writeback: fix uninitialized task_ratelimit

In balance_dirty_pages() task_ratelimit may be not initialized
(initialization skiped by goto pause), and then used when calling
tracing hook.

Fix it by moving the task_ratelimit assignment before goto pause.

Reported-by: Witold Baryluk <baryluk@smp.if.uj.edu.pl>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>

1 files changed, 4 insertions, 4 deletions

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 0360d1b5a1dd..a3278f005230 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -1097,13 +1097,13 @@ static void balance_dirty_pages(struct address_space *mapping,
                 pos_ratio = bdi_position_ratio(bdi, dirty_thresh,
                                                background_thresh, nr_dirty,
                                                bdi_thresh, bdi_dirty);
-                if (unlikely(pos_ratio == 0)) {
+                task_ratelimit = ((u64)dirty_ratelimit * pos_ratio) >>
+                                                        RATELIMIT_CALC_SHIFT;
+                if (unlikely(task_ratelimit == 0)) {
                         pause = max_pause;
                         goto pause;
                 }
-                task_ratelimit = (u64)dirty_ratelimit *
-                                        pos_ratio >> RATELIMIT_CALC_SHIFT;
-                pause = (HZ * pages_dirtied) / (task_ratelimit | 1);
+                pause = HZ * pages_dirtied / task_ratelimit;
                 if (unlikely(pause <= 0)) {
                         trace_balance_dirty_pages(bdi,
                                                   dirty_thresh,