--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/include/linux/percpu_counter.h Sun Jan 11 20:20:11 2009 +0100
@@ -0,0 +1,147 @@
+#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 */