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

Amery Hung
2025-11-06T01:01:20Z

On Wed, Nov 5, 2025 at 4:57 PM Martin KaFai Lau <martin.lau@linux.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;
> > +}
>