[PATCH RFC 3/7] blk-mq: support to track active queues from blk_mq_tags

[Yu Kuai]

From: Yu Kuai <yukuai3@xxxxxxxxxx>

In order to refactor how tags is shared, it's necessary to acquire some
information for each disk/hctx, so that more tags can be assigned to the
one with higher pressure.

Prepare to refactor tag sharing.

Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
---
 block/blk-mq-tag.c     | 13 +++++++++++++
 include/linux/blk-mq.h |  2 ++
 include/linux/blkdev.h |  5 +++++
 3 files changed, 20 insertions(+)

diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index 1c2bde917195..8c527e68d4e4 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -64,6 +64,7 @@ void __blk_mq_driver_tag_busy(struct blk_mq_hw_ctx *hctx)
 void __blk_mq_tag_busy(struct blk_mq_hw_ctx *hctx)
 {
 	struct blk_mq_tags *tags = hctx->tags;
+	struct tag_sharing *tag_sharing;
 
 	/*
 	 * calling test_bit() prior to test_and_set_bit() is intentional,
@@ -75,13 +76,18 @@ void __blk_mq_tag_busy(struct blk_mq_hw_ctx *hctx)
 		if (test_bit(QUEUE_FLAG_HCTX_ACTIVE, &q->queue_flags) ||
 		    test_and_set_bit(QUEUE_FLAG_HCTX_ACTIVE, &q->queue_flags))
 			return;
+
+		tag_sharing = &q->tag_sharing;
 	} else {
 		if (test_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state) ||
 		    test_and_set_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
 			return;
+
+		tag_sharing = &hctx->tag_sharing;
 	}
 
 	spin_lock_irq(&tags->lock);
+	list_add(&tag_sharing->node, &tags->ctl.head);
 	WRITE_ONCE(tags->ctl.active_queues, tags->ctl.active_queues + 1);
 	spin_unlock_irq(&tags->lock);
 }
@@ -111,6 +117,7 @@ static void __blk_mq_driver_tag_idle(struct blk_mq_hw_ctx *hctx)
 void __blk_mq_tag_idle(struct blk_mq_hw_ctx *hctx)
 {
 	struct blk_mq_tags *tags = hctx->tags;
+	struct tag_sharing *tag_sharing;
 
 	if (blk_mq_is_shared_tags(hctx->flags)) {
 		struct request_queue *q = hctx->queue;
@@ -118,12 +125,17 @@ void __blk_mq_tag_idle(struct blk_mq_hw_ctx *hctx)
 		if (!test_and_clear_bit(QUEUE_FLAG_HCTX_ACTIVE,
 					&q->queue_flags))
 			return;
+
+		tag_sharing = &q->tag_sharing;
 	} else {
 		if (!test_and_clear_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
 			return;
+
+		tag_sharing = &hctx->tag_sharing;
 	}
 
 	spin_lock_irq(&tags->lock);
+	list_del_init(&tag_sharing->node);
 	__blk_mq_driver_tag_idle(hctx);
 	WRITE_ONCE(tags->ctl.active_queues, tags->ctl.active_queues - 1);
 	WRITE_ONCE(tags->ctl.share_queues, tags->ctl.active_queues);
@@ -619,6 +631,7 @@ struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags,
 	tags->nr_tags = total_tags;
 	tags->nr_reserved_tags = reserved_tags;
 	spin_lock_init(&tags->lock);
+	INIT_LIST_HEAD(&tags->ctl.head);
 
 	if (blk_mq_init_bitmaps(&tags->bitmap_tags, &tags->breserved_tags,
 				total_tags, reserved_tags, node,
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index bc3ac22edb07..639d618e6ca8 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -390,6 +390,7 @@ struct blk_mq_hw_ctx {
 	 * assigned when a request is dispatched from a hardware queue.
 	 */
 	struct blk_mq_tags	*tags;
+	struct tag_sharing	tag_sharing;
 	/**
 	 * @sched_tags: Tags owned by I/O scheduler. If there is an I/O
 	 * scheduler associated with a request queue, a tag is assigned when
@@ -737,6 +738,7 @@ struct request *blk_mq_alloc_request_hctx(struct request_queue *q,
 struct tag_sharing_ctl {
 	unsigned int active_queues;
 	unsigned int share_queues;
+	struct list_head head;
 };
 
 /*
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 0994707f6a68..62f8fcc20c30 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -375,6 +375,10 @@ struct blk_independent_access_ranges {
 	struct blk_independent_access_range	ia_range[];
 };
 
+struct tag_sharing {
+	struct list_head node;
+};
+
 struct request_queue {
 	struct request		*last_merge;
 	struct elevator_queue	*elevator;
@@ -513,6 +517,7 @@ struct request_queue {
 
 	struct blk_mq_tag_set	*tag_set;
 	struct list_head	tag_set_list;
+	struct tag_sharing	tag_sharing;
 
 	struct dentry		*debugfs_dir;
 	struct dentry		*sched_debugfs_dir;
-- 
2.39.2