1 files changed, 256 insertions, 0 deletions
diff --git a/include/linux/percpu_counter.h b/include/linux/percpu_counter.h
new file mode 100644
index 000000000..d01351b15
--- /dev/null
+++ b/include/linux/percpu_counter.h
@@ -0,0 +1,256 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#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>
+
+/* percpu_counter batch for local add or sub */
+#define PERCPU_COUNTER_LOCAL_BATCH	INT_MAX
+
+#ifdef CONFIG_SMP
+
+struct percpu_counter {
+	raw_spinlock_t lock;
+	s64 count;
+#ifdef CONFIG_HOTPLUG_CPU
+	struct list_head list;	/* All percpu_counters are on a list */
+#endif
+	s32 __percpu *counters;
+};
+
+extern int percpu_counter_batch;
+
+int __percpu_counter_init_many(struct percpu_counter *fbc, s64 amount,
+			       gfp_t gfp, u32 nr_counters,
+			       struct lock_class_key *key);
+
+#define percpu_counter_init_many(fbc, value, gfp, nr_counters)		\
+	({								\
+		static struct lock_class_key __key;			\
+									\
+		__percpu_counter_init_many(fbc, value, gfp, nr_counters,\
+					   &__key);			\
+	})
+
+
+#define percpu_counter_init(fbc, value, gfp)				\
+	percpu_counter_init_many(fbc, value, gfp, 1)
+
+void percpu_counter_destroy_many(struct percpu_counter *fbc, u32 nr_counters);
+static inline void percpu_counter_destroy(struct percpu_counter *fbc)
+{
+	percpu_counter_destroy_many(fbc, 1);
+}
+
+void percpu_counter_set(struct percpu_counter *fbc, s64 amount);
+void percpu_counter_add_batch(struct percpu_counter *fbc, s64 amount,
+			      s32 batch);
+s64 __percpu_counter_sum(struct percpu_counter *fbc);
+int __percpu_counter_compare(struct percpu_counter *fbc, s64 rhs, s32 batch);
+void percpu_counter_sync(struct percpu_counter *fbc);
+
+static inline int percpu_counter_compare(struct percpu_counter *fbc, s64 rhs)
+{
+	return __percpu_counter_compare(fbc, rhs, percpu_counter_batch);
+}
+
+static inline void percpu_counter_add(struct percpu_counter *fbc, s64 amount)
+{
+	percpu_counter_add_batch(fbc, amount, percpu_counter_batch);
+}
+
+/*
+ * With percpu_counter_add_local() and percpu_counter_sub_local(), counts
+ * are accumulated in local per cpu counter and not in fbc->count until
+ * local count overflows PERCPU_COUNTER_LOCAL_BATCH. This makes counter
+ * write efficient.
+ * But percpu_counter_sum(), instead of percpu_counter_read(), needs to be
+ * used to add up the counts from each CPU to account for all the local
+ * counts. So percpu_counter_add_local() and percpu_counter_sub_local()
+ * should be used when a counter is updated frequently and read rarely.
+ */
+static inline void
+percpu_counter_add_local(struct percpu_counter *fbc, s64 amount)
+{
+	percpu_counter_add_batch(fbc, amount, PERCPU_COUNTER_LOCAL_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)
+{
+	/* Prevent reloads of fbc->count */
+	s64 ret = READ_ONCE(fbc->count);
+
+	if (ret >= 0)
+		return ret;
+	return 0;
+}
+
+static inline bool percpu_counter_initialized(struct percpu_counter *fbc)
+{
+	return (fbc->counters != NULL);
+}
+
+#else /* !CONFIG_SMP */
+
+struct percpu_counter {
+	s64 count;
+};
+
+static inline int percpu_counter_init_many(struct percpu_counter *fbc,
+					   s64 amount, gfp_t gfp,
+					   u32 nr_counters)
+{
+	u32 i;
+
+	for (i = 0; i < nr_counters; i++)
+		fbc[i].count = amount;
+
+	return 0;
+}
+
+static inline int percpu_counter_init(struct percpu_counter *fbc, s64 amount,
+				      gfp_t gfp)
+{
+	return percpu_counter_init_many(fbc, amount, gfp, 1);
+}
+
+static inline void percpu_counter_destroy_many(struct percpu_counter *fbc,
+					       u32 nr_counters)
+{
+}
+
+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;
+}
+
+static inline int percpu_counter_compare(struct percpu_counter *fbc, s64 rhs)
+{
+	if (fbc->count > rhs)
+		return 1;
+	else if (fbc->count < rhs)
+		return -1;
+	else
+		return 0;
+}
+
+static inline int
+__percpu_counter_compare(struct percpu_counter *fbc, s64 rhs, s32 batch)
+{
+	return percpu_counter_compare(fbc, rhs);
+}
+
+static inline void
+percpu_counter_add(struct percpu_counter *fbc, s64 amount)
+{
+	unsigned long flags;
+
+	local_irq_save(flags);
+	fbc->count += amount;
+	local_irq_restore(flags);
+}
+
+/* non-SMP percpu_counter_add_local is the same with percpu_counter_add */
+static inline void
+percpu_counter_add_local(struct percpu_counter *fbc, s64 amount)
+{
+	percpu_counter_add(fbc, amount);
+}
+
+static inline void
+percpu_counter_add_batch(struct percpu_counter *fbc, s64 amount, s32 batch)
+{
+	percpu_counter_add(fbc, amount);
+}
+
+static inline s64 percpu_counter_read(struct percpu_counter *fbc)
+{
+	return fbc->count;
+}
+
+/*
+ * percpu_counter is intended to track positive numbers. In the UP case the
+ * number should never be negative.
+ */
+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);
+}
+
+static inline bool percpu_counter_initialized(struct percpu_counter *fbc)
+{
+	return true;
+}
+
+static inline void percpu_counter_sync(struct percpu_counter *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);
+}
+
+static inline void
+percpu_counter_sub_local(struct percpu_counter *fbc, s64 amount)
+{
+	percpu_counter_add_local(fbc, -amount);
+}
+
+#endif /* _LINUX_PERCPU_COUNTER_H */