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

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Date: Fri, 28 Jun 2024 09:45:20 +0200
From: Michal Hocko <mhocko@...e.com>
To: Xiu Jianfeng <xiujianfeng@...wei.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 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.

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
> 

-- 
Michal Hocko
SUSE Labs