Re: [PATCH bpf-next v7 1/2] bpf: htab: Split htab_elem_lru and htab_elem_pcpu off of htab_elem

[Mykyta Yatsenko]

On 9/28/26 4:46 PM, bot+bpf-ci@xxxxxxxxxx wrote:
>> diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
>> index 53c99fe4f176..5db11a21ce98 100644
>> --- a/kernel/bpf/hashtab.c
>> +++ b/kernel/bpf/hashtab.c
> 
> [ ... ]
> 
>> @@ -828,8 +861,12 @@ static __always_inline void *__htab_lru_map_lookup_elem(struct bpf_map *map,
>>  	struct htab_elem *l = __htab_map_lookup_elem(map, key);
>>
>>  	if (l) {
>> -		if (mark)
>> -			bpf_lru_node_set_ref(&l->lru_node);
>> +		if (mark) {
>> +			struct htab_elem_lru *l_lru =
>> +				container_of(l, struct htab_elem_lru, elem);
>> +
>> +			bpf_lru_node_set_ref(&l_lru->lru_node);
>> +		}
>>  		return htab_elem_value(l, map->key_size);
>>  	}
>>
> 
> [ ... ]
> 
>> @@ -1310,16 +1349,19 @@ static long htab_map_update_elem(struct bpf_map *map, void *key, void *value,
>>
>>  static void htab_lru_push_free(struct bpf_htab *htab, struct htab_elem *elem)
>>  {
>> +	struct htab_elem_lru *l = container_of(elem, struct htab_elem_lru, elem);
>> +
>>  	check_and_cancel_fields(htab, elem);
>>  	bpf_map_dec_elem_count(&htab->map);
>> -	bpf_lru_push_free(&htab->lru, &elem->lru_node);
>> +	bpf_lru_push_free(&htab->lru, &l->lru_node);
>>  }
>>
> 
> [ ... ]
> 
>> @@ -1500,15 +1543,18 @@ static long __htab_lru_percpu_map_update_elem(struct bpf_map *map, void *key,
>>  		goto err;
>>
>>  	if (l_old) {
>> -		bpf_lru_node_set_ref(&l_old->lru_node);
>> +		struct htab_elem_lru *l_old_lru =
>> +			container_of(l_old, struct htab_elem_lru, elem);
>> +
>> +		bpf_lru_node_set_ref(&l_old_lru->lru_node);
>>
>>  		/* per-cpu hash map can update value in-place */
>>  		pcpu_copy_value(htab, htab_elem_get_ptr(l_old, key_size),
> 
> [ ... ]
> 
>> @@ -2505,7 +2551,10 @@ static void *htab_lru_percpu_map_lookup_elem(struct bpf_map *map, void *key)
>>  	struct htab_elem *l = __htab_map_lookup_elem(map, key);
>>
>>  	if (l) {
>> -		bpf_lru_node_set_ref(&l->lru_node);
>> +		struct htab_elem_lru *l_lru =
>> +			container_of(l, struct htab_elem_lru, elem);
>> +
>> +		bpf_lru_node_set_ref(&l_lru->lru_node);
>>  		return this_cpu_ptr(htab_elem_get_ptr(l, map->key_size));
>>  	}
>>
>> @@ -2521,7 +2570,10 @@ static void *htab_lru_percpu_map_lookup_percpu_elem(struct bpf_map *map, void *k
>>
>>  	l = __htab_map_lookup_elem(map, key);
>>  	if (l) {
>> -		bpf_lru_node_set_ref(&l->lru_node);
>> +		struct htab_elem_lru *l_lru =
>> +			container_of(l, struct htab_elem_lru, elem);
>> +
>> +		bpf_lru_node_set_ref(&l_lru->lru_node);
>>  		return per_cpu_ptr(htab_elem_get_ptr(l, map->key_size), cpu);
>>  	}
>>
> 
> This isn't a bug, but would a small helper keep these call sites to one
> line, matching the pcpu accessors this patch adds? Each site now repeats
> the same container_of(l, struct htab_elem_lru, elem) boilerplate followed
> by bpf_lru_node_set_ref(). The patch adds htab_elem_get_ptr_to_pptr() and
> htab_elem_set_ptr_to_pptr() for the pcpu variant, but open-codes the
> container_of for the LRU variant at every site.
> 

this sounds like a good refactoring:

static inline void bpf_lru_node_set_ref(struct htab_elem *l)
{
	struct htab_elem_lru *l_lru =
		container_of(l, struct htab_elem_lru, elem);
	
	if (!READ_ONCE(l_lru.lru_node->ref))
		WRITE_ONCE(l_lru.lru_node, 1);
}
> 
> ---
> AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
> See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md
> 
> CI run summary: https://github.com/kernel-patches/bpf/actions/runs/36441357391