Subject: Re: [PATCH 3/5] bpf: convert sock map and hash to map_copy_value

From: Jakub Sitnicki <[email-masked]>
Date: Wed, 11 Mar 2020 14:55:47 +0100

On Tue, Mar 10, 2020 at 06:47 PM CET, Lorenz Bauer wrote:
> Migrate sockmap and sockhash to use map_copy_value instead of
> map_lookup_elem_sys_only.
>
> Signed-off-by: Lorenz Bauer <[email-masked]>
> ---
>  net/core/sock_map.c | 48 ++++++++++++++++++++++++++++++---------------
>  1 file changed, 32 insertions(+), 16 deletions(-)
>
> diff --git a/net/core/sock_map.c b/net/core/sock_map.c
> index a7075b3b4489..03e04426cd21 100644
> --- a/net/core/sock_map.c
> +++ b/net/core/sock_map.c
> @@ -344,19 +344,34 @@ static void *sock_map_lookup(struct bpf_map *map, void *key)
>  	return __sock_map_lookup_elem(map, *(u32 *)key);
>  }
>
> -static void *sock_map_lookup_sys(struct bpf_map *map, void *key)
> +static int __sock_map_copy_value(struct bpf_map *map, struct sock *sk,
> +				 void *value)
> +{
> +	switch (map->value_size) {
> +	case sizeof(u64):
> +		sock_gen_cookie(sk);
> +		*(u64 *)value = atomic64_read(&sk->sk_cookie);

You could use sock_gen_cookie return value to merge the two above
statements into one. sock_gen_cookie also reads out the value.

> +		return 0;
> +
> +	default:
> +		return -ENOSPC;
> +	}
> +}
> +
> +static int sock_map_copy_value(struct bpf_map *map, void *key, void *value)
>  {
>  	struct sock *sk;
> +	int ret = -ENOENT;
>
> -	if (map->value_size != sizeof(u64))
> -		return ERR_PTR(-ENOSPC);
> -
> +	rcu_read_lock();
>  	sk = __sock_map_lookup_elem(map, *(u32 *)key);
>  	if (!sk)
> -		return ERR_PTR(-ENOENT);
> +		goto out;
>
> -	sock_gen_cookie(sk);
> -	return &sk->sk_cookie;
> +	ret = __sock_map_copy_value(map, sk, value);
> +out:
> +	rcu_read_unlock();
> +	return ret;
>  }
>
>  static int __sock_map_delete(struct bpf_stab *stab, struct sock *sk_test,
> @@ -636,7 +651,7 @@ const struct bpf_map_ops sock_map_ops = {
>  	.map_alloc		= sock_map_alloc,
>  	.map_free		= sock_map_free,
>  	.map_get_next_key	= sock_map_get_next_key,
> -	.map_lookup_elem_sys_only = sock_map_lookup_sys,
> +	.map_copy_value		= sock_map_copy_value,
>  	.map_update_elem	= sock_map_update_elem,
>  	.map_delete_elem	= sock_map_delete_elem,
>  	.map_lookup_elem	= sock_map_lookup,
> @@ -1030,19 +1045,20 @@ static void sock_hash_free(struct bpf_map *map)
>  	kfree(htab);
>  }
>
> -static void *sock_hash_lookup_sys(struct bpf_map *map, void *key)
> +static int sock_hash_copy_value(struct bpf_map *map, void *key, void *value)
>  {
>  	struct sock *sk;
> +	int ret = -ENOENT;
>
> -	if (map->value_size != sizeof(u64))
> -		return ERR_PTR(-ENOSPC);
> -
> +	rcu_read_lock();
>  	sk = __sock_hash_lookup_elem(map, key);
>  	if (!sk)
> -		return ERR_PTR(-ENOENT);
> +		goto out;
>
> -	sock_gen_cookie(sk);
> -	return &sk->sk_cookie;
> +	ret = __sock_map_copy_value(map, sk, value);
> +out:
> +	rcu_read_unlock();
> +	return ret;
>  }
>
>  static void *sock_hash_lookup(struct bpf_map *map, void *key)
> @@ -1139,7 +1155,7 @@ const struct bpf_map_ops sock_hash_ops = {
>  	.map_update_elem	= sock_hash_update_elem,
>  	.map_delete_elem	= sock_hash_delete_elem,
>  	.map_lookup_elem	= sock_hash_lookup,
> -	.map_lookup_elem_sys_only = sock_hash_lookup_sys,
> +	.map_copy_value		= sock_hash_copy_value,
>  	.map_release_uref	= sock_hash_release_progs,
>  	.map_check_btf		= map_check_no_btf,
>  };