3.2.60-rc1 review patch. If anyone has any objections, please let me know.
------------------ From: Rik van Riel <[email protected]> commit d5c9fde3dae750889168807038243ff36431d276 upstream. It is possible for "limit - setpoint + 1" to equal zero, after getting truncated to a 32 bit variable, and resulting in a divide by zero error. Using the fully 64 bit divide functions avoids this problem. It also will cause pos_ratio_polynom() to return the correct value when (setpoint - limit) exceeds 2^32. Also uninline pos_ratio_polynom, at Andrew's request. Signed-off-by: Rik van Riel <[email protected]> Reviewed-by: Michal Hocko <[email protected]> Cc: Aneesh Kumar K.V <[email protected]> Cc: Mel Gorman <[email protected]> Cc: Nishanth Aravamudan <[email protected]> Cc: Luiz Capitulino <[email protected]> Cc: Masayoshi Mizuma <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]> [bwh: Backported to 3.2: Adjust context - pos_ratio_polynom() is not a separate function] Signed-off-by: Ben Hutchings <[email protected]> --- mm/page-writeback.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -559,7 +559,7 @@ static unsigned long bdi_position_ratio( * => fast response on large errors; small oscillation near setpoint */ setpoint = (freerun + limit) / 2; - x = div_s64(((s64)setpoint - (s64)dirty) << RATELIMIT_CALC_SHIFT, + x = div64_s64(((s64)setpoint - (s64)dirty) << RATELIMIT_CALC_SHIFT, limit - setpoint + 1); pos_ratio = x; pos_ratio = pos_ratio * x >> RATELIMIT_CALC_SHIFT; @@ -625,7 +625,7 @@ static unsigned long bdi_position_ratio( x_intercept = bdi_setpoint + span; if (bdi_dirty < x_intercept - span / 4) { - pos_ratio = div_u64(pos_ratio * (x_intercept - bdi_dirty), + pos_ratio = div64_u64(pos_ratio * (x_intercept - bdi_dirty), x_intercept - bdi_setpoint + 1); } else pos_ratio /= 4; -- 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/
