2 files changed, 38 insertions, 0 deletions

diff --git a/include/linux/percpu_counter.h b/include/linux/percpu_counter.h
index c88d67b59394..8a7d510ffa9c 100644
--- a/include/linux/percpu_counter.h
+++ b/include/linux/percpu_counter.h
@@ -40,6 +40,7 @@ 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);
+int percpu_counter_compare(struct percpu_counter *fbc, s64 rhs);
 
 static inline void percpu_counter_add(struct percpu_counter *fbc, s64 amount)
 {
@@ -98,6 +99,16 @@ 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 void
 percpu_counter_add(struct percpu_counter *fbc, s64 amount)
 {
diff --git a/lib/percpu_counter.c b/lib/percpu_counter.c
index aeaa6d734447..ec9048e74f44 100644
--- a/lib/percpu_counter.c
+++ b/lib/percpu_counter.c
@@ -137,6 +137,33 @@ static int __cpuinit percpu_counter_hotcpu_callback(struct notifier_block *nb,
         return NOTIFY_OK;
 }
 
+/*
+ * 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)
+{
+        s64     count;
+
+        count = percpu_counter_read(fbc);
+        /* Check to see if rough count will be sufficient for comparison */
+        if (abs(count - rhs) > (percpu_counter_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)
 {
         compute_batch_value();