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

Martin KaFai Lau
2025-11-06T02:18:01Z

On 11/5/25 5:01 PM, Amery Hung wrote:
> 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.

ah. My bad for the noise. Fixed my mail client. Somehow only that one
email got filtered.

>
>> 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;
>>> +}
>>