From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Dumazet <eric.dumazet@gmail.com>
Subject: Re: [PATCH net] net: sched: shrink struct qdisc_skb_cb to 28 bytes
Date: Thu, 18 Sep 2014 12:14:39 -0700
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Cc: Stephen Hemminger <stephen@networkplumber.org>,
	Or Gerlitz <or.gerlitz@gmail.com>,
	Govindarajulu Varadarajan <_govind@gmx.com>,
	Yinghai Lu <yinghai@kernel.org>,
	David Miller <davem@davemloft.net>,
	NetDev <netdev@vger.kernel.org>, ssujith@cisco.com,
	gvaradar@cisco.com, "Christian Benvenuti (benve)" <benve@cisco.com>
To: Joe Perches <joe@perches.com>
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On Thu, 2014-09-18 at 11:07 -0700, Joe Perches wrote:

> > +static inline struct ipoib_cb *ipoib_skb_cb(const struct sk_buff *skb)
> > +{
> > +	BUILD_BUG_ON(sizeof(skb->cb) < sizeof(struct ipoib_cb));
> > +	return (struct ipoib_cb *)skb->cb;
> > +}
> 
> It seems better not to use const for the struct sk_buff * here.
> 
> Neither of the uses take a const struct sk_buff *

Thats pretty standard, check for other similar constructs like that.


static inline struct qdisc_skb_cb *qdisc_skb_cb(const struct sk_buff *skb)
{
        return (struct qdisc_skb_cb *)skb->cb;
}

This allows uses of the helper when the skb is only read (has the const qual)