Rate should never overflow or become zero because it is used as divider.
This patch accumulates it with saturation.
Signed-off-by: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>
---
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:
