netdev - Re: [v2 PATCH] net: Stop decapitating clones that have a head

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Message-ID: <1336019638.12425.16.camel@edumazet-glaptop>
Date:	Thu, 03 May 2012 06:33:58 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Alexander Duyck <alexander.h.duyck@...el.com>
Cc:	netdev@...r.kernel.org, davem@...emloft.net,
	Eric Dumazet <edumazet@...gle.com>,
	Jeff Kirsher <jeffrey.t.kirsher@...el.com>
Subject: Re: [v2 PATCH] net: Stop decapitating clones that have a head_frag

On Wed, 2012-05-02 at 21:18 -0700, Alexander Duyck wrote:
> This change is meant ot prevent stealing the skb->head to use as a page in
> the event that the skb->head was cloned.  This allows the other clones to
> track each other via shinfo->dataref.
> 
> Without this we break down to two methods for tracking the reference count,
> one being dataref, the other being the page count.  As a result it becomes
> difficult to track how many references there are to skb->head.
> 
> Signed-off-by: Alexander Duyck <alexander.h.duyck@...el.com>
> Cc: Eric Dumazet <edumazet@...gle.com>
> Cc: Jeff Kirsher <jeffrey.t.kirsher@...el.com>
> ---
> 
>  net/core/skbuff.c    |    9 +++++----
>  net/ipv4/tcp_input.c |    9 ++-------
>  2 files changed, 7 insertions(+), 11 deletions(-)
> 
> diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> index 52ba2b5..9e8caa0 100644
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -1699,17 +1699,18 @@ static bool __skb_splice_bits(struct sk_buff *skb, struct pipe_inode_info *pipe,
>  			      struct splice_pipe_desc *spd, struct sock *sk)
>  {
>  	int seg;
> -	bool head_is_linear = !skb->head_frag;
> +	bool head_is_locked = !skb->head_frag || skb_cloned(skb);
>  

Thanks

Acked-by: Eric Dumazet <edumazet@...gle.com>



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