netdev - Re: [PATCH 3/6] net: Pass kern from net_proto_family.create to sk

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Date:	Sat, 09 May 2015 09:51:42 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	davem@...emloft.net, Ying Xue <ying.xue@...driver.com>,
	netdev@...r.kernel.org, cwang@...pensource.com, xemul@...nvz.org,
	maxk@....qualcomm.com, stephen@...workplumber.org, tgraf@...g.ch,
	nicolas.dichtel@...nd.com, tom@...bertland.com,
	jchapman@...alix.com, erik.hugne@...csson.com,
	jon.maloy@...csson.com, horms@...ge.net.au,
	Herbert Xu <herbert@...dor.apana.org.au>
Subject: Re: [PATCH 3/6] net: Pass kern from net_proto_family.create to
 sk_alloc

On Fri, 2015-05-08 at 21:09 -0500, Eric W. Biederman wrote:
> In preparation for changing how struct net is refcounted
> on kernel sockets pass the knowledge that we are creating
> a kernel socket from sock_create_kern through to sk_alloc.

...

>  
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index 3262f3e2b8b2..1a1c4f7b3ec5 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -2148,7 +2148,7 @@ static int tun_chr_open(struct inode *inode, struct file * file)
>  	DBG1(KERN_INFO, "tunX: tun_chr_open\n");
>  
>  	tfile = (struct tun_file *)sk_alloc(net, AF_UNSPEC, GFP_KERNEL,
> -					    &tun_proto);
> +					    &tun_proto, 0);
>  	if (!tfile)
>  		return -ENOMEM;
>  	RCU_INIT_POINTER(tfile->tun, NULL);
...

> index 3a4898ec8c67..d8dcf91732b0 100644
> --- a/include/net/sock.h
> +++ b/include/net/sock.h
> @@ -1514,7 +1514,7 @@ static inline void unlock_sock_fast(struct sock *sk, bool slow)
>  
> 
>  struct sock *sk_alloc(struct net *net, int family, gfp_t priority,
> -		      struct proto *prot);
> +		      struct proto *prot, int kern);


Problem adding lot of parameters to functions, is that 0 (or false)
means nothing when we read the code later and we have to go back to
sk_alloc() definition to check.

Sure, at the time you write the code everything is clear, but in 2 years
we wont have the context in our heads.

I would use an enumeration to ease code readability maybe.

enum sk_alloc_kern {
	SK_ALLOC_USER,
	SK_ALLOC_KERN,
};



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