netdev - Re: [PATCH v2 net-next] socket: Move the socket inuse to namespace.

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Message-ID: <6988251D-1B12-4A92-9465-743B9FEA4199@didichuxing.com>
Date:   Tue, 14 Nov 2017 03:23:45 +0000
From:   张军伟(基础平台部) 
        <zhangjunweimartin@...ichuxing.com>
To:     Cong Wang <xiyou.wangcong@...il.com>
CC:     Tonghao Zhang <xiangxia.m.yue@...il.com>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        张同浩(基础平台部) 
        <zhangtonghao@...ichuxing.com>
Subject: Re: [PATCH v2 net-next] socket: Move the socket inuse to namespace.


> On 14 Nov 2017, at 10:09, Cong Wang <xiyou.wangcong@...il.com> wrote:
> 
> On Mon, Nov 13, 2017 at 4:36 AM, Tonghao Zhang <xiangxia.m.yue@...il.com> wrote:
>> From: Tonghao Zhang <xiangxia.m.yue@...il.com>
>> 
>> 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 sock_alloc or sock_release. In
>> the sock_alloc, the private data of inode saves the special
>> _net_. When releasing it, we can access the special _net_ and
>> dec the counter of socket in that namespace.
>> 
>> By the way, we dont use the 'current->nsproxy->net_ns' in the
>> sock_release. In one case，when one task exits, the 'do_exit'
>> may set the current->nsproxy NULL, and then call the sock_release.
>> Use the private data of inode, saving few bytes.
> 
> Why do you need to hold netns refcnt for socket? sock already holds
> it, so you can just access it by sock_net(sock->sk) ?
I think you suggestion is 
replace get_net(net) ===> with sock_net(sock->sk) 
 
If thus, I think it could not work.
Because sock->sk is assigned after sock_alloc.
What we change is done in sock_alloc.
By the way, sock->sk may has been released(NULL) in sock_release.