netdev - RE: [PATCH net-next 1/2] net: permit skb_segment on head_frag frag

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Date:   Tue, 20 Mar 2018 05:30:58 +0000
From:   "Yuan, Linyu (NSB - CN/Shanghai)" <linyu.yuan@...ia-sbell.com>
To:     Yonghong Song <yhs@...com>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "ast@...com" <ast@...com>,
        "daniel@...earbox.net" <daniel@...earbox.net>,
        "diptanu@...com" <diptanu@...com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC:     "kernel-team@...com" <kernel-team@...com>
Subject: RE: [PATCH net-next 1/2] net: permit skb_segment on head_frag
 frag_list skb



> -----Original Message-----
> From: netdev-owner@...r.kernel.org [mailto:netdev-owner@...r.kernel.org]
> On Behalf Of Yonghong Song
> Sent: Tuesday, March 20, 2018 1:16 PM
> To: edumazet@...gle.com; ast@...com; daniel@...earbox.net;
> diptanu@...com; netdev@...r.kernel.org
> Cc: kernel-team@...com
> Subject: [PATCH net-next 1/2] net: permit skb_segment on head_frag frag_list
> skb
> 
> 
>  		while (pos < offset + len) {
>  			if (i >= nfrags) {
> -				BUG_ON(skb_headlen(list_skb));
> +				if (skb_headlen(list_skb) && check_list_skb == list_skb) {
Here cause next BUG_ON always false.
> +				} else {
> +					BUG_ON(skb_headlen(list_skb) && check_list_skb ==
> list_skb);
Just according code logic, no need BUG_ON, right? 
> 
> -				i = 0;
> -				nfrags = skb_shinfo(list_skb)->nr_frags;
> -				frag = skb_shinfo(list_skb)->frags;
> -				frag_skb = list_skb;
> +					i = 0;
> +					nfrags = skb_shinfo(list_skb)->nr_frags;
> +					frag = skb_shinfo(list_skb)->frags;
> +					frag_skb = list_skb;
> 
> -				BUG_ON(!nfrags);
> +					BUG_ON(!nfrags);
> 
> -				if (skb_orphan_frags(frag_skb, GFP_ATOMIC) ||
> -				    skb_zerocopy_clone(nskb, frag_skb,
> -						       GFP_ATOMIC))
> -					goto err;
> +					if (skb_orphan_frags(frag_skb, GFP_ATOMIC) ||
> +					    skb_zerocopy_clone(nskb, frag_skb,
> GFP_ATOMIC))
> +						goto err;
> 
> -				list_skb = list_skb->next;
> +					list_skb = list_skb->next;
> +					check_list_skb = list_skb;
> +				}
>  			}
> 
>  			if (unlikely(skb_shinfo(nskb)->nr_frags >=
> --
> 2.9.5