The patch titled
do not miss MEMCG_MAX events for enforced allocations Date: Fri, 1 Jul
has been added to the -mm mm-unstable branch. Its filename is
mm-memcontrol-do-not-miss-memcg_max-events-for-enforced-allocations.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-memcontrol-do-not-miss-memcg_max-events-for-enforced-allocations.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Roman Gushchin <roman.gushchin@xxxxxxxxx> Subject: mm: memcontrol:
do not miss MEMCG_MAX events for enforced allocations Date: Fri, 1 Jul
2022 20:35:21 -0700 Yafang Shao reported an issue related to the
accounting of bpf memory: if a bpf map is charged indirectly for memory
consumed from an interrupt context and allocations are enforced, MEMCG_MAX
events are not raised.
It's not/less of an issue in a generic case because consequent allocations
from a process context will trigger the reclaim and MEMCG_MAX events.
However a bpf map can belong to a dying/abandoned memory cgroup, so it
might never happen. So the cgroup can significantly exceed the memory.max
limit without even triggering MEMCG_MAX events.
Fix this by making sure that we never enforce allocations without raising
a MEMCG_MAX event.
Link: https://lkml.kernel.org/r/20220702033521.64630-1-roman.gushchin@xxxxxxxxx
Signed-off-by: Roman Gushchin <roman.gushchin@xxxxxxxxx>
Reported-by: Yafang Shao <laoar.shao@xxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Shakeel Butt <shakeelb@xxxxxxxxxx>
Cc: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memcontrol.c | 9 +++++++++
1 file changed, 9 insertions(+)
--- a/mm/memcontrol.c~mm-memcontrol-do-not-miss-memcg_max-events-for-enforced-allocations
+++ a/mm/memcontrol.c
@@ -2712,6 +2712,7 @@ static int try_charge_memcg(struct mem_c
bool passed_oom = false;
bool may_swap = true;
bool drained = false;
+ bool raised_max_event = false;
unsigned long pflags;
retry:
@@ -2751,6 +2752,7 @@ retry:
goto nomem;
memcg_memory_event(mem_over_limit, MEMCG_MAX);
+ raised_max_event = true;
psi_memstall_enter(&pflags);
nr_reclaimed = try_to_free_mem_cgroup_pages(mem_over_limit, nr_pages,
@@ -2818,6 +2820,13 @@ nomem:
return -ENOMEM;
force:
/*
+ * If the allocation has to be enforced, don't forget to raise
+ * a MEMCG_MAX event.
+ */
+ if (!raised_max_event)
+ memcg_memory_event(mem_over_limit, MEMCG_MAX);
+
+ /*
* The allocation either can't fail or will lead to more memory
* being freed very soon. Allow memory usage go over the limit
* temporarily by force charging it.
_
Patches currently in -mm which might be from roman.gushchin@xxxxxxxxx are
mm-memcontrol-introduce-mem_cgroup_ino-and-mem_cgroup_get_from_ino.patch
mm-shrinkers-introduce-debugfs-interface-for-memory-shrinkers.patch
mm-shrinkers-provide-shrinkers-with-names.patch
mm-shrinkers-provide-shrinkers-with-names-fix.patch
mm-docs-document-shrinker-debugfs.patch
tools-add-memcg_shrinkerpy.patch
mm-shrinkers-add-scan-interface-for-shrinker-debugfs.patch
mm-shrinkers-add-scan-interface-for-shrinker-debugfs-fix.patch
mm-memcontrol-do-not-miss-memcg_max-events-for-enforced-allocations.patch
