> -----Original Message----- > From: Rik van Riel [mailto:[email protected]] > Sent: Tuesday, April 29, 2014 3:19 PM > To: [email protected] > Cc: [email protected]; [email protected]; [email protected]; > [email protected]; Motohiro Kosaki JP; > [email protected]; [email protected]; [email protected] > Subject: [PATCH] mm,writeback: fix divide by zero in pos_ratio_polynom > > It is possible for "limit - setpoint + 1" to equal zero, leading to a divide > by zero error. Blindly adding 1 to "limit - setpoint" is not working, > so we need to actually test the divisor before calling div64. > > Signed-off-by: Rik van Riel <[email protected]> > Cc: [email protected]
Fairly obvious fix. Acked-by: KOSAKI Motohiro <[email protected]> > --- > mm/page-writeback.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/mm/page-writeback.c b/mm/page-writeback.c index ef41349..2682516 > 100644 > --- a/mm/page-writeback.c > +++ b/mm/page-writeback.c > @@ -597,11 +597,16 @@ static inline long long pos_ratio_polynom(unsigned long > setpoint, > unsigned long dirty, > unsigned long limit) > { > + unsigned int divisor; > long long pos_ratio; > long x; > > + divisor = limit - setpoint; > + if (!divisor) > + divisor = 1; > + > x = div_s64(((s64)setpoint - (s64)dirty) << RATELIMIT_CALC_SHIFT, > - limit - setpoint + 1); > + divisor); > pos_ratio = x; > pos_ratio = pos_ratio * x >> RATELIMIT_CALC_SHIFT; > pos_ratio = pos_ratio * x >> RATELIMIT_CALC_SHIFT; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
