Re: [PATCH v4 2/2] sock: Move the socket inuse to namespace.

[David Miller <davem@davemloft.net>]

From: Tonghao Zhang <xiangxia.m.yue@gmail.com>
Date: Wed, 22 Nov 2017 17:51:25 -0800

> This patch add a member in struct netns_core. And this is
> a counter for socket_inuse in the _net_ namespace. The patch
> will add/sub counter in the sk_alloc or sk_free. Because socket and
> sock is in pair. It's a easy way to maintain the code and help
> developer to review. More important, it avoids holding the _net_
> namespace again.
> 
> Signed-off-by: Martin Zhang <zhangjunweimartin@didichuxing.com>
> Signed-off-by: Tonghao Zhang <zhangtonghao@didichuxing.com>

First, it is extremely unclear why this is better.  You do not explain
the reason at all.

Second:

> @@ -2646,17 +2646,8 @@ static int __init sock_init(void)
>  #ifdef CONFIG_PROC_FS
>  void socket_seq_show(struct seq_file *seq)
>  {
> -	int cpu;
> -	int counter = 0;
> -
> -	for_each_possible_cpu(cpu)
> -	    counter += per_cpu(sockets_in_use, cpu);
> -
> -	/* It can be negative, by the way. 8) */
> -	if (counter < 0)
> -		counter = 0;
> -
> -	seq_printf(seq, "sockets: used %d\n", counter);

You've deleted the only use of "sockets_in_use" but you have not
removed that per-cpu variable and it's maintainence.

But do not even bother fixing this if you cannot explain properly
why these changes are an improvement.  I do not understant it,
and until I do I cannot consider these changes seriously.

Thank you.