include/linux/res_counter.h

   1 #ifndef __RES_COUNTER_H__
   2 #define __RES_COUNTER_H__
   3
   4 /*
   5  * Resource Counters
   6  * Contain common data types and routines for resource accounting
   7  *
   8  * Copyright 2007 OpenVZ SWsoft Inc
   9  *
  10  * Author: Pavel Emelianov <xemul@openvz.org>
  11  *
  12  */
  13
  14 #include <linux/cgroup.h>
  15
  16 /*
  17  * The core object. the cgroup that wishes to account for some
  18  * resource may include this counter into its structures and use
  19  * the helpers described beyond
  20  */
  21
  22 struct res_counter {
  23         /*
  24          * the current resource consumption level
  25          */
  26         unsigned long usage;
  27         /*
  28          * the limit that usage cannot exceed
  29          */
  30         unsigned long limit;
  31         /*
  32          * the number of unsuccessful attempts to consume the resource
  33          */
  34         unsigned long failcnt;
  35         /*
  36          * the lock to protect all of the above.
  37          * the routines below consider this to be IRQ-safe
  38          */
  39         spinlock_t lock;
  40 };
  41
  42 /*
  43  * Helpers to interact with userspace
  44  * res_counter_read/_write - put/get the specified fields from the
  45  * res_counter struct to/from the user
  46  *
  47  * @counter:     the counter in question
  48  * @member:  the field to work with (see RES_xxx below)
  49  * @buf:     the buffer to opeate on,...
  50  * @nbytes:  its size...
  51  * @pos:     and the offset.
  52  */
  53
  54 ssize_t res_counter_read(struct res_counter *counter, int member,
  55                 const char __user *buf, size_t nbytes, loff_t *pos);
  56 ssize_t res_counter_write(struct res_counter *counter, int member,
  57                 const char __user *buf, size_t nbytes, loff_t *pos);
  58
  59 /*
  60  * the field descriptors. one for each member of res_counter
  61  */
  62
  63 enum {
  64         RES_USAGE,
  65         RES_LIMIT,
  66         RES_FAILCNT,
  67 };
  68
  69 /*
  70  * helpers for accounting
  71  */
  72
  73 void res_counter_init(struct res_counter *counter);
  74
  75 /*
  76  * charge - try to consume more resource.
  77  *
  78  * @counter: the counter
  79  * @val: the amount of the resource. each controller defines its own
  80  *       units, e.g. numbers, bytes, Kbytes, etc
  81  *
  82  * returns 0 on success and <0 if the counter->usage will exceed the
  83  * counter->limit _locked call expects the counter->lock to be taken
  84  */
  85
  86 int res_counter_charge_locked(struct res_counter *counter, unsigned long val);
  87 int res_counter_charge(struct res_counter *counter, unsigned long val);
  88
  89 /*
  90  * uncharge - tell that some portion of the resource is released
  91  *
  92  * @counter: the counter
  93  * @val: the amount of the resource
  94  *
  95  * these calls check for usage underflow and show a warning on the console
  96  * _locked call expects the counter->lock to be taken
  97  */
  98
  99 void res_counter_uncharge_locked(struct res_counter *counter, unsigned long val);
 100 void res_counter_uncharge(struct res_counter *counter, unsigned long val);
 101
 102 static inline bool res_counter_limit_check_locked(struct res_counter *cnt)
 103 {
 104         if (cnt->usage < cnt->limit)
 105                 return true;
 106
 107         return false;
 108 }
 109
 110 /*
 111  * Helper function to detect if the cgroup is within it's limit or
 112  * not. It's currently called from cgroup_rss_prepare()
 113  */
 114 static inline bool res_counter_check_under_limit(struct res_counter *cnt)
 115 {
 116         bool ret;
 117         unsigned long flags;
 118
 119         spin_lock_irqsave(&cnt->lock, flags);
 120         ret = res_counter_limit_check_locked(cnt);
 121         spin_unlock_irqrestore(&cnt->lock, flags);
 122         return ret;
 123 }
 124
 125 #endif