netdev - Re: [PATCH next v5 2/6] bonding: implement bond_poll

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Date:	Wed, 18 Feb 2015 17:19:53 -0800
From:	Mahesh Bandewar <maheshb@...gle.com>
To:	Nikolay Aleksandrov <nikolay@...hat.com>
Cc:	Jay Vosburgh <j.vosburgh@...il.com>,
	Andy Gospodarek <andy@...yhouse.net>,
	Veaceslav Falico <vfalico@...il.com>,
	David Miller <davem@...emloft.net>,
	Maciej Zenczykowski <maze@...gle.com>,
	netdev <netdev@...r.kernel.org>,
	Eric Dumazet <edumazet@...gle.com>
Subject: Re: [PATCH next v5 2/6] bonding: implement bond_poll_controller()

On Wed, Feb 18, 2015 at 4:10 PM, Nikolay Aleksandrov <nikolay@...hat.com> wrote:
> On 02/18/2015 11:31 PM, Mahesh Bandewar wrote:
>> This patches implements the poll_controller support for all
>> bonding driver. If the slaves have poll_controller net_op defined,
>> this implementation calls them. This is mode agnostic implementation
>> and iterates through all slaves (based on mode) and calls respective
>> handler.
>>
>> Signed-off-by: Mahesh Bandewar <maheshb@...gle.com>
>> ---
>> v1:
>>    Initial version
>> v2:
>>    Eliminate bool variable.
>> v3:
>>    Rebase
>> v4:
>>    Removed 3AD port_operational check
>> v5:
>>    Added rtnl protection for bond_for_each_slave()
>>
>>  drivers/net/bonding/bond_main.c | 33 +++++++++++++++++++++++++++++++++
>>  1 file changed, 33 insertions(+)
>>
>
> Hi Mahesh,
> I should've explained more in my review, you cannot sleep in
> bond_poll_controller() so you cannot acquire rtnl like that. I was thinking
> more about using rcu and switching to the _rcu version of
> bond_for_each_slave instead.
>
That makes sense. The path that triggered this netpoll() could have
been holding the rtnl  itself and this would be a problem. I think
using the _rcu variant of the slave iterator is a good idea, my bad!

> Cheers,
>  Nik
>
>> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
>> index b979c265fc51..63e6c0dbe7b3 100644
>> --- a/drivers/net/bonding/bond_main.c
>> +++ b/drivers/net/bonding/bond_main.c
>> @@ -928,6 +928,39 @@ static inline void slave_disable_netpoll(struct slave *slave)
>>
>>  static void bond_poll_controller(struct net_device *bond_dev)
>>  {
>> +     struct bonding *bond = netdev_priv(bond_dev);
>> +     struct slave *slave = NULL;
>> +     struct list_head *iter;
>> +     struct ad_info ad_info;
>> +     struct netpoll_info *ni;
>> +     const struct net_device_ops *ops;
>> +
>> +     if (BOND_MODE(bond) == BOND_MODE_8023AD)
>> +             if (bond_3ad_get_active_agg_info(bond, &ad_info))
>> +                     return;
>> +
>> +     rtnl_lock();
>> +     bond_for_each_slave(bond, slave, iter) {
>> +             ops = slave->dev->netdev_ops;
>> +             if (!bond_slave_is_up(slave) || !ops->ndo_poll_controller)
>> +                     continue;
>> +
>> +             if (BOND_MODE(bond) == BOND_MODE_8023AD) {
>> +                     struct aggregator *agg =
>> +                         SLAVE_AD_INFO(slave)->port.aggregator;
>> +
>> +                     if (agg &&
>> +                         agg->aggregator_identifier != ad_info.aggregator_id)
>> +                             continue;
>> +             }
>> +
>> +             ni = rcu_dereference_bh(slave->dev->npinfo);
>> +             if (down_trylock(&ni->dev_lock))
>> +                     continue;
>> +             ops->ndo_poll_controller(slave->dev);
>> +             up(&ni->dev_lock);
>> +     }
>> +     rtnl_unlock();
>>  }
>>
>>  static void bond_netpoll_cleanup(struct net_device *bond_dev)
>>
>
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