netdev - Re: [PATCH v2 net-next 3/6] bonding: make bond_alb use 8021q's dev->vlan_info instead of vlan

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Message-ID: <20130809112414.GC17510@redhat.com>
Date:	Fri, 9 Aug 2013 13:24:14 +0200
From:	Veaceslav Falico <vfalico@...hat.com>
To:	Nikolay Aleksandrov <nikolay@...hat.com>
Cc:	netdev@...r.kernel.org, Jay Vosburgh <fubar@...ibm.com>,
	Andy Gospodarek <andy@...yhouse.net>
Subject: Re: [PATCH v2 net-next 3/6] bonding: make bond_alb use 8021q's
 dev->vlan_info instead of vlan_list

On Fri, Aug 09, 2013 at 01:13:58PM +0200, Nikolay Aleksandrov wrote:
>On 08/08/2013 06:57 PM, Veaceslav Falico wrote:
>> RFC -> v1: use the changed __vlan_find_dev_next, which now works with
>> 	   vlan's net_device instead of vlan's id. Also, fix a subtle race
>> 	   condition if we remove the only vlan while looping through
>> 	   MAX_LP_BURST - we end up with using the old vlan_id, so set it
>> 	   to 0 if we don't have vlans.
>> v1  -> v2: no change.
>>
>> In alb mode, we only need each vlan's id (that is on top of bond) to tag
>> learning packets, so get them via __vlan_find_dev_next(bond->dev, last_dev).
>>
>> We must also find *any* vlan (including last id stored in current_alb_vlan)
>> if we can't find anything >= current_alb_vlan id.
>>
>> For that, we verify if bond has any vlans at all, and if yes - find the
>> next vlan id after current_alb_vlan id. So, if vlan id is not 0, we tag the
>> skb.
>>
>> CC: Jay Vosburgh <fubar@...ibm.com>
>> CC: Andy Gospodarek <andy@...yhouse.net>
>> Signed-off-by: Veaceslav Falico <vfalico@...hat.com>
>> ---
>>  drivers/net/bonding/bond_alb.c |   47 ++++++++++++++++++++++++++++-----------
>>  drivers/net/bonding/bond_alb.h |    2 +-
>>  2 files changed, 35 insertions(+), 14 deletions(-)
>>
>> diff --git a/drivers/net/bonding/bond_alb.c b/drivers/net/bonding/bond_alb.c
>> index 2684329..ced5753 100644
>> --- a/drivers/net/bonding/bond_alb.c
>> +++ b/drivers/net/bonding/bond_alb.c
>> @@ -974,8 +974,9 @@ static void alb_send_learning_packets(struct slave *slave, u8 mac_addr[])
>>  {
>>  	struct bonding *bond = bond_get_bond_by_slave(slave);
>>  	struct learning_pkt pkt;
>> +	struct net_device *vlan_dev;
>>  	int size = sizeof(struct learning_pkt);
>> -	int i;
>> +	int i, vlan_id;
>Styling nitpick: maybe re-arrange them longest -> shortest ?

Yep, sure, thank you.

>
>>
>>  	memset(&pkt, 0, size);
>>  	memcpy(pkt.mac_dst, mac_addr, ETH_ALEN);
>> @@ -1000,22 +1001,42 @@ static void alb_send_learning_packets(struct slave *slave, u8 mac_addr[])
>>  		skb->priority = TC_PRIO_CONTROL;
>>  		skb->dev = slave->dev;
>>
>> +		rcu_read_lock();
>Would've saved a couple of lines if we could move the rcu_read_lock inside the
>if {} block but I know that you're keeping the bond_vlan_used() result here, but
>I think that with the new functions we're covered i.e. if the vlan has
>disappeared between the call to bond_vlan_used and the afterwards we'll get NULL
>and just drop the packet, but this can be reworked to continue with the packet
>without a vlan if one is not found that is to send it without tag :-)

Yeah, not a lot of sense to hold it, however I don't see right now how it
might save us lines - we need to hold vlan_dev if it's found, and need to
release the lock if it's NULL (before continue).

>>  		if (bond_vlan_used(bond)) {
>> -			struct vlan_entry *vlan;
>> -
>> -			vlan = bond_next_vlan(bond,
>> -					      bond->alb_info.current_alb_vlan);
>> -
>> -			bond->alb_info.current_alb_vlan = vlan;
>> -			if (!vlan) {
>> +			/* first try to find the previously used vlan by
>> +			 * id, which might have gone away already
>> +			 */
>> +			vlan_id = bond->alb_info.current_alb_vlan;
>> +			vlan_dev = __vlan_find_dev_deep(bond->dev,
>> +							htons(ETH_P_8021Q),
>> +							vlan_id);
>> +
>> +			/* search for the next one, if not found - for any */
>> +			if (vlan_dev)
>> +				vlan_dev = __vlan_find_dev_next(bond->dev,
>> +								vlan_dev);
>> +			if (!vlan_dev)
>> +				vlan_dev = __vlan_find_dev_next(bond->dev,
>> +								NULL);
>> +
>This part really looks ambiguous, I've left a comment that concerns it in my
>reply to patch 02.

Yep, seen that, it indeed is not quite clear (though working when you think
a bit about it :) ). I'll address your comment about 02/06 in several days,
I'm travelling now.

>
>> +			if (vlan_dev) {
>> +				vlan_id = vlan_dev_vlan_id(vlan_dev);
>> +				bond->alb_info.current_alb_vlan = vlan_id;
>> +			} else {
>> +				bond->alb_info.current_alb_vlan = 0;
>> +				rcu_read_unlock();
>>  				kfree_skb(skb);
>>  				continue;
>>  			}
>> +		} else
>> +			vlan_id = 0;
>Styling nitpick: if {} else {}

Yep, thanks.

>
>Cheers,
> Nik
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