res_counter.h

Go to the documentation of this file.

#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 <[email protected]>
 *
 * See Documentation/cgroups/resource_counter.txt for more
 * info about what this counter is.
 */

#include <linux/cgroup.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 RESOURCE_MAX (unsigned long long)LLONG_MAX

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));

typedef int (*write_strategy_fn)(const char *buf, unsigned long long *val);

int res_counter_memparse_write_strategy(const char *buf,
                    unsigned long long *res);

int res_counter_write(struct res_counter *counter, int member,
              const char *buffer, write_strategy_fn write_strategy);

/*
 * 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
 */

void res_counter_uncharge_locked(struct res_counter *counter, unsigned long val);
void res_counter_uncharge(struct res_counter *counter, unsigned long val);

void res_counter_uncharge_until(struct res_counter *counter,
                struct res_counter *top,
                unsigned long val);
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;
}

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