linux-kernel - Re: [PATCH v2 15/23] mm: introduce bpf_task_is_oom

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Message-ID: <aQD-RvxrX8_7QtxT@slm.duckdns.org>
Date: Tue, 28 Oct 2025 07:32:54 -1000
From: Tejun Heo <tj@...nel.org>
To: Roman Gushchin <roman.gushchin@...ux.dev>
Cc: Andrew Morton <akpm@...ux-foundation.org>, linux-kernel@...r.kernel.org,
	Alexei Starovoitov <ast@...nel.org>,
	Suren Baghdasaryan <surenb@...gle.com>,
	Michal Hocko <mhocko@...nel.org>,
	Shakeel Butt <shakeel.butt@...ux.dev>,
	Johannes Weiner <hannes@...xchg.org>,
	Andrii Nakryiko <andrii@...nel.org>,
	JP Kobryn <inwardvessel@...il.com>, linux-mm@...ck.org,
	cgroups@...r.kernel.org, bpf@...r.kernel.org,
	Martin KaFai Lau <martin.lau@...nel.org>,
	Song Liu <song@...nel.org>,
	Kumar Kartikeya Dwivedi <memxor@...il.com>
Subject: Re: [PATCH v2 15/23] mm: introduce bpf_task_is_oom_victim() kfunc

On Mon, Oct 27, 2025 at 04:21:58PM -0700, Roman Gushchin wrote:
> Export tsk_is_oom_victim() helper as a BPF kfunc.
> It's very useful to avoid redundant oom kills.
> 
> Signed-off-by: Roman Gushchin <roman.gushchin@...ux.dev>
> ---
>  mm/oom_kill.c | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
> 
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> index 72a346261c79..90bb86dee3cf 100644
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -1397,11 +1397,25 @@ __bpf_kfunc int bpf_out_of_memory(struct mem_cgroup *memcg__nullable,
>  	return ret;
>  }
>  
> +/**
> + * bpf_task_is_oom_victim - Check if the task has been marked as an OOM victim
> + * @task: task to check
> + *
> + * Returns true if the task has been previously selected by the OOM killer
> + * to be killed. It's expected that the task will be destroyed soon and some
> + * memory will be freed, so maybe no additional actions required.
> + */
> +__bpf_kfunc bool bpf_task_is_oom_victim(struct task_struct *task)
> +{
> +	return tsk_is_oom_victim(task);
> +}

In general, I'm not sure it's a good idea to add kfuncs for things which are
trivially accessible. Why can't things like this be provided as BPF helpers?

Thanks.

-- 
tejun