netdev - Re: [PATCH 2/9] bpf: array map: use pre-defined nop map function

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Date:	Mon, 11 Jan 2016 11:08:39 -0800
From:	Alexei Starovoitov <alexei.starovoitov@...il.com>
To:	Ming Lei <tom.leiming@...il.com>
Cc:	linux-kernel@...r.kernel.org, Alexei Starovoitov <ast@...nel.org>,
	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	Daniel Borkmann <daniel@...earbox.net>,
	Martin KaFai Lau <kafai@...com>
Subject: Re: [PATCH 2/9] bpf: array map: use pre-defined nop map function

On Mon, Jan 11, 2016 at 11:56:54PM +0800, Ming Lei wrote:
> So that we can remove the per-map nop map fucntions.
> 
> Signed-off-by: Ming Lei <tom.leiming@...il.com>
> ---
>  kernel/bpf/arraymap.c | 19 +++++--------------
>  1 file changed, 5 insertions(+), 14 deletions(-)
> 
> diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
> index b0799bc..9ad9031 100644
> --- a/kernel/bpf/arraymap.c
> +++ b/kernel/bpf/arraymap.c
> @@ -17,6 +17,8 @@
>  #include <linux/filter.h>
>  #include <linux/perf_event.h>
>  
> +#include "bpf_map.h"
> +
>  /* Called from syscall */
>  static struct bpf_map *array_map_alloc(union bpf_attr *attr)
>  {
> @@ -115,12 +117,6 @@ static int array_map_update_elem(struct bpf_map *map, void *key, void *value,
>  	return 0;
>  }
>  
> -/* Called from syscall or from eBPF program */
> -static int array_map_delete_elem(struct bpf_map *map, void *key)
> -{
> -	return -EINVAL;
> -}
> -
>  /* Called when map->refcnt goes to zero, either from workqueue or from syscall */
>  static void array_map_free(struct bpf_map *map)
>  {
> @@ -142,7 +138,7 @@ static const struct bpf_map_ops array_ops = {
>  	.map_get_next_key = array_map_get_next_key,
>  	.map_lookup_elem = array_map_lookup_elem,
>  	.map_update_elem = array_map_update_elem,
> -	.map_delete_elem = array_map_delete_elem,
> +	.map_delete_elem = map_delete_elem_nop,

I think moving these two callbacks into separate file only
reduces readbility. It doesn't look like that we save any .text this way.