tmpfs: add accurate compare function to percpu_counter library

[pandora-kernel.git] / lib / percpu_counter.c

diff --git a/lib/percpu_counter.c b/lib/percpu_counter.c
index aeaa6d7..ec9048e 100644 (file)
--- 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();