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

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Message-ID: <a76ad1e9-07d5-4ba1-83e4-22fe36a32df0@linux.dev>
Date: Tue, 2 Sep 2025 15:30:04 -0700
From: Martin KaFai Lau <martin.lau@...ux.dev>
To: Roman Gushchin <roman.gushchin@...ux.dev>
Cc: Alexei Starovoitov <alexei.starovoitov@...il.com>,
 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

On 9/2/25 10:31 AM, Roman Gushchin wrote:
> Btw, what's the right way to attach struct ops to a cgroup, if there is
> one? Add a cgroup_id field to the struct and use it in the .reg()

Adding a cgroup id/fd field to the struct bpf_oom_ops will be hard to attach the 
same bpf_oom_ops to multiple cgroups.

> callback? Or there is something better?

There is a link_create.target_fd in the "union bpf_attr". The 
cgroup_bpf_link_attach() is using it as cgroup fd. May be it can be used here 
also. This will limit it to link attach only. Meaning the 
SEC(".struct_ops.link") is supported but not the older SEC(".struct_ops"). I 
think this should be fine.