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#ifndef _LINUX_PERCPU_COUNTER_H
#define _LINUX_PERCPU_COUNTER_H
/*
 * A simple "approximate counter" for use in ext2 and ext3 superblocks.
 *
 * WARNING: these things are HUGE.  4 kbytes per counter on 32-way P4.
 */
 
#include <linux/spinlock.h>
#include <linux/smp.h>
#include <linux/list.h>
#include <linux/threads.h>
#include <linux/percpu.h>
#include <linux/types.h>
 
#ifdef CONFIG_SMP
 
struct percpu_counter {
	spinlock_t lock;
	s64 count;
#ifdef CONFIG_HOTPLUG_CPU
	struct list_head list;	/* All percpu_counters are on a list */
#endif
	s32 *counters;
};
 
#if NR_CPUS >= 16
#define FBC_BATCH	(NR_CPUS*2)
#else
#define FBC_BATCH	(NR_CPUS*4)
#endif
 
int percpu_counter_init(struct percpu_counter *fbc, s64 amount);
int percpu_counter_init_irq(struct percpu_counter *fbc, s64 amount);
void percpu_counter_destroy(struct percpu_counter *fbc);
void percpu_counter_set(struct percpu_counter *fbc, s64 amount);
void __percpu_counter_add(struct percpu_counter *fbc, s64 amount, s32 batch);
s64 __percpu_counter_sum(struct percpu_counter *fbc);
 
static inline void percpu_counter_add(struct percpu_counter *fbc, s64 amount)
{
	__percpu_counter_add(fbc, amount, FBC_BATCH);
}
 
static inline s64 percpu_counter_sum_positive(struct percpu_counter *fbc)
{
	s64 ret = __percpu_counter_sum(fbc);
	return ret < 0 ? 0 : ret;
}
 
static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
{
	return __percpu_counter_sum(fbc);
}
 
static inline s64 percpu_counter_read(struct percpu_counter *fbc)
{
	return fbc->count;
}
 
/*
 * It is possible for the percpu_counter_read() to return a small negative
 * number for some counter which should never be negative.
 *
 */
static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc)
{
	s64 ret = fbc->count;
 
	barrier();		/* Prevent reloads of fbc->count */
	if (ret >= 0)
		return ret;
	return 1;
}
 
#else
 
struct percpu_counter {
	s64 count;
};
 
static inline int percpu_counter_init(struct percpu_counter *fbc, s64 amount)
{
	fbc->count = amount;
	return 0;
}
 
#define percpu_counter_init_irq percpu_counter_init
 
static inline void percpu_counter_destroy(struct percpu_counter *fbc)
{
}
 
static inline void percpu_counter_set(struct percpu_counter *fbc, s64 amount)
{
	fbc->count = amount;
}
 
#define __percpu_counter_add(fbc, amount, batch) \
	percpu_counter_add(fbc, amount)
 
static inline void
percpu_counter_add(struct percpu_counter *fbc, s64 amount)
{
	preempt_disable();
	fbc->count += amount;
	preempt_enable();
}
 
static inline s64 percpu_counter_read(struct percpu_counter *fbc)
{
	return fbc->count;
}
 
static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc)
{
	return fbc->count;
}
 
static inline s64 percpu_counter_sum_positive(struct percpu_counter *fbc)
{
	return percpu_counter_read_positive(fbc);
}
 
static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
{
	return percpu_counter_read(fbc);
}
 
#endif	/* CONFIG_SMP */
 
static inline void percpu_counter_inc(struct percpu_counter *fbc)
{
	percpu_counter_add(fbc, 1);
}
 
static inline void percpu_counter_dec(struct percpu_counter *fbc)
{
	percpu_counter_add(fbc, -1);
}
 
static inline void percpu_counter_sub(struct percpu_counter *fbc, s64 amount)
{
	percpu_counter_add(fbc, -amount);
}
 
#endif /* _LINUX_PERCPU_COUNTER_H */