[RFC V3 4/6] blk-iocost: make iocost pluggable

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

Make blk-iocost pluggable. Then we can close or open it through
/sys/block/xxx/queue/qos.

Signed-off-by: Wang Jianchao (Kuaishou) <jianchao.wan9@gmail.com>
---
 block/blk-iocost.c     | 49 ++++++++++++++++++++++++++----------------
 block/blk-mq-debugfs.c |  2 --
 block/blk-rq-qos.h     |  1 -
 3 files changed, 30 insertions(+), 22 deletions(-)

diff --git a/block/blk-iocost.c b/block/blk-iocost.c
index 769b64394298..73978b540e37 100644
--- a/block/blk-iocost.c
+++ b/block/blk-iocost.c
@@ -660,9 +660,10 @@ static struct ioc *rqos_to_ioc(struct rq_qos *rqos)
 	return container_of(rqos, struct ioc, rqos);
 }
 
+static struct rq_qos_ops ioc_rqos_ops;
 static struct ioc *q_to_ioc(struct request_queue *q)
 {
-	return rqos_to_ioc(rq_qos_id(q, RQ_QOS_COST));
+	return rqos_to_ioc(rq_qos_by_id(q, ioc_rqos_ops.id));
 }
 
 static const char *q_name(struct request_queue *q)
@@ -2810,6 +2811,7 @@ static void ioc_rqos_exit(struct rq_qos *rqos)
 	struct ioc *ioc = rqos_to_ioc(rqos);
 
 	blkcg_deactivate_policy(rqos->q, &blkcg_policy_iocost);
+	rq_qos_deactivate(rqos);
 
 	spin_lock_irq(&ioc->lock);
 	ioc->running = IOC_STOP;
@@ -2820,13 +2822,17 @@ static void ioc_rqos_exit(struct rq_qos *rqos)
 	kfree(ioc);
 }
 
+static int blk_iocost_init(struct request_queue *q);
 static struct rq_qos_ops ioc_rqos_ops = {
+	.name = "iocost",
+	.flags = RQOS_FLAG_CGRP_POL,
 	.throttle = ioc_rqos_throttle,
 	.merge = ioc_rqos_merge,
 	.done_bio = ioc_rqos_done_bio,
 	.done = ioc_rqos_done,
 	.queue_depth_changed = ioc_rqos_queue_depth_changed,
 	.exit = ioc_rqos_exit,
+	.init = blk_iocost_init,
 };
 
 static int blk_iocost_init(struct request_queue *q)
@@ -2856,10 +2862,7 @@ static int blk_iocost_init(struct request_queue *q)
 	}
 
 	rqos = &ioc->rqos;
-	rqos->id = RQ_QOS_COST;
-	rqos->ops = &ioc_rqos_ops;
-	rqos->q = q;
-
+	rq_qos_activate(q, rqos, &ioc_rqos_ops);
 	spin_lock_init(&ioc->lock);
 	timer_setup(&ioc->timer, ioc_timer_fn, 0);
 	INIT_LIST_HEAD(&ioc->active_iocgs);
@@ -2883,10 +2886,9 @@ static int blk_iocost_init(struct request_queue *q)
 	 * called before policy activation completion, can't assume that the
 	 * target bio has an iocg associated and need to test for NULL iocg.
 	 */
-	rq_qos_add(q, rqos);
 	ret = blkcg_activate_policy(q, &blkcg_policy_iocost);
 	if (ret) {
-		rq_qos_del(q, rqos);
+		rq_qos_deactivate(rqos);
 		free_percpu(ioc->pcpu_stat);
 		kfree(ioc);
 		return ret;
@@ -3162,6 +3164,7 @@ static ssize_t ioc_qos_write(struct kernfs_open_file *of, char *input,
 			     size_t nbytes, loff_t off)
 {
 	struct block_device *bdev;
+	struct rq_qos *rqos;
 	struct ioc *ioc;
 	u32 qos[NR_QOS_PARAMS];
 	bool enable, user;
@@ -3172,12 +3175,10 @@ static ssize_t ioc_qos_write(struct kernfs_open_file *of, char *input,
 	if (IS_ERR(bdev))
 		return PTR_ERR(bdev);
 
-	ioc = q_to_ioc(bdev_get_queue(bdev));
-	if (!ioc) {
-		ret = blk_iocost_init(bdev_get_queue(bdev));
-		if (ret)
-			goto err;
-		ioc = q_to_ioc(bdev_get_queue(bdev));
+	rqos = rq_qos_get(bdev_get_queue(bdev), ioc_rqos_ops.id);
+	if (!rqos) {
+		ret = -EOPNOTSUPP;
+		goto err;
 	}
 
 	spin_lock_irq(&ioc->lock);
@@ -3329,6 +3330,7 @@ static ssize_t ioc_cost_model_write(struct kernfs_open_file *of, char *input,
 				    size_t nbytes, loff_t off)
 {
 	struct block_device *bdev;
+	struct rq_qos *rqos;
 	struct ioc *ioc;
 	u64 u[NR_I_LCOEFS];
 	bool user;
@@ -3339,12 +3341,10 @@ static ssize_t ioc_cost_model_write(struct kernfs_open_file *of, char *input,
 	if (IS_ERR(bdev))
 		return PTR_ERR(bdev);
 
-	ioc = q_to_ioc(bdev_get_queue(bdev));
+	rqos = rq_qos_get(bdev_get_queue(bdev), ioc_rqos_ops.id);
 	if (!ioc) {
-		ret = blk_iocost_init(bdev_get_queue(bdev));
-		if (ret)
-			goto err;
-		ioc = q_to_ioc(bdev_get_queue(bdev));
+		ret = -EOPNOTSUPP;
+		goto err;
 	}
 
 	spin_lock_irq(&ioc->lock);
@@ -3441,12 +3441,23 @@ static struct blkcg_policy blkcg_policy_iocost = {
 
 static int __init ioc_init(void)
 {
-	return blkcg_policy_register(&blkcg_policy_iocost);
+	int ret;
+
+	ret = rq_qos_register(&ioc_rqos_ops);
+	if (ret)
+		return ret;
+
+	ret = blkcg_policy_register(&blkcg_policy_iocost);
+	if (ret)
+		rq_qos_unregister(&ioc_rqos_ops);
+
+	return ret;
 }
 
 static void __exit ioc_exit(void)
 {
 	blkcg_policy_unregister(&blkcg_policy_iocost);
+	rq_qos_unregister(&ioc_rqos_ops);
 }
 
 module_init(ioc_init);
diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c
index ec1f74bdea74..652cd754dbd3 100644
--- a/block/blk-mq-debugfs.c
+++ b/block/blk-mq-debugfs.c
@@ -826,8 +826,6 @@ 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_COST:
-		return "cost";
 	case RQ_QOS_IOPRIO:
 		return "ioprio";
 	}
diff --git a/block/blk-rq-qos.h b/block/blk-rq-qos.h
index 2a919db52fef..6d691527cb51 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_COST,
 	RQ_QOS_IOPRIO,
 };
 
-- 
2.17.1