#ifndef _BLK_CGROUP_H
  #define _BLK_CGROUP_H
  /*
   * Common Block IO controller cgroup interface
   *
   * Based on ideas and code from CFQ, CFS and BFQ:
   * Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
   *
   * Copyright (C) 2008 Fabio Checconi <fabio@gandalf.sssup.it>
   *		      Paolo Valente <paolo.valente@unimore.it>
   *
   * Copyright (C) 2009 Vivek Goyal <vgoyal@redhat.com>
   * 	              Nauman Rafique <nauman@google.com>
   */
  
  #include <linux/cgroup.h>

  #include <linux/u64_stats_sync.h>

  #include <linux/seq_file.h>

  #include <linux/radix-tree.h>

  #include <linux/blkdev.h>

  /* Max limits for throttle policy */
  #define THROTL_IOPS_MAX		UINT_MAX

  /* CFQ specific, out here for blkcg->cfq_weight */
  #define CFQ_WEIGHT_MIN		10
  #define CFQ_WEIGHT_MAX		1000
  #define CFQ_WEIGHT_DEFAULT	500

  #ifdef CONFIG_BLK_CGROUP

  enum blkg_rwstat_type {
  	BLKG_RWSTAT_READ,
  	BLKG_RWSTAT_WRITE,
  	BLKG_RWSTAT_SYNC,
  	BLKG_RWSTAT_ASYNC,
  
  	BLKG_RWSTAT_NR,
  	BLKG_RWSTAT_TOTAL = BLKG_RWSTAT_NR,

  };

  struct blkcg_gq;

  struct blkcg {

  	struct cgroup_subsys_state	css;
  	spinlock_t			lock;

  
  	struct radix_tree_root		blkg_tree;
  	struct blkcg_gq			*blkg_hint;

  	struct hlist_head		blkg_list;

  
  	/* for policies to test whether associated blkcg has changed */

  	uint64_t			id;

  	/* TODO: per-policy storage in blkcg */

  	unsigned int			cfq_weight;	/* belongs to cfq */

  	unsigned int			cfq_leaf_weight;

  };

  struct blkg_stat {
  	struct u64_stats_sync		syncp;
  	uint64_t			cnt;
  };
  
  struct blkg_rwstat {
  	struct u64_stats_sync		syncp;
  	uint64_t			cnt[BLKG_RWSTAT_NR];
  };

  /*
   * A blkcg_gq (blkg) is association between a block cgroup (blkcg) and a
   * request_queue (q).  This is used by blkcg policies which need to track
   * information per blkcg - q pair.
   *
   * There can be multiple active blkcg policies and each has its private
   * data on each blkg, the size of which is determined by
   * blkcg_policy->pd_size.  blkcg core allocates and frees such areas
   * together with blkg and invokes pd_init/exit_fn() methods.
   *
   * Such private data must embed struct blkg_policy_data (pd) at the
   * beginning and pd_size can't be smaller than pd.
   */

  struct blkg_policy_data {

  	/* the blkg and policy id this per-policy data belongs to */

  	struct blkcg_gq			*blkg;

  	int				plid;

  	/* used during policy activation */

  	struct list_head		alloc_node;

  };

  /* association between a blk cgroup and a request queue */
  struct blkcg_gq {

  	/* Pointer to the associated request_queue */

  	struct request_queue		*q;
  	struct list_head		q_node;
  	struct hlist_node		blkcg_node;

  	struct blkcg			*blkcg;

  
  	/* all non-root blkcg_gq's are guaranteed to have access to parent */
  	struct blkcg_gq			*parent;

  	/* request allocation list for this blkcg-q pair */
  	struct request_list		rl;

  	/* reference count */

  	int				refcnt;

  	/* is this blkg online? protected by both blkcg and q locks */
  	bool				online;

  	struct blkg_policy_data		*pd[BLKCG_MAX_POLS];

  	struct rcu_head			rcu_head;

  };

  typedef void (blkcg_pol_init_pd_fn)(struct blkcg_gq *blkg);

  typedef void (blkcg_pol_online_pd_fn)(struct blkcg_gq *blkg);
  typedef void (blkcg_pol_offline_pd_fn)(struct blkcg_gq *blkg);

  typedef void (blkcg_pol_exit_pd_fn)(struct blkcg_gq *blkg);
  typedef void (blkcg_pol_reset_pd_stats_fn)(struct blkcg_gq *blkg);

  struct blkcg_policy {

  	int				plid;
  	/* policy specific private data size */

  	size_t				pd_size;

  	/* cgroup files for the policy */
  	struct cftype			*cftypes;

  
  	/* operations */
  	blkcg_pol_init_pd_fn		*pd_init_fn;

  	blkcg_pol_online_pd_fn		*pd_online_fn;
  	blkcg_pol_offline_pd_fn		*pd_offline_fn;

  	blkcg_pol_exit_pd_fn		*pd_exit_fn;
  	blkcg_pol_reset_pd_stats_fn	*pd_reset_stats_fn;

  };

  extern struct blkcg blkcg_root;

  struct blkcg_gq *blkg_lookup(struct blkcg *blkcg, struct request_queue *q);
  struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg,
  				    struct request_queue *q);

  int blkcg_init_queue(struct request_queue *q);
  void blkcg_drain_queue(struct request_queue *q);
  void blkcg_exit_queue(struct request_queue *q);

  /* Blkio controller policy registration */

  int __init blkcg_policy_register(struct blkcg_policy *pol);

  void blkcg_policy_unregister(struct blkcg_policy *pol);

  int blkcg_activate_policy(struct request_queue *q,

  			  const struct blkcg_policy *pol);

  void blkcg_deactivate_policy(struct request_queue *q,

  			     const struct blkcg_policy *pol);

  void blkcg_print_blkgs(struct seq_file *sf, struct blkcg *blkcg,

  		       u64 (*prfill)(struct seq_file *,
  				     struct blkg_policy_data *, int),

  		       const struct blkcg_policy *pol, int data,

  		       bool show_total);

  u64 __blkg_prfill_u64(struct seq_file *sf, struct blkg_policy_data *pd, u64 v);
  u64 __blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd,

  			 const struct blkg_rwstat *rwstat);

  u64 blkg_prfill_stat(struct seq_file *sf, struct blkg_policy_data *pd, int off);
  u64 blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd,
  		       int off);

  u64 blkg_stat_recursive_sum(struct blkg_policy_data *pd, int off);
  struct blkg_rwstat blkg_rwstat_recursive_sum(struct blkg_policy_data *pd,
  					     int off);

  struct blkg_conf_ctx {

  	struct gendisk			*disk;

  	struct blkcg_gq			*blkg;

  	u64				v;

  };

  int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
  		   const char *input, struct blkg_conf_ctx *ctx);

  void blkg_conf_finish(struct blkg_conf_ctx *ctx);

  static inline struct blkcg *css_to_blkcg(struct cgroup_subsys_state *css)
  {
  	return css ? container_of(css, struct blkcg, css) : NULL;
  }

  static inline struct blkcg *task_blkcg(struct task_struct *tsk)
  {

  	return css_to_blkcg(task_css(tsk, blkio_cgrp_id));

  }
  
  static inline struct blkcg *bio_blkcg(struct bio *bio)
  {
  	if (bio && bio->bi_css)

  		return css_to_blkcg(bio->bi_css);

  	return task_blkcg(current);
  }

  /**

   * blkcg_parent - get the parent of a blkcg
   * @blkcg: blkcg of interest
   *
   * Return the parent blkcg of @blkcg.  Can be called anytime.
   */
  static inline struct blkcg *blkcg_parent(struct blkcg *blkcg)
  {

  	return css_to_blkcg(blkcg->css.parent);

  }
  
  /**

   * blkg_to_pdata - get policy private data
   * @blkg: blkg of interest
   * @pol: policy of interest
   *
   * Return pointer to private data associated with the @blkg-@pol pair.
   */

  static inline struct blkg_policy_data *blkg_to_pd(struct blkcg_gq *blkg,
  						  struct blkcg_policy *pol)

  {

  	return blkg ? blkg->pd[pol->plid] : NULL;

  }
  
  /**
   * pdata_to_blkg - get blkg associated with policy private data

   * @pd: policy private data of interest

   *

   * @pd is policy private data.  Determine the blkg it's associated with.

   */

  static inline struct blkcg_gq *pd_to_blkg(struct blkg_policy_data *pd)

  {

  	return pd ? pd->blkg : NULL;

  }

  /**
   * blkg_path - format cgroup path of blkg
   * @blkg: blkg of interest
   * @buf: target buffer
   * @buflen: target buffer length
   *
   * Format the path of the cgroup of @blkg into @buf.
   */

  static inline int blkg_path(struct blkcg_gq *blkg, char *buf, int buflen)

  {

  	char *p;

  	p = cgroup_path(blkg->blkcg->css.cgroup, buf, buflen);
  	if (!p) {

  		strncpy(buf, "<unavailable>", buflen);

  		return -ENAMETOOLONG;
  	}
  
  	memmove(buf, p, buf + buflen - p);
  	return 0;

  }

  /**
   * blkg_get - get a blkg reference
   * @blkg: blkg to get
   *
   * The caller should be holding queue_lock and an existing reference.
   */

  static inline void blkg_get(struct blkcg_gq *blkg)

  {
  	lockdep_assert_held(blkg->q->queue_lock);
  	WARN_ON_ONCE(!blkg->refcnt);
  	blkg->refcnt++;
  }

  void __blkg_release_rcu(struct rcu_head *rcu);

  
  /**
   * blkg_put - put a blkg reference
   * @blkg: blkg to put
   *
   * The caller should be holding queue_lock.
   */

  static inline void blkg_put(struct blkcg_gq *blkg)

  {
  	lockdep_assert_held(blkg->q->queue_lock);
  	WARN_ON_ONCE(blkg->refcnt <= 0);
  	if (!--blkg->refcnt)

  		call_rcu(&blkg->rcu_head, __blkg_release_rcu);

  }

  struct blkcg_gq *__blkg_lookup(struct blkcg *blkcg, struct request_queue *q,
  			       bool update_hint);
  
  /**
   * blkg_for_each_descendant_pre - pre-order walk of a blkg's descendants
   * @d_blkg: loop cursor pointing to the current descendant

   * @pos_css: used for iteration

   * @p_blkg: target blkg to walk descendants of
   *
   * Walk @c_blkg through the descendants of @p_blkg.  Must be used with RCU
   * read locked.  If called under either blkcg or queue lock, the iteration
   * is guaranteed to include all and only online blkgs.  The caller may

   * update @pos_css by calling css_rightmost_descendant() to skip subtree.

   * @p_blkg is included in the iteration and the first node to be visited.

   */

  #define blkg_for_each_descendant_pre(d_blkg, pos_css, p_blkg)		\
  	css_for_each_descendant_pre((pos_css), &(p_blkg)->blkcg->css)	\
  		if (((d_blkg) = __blkg_lookup(css_to_blkcg(pos_css),	\

  					      (p_blkg)->q, false)))

  /**

   * blkg_for_each_descendant_post - post-order walk of a blkg's descendants
   * @d_blkg: loop cursor pointing to the current descendant

   * @pos_css: used for iteration

   * @p_blkg: target blkg to walk descendants of
   *
   * Similar to blkg_for_each_descendant_pre() but performs post-order

   * traversal instead.  Synchronization rules are the same.  @p_blkg is
   * included in the iteration and the last node to be visited.

   */

  #define blkg_for_each_descendant_post(d_blkg, pos_css, p_blkg)		\
  	css_for_each_descendant_post((pos_css), &(p_blkg)->blkcg->css)	\
  		if (((d_blkg) = __blkg_lookup(css_to_blkcg(pos_css),	\

  					      (p_blkg)->q, false)))
  
  /**

   * blk_get_rl - get request_list to use
   * @q: request_queue of interest
   * @bio: bio which will be attached to the allocated request (may be %NULL)
   *
   * The caller wants to allocate a request from @q to use for @bio.  Find
   * the request_list to use and obtain a reference on it.  Should be called
   * under queue_lock.  This function is guaranteed to return non-%NULL
   * request_list.
   */
  static inline struct request_list *blk_get_rl(struct request_queue *q,
  					      struct bio *bio)
  {
  	struct blkcg *blkcg;
  	struct blkcg_gq *blkg;
  
  	rcu_read_lock();
  
  	blkcg = bio_blkcg(bio);
  
  	/* bypass blkg lookup and use @q->root_rl directly for root */
  	if (blkcg == &blkcg_root)
  		goto root_rl;
  
  	/*
  	 * Try to use blkg->rl.  blkg lookup may fail under memory pressure
  	 * or if either the blkcg or queue is going away.  Fall back to
  	 * root_rl in such cases.
  	 */
  	blkg = blkg_lookup_create(blkcg, q);
  	if (unlikely(IS_ERR(blkg)))
  		goto root_rl;
  
  	blkg_get(blkg);
  	rcu_read_unlock();
  	return &blkg->rl;
  root_rl:
  	rcu_read_unlock();
  	return &q->root_rl;
  }
  
  /**
   * blk_put_rl - put request_list
   * @rl: request_list to put
   *
   * Put the reference acquired by blk_get_rl().  Should be called under
   * queue_lock.
   */
  static inline void blk_put_rl(struct request_list *rl)
  {
  	/* root_rl may not have blkg set */
  	if (rl->blkg && rl->blkg->blkcg != &blkcg_root)
  		blkg_put(rl->blkg);
  }
  
  /**
   * blk_rq_set_rl - associate a request with a request_list
   * @rq: request of interest
   * @rl: target request_list
   *
   * Associate @rq with @rl so that accounting and freeing can know the
   * request_list @rq came from.
   */
  static inline void blk_rq_set_rl(struct request *rq, struct request_list *rl)
  {
  	rq->rl = rl;
  }
  
  /**
   * blk_rq_rl - return the request_list a request came from
   * @rq: request of interest
   *
   * Return the request_list @rq is allocated from.
   */
  static inline struct request_list *blk_rq_rl(struct request *rq)
  {
  	return rq->rl;
  }
  
  struct request_list *__blk_queue_next_rl(struct request_list *rl,
  					 struct request_queue *q);
  /**
   * blk_queue_for_each_rl - iterate through all request_lists of a request_queue
   *
   * Should be used under queue_lock.
   */
  #define blk_queue_for_each_rl(rl, q)	\
  	for ((rl) = &(q)->root_rl; (rl); (rl) = __blk_queue_next_rl((rl), (q)))

  static inline void blkg_stat_init(struct blkg_stat *stat)
  {
  	u64_stats_init(&stat->syncp);
  }

  /**

   * blkg_stat_add - add a value to a blkg_stat
   * @stat: target blkg_stat
   * @val: value to add
   *
   * Add @val to @stat.  The caller is responsible for synchronizing calls to
   * this function.
   */
  static inline void blkg_stat_add(struct blkg_stat *stat, uint64_t val)
  {
  	u64_stats_update_begin(&stat->syncp);
  	stat->cnt += val;
  	u64_stats_update_end(&stat->syncp);
  }
  
  /**
   * blkg_stat_read - read the current value of a blkg_stat
   * @stat: blkg_stat to read
   *
   * Read the current value of @stat.  This function can be called without
   * synchroniztion and takes care of u64 atomicity.
   */
  static inline uint64_t blkg_stat_read(struct blkg_stat *stat)
  {
  	unsigned int start;
  	uint64_t v;
  
  	do {

  		start = u64_stats_fetch_begin_irq(&stat->syncp);

  		v = stat->cnt;

  	} while (u64_stats_fetch_retry_irq(&stat->syncp, start));

  
  	return v;
  }
  
  /**
   * blkg_stat_reset - reset a blkg_stat
   * @stat: blkg_stat to reset
   */
  static inline void blkg_stat_reset(struct blkg_stat *stat)
  {
  	stat->cnt = 0;
  }
  
  /**

   * blkg_stat_merge - merge a blkg_stat into another
   * @to: the destination blkg_stat
   * @from: the source
   *
   * Add @from's count to @to.
   */
  static inline void blkg_stat_merge(struct blkg_stat *to, struct blkg_stat *from)
  {
  	blkg_stat_add(to, blkg_stat_read(from));
  }

  static inline void blkg_rwstat_init(struct blkg_rwstat *rwstat)
  {
  	u64_stats_init(&rwstat->syncp);
  }

  /**

   * blkg_rwstat_add - add a value to a blkg_rwstat
   * @rwstat: target blkg_rwstat
   * @rw: mask of REQ_{WRITE|SYNC}
   * @val: value to add
   *
   * Add @val to @rwstat.  The counters are chosen according to @rw.  The
   * caller is responsible for synchronizing calls to this function.
   */
  static inline void blkg_rwstat_add(struct blkg_rwstat *rwstat,
  				   int rw, uint64_t val)
  {
  	u64_stats_update_begin(&rwstat->syncp);
  
  	if (rw & REQ_WRITE)
  		rwstat->cnt[BLKG_RWSTAT_WRITE] += val;
  	else
  		rwstat->cnt[BLKG_RWSTAT_READ] += val;
  	if (rw & REQ_SYNC)
  		rwstat->cnt[BLKG_RWSTAT_SYNC] += val;
  	else
  		rwstat->cnt[BLKG_RWSTAT_ASYNC] += val;
  
  	u64_stats_update_end(&rwstat->syncp);
  }
  
  /**
   * blkg_rwstat_read - read the current values of a blkg_rwstat
   * @rwstat: blkg_rwstat to read
   *
   * Read the current snapshot of @rwstat and return it as the return value.
   * This function can be called without synchronization and takes care of
   * u64 atomicity.
   */

  static inline struct blkg_rwstat blkg_rwstat_read(struct blkg_rwstat *rwstat)

  {
  	unsigned int start;
  	struct blkg_rwstat tmp;
  
  	do {

  		start = u64_stats_fetch_begin_irq(&rwstat->syncp);

  		tmp = *rwstat;

  	} while (u64_stats_fetch_retry_irq(&rwstat->syncp, start));

  
  	return tmp;
  }
  
  /**

   * blkg_rwstat_total - read the total count of a blkg_rwstat

   * @rwstat: blkg_rwstat to read
   *
   * Return the total count of @rwstat regardless of the IO direction.  This
   * function can be called without synchronization and takes care of u64
   * atomicity.
   */

  static inline uint64_t blkg_rwstat_total(struct blkg_rwstat *rwstat)

  {
  	struct blkg_rwstat tmp = blkg_rwstat_read(rwstat);
  
  	return tmp.cnt[BLKG_RWSTAT_READ] + tmp.cnt[BLKG_RWSTAT_WRITE];
  }
  
  /**
   * blkg_rwstat_reset - reset a blkg_rwstat
   * @rwstat: blkg_rwstat to reset
   */
  static inline void blkg_rwstat_reset(struct blkg_rwstat *rwstat)
  {
  	memset(rwstat->cnt, 0, sizeof(rwstat->cnt));
  }

  /**
   * blkg_rwstat_merge - merge a blkg_rwstat into another
   * @to: the destination blkg_rwstat
   * @from: the source
   *
   * Add @from's counts to @to.
   */
  static inline void blkg_rwstat_merge(struct blkg_rwstat *to,
  				     struct blkg_rwstat *from)
  {
  	struct blkg_rwstat v = blkg_rwstat_read(from);
  	int i;
  
  	u64_stats_update_begin(&to->syncp);
  	for (i = 0; i < BLKG_RWSTAT_NR; i++)
  		to->cnt[i] += v.cnt[i];
  	u64_stats_update_end(&to->syncp);
  }

  #else	/* CONFIG_BLK_CGROUP */
  
  struct cgroup;

  struct blkcg;

  struct blkg_policy_data {
  };

  struct blkcg_gq {

  };

  struct blkcg_policy {

  };

  static inline struct blkcg_gq *blkg_lookup(struct blkcg *blkcg, void *key) { return NULL; }

  static inline int blkcg_init_queue(struct request_queue *q) { return 0; }
  static inline void blkcg_drain_queue(struct request_queue *q) { }
  static inline void blkcg_exit_queue(struct request_queue *q) { }

  static inline int __init blkcg_policy_register(struct blkcg_policy *pol) { return 0; }

  static inline void blkcg_policy_unregister(struct blkcg_policy *pol) { }

  static inline int blkcg_activate_policy(struct request_queue *q,

  					const struct blkcg_policy *pol) { return 0; }

  static inline void blkcg_deactivate_policy(struct request_queue *q,

  					   const struct blkcg_policy *pol) { }

  static inline struct blkcg *bio_blkcg(struct bio *bio) { return NULL; }

  static inline struct blkg_policy_data *blkg_to_pd(struct blkcg_gq *blkg,
  						  struct blkcg_policy *pol) { return NULL; }
  static inline struct blkcg_gq *pd_to_blkg(struct blkg_policy_data *pd) { return NULL; }

  static inline char *blkg_path(struct blkcg_gq *blkg) { return NULL; }
  static inline void blkg_get(struct blkcg_gq *blkg) { }
  static inline void blkg_put(struct blkcg_gq *blkg) { }

  static inline struct request_list *blk_get_rl(struct request_queue *q,
  					      struct bio *bio) { return &q->root_rl; }
  static inline void blk_put_rl(struct request_list *rl) { }
  static inline void blk_rq_set_rl(struct request *rq, struct request_list *rl) { }
  static inline struct request_list *blk_rq_rl(struct request *rq) { return &rq->q->root_rl; }
  
  #define blk_queue_for_each_rl(rl, q)	\
  	for ((rl) = &(q)->root_rl; (rl); (rl) = NULL)

  #endif	/* CONFIG_BLK_CGROUP */
  #endif	/* _BLK_CGROUP_H */