linux-kernel - Re: [PATCH v1 01/14] mm: introduce bpf struct ops for OOM handling

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Message-ID: <aLk0FuezkcInlM_r@slm.duckdns.org>
Date: Wed, 3 Sep 2025 20:39:18 -1000
From: Tejun Heo <tj@...nel.org>
To: Roman Gushchin <roman.gushchin@...ux.dev>
Cc: Alexei Starovoitov <alexei.starovoitov@...il.com>,
	Martin KaFai Lau <martin.lau@...ux.dev>,
	Kumar Kartikeya Dwivedi <memxor@...il.com>,
	linux-mm <linux-mm@...ck.org>, bpf <bpf@...r.kernel.org>,
	Suren Baghdasaryan <surenb@...gle.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Michal Hocko <mhocko@...e.com>,
	David Rientjes <rientjes@...gle.com>,
	Matt Bobrowski <mattbobrowski@...gle.com>,
	Song Liu <song@...nel.org>, Alexei Starovoitov <ast@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v1 01/14] mm: introduce bpf struct ops for OOM handling

Hello,

On Wed, Sep 03, 2025 at 04:30:16PM -0700, Roman Gushchin wrote:
...
> > - I'm passing in cgroup_id as an optional field in struct_ops and then in
> >   enable path, look up the matching cgroup, verify it can attach there and
> >   insert and update data structures accordingly:
> >
> >   https://git.kernel.org/pub/scm/linux/kernel/git/tj/sched_ext.git/tree/kernel/sched/ext.c?h=scx-hier-prototype#n5280
> 
> Yeah, we discussed this option with Martin up in this thread. It doesn't
> look as the best possible solution, but maybe the best we have at the moment.
> 
> Ideally, I want something like this:
> 
> void test_oom(void)
> {
> 	struct test_oom *skel;
> 	int err, cgroup_fd;
> 
>         cgroup_fd = open(...);
>         if (cgroup_fd < 0)
> 		goto cleanup;
> 
> 	skel = test_oom__open_and_load();
>         if (!skel)
> 		goto cleanup;
> 
> 	err = test_oom__attach_cgroup(skel, cgroup_fd);
> 	if (CHECK_FAIL(err))
> 		goto cleanup;

Yeah, that'd look better but are there practical differences? The only one I
can think of is fs based permission check but that can be done separately
too.

Thanks.

-- 
tejun