1 files changed, 107 insertions, 0 deletions

diff --git a/include/linux/percpu_counter.h b/include/linux/percpu_counter.h
new file mode 100644
index 000000000000..bd6708e2c027
--- /dev/null
+++ b/include/linux/percpu_counter.h
@@ -0,0 +1,107 @@
+#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/config.h>
+#include <linux/spinlock.h>
+#include <linux/smp.h>
+#include <linux/threads.h>
+#include <linux/percpu.h>
+
+#ifdef CONFIG_SMP
+
+struct percpu_counter {
+        spinlock_t lock;
+        long count;
+        long *counters;
+};
+
+#if NR_CPUS >= 16
+#define FBC_BATCH       (NR_CPUS*2)
+#else
+#define FBC_BATCH       (NR_CPUS*4)
+#endif
+
+static inline void percpu_counter_init(struct percpu_counter *fbc)
+{
+        spin_lock_init(&fbc->lock);
+        fbc->count = 0;
+        fbc->counters = alloc_percpu(long);
+}
+
+static inline void percpu_counter_destroy(struct percpu_counter *fbc)
+{
+        free_percpu(fbc->counters);
+}
+
+void percpu_counter_mod(struct percpu_counter *fbc, long amount);
+
+static inline long 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 long percpu_counter_read_positive(struct percpu_counter *fbc)
+{
+        long ret = fbc->count;
+
+        barrier();              /* Prevent reloads of fbc->count */
+        if (ret > 0)
+                return ret;
+        return 1;
+}
+
+#else
+
+struct percpu_counter {
+        long count;
+};
+
+static inline void percpu_counter_init(struct percpu_counter *fbc)
+{
+        fbc->count = 0;
+}
+
+static inline void percpu_counter_destroy(struct percpu_counter *fbc)
+{
+}
+
+static inline void
+percpu_counter_mod(struct percpu_counter *fbc, long amount)
+{
+        preempt_disable();
+        fbc->count += amount;
+        preempt_enable();
+}
+
+static inline long percpu_counter_read(struct percpu_counter *fbc)
+{
+        return fbc->count;
+}
+
+static inline long percpu_counter_read_positive(struct percpu_counter *fbc)
+{
+        return fbc->count;
+}
+
+#endif  /* CONFIG_SMP */
+
+static inline void percpu_counter_inc(struct percpu_counter *fbc)
+{
+        percpu_counter_mod(fbc, 1);
+}
+
+static inline void percpu_counter_dec(struct percpu_counter *fbc)
+{
+        percpu_counter_mod(fbc, -1);
+}
+
+#endif /* _LINUX_PERCPU_COUNTER_H */