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SubjectRe: [PATCH v3] cgroup/bpf: fast path skb BPF filtering
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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@kernel.org/
>

--
Pavel Begunkov

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