[PATCH RFC v7 05/12] blk-mq: Record nr_active_requests per queue for when using shared sbitmap

[John Garry <john.garry@huawei.com>]

The per-hctx nr_active value can no longer be used to fairly assign a share
of tag depth per request queue for when using a shared sbitmap, as it does
not consider that the tags are shared tags over all hctx's.

For this case, record the nr_active_requests per request_queue, and make
the judgment based on that value.

Also introduce a debugfs version of per-hctx blk_mq_debugfs_attr, omitting
hctx_active_show() (as blk_mq_hw_ctx.nr_active is no longer maintained for
the case of shared sbitmap) and other entries which we can add which would
be revised specifically for when using a shared sbitmap.

Co-developed-with: Kashyap Desai <kashyap.desai@broadcom.com>
Signed-off-by: John Garry <john.garry@huawei.com>
---
 block/blk-core.c       |  2 ++
 block/blk-mq-debugfs.c | 23 ++++++++++++++++++++++-
 block/blk-mq-tag.c     | 10 ++++++----
 block/blk-mq.c         |  6 +++---
 block/blk-mq.h         | 28 +++++++++++++++++++++++++++-
 include/linux/blkdev.h |  2 ++
 6 files changed, 62 insertions(+), 9 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index 03252af8c82c..c622453c1363 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -529,6 +529,8 @@ struct request_queue *__blk_alloc_queue(int node_id)
 	q->backing_dev_info->capabilities = BDI_CAP_CGROUP_WRITEBACK;
 	q->node = node_id;
 
+	atomic_set(&q->nr_active_requests_shared_sbitmap, 0);
+
 	timer_setup(&q->backing_dev_info->laptop_mode_wb_timer,
 		    laptop_mode_timer_fn, 0);
 	timer_setup(&q->timeout, blk_rq_timed_out_timer, 0);
diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c
index a400b6698dff..0fa3af41ab65 100644
--- a/block/blk-mq-debugfs.c
+++ b/block/blk-mq-debugfs.c
@@ -796,6 +796,23 @@ static const struct blk_mq_debugfs_attr blk_mq_debugfs_hctx_attrs[] = {
 	{},
 };
 
+static const struct blk_mq_debugfs_attr blk_mq_debugfs_hctx_shared_sbitmap_attrs[] = {
+	{"state", 0400, hctx_state_show},
+	{"flags", 0400, hctx_flags_show},
+	{"dispatch", 0400, .seq_ops = &hctx_dispatch_seq_ops},
+	{"busy", 0400, hctx_busy_show},
+	{"ctx_map", 0400, hctx_ctx_map_show},
+	{"sched_tags", 0400, hctx_sched_tags_show},
+	{"sched_tags_bitmap", 0400, hctx_sched_tags_bitmap_show},
+	{"io_poll", 0600, hctx_io_poll_show, hctx_io_poll_write},
+	{"dispatched", 0600, hctx_dispatched_show, hctx_dispatched_write},
+	{"queued", 0600, hctx_queued_show, hctx_queued_write},
+	{"run", 0600, hctx_run_show, hctx_run_write},
+	{"active", 0400, hctx_active_show},
+	{"dispatch_busy", 0400, hctx_dispatch_busy_show},
+	{}
+};
+
 static const struct blk_mq_debugfs_attr blk_mq_debugfs_ctx_attrs[] = {
 	{"default_rq_list", 0400, .seq_ops = &ctx_default_rq_list_seq_ops},
 	{"read_rq_list", 0400, .seq_ops = &ctx_read_rq_list_seq_ops},
@@ -878,13 +895,17 @@ void blk_mq_debugfs_register_hctx(struct request_queue *q,
 				  struct blk_mq_hw_ctx *hctx)
 {
 	struct blk_mq_ctx *ctx;
+	struct blk_mq_tag_set *set = q->tag_set;
 	char name[20];
 	int i;
 
 	snprintf(name, sizeof(name), "hctx%u", hctx->queue_num);
 	hctx->debugfs_dir = debugfs_create_dir(name, q->debugfs_dir);
 
-	debugfs_create_files(hctx->debugfs_dir, hctx, blk_mq_debugfs_hctx_attrs);
+	if (blk_mq_is_sbitmap_shared(set))
+		debugfs_create_files(hctx->debugfs_dir, hctx, blk_mq_debugfs_hctx_shared_sbitmap_attrs);
+	else
+		debugfs_create_files(hctx->debugfs_dir, hctx, blk_mq_debugfs_hctx_attrs);
 
 	hctx_for_each_ctx(hctx, ctx, i)
 		blk_mq_debugfs_register_ctx(hctx, ctx);
diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index 92843e3e1a2a..7db16e49f6f6 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -60,9 +60,11 @@ void __blk_mq_tag_idle(struct blk_mq_hw_ctx *hctx)
  * For shared tag users, we track the number of currently active users
  * and attempt to provide a fair share of the tag depth for each of them.
  */
-static inline bool hctx_may_queue(struct blk_mq_hw_ctx *hctx,
+static inline bool hctx_may_queue(struct blk_mq_alloc_data *data,
 				  struct sbitmap_queue *bt)
 {
+	struct blk_mq_hw_ctx *hctx = data->hctx;
+	struct request_queue *q = data->q;
 	unsigned int depth, users;
 
 	if (!hctx || !(hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED))
@@ -84,15 +86,15 @@ static inline bool hctx_may_queue(struct blk_mq_hw_ctx *hctx,
 	 * Allow at least some tags
 	 */
 	depth = max((bt->sb.depth + users - 1) / users, 4U);
-	return atomic_read(&hctx->nr_active) < depth;
+	return __blk_mq_active_requests(hctx, q) < depth;
 }
 
 static int __blk_mq_get_tag(struct blk_mq_alloc_data *data,
 			    struct sbitmap_queue *bt)
 {
 	if (!(data->flags & BLK_MQ_REQ_INTERNAL) &&
-	    !hctx_may_queue(data->hctx, bt))
-		return BLK_MQ_NO_TAG;
+	    !hctx_may_queue(data, bt))
+		return -1;
 	if (data->shallow_depth)
 		return __sbitmap_queue_get_shallow(bt, data->shallow_depth);
 	else
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 77120dd4e4d5..0f7e062a1665 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -283,7 +283,7 @@ static struct request *blk_mq_rq_ctx_init(struct blk_mq_alloc_data *data,
 	} else {
 		if (data->hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED) {
 			rq_flags = RQF_MQ_INFLIGHT;
-			atomic_inc(&data->hctx->nr_active);
+			__blk_mq_inc_active_requests(data->hctx, data->q);
 		}
 		rq->tag = tag;
 		rq->internal_tag = BLK_MQ_NO_TAG;
@@ -527,7 +527,7 @@ void blk_mq_free_request(struct request *rq)
 
 	ctx->rq_completed[rq_is_sync(rq)]++;
 	if (rq->rq_flags & RQF_MQ_INFLIGHT)
-		atomic_dec(&hctx->nr_active);
+		__blk_mq_dec_active_requests(hctx, q);
 
 	if (unlikely(laptop_mode && !blk_rq_is_passthrough(rq)))
 		laptop_io_completion(q->backing_dev_info);
@@ -1073,7 +1073,7 @@ bool blk_mq_get_driver_tag(struct request *rq)
 	if (rq->tag >= 0) {
 		if (shared) {
 			rq->rq_flags |= RQF_MQ_INFLIGHT;
-			atomic_inc(&data.hctx->nr_active);
+			__blk_mq_inc_active_requests(rq->mq_hctx, rq->q);
 		}
 		data.hctx->tags->rqs[rq->tag] = rq;
 	}
diff --git a/block/blk-mq.h b/block/blk-mq.h
index 1a283c707215..9c1e612c2298 100644
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -202,6 +202,32 @@ static inline bool blk_mq_get_dispatch_budget(struct blk_mq_hw_ctx *hctx)
 	return true;
 }
 
+static inline void __blk_mq_inc_active_requests(struct blk_mq_hw_ctx *hctx,
+						struct request_queue *q)
+{
+	if (blk_mq_is_sbitmap_shared(q->tag_set))
+		atomic_inc(&q->nr_active_requests_shared_sbitmap);
+	else
+		atomic_inc(&hctx->nr_active);
+}
+
+static inline void __blk_mq_dec_active_requests(struct blk_mq_hw_ctx *hctx,
+						struct request_queue *q)
+{
+	if (blk_mq_is_sbitmap_shared(q->tag_set))
+		atomic_dec(&q->nr_active_requests_shared_sbitmap);
+	else
+		atomic_dec(&hctx->nr_active);
+}
+
+static inline int __blk_mq_active_requests(struct blk_mq_hw_ctx *hctx,
+					   struct request_queue *q)
+{
+	if (blk_mq_is_sbitmap_shared(q->tag_set))
+		return atomic_read(&q->nr_active_requests_shared_sbitmap);
+	return atomic_read(&hctx->nr_active);
+}
+
 static inline void __blk_mq_put_driver_tag(struct blk_mq_hw_ctx *hctx,
 					   struct request *rq)
 {
@@ -210,7 +236,7 @@ static inline void __blk_mq_put_driver_tag(struct blk_mq_hw_ctx *hctx,
 
 	if (rq->rq_flags & RQF_MQ_INFLIGHT) {
 		rq->rq_flags &= ~RQF_MQ_INFLIGHT;
-		atomic_dec(&hctx->nr_active);
+		__blk_mq_dec_active_requests(hctx, rq->q);
 	}
 }
 
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 8fd900998b4e..c536278bec9e 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -488,6 +488,8 @@ struct request_queue {
 	struct timer_list	timeout;
 	struct work_struct	timeout_work;
 
+	atomic_t		nr_active_requests_shared_sbitmap;
+
 	struct list_head	icq_list;
 #ifdef CONFIG_BLK_CGROUP
 	DECLARE_BITMAP		(blkcg_pols, BLKCG_MAX_POLS);
-- 
2.26.2