netdev - Re: [PATCH net 2/2] net/bonding: correctly proxy slave neigh param setup ndo function

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Date:	Wed, 04 Apr 2012 09:56:22 -0700
From:	Jay Vosburgh <fubar@...ibm.com>
To:	Or Gerlitz <ogerlitz@...lanox.com>
cc:	davem@...emloft.net, roland@...nel.org, netdev@...r.kernel.org,
	Shlomo Pongratz <shlomop@...lanox.com>
Subject: Re: [PATCH net 2/2] net/bonding: correctly proxy slave neigh param setup ndo function

Or Gerlitz <ogerlitz@...lanox.com> wrote:

>On 4/4/2012 1:53 AM, Jay Vosburgh wrote:
>> Or Gerlitz<ogerlitz@...lanox.com>  wrote:
>>
>>> From: Shlomo Pongratz<shlomop@...lanox.com>
>>>
>>> The current implemenation was buggy for slaves who use ndo_neigh_setup,
>>> since the networking stack invokes the bonding device ndo entry (from
>>> neigh_params_alloc) before any devices are enslaved, and the bonding
>>> driver can't further delegate the call at that point in time. As a
>>> result when bonding IPoIB devices, the neigh_cleanup hasn't been called.
>>>
>>> Fix that by deferring the actual call into the slave ndo_neigh_setup
>> >from the time the bonding neigh_setup is called.
>>>
>>> Signed-off-by: Shlomo Pongratz<shlomop@...lanox.com>
>>> ---
>>> drivers/net/bonding/bond_main.c |   51 ++++++++++++++++++++++++++++++++------
>>> 1 files changed, 43 insertions(+), 8 deletions(-)
>>>
>>> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
>>> index b0a278d..2eed155 100644
>>> --- a/drivers/net/bonding/bond_main.c
>>> +++ b/drivers/net/bonding/bond_main.c
>>> @@ -3707,17 +3707,52 @@ static void bond_set_multicast_list(struct net_device *bond_dev)
>>> 	read_unlock(&bond->lock);
>>> }
>>>
>>> -static int bond_neigh_setup(struct net_device *dev, struct neigh_parms *parms)
>>> +static int bond_neigh_init(struct neighbour *n)
>>> {
>>> -	struct bonding *bond = netdev_priv(dev);
>>> +	struct bonding *bond = netdev_priv(n->dev);
>>> 	struct slave *slave = bond->first_slave;
>>> +	const struct net_device_ops *slave_ops;
>>> +	struct neigh_parms parms;
>>> +	int ret;
>>> +
>>> +	if (!slave)
>>> +		return 0;
>>> +
>>> +	slave_ops = slave->dev->netdev_ops;
>>> +
>>> +	if (!slave_ops->ndo_neigh_setup)
>>> +		return 0;
>>> +
>>> +	parms.neigh_setup = NULL;
>>> +	parms.neigh_cleanup = NULL;
>>> +	ret = slave_ops->ndo_neigh_setup(slave->dev,&parms);
>>> +	if (ret)
>>> +		return ret;
>>> +
>>> +	/*
>>> +	 * must bind here to the slave clenaup. Since when last slave is removed
>>> +	 * there will be no slave device to dereference in a bonding
>>> +	 * neigh_cleanup function that we have could add.
>>> +	 */
>>> +	n->parms->neigh_cleanup = parms.neigh_cleanup;
>>
>> 	I'd write this comment as:
>>
>> 	/* Assign slave's neigh_cleanup to neighbour in case cleanup is
>> 	 * called after bond has been destroyed.  Assumes that all slaves
>> 	 * utilize the same neigh_cleanup (true at this writing as only user
>> 	 * is ipoib).
>> 	 */
>>
>> 	I.e., this logic works only because there cannot currently be a
>> situation wherein two slaves have different neigh_cleanup functions
>> (including one slave with a neigh_cleanup, and another without).
>
>Jay, we do need that proxy-ing for the specific case of deleting the last
>slave, since in bond_release
>the address change and the event emission happen --after-- calling
>bond_detach_slave. Still, will pick
>your phrasing for the comment and replace "after bond has been destroyed"
>with "after last slave has been detached"

	Yes, I understand that the proxying is needed; the point of the
comment is that if there's ever a situation in the future that two
slaves have different neigh_cleanup functions, this methodology will not
work.  There is no guarantee that the slave on which ndo_neigh_setup is
called on will also be the last slave to be removed.

	The change to the comment is ok; I was thinking about ipoib
always destroying the bond itself immediately after releasing the final
slave, so for ipoib, the two events always happen together.

	-J

>>
>> +	/* Does slave implement neigh_setup ? */
>> +	if (!parms.neigh_setup)
>> +		return 0;
>>
>> 	I don't think this comment is necessary.
>
>okay, will remove
>
>Or.
>

---
	-Jay Vosburgh, IBM Linux Technology Center, fubar@...ibm.com

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