[PATCH RFC 1/7] blk-mq: factor out a structure from blk_mq_tags to control tag sharing

Yu Kuai
2023-06-18T08:09:07Z

From: Yu Kuai <yukuai3@huawei.com>

Currently tags is fair shared, and the new structure contains only one
field active_queues. There are no functional changes and prepare to
refactor tag sharing.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
---
block/blk-mq-debugfs.c | 2 +-
block/blk-mq-tag.c | 8 ++++----
block/blk-mq.h | 2 +-
include/linux/blk-mq.h | 10 ++++++++--
4 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c
index c3b5930106b2..431aaa3eb181 100644
--- a/block/blk-mq-debugfs.c
+++ b/block/blk-mq-debugfs.c
@@ -401,7 +401,7 @@ static void blk_mq_debugfs_tags_show(struct seq_file *m,
seq_printf(m, "nr_tags=%u\n", tags->nr_tags);
seq_printf(m, "nr_reserved_tags=%u\n", tags->nr_reserved_tags);
seq_printf(m, "active_queues=%d\n",
- READ_ONCE(tags->active_queues));
+ READ_ONCE(tags->ctl.active_queues));

seq_puts(m, "\nbitmap_tags:\n");
sbitmap_queue_show(&tags->bitmap_tags, m);
diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index cc57e2dd9a0b..fe41a0d34fc0 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -57,8 +57,8 @@ void __blk_mq_tag_busy(struct blk_mq_hw_ctx *hctx)
}

spin_lock_irq(&tags->lock);
- users = tags->active_queues + 1;
- WRITE_ONCE(tags->active_queues, users);
+ users = tags->ctl.active_queues + 1;
+ WRITE_ONCE(tags->ctl.active_queues, users);
blk_mq_update_wake_batch(tags, users);
spin_unlock_irq(&tags->lock);
}
@@ -94,8 +94,8 @@ void __blk_mq_tag_idle(struct blk_mq_hw_ctx *hctx)
}

spin_lock_irq(&tags->lock);
- users = tags->active_queues - 1;
- WRITE_ONCE(tags->active_queues, users);
+ users = tags->ctl.active_queues - 1;
+ WRITE_ONCE(tags->ctl.active_queues, users);
blk_mq_update_wake_batch(tags, users);
spin_unlock_irq(&tags->lock);

diff --git a/block/blk-mq.h b/block/blk-mq.h
index 1743857e0b01..ca1c13127868 100644
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -412,7 +412,7 @@ static inline bool hctx_may_queue(struct blk_mq_hw_ctx *hctx,
return true;
}

- users = READ_ONCE(hctx->tags->active_queues);
+ users = READ_ONCE(hctx->tags->ctl.active_queues);
if (!users)
return true;

diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index f401067ac03a..8d2cd6b9d305 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -733,13 +733,16 @@ struct request *blk_mq_alloc_request_hctx(struct request_queue *q,
blk_opf_t opf, blk_mq_req_flags_t flags,
unsigned int hctx_idx);

+struct tag_sharing_ctl {
+ unsigned int active_queues;
+};
+
/*
* Tag address space map.
*/
struct blk_mq_tags {
unsigned int nr_tags;
unsigned int nr_reserved_tags;
- unsigned int active_queues;

struct sbitmap_queue bitmap_tags;
struct sbitmap_queue breserved_tags;
@@ -750,9 +753,12 @@ struct blk_mq_tags {

/*
* used to clear request reference in rqs[] before freeing one
- * request pool
+ * request pool, and to protect tag_sharing_ctl.
*/
spinlock_t lock;
+
+ /* used when tags is shared for multiple request_queue or hctx. */
+ struct tag_sharing_ctl ctl;
};

static inline struct request *blk_mq_tag_to_rq(struct blk_mq_tags *tags,
--
2.39.2