#ifndef RQ_QOS_H
  #define RQ_QOS_H
  
  #include <linux/kernel.h>
  #include <linux/blkdev.h>
  #include <linux/blk_types.h>
  #include <linux/atomic.h>
  #include <linux/wait.h>
  
  enum rq_qos_id {
  	RQ_QOS_WBT,
  	RQ_QOS_CGROUP,
  };
  
  struct rq_wait {
  	wait_queue_head_t wait;
  	atomic_t inflight;
  };
  
  struct rq_qos {
  	struct rq_qos_ops *ops;
  	struct request_queue *q;
  	enum rq_qos_id id;
  	struct rq_qos *next;
  };
  
  struct rq_qos_ops {

  	void (*throttle)(struct rq_qos *, struct bio *, spinlock_t *);
  	void (*track)(struct rq_qos *, struct request *, struct bio *);

  	void (*issue)(struct rq_qos *, struct request *);
  	void (*requeue)(struct rq_qos *, struct request *);
  	void (*done)(struct rq_qos *, struct request *);

  	void (*done_bio)(struct rq_qos *, struct bio *);

  	void (*cleanup)(struct rq_qos *, struct bio *);

  	void (*exit)(struct rq_qos *);
  };
  
  struct rq_depth {
  	unsigned int max_depth;
  
  	int scale_step;
  	bool scaled_max;
  
  	unsigned int queue_depth;
  	unsigned int default_depth;
  };
  
  static inline struct rq_qos *rq_qos_id(struct request_queue *q,
  				       enum rq_qos_id id)
  {
  	struct rq_qos *rqos;
  	for (rqos = q->rq_qos; rqos; rqos = rqos->next) {
  		if (rqos->id == id)
  			break;
  	}
  	return rqos;
  }
  
  static inline struct rq_qos *wbt_rq_qos(struct request_queue *q)
  {
  	return rq_qos_id(q, RQ_QOS_WBT);
  }
  
  static inline struct rq_qos *blkcg_rq_qos(struct request_queue *q)
  {
  	return rq_qos_id(q, RQ_QOS_CGROUP);
  }
  
  static inline void rq_wait_init(struct rq_wait *rq_wait)
  {
  	atomic_set(&rq_wait->inflight, 0);
  	init_waitqueue_head(&rq_wait->wait);
  }
  
  static inline void rq_qos_add(struct request_queue *q, struct rq_qos *rqos)
  {
  	rqos->next = q->rq_qos;
  	q->rq_qos = rqos;
  }
  
  static inline void rq_qos_del(struct request_queue *q, struct rq_qos *rqos)
  {
  	struct rq_qos *cur, *prev = NULL;
  	for (cur = q->rq_qos; cur; cur = cur->next) {
  		if (cur == rqos) {
  			if (prev)
  				prev->next = rqos->next;
  			else
  				q->rq_qos = cur;
  			break;
  		}
  		prev = cur;
  	}
  }

  bool rq_wait_inc_below(struct rq_wait *rq_wait, unsigned int limit);

  void rq_depth_scale_up(struct rq_depth *rqd);
  void rq_depth_scale_down(struct rq_depth *rqd, bool hard_throttle);
  bool rq_depth_calc_max_depth(struct rq_depth *rqd);

  void rq_qos_cleanup(struct request_queue *, struct bio *);

  void rq_qos_done(struct request_queue *, struct request *);
  void rq_qos_issue(struct request_queue *, struct request *);
  void rq_qos_requeue(struct request_queue *, struct request *);

  void rq_qos_done_bio(struct request_queue *q, struct bio *bio);

  void rq_qos_throttle(struct request_queue *, struct bio *, spinlock_t *);
  void rq_qos_track(struct request_queue *q, struct request *, struct bio *);

  void rq_qos_exit(struct request_queue *);
  #endif