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Date: Thu, 20 Mar 2014 16:01:59 +0000
From: Zoltan Kiss <zoltan.kiss@citrix.com>
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To: Thomas Graf <tgraf@redhat.com>, Jesse Gross <jesse@nicira.com>,
        <pshelar@nicira.com>, <dev@openvswitch.org>
CC: "David S. Miller" <davem@davemloft.net>,
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Subject: Re: [PATCH v2] core, nfqueue, openvswitch: Orphan frags in skb_zerocopy
 and handle errors
References: <1395263249-16450-1-git-send-email-zoltan.kiss@citrix.com> <532ADC33.5040607@redhat.com> <532AE010.9050903@redhat.com>
In-Reply-To: <532AE010.9050903@redhat.com>
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On 20/03/14 12:33, Thomas Graf wrote:
> On 03/20/2014 01:16 PM, Thomas Graf wrote:
>> On 03/19/2014 10:07 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@citrix.com>
>>
>> Acked-by: Thomas Graf <tgraf@redhat.com>
>
> I take this back ;)
>
>>> ---
>>> +    if (unlikely(skb_orphan_frags(to, GFP_ATOMIC))) {
>>> +        skb_tx_error(to);
>>> +        return -ENOMEM;
>>> +    }
>
> Just noticed that you orphan the Netlink skb frags which do not
> exist yet instead of the source skb frags.
Oh, sorry, I'll fix this up.

>
>> Did you consider calling skb_tx_error() for Netlink message
>> allocation failures for the upcall as well? That memory pressure
>> is currently not reported back.
Yeah, that makes sense, I'll fix it the callers. Btw. I guess that just 
provides some statistical data for the creator of the skb. At least for 
netback it only increment a stat counter.

Zoli