rq->mq_hctx;

- if (rq->tag != BLK_MQ_NO_TAG &&
- !(hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED)) {
- hctx->tags->rqs[rq->tag] = rq;
- return true;
- }
+ if (rq->tag == BLK_MQ_NO_TAG && !__blk_mq_alloc_driver_tag(rq))
+ return false;

- return __blk_mq_get_driver_tag(hctx, rq);
+ hctx->tags->rqs[rq->tag] = rq;
+ return true;
}

static inline void blk_mq_clear_mq_map(struct blk_mq_queue_map *qmap)
--
2.40.1