The two variables 'numerator' and 'denominator', though they are declared as long, they should actually be unsigned long (according to the implementation of the fprop_fraction_percpu() function) And do_div() does a 64-by-32 division, while the divisor 'denominator' is unsigned long, thus 64-bit on 64-bit platforms. Hence the proper function to call is div64_ul(). 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 2d658b2..c74c6bd 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -766,7 +766,7 @@ static unsigned long __wb_calc_thresh(struct dirty_throttle_control *dtc) struct wb_domain *dom = dtc_dom(dtc); unsigned long thresh = dtc->thresh; u64 wb_thresh; - long numerator, denominator; + unsigned long numerator, denominator; unsigned long wb_min_ratio, wb_max_ratio; /* @@ -777,7 +777,7 @@ static unsigned long __wb_calc_thresh(struct dirty_throttle_control *dtc) wb_thresh = (thresh * (100 - bdi_min_ratio)) / 100; wb_thresh *= numerator; - do_div(wb_thresh, denominator); + wb_thresh = div64_ul(wb_thresh, denominator); wb_min_max_ratio(dtc->wb, &wb_min_ratio, &wb_max_ratio); -- 1.8.3.1
