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From: Miaohe Lin <linmiaohe@huawei.com>
To: Shakeel Butt <shakeelb@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>,
	Michal Hocko <mhocko@kernel.org>,
	Vladimir Davydov <vdavydov.dev@gmail.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Roman Gushchin <guro@fb.com>,
	Matthew Wilcox <willy@infradead.org>, <alexs@kernel.org>,
	Wei Yang <richard.weiyang@gmail.com>,
	Muchun Song <songmuchun@bytedance.com>,
	Linux MM <linux-mm@kvack.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Cgroups <cgroups@vger.kernel.org>
Subject: Re: [PATCH 5/5] mm, memcg: always call __mod_node_page_state() with preempt disabled
Date: Fri, 30 Jul 2021 09:52:20 +0800	[thread overview]
Message-ID: <29c4bb2a-ceaf-6c8b-c222-38b30460780f@huawei.com> (raw)
In-Reply-To: <CALvZod6n1EwcyLTi=Eb8t=NVVPLRh9=Ng=VJ93pQyCRkOcLo9Q@mail.gmail.com>

On 2021/7/29 22:39, Shakeel Butt wrote:
> On Thu, Jul 29, 2021 at 5:58 AM Miaohe Lin <linmiaohe@huawei.com> wrote:
>>
>> We should always ensure __mod_node_page_state() is called with preempt
>> disabled or percpu ops may manipulate the wrong cpu when preempt happened.
>>
>> Fixes: b4e0b68fbd9d ("mm: memcontrol: use obj_cgroup APIs to charge kmem pages")
>> Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
>> ---
>>  mm/memcontrol.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
>> index 70a32174e7c4..616d1a72ece3 100644
>> --- a/mm/memcontrol.c
>> +++ b/mm/memcontrol.c
>> @@ -697,8 +697,8 @@ void __mod_lruvec_page_state(struct page *page, enum node_stat_item idx,
>>         memcg = page_memcg(head);
>>         /* Untracked pages have no memcg, no lruvec. Update only the node */
>>         if (!memcg) {
>> -               rcu_read_unlock();
>>                 __mod_node_page_state(pgdat, idx, val);
>> +               rcu_read_unlock();
> 
> This rcu is for page_memcg. The preemption and interrupts are disabled
> across __mod_lruvec_page_state().
> 

I thought it's used to protect __mod_node_page_state(). Looks somewhat confusing for me.
Many thanks for pointing this out!

>>                 return;
>>         }
>>
>> --
>> 2.23.0
>>
> .
> 


  reply	other threads:[~2021-07-30  1:52 UTC|newest]

Thread overview: 53+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-29 12:57 [PATCH 0/5] Cleanups and fixup for memcontrol Miaohe Lin
2021-07-29 12:57 ` [PATCH 1/5] mm, memcg: remove unused functions Miaohe Lin
2021-07-29 14:07   ` Shakeel Butt
2021-07-29 14:07     ` Shakeel Butt
2021-07-30  2:39   ` Muchun Song
2021-07-30  2:39     ` Muchun Song
2021-07-30  2:57   ` Roman Gushchin
2021-07-30  6:45   ` Michal Hocko
2021-07-29 12:57 ` [PATCH 2/5] mm, memcg: narrow the scope of percpu_charge_mutex Miaohe Lin
2021-07-30  2:42   ` Muchun Song
2021-07-30  2:42     ` Muchun Song
2021-07-30  3:06   ` Roman Gushchin
2021-07-30  6:50     ` Michal Hocko
2021-07-31  2:29       ` Miaohe Lin
2021-08-02  6:49         ` Michal Hocko
2021-08-02  9:54           ` Miaohe Lin
2021-08-03  3:40         ` Roman Gushchin
2021-08-03  6:29           ` Miaohe Lin
2021-08-03  7:11             ` Michal Hocko
2021-08-03  7:13               ` Roman Gushchin
2021-08-03  7:27                 ` Michal Hocko
2021-08-03  9:33             ` Muchun Song
2021-08-03  9:33               ` Muchun Song
2021-08-03 10:50               ` Miaohe Lin
2021-08-03 14:15       ` Johannes Weiner
2021-08-04  8:20         ` Michal Hocko
2021-08-05  1:44           ` Miaohe Lin
2021-07-30  6:46   ` Michal Hocko
2021-07-29 12:57 ` [PATCH 3/5] mm, memcg: save some atomic ops when flush is already true Miaohe Lin
2021-07-29 14:40   ` Shakeel Butt
2021-07-29 14:40     ` Shakeel Butt
2021-07-30  2:37   ` Muchun Song
2021-07-30  2:37     ` Muchun Song
2021-07-30  3:07   ` Roman Gushchin
2021-07-30  6:51   ` Michal Hocko
2021-07-29 12:57 ` [PATCH 4/5] mm, memcg: avoid possible NULL pointer dereferencing in mem_cgroup_init() Miaohe Lin
2021-07-29 13:52   ` Matthew Wilcox
2021-07-30  1:50     ` Miaohe Lin
2021-07-30  3:12   ` Roman Gushchin
2021-07-30  6:29     ` Miaohe Lin
2021-07-30  6:44     ` Michal Hocko
2021-07-31  2:05       ` Miaohe Lin
2021-08-02  6:43         ` Michal Hocko
2021-08-02 10:00           ` Miaohe Lin
2021-08-02 10:42             ` Michal Hocko
2021-08-02 11:18               ` Miaohe Lin
2021-07-29 12:57 ` [PATCH 5/5] mm, memcg: always call __mod_node_page_state() with preempt disabled Miaohe Lin
2021-07-29 14:39   ` Shakeel Butt
2021-07-29 14:39     ` Shakeel Butt
2021-07-30  1:52     ` Miaohe Lin [this message]
2021-07-30  2:33       ` [External] " Muchun Song
2021-07-30  2:33         ` Muchun Song
2021-07-30  2:46         ` Miaohe Lin

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