David Hildenbrand <david@xxxxxxxxxx> writes:
...
>
> I would have done it slightly differently, something like:
>
>
> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
> index d213ead956750..4b02f18f7d01f 100644
> --- a/mm/page-writeback.c
> +++ b/mm/page-writeback.c
> @@ -685,13 +685,15 @@ static int bdi_check_pages_limit(unsigned long pages)
> return 0;
> }
> -static unsigned long bdi_ratio_from_pages(unsigned long pages)
> +static long bdi_ratio_from_pages(unsigned long pages)
> {
> unsigned long background_thresh;
> unsigned long dirty_thresh;
> unsigned long ratio;
> global_dirty_limits(&background_thresh, &dirty_thresh);
> + if (!dirty_thresh)
> + return -EINVAL;
> ratio = div64_u64(pages * 100ULL * BDI_RATIO_SCALE, dirty_thresh);
> return ratio;
> @@ -790,13 +792,15 @@ int bdi_set_min_bytes(struct backing_dev_info *bdi, u64 min_bytes)
> {
> int ret;
> unsigned long pages = min_bytes >> PAGE_SHIFT;
> - unsigned long min_ratio;
> + long min_ratio;
> ret = bdi_check_pages_limit(pages);
> if (ret)
> return ret;
> min_ratio = bdi_ratio_from_pages(pages);
> + if (min_ratio < 0)
> + return min_ratio;
> return __bdi_set_min_ratio(bdi, min_ratio);
> }
> @@ -809,13 +813,15 @@ int bdi_set_max_bytes(struct backing_dev_info *bdi, u64
> max_bytes)
> {
> int ret;
> unsigned long pages = max_bytes >> PAGE_SHIFT;
> - unsigned long max_ratio;
> + long max_ratio;
> ret = bdi_check_pages_limit(pages);
> if (ret)
> return ret;
> max_ratio = bdi_ratio_from_pages(pages);
> + if (min_ratio < 0)
I assume you meant max_ratio.
> + return min_ratio;
> return __bdi_set_max_ratio(bdi, max_ratio);
> }
> -- Cheers,
>
I'll use your recommendation for the next version of the patch.
