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
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: Jingbo Xu <jefflexu@xxxxxxxxxxxxxxxxx>
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@xxxxxxxxxxxxxxxxx
Fixes: 8021fb3232f2 ("mm: split off __bdi_set_min_ratio() function")
Signed-off-by: Jingbo Xu <jefflexu@xxxxxxxxxxxxxxxxx>
Reported-by: Joseph Qi <joseph.qi@xxxxxxxxxxxxxxxxx>
Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Stefan Roesch <shr@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
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@xxxxxxxxxxxxxxxxx are
mm-fix-arithmetic-for-bdi-min_ratio.patch
mm-fix-arithmetic-for-max_prop_frac-when-setting-max_ratio.patch
