Re: [PATCH v3] cgroup/bpf: fast path skb BPF filtering

[Pavel Begunkov]

On 12/15/21 16:40, Jakub Kicinski wrote:
> On Wed, 15 Dec 2021 14:49:18 +0000 Pavel Begunkov wrote:
> > +static inline bool
> > +__cgroup_bpf_prog_array_is_empty(struct cgroup_bpf *cgrp_bpf,
> > +				 enum cgroup_bpf_attach_type type)
> > +{
> > +	struct bpf_prog_array *array = rcu_access_pointer(cgrp_bpf->effective[type]);
> > +
> > +	return array == &bpf_empty_prog_array.hdr;
> > +}
> > +
> > +#define CGROUP_BPF_TYPE_ENABLED(sk, atype)				       \
> > +({									       \
> > +	struct cgroup *__cgrp = sock_cgroup_ptr(&(sk)->sk_cgrp_data);	       \
> > +									       \
> > +	!__cgroup_bpf_prog_array_is_empty(&__cgrp->bpf, (atype));	       \
> > +})
> > +
>
> > diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> > index e7a163a3146b..0d2195c6fb2a 100644
> > --- a/include/linux/bpf.h
> > +++ b/include/linux/bpf.h
> > @@ -1161,6 +1161,19 @@ struct bpf_prog_array {
> >   	struct bpf_prog_array_item items[];
> >   };
> >   
> > +struct bpf_empty_prog_array {
> > +	struct bpf_prog_array hdr;
> > +	struct bpf_prog *null_prog;
> > +};
> > +
> > +/* to avoid allocating empty bpf_prog_array for cgroups that
> > + * don't have bpf program attached use one global 'bpf_empty_prog_array'
> > + * It will not be modified the caller of bpf_prog_array_alloc()
> > + * (since caller requested prog_cnt == 0)
> > + * that pointer should be 'freed' by bpf_prog_array_free()
> > + */
> > +extern struct bpf_empty_prog_array bpf_empty_prog_array;
>
> mumble mumble, this adds more "fun" dependencies [1] Maybe I'm going

Header dependencies? It's declared right after struct bpf_prog_array,
and the other member is a pointer, so not sure what can go wrong.


> about this all wrong, maybe I should be pulling out struct cgroup_bpf
> so that cgroup.h does not need bpf-cgroup, not breaking bpf <-> bpf-cgroup.
> Alexei, WDYT?
>
> [1] https://lore.kernel.org/all/20211215061916.715513-2-kuba@xxxxxxxxxx/

--
Pavel Begunkov