linux-kernel - Re: [PATCH] core, nfqueue, openvswitch: Orphan frags in skb

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Message-ID: <532A06FC.5000001@citrix.com>
Date:	Wed, 19 Mar 2014 21:07:08 +0000
From:	Zoltan Kiss <zoltan.kiss@...rix.com>
To:	Thomas Graf <tgraf@...hat.com>, Jesse Gross <jesse@...ira.com>,
	<pshelar@...ira.com>, <dev@...nvswitch.org>
CC:	"David S. Miller" <davem@...emloft.net>,
	Pablo Neira Ayuso <pablo@...filter.org>,
	Patrick McHardy <kaber@...sh.net>,
	Jozsef Kadlecsik <kadlec@...ckhole.kfki.hu>,
	Eric Dumazet <edumazet@...gle.com>,
	Daniel Borkmann <dborkman@...hat.com>,
	Tom Herbert <therbert@...gle.com>,
	Jason Wang <jasowang@...hat.com>,
	Florian Westphal <fw@...len.de>, Joe Perches <joe@...ches.com>,
	Simon Horman <horms@...ge.net.au>,
	Jiri Pirko <jiri@...nulli.us>,
	"Michael S. Tsirkin" <mst@...hat.com>,
	Paul Durrant <Paul.Durrant@...rix.com>,
	Jan Beulich <JBeulich@...e.com>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Miklos Szeredi <mszeredi@...e.cz>,
	<netfilter-devel@...r.kernel.org>, <netfilter@...r.kernel.org>,
	<coreteam@...filter.org>, <xen-devel@...ts.xenproject.org>,
	<netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<kvm@...r.kernel.org>
Subject: Re: [PATCH] core, nfqueue, openvswitch: Orphan frags in skb_zerocopy
 and handle errors

On 19/03/14 20:47, Thomas Graf wrote:
> On 03/19/2014 09:38 PM, Zoltan Kiss wrote:
>> skb_zerocopy can copy elements of the frags array between skbs, but it
>> doesn't
>> orphan them. Also, it doesn't handle errors, so this patch takes care
>> of that
>> as well.
>>
>> Signed-off-by: Zoltan Kiss <zoltan.kiss@...rix.com>
>> ---
>
>> +    if (unlikely(skb_orphan_frags(to, GFP_ATOMIC))) {
>> +        skb_tx_error(to);
>> +        return -ENOMEM;
>>       }
>
> I think you should move this down to right before we iterate over the
> frags.

I agree, I was mislead by that __skb_fill_page_desc, but now I see it is 
actually the head buffer of the source, not a frag from there. And in 
case of a failure in skb_copy_bits we can spare an orphan_frag.

Zoli

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