#ifndef __RES_COUNTER_H__
  #define __RES_COUNTER_H__
  
  /*
   * Resource Counters
   * Contain common data types and routines for resource accounting
   *
   * Copyright 2007 OpenVZ SWsoft Inc
   *
   * Author: Pavel Emelianov <xemul@openvz.org>
   *
   * See Documentation/cgroups/resource_counter.txt for more
   * info about what this counter is.
   */
  
  #include <linux/spinlock.h>
  #include <linux/errno.h>
  
  /*
   * The core object. the cgroup that wishes to account for some
   * resource may include this counter into its structures and use
   * the helpers described beyond
   */
  
  struct res_counter {
  	/*
  	 * the current resource consumption level
  	 */
  	unsigned long long usage;
  	/*
  	 * the maximal value of the usage from the counter creation
  	 */
  	unsigned long long max_usage;
  	/*
  	 * the limit that usage cannot exceed
  	 */
  	unsigned long long limit;
  	/*
  	 * the limit that usage can be exceed
  	 */
  	unsigned long long soft_limit;
  	/*
  	 * the number of unsuccessful attempts to consume the resource
  	 */
  	unsigned long long failcnt;
  	/*
  	 * the lock to protect all of the above.
  	 * the routines below consider this to be IRQ-safe
  	 */
  	spinlock_t lock;
  	/*
  	 * Parent counter, used for hierarchial resource accounting
  	 */
  	struct res_counter *parent;
  };
  
  #define RES_COUNTER_MAX ULLONG_MAX
  
  /**
   * Helpers to interact with userspace
   * res_counter_read_u64() - returns the value of the specified member.
   * res_counter_read/_write - put/get the specified fields from the
   * res_counter struct to/from the user
   *
   * @counter:     the counter in question
   * @member:  the field to work with (see RES_xxx below)
   * @buf:     the buffer to opeate on,...
   * @nbytes:  its size...
   * @pos:     and the offset.
   */
  
  u64 res_counter_read_u64(struct res_counter *counter, int member);
  
  ssize_t res_counter_read(struct res_counter *counter, int member,
  		const char __user *buf, size_t nbytes, loff_t *pos,
  		int (*read_strategy)(unsigned long long val, char *s));
  
  int res_counter_memparse_write_strategy(const char *buf,
  					unsigned long long *res);
  
  /*
   * the field descriptors. one for each member of res_counter
   */
  
  enum {
  	RES_USAGE,
  	RES_MAX_USAGE,
  	RES_LIMIT,
  	RES_FAILCNT,
  	RES_SOFT_LIMIT,
  };
  
  /*
   * helpers for accounting
   */
  
  void res_counter_init(struct res_counter *counter, struct res_counter *parent);
  
  /*
   * charge - try to consume more resource.
   *
   * @counter: the counter
   * @val: the amount of the resource. each controller defines its own
   *       units, e.g. numbers, bytes, Kbytes, etc
   *
   * returns 0 on success and <0 if the counter->usage will exceed the
   * counter->limit _locked call expects the counter->lock to be taken
   *
   * charge_nofail works the same, except that it charges the resource
   * counter unconditionally, and returns < 0 if the after the current
   * charge we are over limit.
   */
  
  int __must_check res_counter_charge_locked(struct res_counter *counter,
  					   unsigned long val, bool force);
  int __must_check res_counter_charge(struct res_counter *counter,
  		unsigned long val, struct res_counter **limit_fail_at);
  int res_counter_charge_nofail(struct res_counter *counter,
  		unsigned long val, struct res_counter **limit_fail_at);
  
  /*
   * uncharge - tell that some portion of the resource is released
   *
   * @counter: the counter
   * @val: the amount of the resource
   *
   * these calls check for usage underflow and show a warning on the console
   * _locked call expects the counter->lock to be taken
   *
   * returns the total charges still present in @counter.
   */
  
  u64 res_counter_uncharge_locked(struct res_counter *counter, unsigned long val);
  u64 res_counter_uncharge(struct res_counter *counter, unsigned long val);
  
  u64 res_counter_uncharge_until(struct res_counter *counter,
  			       struct res_counter *top,
  			       unsigned long val);
  /**
   * res_counter_margin - calculate chargeable space of a counter
   * @cnt: the counter
   *
   * Returns the difference between the hard limit and the current usage
   * of resource counter @cnt.
   */
  static inline unsigned long long res_counter_margin(struct res_counter *cnt)
  {
  	unsigned long long margin;
  	unsigned long flags;
  
  	spin_lock_irqsave(&cnt->lock, flags);
  	if (cnt->limit > cnt->usage)
  		margin = cnt->limit - cnt->usage;
  	else
  		margin = 0;
  	spin_unlock_irqrestore(&cnt->lock, flags);
  	return margin;
  }
  
  /**
   * Get the difference between the usage and the soft limit
   * @cnt: The counter
   *
   * Returns 0 if usage is less than or equal to soft limit
   * The difference between usage and soft limit, otherwise.
   */
  static inline unsigned long long
  res_counter_soft_limit_excess(struct res_counter *cnt)
  {
  	unsigned long long excess;
  	unsigned long flags;
  
  	spin_lock_irqsave(&cnt->lock, flags);
  	if (cnt->usage <= cnt->soft_limit)
  		excess = 0;
  	else
  		excess = cnt->usage - cnt->soft_limit;
  	spin_unlock_irqrestore(&cnt->lock, flags);
  	return excess;
  }
  
  static inline void res_counter_reset_max(struct res_counter *cnt)
  {
  	unsigned long flags;
  
  	spin_lock_irqsave(&cnt->lock, flags);
  	cnt->max_usage = cnt->usage;
  	spin_unlock_irqrestore(&cnt->lock, flags);
  }
  
  static inline void res_counter_reset_failcnt(struct res_counter *cnt)
  {
  	unsigned long flags;
  
  	spin_lock_irqsave(&cnt->lock, flags);
  	cnt->failcnt = 0;
  	spin_unlock_irqrestore(&cnt->lock, flags);
  }
  
  static inline int res_counter_set_limit(struct res_counter *cnt,
  		unsigned long long limit)
  {
  	unsigned long flags;
  	int ret = -EBUSY;
  
  	spin_lock_irqsave(&cnt->lock, flags);
  	if (cnt->usage <= limit) {
  		cnt->limit = limit;
  		ret = 0;
  	}
  	spin_unlock_irqrestore(&cnt->lock, flags);
  	return ret;
  }
  
  static inline int
  res_counter_set_soft_limit(struct res_counter *cnt,
  				unsigned long long soft_limit)
  {
  	unsigned long flags;
  
  	spin_lock_irqsave(&cnt->lock, flags);
  	cnt->soft_limit = soft_limit;
  	spin_unlock_irqrestore(&cnt->lock, flags);
  	return 0;
  }
  
  #endif