netdev - Re: [PATCH] net-sched: add packet length pointer parameter for qdisc

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Message-ID: <20080731070233.GA4769@ff.dom.local>
Date:	Thu, 31 Jul 2008 07:02:33 +0000
From:	Jarek Poplawski <jarkao2@...il.com>
To:	Jussi Kivilinna <jussi.kivilinna@...et.fi>
Cc:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH] net-sched: add packet length pointer parameter for
	qdisc_enqueue

On 30-07-2008 20:55, Jussi Kivilinna wrote:
> Pass packet length to caller through pointer so that length is
> available to caller even if inner qdisc frees skb.
...
> diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
> index b5f40d7..a428b93 100644
> --- a/include/net/sch_generic.h
> +++ b/include/net/sch_generic.h
> @@ -331,19 +331,22 @@ static inline unsigned int qdisc_pkt_len(struct sk_buff *skb)
>  	return qdisc_skb_cb(skb)->pkt_len;
>  }
>  
> -static inline int qdisc_enqueue(struct sk_buff *skb, struct Qdisc *sch)
> +static inline int qdisc_enqueue(struct sk_buff *skb, struct Qdisc *sch,
> +				unsigned int *pkt_len)
>  {
>  #ifdef CONFIG_NET_SCHED
>  	if (sch->stab)
>  		qdisc_calculate_pkt_len(skb, sch->stab);
>  #endif
> +	if (likely(pkt_len != NULL))
> +		*pkt_len = qdisc_pkt_len(skb);
>  	return sch->enqueue(skb, sch);
>  }

As I've written before, IMHO using an skb after enqueuing should be
avoided unless we refcounted it or the returned code is clear enough,
so the idea of this patch could be right to me. But, I guess, you are
changing here the way it's done: the size is calculated before the
current enqueing instead of after the last one.

BTW, since I don't really get this "stab" idea enough, I wonder how
it is expected to be used: with a top qdisc, a leaf one or some
summing?

Jarek P.
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