2 files changed, 35 insertions, 0 deletions

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 6e6e62648a4d..3984c4eb41fd 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -284,6 +284,13 @@ struct zone {
         unsigned long watermark[NR_WMARK];
 
         /*
+         * When free pages are below this point, additional steps are taken
+         * when reading the number of free pages to avoid per-cpu counter
+         * drift allowing watermarks to be breached
+         */
+        unsigned long percpu_drift_mark;
+
+        /*
          * We don't know if the memory that we're going to allocate will be freeable
          * or/and it will be released eventually, so to avoid totally wasting several
          * GB of ram we must reserve some of the lower zone memory (otherwise we risk
@@ -441,6 +448,12 @@ static inline int zone_is_oom_locked(const struct zone *zone)
         return test_bit(ZONE_OOM_LOCKED, &zone->flags);
 }
 
+#ifdef CONFIG_SMP
+unsigned long zone_nr_free_pages(struct zone *zone);
+#else
+#define zone_nr_free_pages(zone) zone_page_state(zone, NR_FREE_PAGES)
+#endif /* CONFIG_SMP */
+
 /*
  * The "priority" of VM scanning is how much of the queues we will scan in one
  * go. A value of 12 for DEF_PRIORITY implies that we will scan 1/4096th of the
diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h
index 7f43ccdc1d38..eaaea37b3b75 100644
--- a/include/linux/vmstat.h
+++ b/include/linux/vmstat.h
@@ -170,6 +170,28 @@ static inline unsigned long zone_page_state(struct zone *zone,
         return x;
 }
 
+/*
+ * More accurate version that also considers the currently pending
+ * deltas. For that we need to loop over all cpus to find the current
+ * deltas. There is no synchronization so the result cannot be
+ * exactly accurate either.
+ */
+static inline unsigned long zone_page_state_snapshot(struct zone *zone,
+                                        enum zone_stat_item item)
+{
+        long x = atomic_long_read(&zone->vm_stat[item]);
+
+#ifdef CONFIG_SMP
+        int cpu;
+        for_each_online_cpu(cpu)
+                x += per_cpu_ptr(zone->pageset, cpu)->vm_stat_diff[item];
+
+        if (x < 0)
+                x = 0;
+#endif
+        return x;
+}
+
 extern unsigned long global_reclaimable_pages(void);
 extern unsigned long zone_reclaimable_pages(struct zone *zone);