From bcf2450f46cdce86a2a7e007d0b0a1bd68695e6c Mon Sep 17 00:00:00 2001 From: Jingbo Xu Date: Thu, 11 Dec 2025 10:35:06 +0800 Subject: [PATCH] mm: fix arithmetic for bdi min_ratio commit e0646b7590084a5bf3b056d3ad871d9379d2c25a upstream. 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 Link: https://lkml.kernel.org/r/20231219142508.86265-2-jefflexu@linux.alibaba.com Fixes: 8021fb3232f2 ("mm: split off __bdi_set_min_ratio() function") Signed-off-by: Jingbo Xu Reported-by: Joseph Qi Cc: Matthew Wilcox (Oracle) Cc: Stefan Roesch Signed-off-by: Andrew Morton Signed-off-by: Greg Kroah-Hartman --- mm/page-writeback.c | 1 - 1 file changed, 1 deletion(-) diff --git a/mm/page-writeback.c b/mm/page-writeback.c index 9ceb841af819..3929bb0a7501 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -714,7 +714,6 @@ 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) {