Messages in this thread Patch in this message |  | | Date | Tue, 29 Apr 2014 15:19:10 -0400 | From | Rik van Riel <> | Subject | [PATCH] mm,writeback: fix divide by zero in pos_ratio_polynom |
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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 <riel@redhat.com> Cc: stable@vger.kernel.org --- 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;
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