netdev - Re: [PATCH v2 bpf-next 2/4] bpf: Support associating BPF program with struct

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Message-ID: <CAMB2axO9GN=EMK2uLxqDLFkNk-V8sA7Rdb9LH3u6xx7fpCTyRA@mail.gmail.com>
Date: Fri, 17 Oct 2025 09:38:53 -0700
From: Amery Hung <ameryhung@...il.com>
To: Martin KaFai Lau <martin.lau@...ux.dev>
Cc: netdev@...r.kernel.org, alexei.starovoitov@...il.com, andrii@...nel.org, 
	daniel@...earbox.net, tj@...nel.org, martin.lau@...nel.org, 
	kernel-team@...a.com, bpf@...r.kernel.org
Subject: Re: [PATCH v2 bpf-next 2/4] bpf: Support associating BPF program with struct_ops

On Thu, Oct 16, 2025 at 5:19 PM Martin KaFai Lau <martin.lau@...ux.dev> wrote:
>
>
>
> On 10/16/25 1:45 PM, Amery Hung wrote:
> > Each associated programs except struct_ops programs of the map will take
> > a refcount on the map to pin it so that prog->aux->st_ops_assoc, if set,
> > is always valid. However, it is not guaranteed whether the map members
> > are fully updated nor is it attached or not. For example, a BPF program
> > can be associated with a struct_ops map before map_update. The
>
> Forgot to ask this, should it at least ensure the map is fully updated
> or it does not help in the use case?

It makes sense and is necessary. Originally, I thought we don't need
to make any promise about the state of the map since the struct_ops
implementers have to track the state of the struct_ops themselves
anyways. However, checking the state stored in kdata that may be
incomplete does not look right.

I will only return kdata from bpf_prog_get_assoc_struct_ops () when
kvalue->common.state == READY or INUSE.

If tracking the state in struct_ops kdata is overly complicated for
struct_ops implementers, then we might need to consider changing the
associated struct_ops from map to link.

>
> > struct_ops implementer will be responsible for maintaining and checking
> > the state of the associated struct_ops map before accessing it.
>