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

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Message-ID: <20140224132926.GF8981@redhat.com>
Date:	Mon, 24 Feb 2014 15:29:26 +0200
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Qin Chuanyu <qinchuanyu@...wei.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 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?

I would expect orphan frags in
__netif_receive_skb_core to be enough.


> ---
>  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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