summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authorRik van Riel <riel@surriel.com>2021-09-09 04:10:08 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2021-09-09 04:45:53 +0300
commit32d4f4b782bb8f0ceb78c6b5dc46eb577ae25bf7 (patch)
tree20e7e2215804e2287a9e690959927d5280f6c40d
parent13db8c50477d83ad3e3b9b0ae247e5cd833a7ae4 (diff)
downloadlinux-32d4f4b782bb8f0ceb78c6b5dc46eb577ae25bf7.tar.xz
mm,vmscan: fix divide by zero in get_scan_count
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@imladris.surriel.com Fixes: f56ce412a59d ("mm: memcontrol: fix occasional OOMs due to proportional memory.low reclaim") Signed-off-by: Rik van Riel <riel@surriel.com> Acked-by: Roman Gushchin <guro@fb.com> Acked-by: Michal Hocko <mhocko@suse.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Chris Down <chris@chrisdown.name> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/vmscan.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 740d03e6dae2..74296c2d1fed 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2715,7 +2715,7 @@ 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