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

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Message-ID: <CAM_iQpXrSTVDeW82BLTT1EdjRkvUHBGZJU2iWy8gSzaAfqRjzg@mail.gmail.com>
Date:   Mon, 13 Nov 2017 21:58:17 -0800
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     张军伟(基础平台部) 
        <zhangjunweimartin@...ichuxing.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 Mon, Nov 13, 2017 at 7:23 PM, 张军伟(基础平台部)
<zhangjunweimartin@...ichuxing.com> wrote:
>
>> 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)

Not literally, but essentially yes.


>
> If thus, I think it could not work.
> Because sock->sk is assigned after sock_alloc.
> What we change is done in sock_alloc.

You don't have to do it in sock_alloc().


> By the way, sock->sk may has been released(NULL) in sock_release.

My point is since sock is always paired with a sk and sk already
holds refcnt, you don't need to hold it again, it looks unnecessary.