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

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Message-ID: <1f2711b1-d809-4063-804b-7b2a3c8d933e@linux.dev>
Date: Fri, 22 Aug 2025 12:27:48 -0700
From: Martin KaFai Lau <martin.lau@...ux.dev>
To: Roman Gushchin <roman.gushchin@...ux.dev>,
 Kumar Kartikeya Dwivedi <memxor@...il.com>
Cc: linux-mm@...ck.org, 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>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 01/14] mm: introduce bpf struct ops for OOM handling

On 8/20/25 5:24 PM, Roman Gushchin wrote:
>> How is it decided who gets to run before the other? Is it based on
>> order of attachment (which can be non-deterministic)?
> Yeah, now it's the order of attachment.
> 
>> There was a lot of discussion on something similar for tc progs, and
>> we went with specific flags that capture partial ordering constraints
>> (instead of priorities that may collide).
>> https://lore.kernel.org/all/20230719140858.13224-2-daniel@iogearbox.net
>> It would be nice if we can find a way of making this consistent.

+1

The cgroup bpf prog has recently added the mprog api support also. If the simple 
order of attachment is not enough and needs to have specific ordering, we should 
make the bpf struct_ops support the same mprog api instead of asking each 
subsystem creating its own.

fyi, another need for struct_ops ordering is to upgrade the 
BPF_PROG_TYPE_SOCK_OPS api to struct_ops for easier extension in the future. 
Slide 13 in https://drive.google.com/file/d/1wjKZth6T0llLJ_ONPAL_6Q_jbxbAjByp/view