+cc fsdevel
On 12/18/23 11:16 AM, Jingbo Xu wrote:
> bdi->[min|max]_ratio are both part per million. Fix the wrong
> arithmetic when setting bdi's min_ratio and max_ratio.
>
> Fixes: efc3e6ad53ea ("mm: split off __bdi_set_max_ratio() function")
> Fixes: 8021fb3232f2 ("mm: split off __bdi_set_min_ratio() function")
> Reported-by: Joseph Qi <joseph.qi@xxxxxxxxxxxxxxxxx>
> Signed-off-by: Jingbo Xu <jefflexu@xxxxxxxxxxxxxxxxx>
> ---
> mm/page-writeback.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
> index ee2fd6a6af40..b393b3281ce9 100644
> --- a/mm/page-writeback.c
> +++ b/mm/page-writeback.c
> @@ -692,7 +692,6 @@ static int __bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ra
>
> if (min_ratio > 100 * BDI_RATIO_SCALE)
> return -EINVAL;
> - min_ratio *= BDI_RATIO_SCALE;
>
> spin_lock_bh(&bdi_lock);
> if (min_ratio > bdi->max_ratio) {
> @@ -729,7 +728,8 @@ static int __bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned int max_ra
> ret = -EINVAL;
> } else {
> bdi->max_ratio = max_ratio;
> - bdi->max_prop_frac = (FPROP_FRAC_BASE * max_ratio) / 100;
> + bdi->max_prop_frac = div64_u64(FPROP_FRAC_BASE * max_ratio,
> + 100UL * BDI_RATIO_SCALE);
> }
> spin_unlock_bh(&bdi_lock);
>
--
Thanks,
Jingbo
