netdev - Re: [PATCH net-next] net: sock: add the case if sk is NULL

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Date:   Mon, 09 Aug 2021 06:12:55 +0000
From:   yajun.deng@...ux.dev
To:     "Jakub Kicinski" <kuba@...nel.org>
Cc:     davem@...emloft.net, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next] net: sock: add the case if sk is NULL

August 6, 2021 9:11 PM, "Jakub Kicinski" <kuba@...nel.org> wrote:

> On Fri, 6 Aug 2021 14:38:15 +0800 Yajun Deng wrote:
> 
>> Add the case if sk is NULL in sock_{put, hold},
>> The caller is free to use it.
>> 
>> Signed-off-by: Yajun Deng <yajun.deng@...ux.dev>
> 
> The obvious complaint about this patch (and your previous netdev patch)
> is that you're spraying branches everywhere in the code. Sure, it may

Sorry for that, I'll be more normative in later submission.
> be okay for free(), given how expensive of an operation that is but
> is having refcounting functions accept NULL really the best practice?
> 
> Can you give us examples in the kernel where that's the case?

0   include/net/neighbour.h         neigh_clone()
1   include/linux/cgroup.h          get_cgroup_ns() and put_cgroup_ns()  (This is very similar to my submission)
2   include/linux/ipc_namespace.h   get_ipc_ns()
3   include/linux/posix_acl.h       posix_acl_dup()
4   include/linux/pid.h             get_pid()
5   include/linux/user_namespace.h  get_user_ns()