linux-kernel - Re: [PATCH -next] mm: memcg: adjust the warning when seq

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Date: Fri, 28 Jun 2024 16:09:02 +0800
From: xiujianfeng <xiujianfeng@...wei.com>
To: Michal Hocko <mhocko@...e.com>
CC: <hannes@...xchg.org>, <roman.gushchin@...ux.dev>,
	<shakeel.butt@...ux.dev>, <muchun.song@...ux.dev>,
	<akpm@...ux-foundation.org>, <cgroups@...r.kernel.org>, <linux-mm@...ck.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -next] mm: memcg: adjust the warning when seq_buf
 overflows



On 2024/6/28 15:45, Michal Hocko wrote:
> On Fri 28-06-24 07:23:33, Xiu Jianfeng wrote:
>> Currently it uses WARN_ON_ONCE() if seq_buf overflows when user reads
>> memory.stat, the only advantage of WARN_ON_ONCE is that the splat is
>> so verbose that it gets noticed. And also it panics the system if
>> panic_on_warn is enabled. It seems like the warning is just an over
>> reaction and a simple pr_warn should just achieve the similar effect.
>>
>> Suggested-by: Michal Hocko <mhocko@...e.com>
>> Signed-off-by: Xiu Jianfeng <xiujianfeng@...wei.com>
> 
> Acked-by: Michal Hocko <mhocko@...e.com>
> 
> I would just squash this with other patch removing it from
> memcg_stat_format. But this is up to you.

Sorry, I might have misunderstood, if you can squash them, it looks good
to me, thanks.

> 
> Thanks!
> 
>> ---
>>  mm/memcontrol.c | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
>> index c251bbe35f4b..8e5590ac43d7 100644
>> --- a/mm/memcontrol.c
>> +++ b/mm/memcontrol.c
>> @@ -1484,7 +1484,8 @@ static void memory_stat_format(struct mem_cgroup *memcg, struct seq_buf *s)
>>  		memcg_stat_format(memcg, s);
>>  	else
>>  		memcg1_stat_format(memcg, s);
>> -	WARN_ON_ONCE(seq_buf_has_overflowed(s));
>> +	if (seq_buf_has_overflowed(s))
>> +		pr_warn("%s: Warning, stat buffer overflow, please report\n", __func__);
>>  }
>>  
>>  /**
>> -- 
>> 2.34.1
>>
>