Re: [PATCH bpf-next v2 22/35] bpf: eliminate rlimit-based memory accounting for bpf ringbuffer

[Song Liu]

On Mon, Jul 27, 2020 at 12:22 PM Roman Gushchin <guro@xxxxxx> wrote:
>
> Do not use rlimit-based memory accounting for bpf ringbuffer.
> It has been replaced with the memcg-based memory accounting.
>
> bpf_ringbuf_alloc() can't return anything except ERR_PTR(-ENOMEM)
> and a valid pointer, so to simplify the code make it return NULL
> in the first case. This allows to drop a couple of lines in
> ringbuf_map_alloc() and also makes it look similar to other memory
> allocating function like kmalloc().
>
> Signed-off-by: Roman Gushchin <guro@xxxxxx>

Acked-by: Song Liu <songliubraving@xxxxxx>

> ---
>  kernel/bpf/ringbuf.c | 24 ++++--------------------
>  1 file changed, 4 insertions(+), 20 deletions(-)
>
> diff --git a/kernel/bpf/ringbuf.c b/kernel/bpf/ringbuf.c
> index e8e2c39cbdc9..e687b798d097 100644
> --- a/kernel/bpf/ringbuf.c
> +++ b/kernel/bpf/ringbuf.c
> @@ -48,7 +48,6 @@ struct bpf_ringbuf {
>
>  struct bpf_ringbuf_map {
>         struct bpf_map map;
> -       struct bpf_map_memory memory;
>         struct bpf_ringbuf *rb;
>  };
>
> @@ -135,7 +134,7 @@ static struct bpf_ringbuf *bpf_ringbuf_alloc(size_t data_sz, int numa_node)
>
>         rb = bpf_ringbuf_area_alloc(data_sz, numa_node);
>         if (!rb)
> -               return ERR_PTR(-ENOMEM);
> +               return NULL;
>
>         spin_lock_init(&rb->spinlock);
>         init_waitqueue_head(&rb->waitq);
> @@ -151,8 +150,6 @@ static struct bpf_ringbuf *bpf_ringbuf_alloc(size_t data_sz, int numa_node)
>  static struct bpf_map *ringbuf_map_alloc(union bpf_attr *attr)
>  {
>         struct bpf_ringbuf_map *rb_map;
> -       u64 cost;
> -       int err;
>
>         if (attr->map_flags & ~RINGBUF_CREATE_FLAG_MASK)
>                 return ERR_PTR(-EINVAL);
> @@ -174,26 +171,13 @@ static struct bpf_map *ringbuf_map_alloc(union bpf_attr *attr)
>
>         bpf_map_init_from_attr(&rb_map->map, attr);
>
> -       cost = sizeof(struct bpf_ringbuf_map) +
> -              sizeof(struct bpf_ringbuf) +
> -              attr->max_entries;
> -       err = bpf_map_charge_init(&rb_map->map.memory, cost);
> -       if (err)
> -               goto err_free_map;
> -
>         rb_map->rb = bpf_ringbuf_alloc(attr->max_entries, rb_map->map.numa_node);
> -       if (IS_ERR(rb_map->rb)) {
> -               err = PTR_ERR(rb_map->rb);
> -               goto err_uncharge;
> +       if (!rb_map->rb) {
> +               kfree(rb_map);
> +               return ERR_PTR(-ENOMEM);
>         }
>
>         return &rb_map->map;
> -
> -err_uncharge:
> -       bpf_map_charge_finish(&rb_map->map.memory);
> -err_free_map:
> -       kfree(rb_map);
> -       return ERR_PTR(err);
>  }
>
>  static void bpf_ringbuf_free(struct bpf_ringbuf *rb)
> --
> 2.26.2
>