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mm: memcontrol: do not miss MEMCG_MAX events for enforced allocations

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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 direct reclaim and
MEMCG_MAX events will be raised.  However a bpf map can belong to a
dying/abandoned memory cgroup, so there will be no allocations from a
process context and no MEMCG_MAX events will be triggered.

Link: https://lkml.kernel.org/r/20220702033521.64630-1-roman.gushchin@linux.dev
Signed-off-by: Roman Gushchin <roman.gushchin@linux.dev>
Reported-by: Yafang Shao <laoar.shao@gmail.com>
Acked-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Roman Gushchin 2022-07-01 20:35:21 -07:00 committed by akpm
parent ccac11da67
commit d6e103a757
1 changed files with 9 additions and 0 deletions
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9
mm/memcontrol.c
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@ -2577,6 +2577,7 @@ static int try_charge_memcg(struct mem_cgroup *memcg, gfp_t gfp_mask,
bool passed_oom = false;
bool may_swap = true;
bool drained = false;
bool raised_max_event = false;
unsigned long pflags;
retry:
@ -2616,6 +2617,7 @@ 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,
@ -2682,6 +2684,13 @@ nomem:
if (!(gfp_mask & (__GFP_NOFAIL | __GFP_HIGH)))
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