The variables 'min' and 'max' are unsigned long and
do_div truncates them to 32 bits, which means it can test
non-zero and be truncated to zero for division.
Fix this issue by using div64_ul() instead.
Fixes: 693108a8a667 ("writeback: make bdi->min/max_ratio handling cgroup writeback aware")
Signed-off-by: Wen Yang <wenyang@xxxxxxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Qian Cai <cai@xxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Cc: linux-mm@xxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
---
mm/page-writeback.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 50055d2..2d658b2 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -201,11 +201,11 @@ static void wb_min_max_ratio(struct bdi_writeback *wb,
if (this_bw < tot_bw) {
if (min) {
min *= this_bw;
- do_div(min, tot_bw);
+ min = div64_ul(min, tot_bw);
}
if (max < 100) {
max *= this_bw;
- do_div(max, tot_bw);
+ max = div64_ul(max, tot_bw);
}
}
--
1.8.3.1
