[PATCH 12/14] blk-mq: introduce pointers to dispatch lock & list

[Ming Lei <ming.lei@redhat.com>]

Prepare to support per-request-queue dispatch list,
so introduce dispatch lock and list for avoiding to
do runtime check.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
 block/blk-mq-debugfs.c | 10 +++++-----
 block/blk-mq.c         |  7 +++++--
 block/blk-mq.h         | 26 +++++++++++++-------------
 include/linux/blk-mq.h |  3 +++
 4 files changed, 26 insertions(+), 20 deletions(-)

diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c
index c4f70b453c76..4f8cddb8505f 100644
--- a/block/blk-mq-debugfs.c
+++ b/block/blk-mq-debugfs.c
@@ -370,23 +370,23 @@ static void *hctx_dispatch_start(struct seq_file *m, loff_t *pos)
 {
 	struct blk_mq_hw_ctx *hctx = m->private;
 
-	spin_lock(&hctx->lock);
-	return seq_list_start(&hctx->dispatch, *pos);
+	spin_lock(hctx->dispatch_lock);
+	return seq_list_start(hctx->dispatch_list, *pos);
 }
 
 static void *hctx_dispatch_next(struct seq_file *m, void *v, loff_t *pos)
 {
 	struct blk_mq_hw_ctx *hctx = m->private;
 
-	return seq_list_next(v, &hctx->dispatch, pos);
+	return seq_list_next(v, hctx->dispatch_list, pos);
 }
 
 static void hctx_dispatch_stop(struct seq_file *m, void *v)
-	__releases(&hctx->lock)
+	__releases(hctx->dispatch_lock)
 {
 	struct blk_mq_hw_ctx *hctx = m->private;
 
-	spin_unlock(&hctx->lock);
+	spin_unlock(hctx->dispatch_lock);
 }
 
 static const struct seq_operations hctx_dispatch_seq_ops = {
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 785145f60c1d..9b8b3a740d18 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1925,8 +1925,11 @@ static void blk_mq_exit_hw_queues(struct request_queue *q,
 static void blk_mq_init_dispatch(struct request_queue *q,
 		struct blk_mq_hw_ctx *hctx)
 {
-	spin_lock_init(&hctx->lock);
-	INIT_LIST_HEAD(&hctx->dispatch);
+	hctx->dispatch_lock = &hctx->lock;
+	hctx->dispatch_list = &hctx->dispatch;
+
+	spin_lock_init(hctx->dispatch_lock);
+	INIT_LIST_HEAD(hctx->dispatch_list);
 }
 
 static int blk_mq_init_hctx(struct request_queue *q,
diff --git a/block/blk-mq.h b/block/blk-mq.h
index 2ed355881996..d9795cbba1bb 100644
--- a/block/blk-mq.h
+++ b/block/blk-mq.h
@@ -152,38 +152,38 @@ static inline void blk_mq_hctx_clear_busy(struct blk_mq_hw_ctx *hctx)
 
 static inline bool blk_mq_has_dispatch_rqs(struct blk_mq_hw_ctx *hctx)
 {
-	return !list_empty_careful(&hctx->dispatch);
+	return !list_empty_careful(hctx->dispatch_list);
 }
 
 static inline void blk_mq_add_rq_to_dispatch(struct blk_mq_hw_ctx *hctx,
 		struct request *rq)
 {
-	spin_lock(&hctx->lock);
-	list_add(&rq->queuelist, &hctx->dispatch);
-	spin_unlock(&hctx->lock);
+	spin_lock(hctx->dispatch_lock);
+	list_add(&rq->queuelist, hctx->dispatch_list);
+	spin_unlock(hctx->dispatch_lock);
 }
 
 static inline void blk_mq_add_list_to_dispatch(struct blk_mq_hw_ctx *hctx,
 		struct list_head *list)
 {
-	spin_lock(&hctx->lock);
-	list_splice_init(list, &hctx->dispatch);
-	spin_unlock(&hctx->lock);
+	spin_lock(hctx->dispatch_lock);
+	list_splice_init(list, hctx->dispatch_list);
+	spin_unlock(hctx->dispatch_lock);
 }
 
 static inline void blk_mq_add_list_to_dispatch_tail(struct blk_mq_hw_ctx *hctx,
 						    struct list_head *list)
 {
-	spin_lock(&hctx->lock);
-	list_splice_tail_init(list, &hctx->dispatch);
-	spin_unlock(&hctx->lock);
+	spin_lock(hctx->dispatch_lock);
+	list_splice_tail_init(list, hctx->dispatch_list);
+	spin_unlock(hctx->dispatch_lock);
 }
 
 static inline void blk_mq_take_list_from_dispatch(struct blk_mq_hw_ctx *hctx,
 		struct list_head *list)
 {
-	spin_lock(&hctx->lock);
-	list_splice_init(&hctx->dispatch, list);
+	spin_lock(hctx->dispatch_lock);
+	list_splice_init(hctx->dispatch_list, list);
 
 	/*
 	 * BUSY won't be cleared until all requests
@@ -191,7 +191,7 @@ static inline void blk_mq_take_list_from_dispatch(struct blk_mq_hw_ctx *hctx,
 	 */
 	if (!list_empty(list))
 		blk_mq_hctx_set_busy(hctx);
-	spin_unlock(&hctx->lock);
+	spin_unlock(hctx->dispatch_lock);
 }
 
 #endif
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index 14f2ad3af31f..016f16c48f72 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -22,6 +22,9 @@ struct blk_mq_hw_ctx {
 
 	unsigned long		flags;		/* BLK_MQ_F_* flags */
 
+	spinlock_t		*dispatch_lock;
+	struct list_head	*dispatch_list;
+
 	void			*sched_data;
 	struct request_queue	*queue;
 	struct blk_flush_queue	*fq;
-- 
2.9.4