Rate should never overflow or become zero because it is used as divider. This patch accumulates it with saturation.
Signed-off-by: Konstantin Khlebnikov <[email protected]> --- block/bfq-iosched.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index aeca22d91101..a236c8d541b5 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -2546,7 +2546,8 @@ static void bfq_reset_rate_computation(struct bfq_data *bfqd, static void bfq_update_rate_reset(struct bfq_data *bfqd, struct request *rq) { - u32 rate, weight, divisor; + u32 weight, divisor; + u64 rate; /* * For the convergence property to hold (see comments on @@ -2634,9 +2635,10 @@ static void bfq_update_rate_reset(struct bfq_data *bfqd, struct request *rq) */ bfqd->peak_rate *= divisor-1; bfqd->peak_rate /= divisor; - rate /= divisor; /* smoothing constant alpha = 1/divisor */ + do_div(rate, divisor); /* smoothing constant alpha = 1/divisor */ - bfqd->peak_rate += rate; + /* rate should never overlow or become zero */ + bfqd->peak_rate = clamp_t(u64, rate + bfqd->peak_rate, 1, U32_MAX); update_thr_responsiveness_params(bfqd); reset_computation:
