netdev - Re: [patch net-next-2.6] bonding: remove skb_share_check in handle

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Message-ID: <20110302211238.GC3360@psychotron.redhat.com>
Date:	Wed, 2 Mar 2011 22:12:38 +0100
From:	Jiri Pirko <jpirko@...hat.com>
To:	Nicolas de Pesloüan 
	<nicolas.2p.debian@...il.com>
Cc:	Andy Gospodarek <andy@...yhouse.net>, netdev@...r.kernel.org,
	davem@...emloft.net, fubar@...ibm.com, eric.dumazet@...il.com
Subject: Re: [patch net-next-2.6] bonding: remove skb_share_check in
 handle_frame

Wed, Mar 02, 2011 at 09:47:50PM CET, nicolas.2p.debian@...il.com wrote:
>Le 02/03/2011 11:03, Jiri Pirko a écrit :
>>Tue, Mar 01, 2011 at 09:38:43PM CET, andy@...yhouse.net wrote:
>>>On Tue, Mar 01, 2011 at 10:29:07AM +0100, Jiri Pirko wrote:
>>>>Unapplicable, sorry (wrong branch :(). Here's corrected patch:
>>>>
>>>>Subject: [PATCH net-next-2.6 v2] bonding: remove skb_share_check in handle_frame
>>>>
>>>>No need to do share check here.
>>>>
>>>>Signed-off-by: Jiri Pirko<jpirko@...hat.com>
>>>>---
>>>>  drivers/net/bonding/bond_main.c |    3 ---
>>>>  1 files changed, 0 insertions(+), 3 deletions(-)
>>>>
>>>>diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
>>>>index 584f97b..367ea60 100644
>>>>--- a/drivers/net/bonding/bond_main.c
>>>>+++ b/drivers/net/bonding/bond_main.c
>>>>@@ -1498,9 +1498,6 @@ static struct sk_buff *bond_handle_frame(struct sk_buff *skb)
>>>>  	struct net_device *slave_dev;
>>>>  	struct net_device *bond_dev;
>>>>
>>>>-	skb = skb_share_check(skb, GFP_ATOMIC);
>>>>-	if (unlikely(!skb))
>>>>-		return NULL;
>>>>  	slave_dev = skb->dev;
>>>>  	bond_dev = ACCESS_ONCE(slave_dev->master);
>>>>  	if (unlikely(!bond_dev))
>>>>--
>>>>1.7.3.4
>>>>
>>>
>>>Why did you decide to get rid of it here rather than the 3 places in the
>>>bonding driver where it is currently needed?  I think this can cover
>>>those cases since bond_handle_frame will be called after the ptype_all
>>>handlers before any of the ptype handlers.
>>
>>I have already a patch prepared which converts bond ptype handlers into
>>being called from bond_handle_frame. You are propably right that this
>>should probably stay here.
>
>Hi Jiri,
>
>Do you plan to call the bonding ARP handler from inside bond_handle_frame()?

I do - it's part of patchset I've cooked (going to test that tomorrow).

>
>A few days ago
>(http://marc.info/?l=linux-netdev&m=129883949022340&w=2), I noticed
>that it is not possible to call the bonding ARP handler from inside
>the bonding rx_handler, because some frame processing may be required
>after the bonding rx_handler call, to put the frame in a suitable
>state for the bonding ARP handler.

Do you see another scenario besides the next one?

>
>This is at least true with the following setup, eth0 -> bond0 ->
>bond0.100, where the ARP frames are VLAN tagged at the time the
>bonding rx_handler process them.

Isn't this scenario resolved by vlan_on_bond_hook ?

eth0
  ->rx_handler -> another round
bond0
  ->vlan_hwaccel_do_receive -> __netif_receive_skb
bond0.100
  ->vlan_on_bond_hook -> reinject to bond0


>
>	Nicolas.
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