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 long usage;
  27         /*
  28          * the limit that usage cannot exceed
  29          */
  30         unsigned long long limit;
  31         /*
  32          * the number of unsuccessful attempts to consume the resource
  33          */
  34         unsigned long 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                 int (*read_strategy)(unsigned long long val, char *s));
  57 ssize_t res_counter_write(struct res_counter *counter, int member,
  58                 const char __user *buf, size_t nbytes, loff_t *pos,
  59                 int (*write_strategy)(char *buf, unsigned long long *val));
  60
  61 /*
  62  * the field descriptors. one for each member of res_counter
  63  */
  64
  65 enum {
  66         RES_USAGE,
  67         RES_LIMIT,
  68         RES_FAILCNT,
  69 };
  70
  71 /*
  72  * helpers for accounting
  73  */
  74
  75 void res_counter_init(struct res_counter *counter);
  76
  77 /*
  78  * charge - try to consume more resource.
  79  *
  80  * @counter: the counter
  81  * @val: the amount of the resource. each controller defines its own
  82  *       units, e.g. numbers, bytes, Kbytes, etc
  83  *
  84  * returns 0 on success and <0 if the counter->usage will exceed the
  85  * counter->limit _locked call expects the counter->lock to be taken
  86  */
  87
  88 int res_counter_charge_locked(struct res_counter *counter, unsigned long val);
  89 int res_counter_charge(struct res_counter *counter, unsigned long val);
  90
  91 /*
  92  * uncharge - tell that some portion of the resource is released
  93  *
  94  * @counter: the counter
  95  * @val: the amount of the resource
  96  *
  97  * these calls check for usage underflow and show a warning on the console
  98  * _locked call expects the counter->lock to be taken
  99  */
 100
 101 void res_counter_uncharge_locked(struct res_counter *counter, unsigned long val);
 102 void res_counter_uncharge(struct res_counter *counter, unsigned long val);
 103
 104 static inline bool res_counter_limit_check_locked(struct res_counter *cnt)
 105 {
 106         if (cnt->usage < cnt->limit)
 107                 return true;
 108
 109         return false;
 110 }
 111
 112 /*
 113  * Helper function to detect if the cgroup is within it's limit or
 114  * not. It's currently called from cgroup_rss_prepare()
 115  */
 116 static inline bool res_counter_check_under_limit(struct res_counter *cnt)
 117 {
 118         bool ret;
 119         unsigned long flags;
 120
 121         spin_lock_irqsave(&cnt->lock, flags);
 122         ret = res_counter_limit_check_locked(cnt);
 123         spin_unlock_irqrestore(&cnt->lock, flags);
 124         return ret;
 125 }
 126
 127 #endif