netdev - Re: [PATCH bpf-next v5 2/7] bpf: Support associating BPF program with struct

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Message-ID: <CAMB2axP7z6xWs_YuLDEKi1ciz0QE9b507nDf5FcydNjWq8MogA@mail.gmail.com>
Date: Wed, 5 Nov 2025 17:01:08 -0800
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 bpf-next v5 2/7] bpf: Support associating BPF program with struct_ops

On Wed, Nov 5, 2025 at 4:57 PM Martin KaFai Lau <martin.lau@...ux.dev> wrote:
>
>
>
> On 11/4/25 9:26 AM, Amery Hung wrote:
> > +void *bpf_prog_get_assoc_struct_ops(const struct bpf_prog_aux *aux)
> > +{
> > +     struct bpf_map *st_ops_assoc = READ_ONCE(aux->st_ops_assoc);
> > +     struct bpf_struct_ops_map *st_map;
> > +
> > +     if (!st_ops_assoc || st_ops_assoc == BPF_PTR_POISON)
> > +             return NULL;
> > +
> > +     st_map = (struct bpf_struct_ops_map *)st_ops_assoc;
> > +
> > +     if (smp_load_acquire(&st_map->kvalue.common.state) == BPF_STRUCT_OPS_STATE_INIT) {
> > +             bpf_map_put(st_ops_assoc);
>
> hmm... why bpf_map_put is needed?
>

AI also caught this. This is not needed. I overlooked it when changing
from v4, where bpf_prog_get_assoc_struct_ops() used to first bump the
refcount.

> Should the state be checked only once during assoc time instead of
> checking it every time bpf_prog_get_assoc_struct_ops is called?
>
> > +             return NULL;
> > +     }
> > +
> > +     return &st_map->kvalue.data;
> > +}
>