netdev - Re: [PATCH] bridge: orphan frags on local receive

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Message-ID: <530BF9CD.3080802@huawei.com>
Date:	Tue, 25 Feb 2014 10:02:53 +0800
From:	Qin Chuanyu <qinchuanyu@...wei.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>
CC:	<davem@...emloft.net>, KVM list <kvm@...r.kernel.org>,
	<netdev@...r.kernel.org>
Subject: Re: [PATCH] bridge: orphan frags on local receive

On 2014/2/24 23:49, Michael S. Tsirkin wrote:
> On Mon, Feb 24, 2014 at 09:52:11PM +0800, Qin Chuanyu wrote:
>> On 2014/2/24 21:29, Michael S. Tsirkin wrote:
>>> On Mon, Feb 24, 2014 at 09:12:20PM +0800, Qin Chuanyu wrote:
>>>> with vhost tx zero_copy, guest nic might get hang when host reserving
>>>> skb in socket queue delivered by guest, the case has been solved in
>>>> tun, it also been needed by bridge. This could easily happened when a
>>>> LAST_ACK state tcp occuring between guest and host.
>>>>
>>>> Signed-off-by: Chuanyu Qin <qinchuanyu@...wei.com>
>>>
>>> Do you actually observe guest hang?
>>>
>> yes, guest nic could not xmit any more until the skb holded by host has
>> been freed, the mainly reason is that though virtio-net could use vring
>> desc out of order, but ubufs is been used by vhost in order. so only
>> one skb could cause guest nic hang.
>>> I would expect orphan frags in
>>> __netif_receive_skb_core to be enough.
>>>
>> yes, it would be better. I would deliver another patch soon.
>
> well __netif_receive_skb_core already calls orphan frags already.
> What's left to do?
>
None :) , I will use with this change.
>>>
>>>> ---
>>>>   net/bridge/br_input.c |    3 +++
>>>>   1 files changed, 3 insertions(+), 0 deletions(-)
>>>>
>>>> diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c
>>>> index 28d5446..744e27a 100644
>>>> --- a/net/bridge/br_input.c
>>>> +++ b/net/bridge/br_input.c
>>>> @@ -117,6 +117,8 @@ int br_handle_frame_finish(struct sk_buff *skb)
>>>>   		br->dev->stats.multicast++;
>>>>   	} else if ((dst = __br_fdb_get(br, dest, vid)) &&
>>>>   			dst->is_local) {
>>>> +		if (unlikely(skb_orphan_frags(skb, GFP_ATOMIC)))
>>>> +			goto drop;
>>>>   		skb2 = skb;
>>>>   		/* Do not forward the packet since it's local. */
>>>>   		skb = NULL;
>>>> @@ -136,6 +138,7 @@ int br_handle_frame_finish(struct sk_buff *skb)
>>>>   out:
>>>>   	return 0;
>>>>   drop:
>>>> +	skb_tx_error(skb);
>>>>   	kfree_skb(skb);
>>>>   	goto out;
>>>>   }
>>>> --
>>>> 1.7.3.1.msysgit.0
>>>
>>>
>>
>
> .
>


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