This is a note to let you know that I've just added the patch titled
mm,vmscan: fix divide by zero in get_scan_count
to the 5.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
mm-vmscan-fix-divide-by-zero-in-get_scan_count.patch
and it can be found in the queue-5.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 32d4f4b782bb8f0ceb78c6b5dc46eb577ae25bf7 Mon Sep 17 00:00:00 2001
From: Rik van Riel <riel@xxxxxxxxxxx>
Date: Wed, 8 Sep 2021 18:10:08 -0700
Subject: mm,vmscan: fix divide by zero in get_scan_count
From: Rik van Riel <riel@xxxxxxxxxxx>
commit 32d4f4b782bb8f0ceb78c6b5dc46eb577ae25bf7 upstream.
Commit f56ce412a59d ("mm: memcontrol: fix occasional OOMs due to
proportional memory.low reclaim") introduced a divide by zero corner
case when oomd is being used in combination with cgroup memory.low
protection.
When oomd decides to kill a cgroup, it will force the cgroup memory to
be reclaimed after killing the tasks, by writing to the memory.max file
for that cgroup, forcing the remaining page cache and reclaimable slab
to be reclaimed down to zero.
Previously, on cgroups with some memory.low protection that would result
in the memory being reclaimed down to the memory.low limit, or likely
not at all, having the page cache reclaimed asynchronously later.
With f56ce412a59d the oomd write to memory.max tries to reclaim all the
way down to zero, which may race with another reclaimer, to the point of
ending up with the divide by zero below.
This patch implements the obvious fix.
Link: https://lkml.kernel.org/r/20210826220149.058089c6@xxxxxxxxxxxxxxxxxxxx
Fixes: f56ce412a59d ("mm: memcontrol: fix occasional OOMs due to proportional memory.low reclaim")
Signed-off-by: Rik van Riel <riel@xxxxxxxxxxx>
Acked-by: Roman Gushchin <guro@xxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Acked-by: Chris Down <chris@xxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
mm/vmscan.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2592,7 +2592,7 @@ out:
cgroup_size = max(cgroup_size, protection);
scan = lruvec_size - lruvec_size * protection /
- cgroup_size;
+ (cgroup_size + 1);
/*
* Minimally target SWAP_CLUSTER_MAX pages to keep
Patches currently in stable-queue which might be from riel@xxxxxxxxxxx are
queue-5.14/mm-vmscan-fix-divide-by-zero-in-get_scan_count.patch
