Re: [PATCH bpf-next v9 6/8] libbpf: Update a bpf_link with another struct_ops.

[Kui-Feng Lee <sinquersw@xxxxxxxxx>]

On 3/21/23 14:04, Martin KaFai Lau wrote:
> On 3/20/23 12:56 PM, Kui-Feng Lee wrote:
> > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> > index 56a60ab2ca8f..f84d68c049e3 100644
> > --- a/tools/lib/bpf/libbpf.c
> > +++ b/tools/lib/bpf/libbpf.c
> > @@ -11639,6 +11639,11 @@ struct bpf_link 
> > *bpf_map__attach_struct_ops(const struct bpf_map *map)
> >       /* kern_vdata should be prepared during the loading phase. */
> >       err = bpf_map_update_elem(map->fd, &zero, 
> > map->st_ops->kern_vdata, 0);
> > +    /* It can be EBUSY if the map has been used to create or
> > +     * update a link before.  We don't allow updating the value of
> > +     * a struct_ops once it is set.  That ensures that the value
> > +     * never changed.  So, it is safe to skip EBUSY.
> > +     */
>
> This belongs to the earlier patch (4?).

Got it!

> >       if (err && err != -EBUSY) {
> >           free(link);
> >           return libbpf_err_ptr(err);