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

Qin Chuanyu
2014-02-24T13:52:11Z

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@huawei.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.
>
>> ---
>> 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
>
>