Commit d6e103a7 authored by Roman Gushchin's avatar Roman Gushchin Committed by Andrew Morton
Browse files

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

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: default avatarRoman Gushchin <roman.gushchin@linux.dev>
Reported-by: default avatarYafang Shao <laoar.shao@gmail.com>
Acked-by: default avatarShakeel Butt <shakeelb@google.com>
Acked-by: default avatarMichal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent ccac11da

mm/memcontrol.c

+9 −0
Original line number Diff line number Diff line
@@ -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 @@ static int try_charge_memcg(struct mem_cgroup *memcg, gfp_t gfp_mask, 
		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 @@ static int try_charge_memcg(struct mem_cgroup *memcg, gfp_t gfp_mask, 
	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