Merge tag 'lsk-v3.10-15.05-android' into develop-3.10

[firefly-linux-kernel-4.4.55.git] / mm / page-writeback.c

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 5a45b9d0acd4650f908adaed20e40cbde21548b1..cdbe3cd0f86d9e679329ae9b6f1b42ab3f38d6e6 100644 (file)
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -794,8 +794,11 @@ static void bdi_update_write_bandwidth(struct backing_dev_info *bdi,
         *                   bw * elapsed + write_bandwidth * (period - elapsed)
         * write_bandwidth = ---------------------------------------------------
         *                                          period
+        *
+        * @written may have decreased due to account_page_redirty().
+        * Avoid underflowing @bw calculation.
         */
-       bw = written - bdi->written_stamp;
+       bw = written - min(written, bdi->written_stamp);
        bw *= HZ;
        if (unlikely(elapsed > period)) {
                do_div(bw, elapsed);
@@ -859,7 +862,7 @@ static void global_update_bandwidth(unsigned long thresh,
                                    unsigned long now)
 {
        static DEFINE_SPINLOCK(dirty_lock);
-       static unsigned long update_time;
+       static unsigned long update_time = INITIAL_JIFFIES;
 
        /*
         * check locklessly first to optimize away locking for the most time