v4.19.13 snapshot.
diff --git a/lib/percpu_counter.c b/lib/percpu_counter.c
new file mode 100644
index 0000000..a66595b
--- /dev/null
+++ b/lib/percpu_counter.c
@@ -0,0 +1,238 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Fast batching percpu counters.
+ */
+
+#include <linux/percpu_counter.h>
+#include <linux/mutex.h>
+#include <linux/init.h>
+#include <linux/cpu.h>
+#include <linux/module.h>
+#include <linux/debugobjects.h>
+
+#ifdef CONFIG_HOTPLUG_CPU
+static LIST_HEAD(percpu_counters);
+static DEFINE_SPINLOCK(percpu_counters_lock);
+#endif
+
+#ifdef CONFIG_DEBUG_OBJECTS_PERCPU_COUNTER
+
+static struct debug_obj_descr percpu_counter_debug_descr;
+
+static bool percpu_counter_fixup_free(void *addr, enum debug_obj_state state)
+{
+ struct percpu_counter *fbc = addr;
+
+ switch (state) {
+ case ODEBUG_STATE_ACTIVE:
+ percpu_counter_destroy(fbc);
+ debug_object_free(fbc, &percpu_counter_debug_descr);
+ return true;
+ default:
+ return false;
+ }
+}
+
+static struct debug_obj_descr percpu_counter_debug_descr = {
+ .name = "percpu_counter",
+ .fixup_free = percpu_counter_fixup_free,
+};
+
+static inline void debug_percpu_counter_activate(struct percpu_counter *fbc)
+{
+ debug_object_init(fbc, &percpu_counter_debug_descr);
+ debug_object_activate(fbc, &percpu_counter_debug_descr);
+}
+
+static inline void debug_percpu_counter_deactivate(struct percpu_counter *fbc)
+{
+ debug_object_deactivate(fbc, &percpu_counter_debug_descr);
+ debug_object_free(fbc, &percpu_counter_debug_descr);
+}
+
+#else /* CONFIG_DEBUG_OBJECTS_PERCPU_COUNTER */
+static inline void debug_percpu_counter_activate(struct percpu_counter *fbc)
+{ }
+static inline void debug_percpu_counter_deactivate(struct percpu_counter *fbc)
+{ }
+#endif /* CONFIG_DEBUG_OBJECTS_PERCPU_COUNTER */
+
+void percpu_counter_set(struct percpu_counter *fbc, s64 amount)
+{
+ int cpu;
+ unsigned long flags;
+
+ raw_spin_lock_irqsave(&fbc->lock, flags);
+ for_each_possible_cpu(cpu) {
+ s32 *pcount = per_cpu_ptr(fbc->counters, cpu);
+ *pcount = 0;
+ }
+ fbc->count = amount;
+ raw_spin_unlock_irqrestore(&fbc->lock, flags);
+}
+EXPORT_SYMBOL(percpu_counter_set);
+
+/**
+ * This function is both preempt and irq safe. The former is due to explicit
+ * preemption disable. The latter is guaranteed by the fact that the slow path
+ * is explicitly protected by an irq-safe spinlock whereas the fast patch uses
+ * this_cpu_add which is irq-safe by definition. Hence there is no need muck
+ * with irq state before calling this one
+ */
+void percpu_counter_add_batch(struct percpu_counter *fbc, s64 amount, s32 batch)
+{
+ s64 count;
+
+ preempt_disable();
+ count = __this_cpu_read(*fbc->counters) + amount;
+ if (count >= batch || count <= -batch) {
+ unsigned long flags;
+ raw_spin_lock_irqsave(&fbc->lock, flags);
+ fbc->count += count;
+ __this_cpu_sub(*fbc->counters, count - amount);
+ raw_spin_unlock_irqrestore(&fbc->lock, flags);
+ } else {
+ this_cpu_add(*fbc->counters, amount);
+ }
+ preempt_enable();
+}
+EXPORT_SYMBOL(percpu_counter_add_batch);
+
+/*
+ * Add up all the per-cpu counts, return the result. This is a more accurate
+ * but much slower version of percpu_counter_read_positive()
+ */
+s64 __percpu_counter_sum(struct percpu_counter *fbc)
+{
+ s64 ret;
+ int cpu;
+ unsigned long flags;
+
+ raw_spin_lock_irqsave(&fbc->lock, flags);
+ ret = fbc->count;
+ for_each_online_cpu(cpu) {
+ s32 *pcount = per_cpu_ptr(fbc->counters, cpu);
+ ret += *pcount;
+ }
+ raw_spin_unlock_irqrestore(&fbc->lock, flags);
+ return ret;
+}
+EXPORT_SYMBOL(__percpu_counter_sum);
+
+int __percpu_counter_init(struct percpu_counter *fbc, s64 amount, gfp_t gfp,
+ struct lock_class_key *key)
+{
+ unsigned long flags __maybe_unused;
+
+ raw_spin_lock_init(&fbc->lock);
+ lockdep_set_class(&fbc->lock, key);
+ fbc->count = amount;
+ fbc->counters = alloc_percpu_gfp(s32, gfp);
+ if (!fbc->counters)
+ return -ENOMEM;
+
+ debug_percpu_counter_activate(fbc);
+
+#ifdef CONFIG_HOTPLUG_CPU
+ INIT_LIST_HEAD(&fbc->list);
+ spin_lock_irqsave(&percpu_counters_lock, flags);
+ list_add(&fbc->list, &percpu_counters);
+ spin_unlock_irqrestore(&percpu_counters_lock, flags);
+#endif
+ return 0;
+}
+EXPORT_SYMBOL(__percpu_counter_init);
+
+void percpu_counter_destroy(struct percpu_counter *fbc)
+{
+ unsigned long flags __maybe_unused;
+
+ if (!fbc->counters)
+ return;
+
+ debug_percpu_counter_deactivate(fbc);
+
+#ifdef CONFIG_HOTPLUG_CPU
+ spin_lock_irqsave(&percpu_counters_lock, flags);
+ list_del(&fbc->list);
+ spin_unlock_irqrestore(&percpu_counters_lock, flags);
+#endif
+ free_percpu(fbc->counters);
+ fbc->counters = NULL;
+}
+EXPORT_SYMBOL(percpu_counter_destroy);
+
+int percpu_counter_batch __read_mostly = 32;
+EXPORT_SYMBOL(percpu_counter_batch);
+
+static int compute_batch_value(unsigned int cpu)
+{
+ int nr = num_online_cpus();
+
+ percpu_counter_batch = max(32, nr*2);
+ return 0;
+}
+
+static int percpu_counter_cpu_dead(unsigned int cpu)
+{
+#ifdef CONFIG_HOTPLUG_CPU
+ struct percpu_counter *fbc;
+
+ compute_batch_value(cpu);
+
+ spin_lock_irq(&percpu_counters_lock);
+ list_for_each_entry(fbc, &percpu_counters, list) {
+ s32 *pcount;
+
+ raw_spin_lock(&fbc->lock);
+ pcount = per_cpu_ptr(fbc->counters, cpu);
+ fbc->count += *pcount;
+ *pcount = 0;
+ raw_spin_unlock(&fbc->lock);
+ }
+ spin_unlock_irq(&percpu_counters_lock);
+#endif
+ return 0;
+}
+
+/*
+ * Compare counter against given value.
+ * Return 1 if greater, 0 if equal and -1 if less
+ */
+int __percpu_counter_compare(struct percpu_counter *fbc, s64 rhs, s32 batch)
+{
+ s64 count;
+
+ count = percpu_counter_read(fbc);
+ /* Check to see if rough count will be sufficient for comparison */
+ if (abs(count - rhs) > (batch * num_online_cpus())) {
+ if (count > rhs)
+ return 1;
+ else
+ return -1;
+ }
+ /* Need to use precise count */
+ count = percpu_counter_sum(fbc);
+ if (count > rhs)
+ return 1;
+ else if (count < rhs)
+ return -1;
+ else
+ return 0;
+}
+EXPORT_SYMBOL(__percpu_counter_compare);
+
+static int __init percpu_counter_startup(void)
+{
+ int ret;
+
+ ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "lib/percpu_cnt:online",
+ compute_batch_value, NULL);
+ WARN_ON(ret < 0);
+ ret = cpuhp_setup_state_nocalls(CPUHP_PERCPU_CNT_DEAD,
+ "lib/percpu_cnt:dead", NULL,
+ percpu_counter_cpu_dead);
+ WARN_ON(ret < 0);
+ return 0;
+}
+module_init(percpu_counter_startup);