+ mm-fix-arithmetic-for-bdi-min_ratio.patch added to mm-hotfixes-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm: fix arithmetic for bdi min_ratio
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     mm-fix-arithmetic-for-bdi-min_ratio.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-fix-arithmetic-for-bdi-min_ratio.patch

This patch will later appear in the mm-hotfixes-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Jingbo Xu <jefflexu@linux.alibaba.com>
Subject: mm: fix arithmetic for bdi min_ratio
Date: Tue, 19 Dec 2023 22:25:07 +0800

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 <jefflexu@linux.alibaba.com>
Reported-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Stefan Roesch <shr@devkernel.io>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/page-writeback.c |    1 -
 1 file changed, 1 deletion(-)

--- a/mm/page-writeback.c~mm-fix-arithmetic-for-bdi-min_ratio
+++ a/mm/page-writeback.c
@@ -692,7 +692,6 @@ static int __bdi_set_min_ratio(struct ba
 
 	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) {
_

Patches currently in -mm which might be from jefflexu@linux.alibaba.com are

mm-fix-arithmetic-for-bdi-min_ratio.patch
mm-fix-arithmetic-for-max_prop_frac-when-setting-max_ratio.patch