netdev - Re: [PATCH bpf-next v6 07/17] bpf: XDP metadata RX kfuncs

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Message-ID: <CAKH8qBvaTUH+gSYRXpmuLBS90=pAumvZ6dPyzdFrBndpEx3+sQ@mail.gmail.com>
Date:   Fri, 6 Jan 2023 09:17:17 -0800
From:   Stanislav Fomichev <sdf@...gle.com>
To:     Martin KaFai Lau <martin.lau@...ux.dev>
Cc:     ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
        song@...nel.org, yhs@...com, john.fastabend@...il.com,
        kpsingh@...nel.org, haoluo@...gle.com, jolsa@...nel.org,
        David Ahern <dsahern@...il.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Willem de Bruijn <willemb@...gle.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Anatoly Burakov <anatoly.burakov@...el.com>,
        Alexander Lobakin <alexandr.lobakin@...el.com>,
        Magnus Karlsson <magnus.karlsson@...il.com>,
        Maryam Tahhan <mtahhan@...hat.com>, xdp-hints@...-project.net,
        netdev@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH bpf-next v6 07/17] bpf: XDP metadata RX kfuncs

On Thu, Jan 5, 2023 at 4:48 PM Martin KaFai Lau <martin.lau@...ux.dev> wrote:
>
> On 1/4/23 1:59 PM, Stanislav Fomichev wrote:
> > +void *bpf_dev_bound_resolve_kfunc(struct bpf_prog *prog, u32 func_id)
> > +{
> > +     const struct xdp_metadata_ops *ops;
> > +     void *p = NULL;
> > +
> > +     /* We don't hold bpf_devs_lock while resolving several
> > +      * kfuncs and can race with the unregister_netdevice().
> > +      * We rely on bpf_dev_bound_match() check at attach
> > +      * to render this program unusable.
> > +      */
> > +     down_read(&bpf_devs_lock);
> > +     if (!prog->aux->offload || !prog->aux->offload->netdev)
>
> nit. !prog->aux->offload->netdev check is not needed. Testing
> !prog->aux->offload should be as good.

Yeah, true, will remove, thanks!