[RFC V2 2/6] blk-wbt: make wbt pluggable

["Wang Jianchao (Kuaishou)" <jianchao.wan9@gmail.com>]

This patch makes wbt pluggable through /sys/block/xxx/queue/qos.

Signed-off-by: Wang Jianchao (Kuaishou) <jianchao.wan9@gmail.com>
---
 block/blk-mq-debugfs.c |  2 --
 block/blk-rq-qos.h     |  8 ++------
 block/blk-sysfs.c      |  7 ++-----
 block/blk-wbt.c        | 30 +++++++++++++++++++++++++-----
 block/blk-wbt.h        |  8 ++++----
 5 files changed, 33 insertions(+), 22 deletions(-)

diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c
index 30f064872581..c7b17576a65f 100644
--- a/block/blk-mq-debugfs.c
+++ b/block/blk-mq-debugfs.c
@@ -823,8 +823,6 @@ void blk_mq_debugfs_unregister_sched(struct request_queue *q)
 static const char *rq_qos_id_to_name(enum rq_qos_id id)
 {
 	switch (id) {
-	case RQ_QOS_WBT:
-		return "wbt";
 	case RQ_QOS_LATENCY:
 		return "latency";
 	case RQ_QOS_COST:
diff --git a/block/blk-rq-qos.h b/block/blk-rq-qos.h
index c2b9b41f8fd4..de82eb951bdd 100644
--- a/block/blk-rq-qos.h
+++ b/block/blk-rq-qos.h
@@ -14,7 +14,6 @@
 struct blk_mq_debugfs_attr;
 
 enum rq_qos_id {
-	RQ_QOS_WBT,
 	RQ_QOS_LATENCY,
 	RQ_QOS_COST,
 	RQ_QOS_IOPRIO,
@@ -86,11 +85,6 @@ static inline struct rq_qos *rq_qos_by_id(struct request_queue *q, int id)
 	return rqos;
 }
 
-static inline struct rq_qos *wbt_rq_qos(struct request_queue *q)
-{
-	return rq_qos_by_id(q, RQ_QOS_WBT);
-}
-
 static inline struct rq_qos *blkcg_rq_qos(struct request_queue *q)
 {
 	return rq_qos_by_id(q, RQ_QOS_LATENCY);
@@ -158,6 +152,8 @@ ssize_t queue_qos_store(struct request_queue *q, const char *page,
 			  size_t count);
 struct rq_qos *rq_qos_get(struct request_queue *q, int id);
 void rq_qos_put(struct rq_qos *rqos);
+int rq_qos_switch(struct request_queue *q, const struct rq_qos_ops *ops,
+		struct rq_qos *rqos);
 
 static inline struct rq_qos *rq_qos_by_name(struct request_queue *q,
 		const char *name)
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index c02747db4e3b..f9021cf10d06 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -483,11 +483,8 @@ static ssize_t queue_wb_lat_store(struct request_queue *q, const char *page,
 		return -EINVAL;
 
 	rqos = wbt_rq_qos(q);
-	if (!rqos) {
-		ret = wbt_init(q);
-		if (ret)
-			return ret;
-	}
+	if (!rqos)
+		return -EOPNOTSUPP;
 
 	if (val == -1)
 		val = wbt_default_latency_nsec(q);
diff --git a/block/blk-wbt.c b/block/blk-wbt.c
index 88265ae4fa41..ce4b41e50564 100644
--- a/block/blk-wbt.c
+++ b/block/blk-wbt.c
@@ -31,6 +31,13 @@
 #define CREATE_TRACE_POINTS
 #include <trace/events/wbt.h>
 
+static struct rq_qos_ops wbt_rqos_ops;
+
+struct rq_qos *wbt_rq_qos(struct request_queue *q)
+{
+	return rq_qos_by_id(q, wbt_rqos_ops.id);
+}
+
 static inline void wbt_clear_state(struct request *rq)
 {
 	rq->wbt_flags = 0;
@@ -656,7 +663,7 @@ void wbt_enable_default(struct request_queue *q)
 		return;
 
 	if (queue_is_mq(q) && IS_ENABLED(CONFIG_BLK_WBT_MQ))
-		wbt_init(q);
+		rq_qos_switch(q, &wbt_rqos_ops, NULL);
 }
 EXPORT_SYMBOL_GPL(wbt_enable_default);
 
@@ -696,6 +703,7 @@ static void wbt_exit(struct rq_qos *rqos)
 	struct rq_wb *rwb = RQWB(rqos);
 	struct request_queue *q = rqos->q;
 
+	rq_qos_deactivate(rqos);
 	blk_stat_remove_callback(q, rwb->cb);
 	blk_stat_free_callback(rwb->cb);
 	kfree(rwb);
@@ -806,7 +814,9 @@ static const struct blk_mq_debugfs_attr wbt_debugfs_attrs[] = {
 };
 #endif
 
+int wbt_init(struct request_queue *q);
 static struct rq_qos_ops wbt_rqos_ops = {
+	.name = "wbt",
 	.throttle = wbt_wait,
 	.issue = wbt_issue,
 	.track = wbt_track,
@@ -815,6 +825,7 @@ static struct rq_qos_ops wbt_rqos_ops = {
 	.cleanup = wbt_cleanup,
 	.queue_depth_changed = wbt_queue_depth_changed,
 	.exit = wbt_exit,
+	.init = wbt_init,
 #ifdef CONFIG_BLK_DEBUG_FS
 	.debugfs_attrs = wbt_debugfs_attrs,
 #endif
@@ -838,9 +849,6 @@ int wbt_init(struct request_queue *q)
 	for (i = 0; i < WBT_NUM_RWQ; i++)
 		rq_wait_init(&rwb->rq_wait[i]);
 
-	rwb->rqos.id = RQ_QOS_WBT;
-	rwb->rqos.ops = &wbt_rqos_ops;
-	rwb->rqos.q = q;
 	rwb->last_comp = rwb->last_issue = jiffies;
 	rwb->win_nsec = RWB_WINDOW_NSEC;
 	rwb->enable_state = WBT_STATE_ON_DEFAULT;
@@ -850,7 +858,7 @@ int wbt_init(struct request_queue *q)
 	/*
 	 * Assign rwb and add the stats callback.
 	 */
-	rq_qos_add(q, &rwb->rqos);
+	rq_qos_activate(q, &rwb->rqos, &wbt_rqos_ops);
 	blk_stat_add_callback(q, rwb->cb);
 
 	rwb->min_lat_nsec = wbt_default_latency_nsec(q);
@@ -860,3 +868,15 @@ int wbt_init(struct request_queue *q)
 
 	return 0;
 }
+
+static __init int wbt_mod_init(void)
+{
+	return rq_qos_register(&wbt_rqos_ops);
+}
+
+static __exit void wbt_mod_exit(void)
+{
+	return rq_qos_unregister(&wbt_rqos_ops);
+}
+module_init(wbt_mod_init);
+module_exit(wbt_mod_exit);
diff --git a/block/blk-wbt.h b/block/blk-wbt.h
index 2eb01becde8c..72e9602df330 100644
--- a/block/blk-wbt.h
+++ b/block/blk-wbt.h
@@ -88,7 +88,7 @@ static inline unsigned int wbt_inflight(struct rq_wb *rwb)
 
 #ifdef CONFIG_BLK_WBT
 
-int wbt_init(struct request_queue *);
+struct rq_qos *wbt_rq_qos(struct request_queue *q);
 void wbt_disable_default(struct request_queue *);
 void wbt_enable_default(struct request_queue *);
 
@@ -101,12 +101,12 @@ u64 wbt_default_latency_nsec(struct request_queue *);
 
 #else
 
-static inline void wbt_track(struct request *rq, enum wbt_flags flags)
+static inline struct rq_qos *wbt_rq_qos(struct request_queue *q)
 {
+	return NULL;
 }
-static inline int wbt_init(struct request_queue *q)
+static inline void wbt_track(struct request *rq, enum wbt_flags flags)
 {
-	return -EINVAL;
 }
 static inline void wbt_disable_default(struct request_queue *q)
 {
-- 
2.17.1