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Subject[PATCH v2 1/2] mm: fix arithmetic for bdi min_ratio
Date
Since now bdi->min_ratio is part per million, fix the wrong arithmetic.
Otherwise it will fail with -EINVAL when setting a reasonable min_ratio,
as it tries to set min_ratio to (min_ratio * BDI_RATIO_SCALE) in
percentage unit, which exceeds 100% anyway.

# cat /sys/class/bdi/253\:0/min_ratio
0
# cat /sys/class/bdi/253\:0/max_ratio
100
# echo 1 > /sys/class/bdi/253\:0/min_ratio
-bash: echo: write error: Invalid argument

Fixes: 8021fb3232f2 ("mm: split off __bdi_set_min_ratio() function")
Reported-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Signed-off-by: Jingbo Xu <jefflexu@linux.alibaba.com>
---
mm/page-writeback.c | 1 -
1 file changed, 1 deletion(-)

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index ee2fd6a6af40..2140382dd768 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) {
--
2.19.1.6.gb485710b

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