* [PATCH next v5 2/6] bonding: implement bond_poll_controller()
@ 2015-02-18 22:31 Mahesh Bandewar
2015-02-19 0:10 ` Nikolay Aleksandrov
0 siblings, 1 reply; 6+ messages in thread
From: Mahesh Bandewar @ 2015-02-18 22:31 UTC (permalink / raw)
To: Jay Vosburgh, Andy Gospodarek, Veaceslav Falico,
Nikolay Aleksandrov, David Miller
Cc: Mahesh Bandewar, Maciej Zenczykowski, netdev, Eric Dumazet
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@google.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(+)
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)
--
2.2.0.rc0.207.ga3a616c
^ permalink raw reply related [flat|nested] 6+ messages in thread* Re: [PATCH next v5 2/6] bonding: implement bond_poll_controller()
2015-02-18 22:31 [PATCH next v5 2/6] bonding: implement bond_poll_controller() Mahesh Bandewar
@ 2015-02-19 0:10 ` Nikolay Aleksandrov
2015-02-19 1:19 ` Mahesh Bandewar
0 siblings, 1 reply; 6+ messages in thread
From: Nikolay Aleksandrov @ 2015-02-19 0:10 UTC (permalink / raw)
To: Mahesh Bandewar, Jay Vosburgh, Andy Gospodarek, Veaceslav Falico,
David Miller
Cc: Maciej Zenczykowski, netdev, Eric Dumazet
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@google.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.
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)
>
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH next v5 2/6] bonding: implement bond_poll_controller()
2015-02-19 0:10 ` Nikolay Aleksandrov
@ 2015-02-19 1:19 ` Mahesh Bandewar
2015-02-19 1:30 ` Mahesh Bandewar
0 siblings, 1 reply; 6+ messages in thread
From: Mahesh Bandewar @ 2015-02-19 1:19 UTC (permalink / raw)
To: Nikolay Aleksandrov
Cc: Jay Vosburgh, Andy Gospodarek, Veaceslav Falico, David Miller,
Maciej Zenczykowski, netdev, Eric Dumazet
On Wed, Feb 18, 2015 at 4:10 PM, Nikolay Aleksandrov <nikolay@redhat.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@google.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)
>>
>
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH next v5 2/6] bonding: implement bond_poll_controller()
2015-02-19 1:19 ` Mahesh Bandewar
@ 2015-02-19 1:30 ` Mahesh Bandewar
2015-02-19 2:26 ` Maciej Żenczykowski
0 siblings, 1 reply; 6+ messages in thread
From: Mahesh Bandewar @ 2015-02-19 1:30 UTC (permalink / raw)
To: Nikolay Aleksandrov
Cc: Jay Vosburgh, Andy Gospodarek, Veaceslav Falico, David Miller,
Maciej Zenczykowski, netdev, Eric Dumazet
On Wed, Feb 18, 2015 at 5:19 PM, Mahesh Bandewar <maheshb@google.com> wrote:
> On Wed, Feb 18, 2015 at 4:10 PM, Nikolay Aleksandrov <nikolay@redhat.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@google.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!
>
... however we cannot use the _rcu variant either since there is the
netpoll mutex (ni->dev_lock)!
The fact that we are here itself means that something bad had happened
and trying to take additional lock(s) would complicate the situation
further.
>> 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)
>>>
>>
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH next v5 2/6] bonding: implement bond_poll_controller()
2015-02-19 1:30 ` Mahesh Bandewar
@ 2015-02-19 2:26 ` Maciej Żenczykowski
2015-02-19 5:06 ` Mahesh Bandewar
0 siblings, 1 reply; 6+ messages in thread
From: Maciej Żenczykowski @ 2015-02-19 2:26 UTC (permalink / raw)
To: Mahesh Bandewar
Cc: Nikolay Aleksandrov, Jay Vosburgh, Andy Gospodarek,
Veaceslav Falico, David Miller, netdev, Eric Dumazet
>>> 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!
>>
> ... however we cannot use the _rcu variant either since there is the
> netpoll mutex (ni->dev_lock)!
> The fact that we are here itself means that something bad had happened
> and trying to take additional lock(s) would complicate the situation
> further.
I think you might be incorrectly assuming that we only get here on
kernel crashes,
upstream (netconsole) [may] violate[s] this assumption.
(background: internally we don't consider netconsole production
worthy, but we do
'abuse' the netpoll support framework to generate a minimal network
dump on kernel crash,
in which case if we crash or otherwise violate assumptions while
crashing, we're not any worse off...)
- Maciej
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH next v5 2/6] bonding: implement bond_poll_controller()
2015-02-19 2:26 ` Maciej Żenczykowski
@ 2015-02-19 5:06 ` Mahesh Bandewar
0 siblings, 0 replies; 6+ messages in thread
From: Mahesh Bandewar @ 2015-02-19 5:06 UTC (permalink / raw)
To: Maciej Żenczykowski
Cc: Nikolay Aleksandrov, Jay Vosburgh, Andy Gospodarek,
Veaceslav Falico, David Miller, netdev, Eric Dumazet
On Wed, Feb 18, 2015 at 6:26 PM, Maciej Żenczykowski <maze@google.com> wrote:
>>>> 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!
>>>
>> ... however we cannot use the _rcu variant either since there is the
>> netpoll mutex (ni->dev_lock)!
>> The fact that we are here itself means that something bad had happened
>> and trying to take additional lock(s) would complicate the situation
>> further.
>
> I think you might be incorrectly assuming that we only get here on
> kernel crashes,
> upstream (netconsole) [may] violate[s] this assumption.
>
> (background: internally we don't consider netconsole production
> worthy, but we do
> 'abuse' the netpoll support framework to generate a minimal network
> dump on kernel crash,
> in which case if we crash or otherwise violate assumptions while
> crashing, we're not any worse off...)
>
I think irrespective of how we use it, there are few contradictory things here -
(a) If it can't sleep in netpoll() (which I agree with) then that
netpoll mutex does not make sense. But if it can then rtnl isn't a
wrong thing.
(b) If the netpoll mutex is right then slaves can not be iterated with
rcu protection.
(c) If we takeout the netpoll-mutex, then everything seems right but
can we really do that?
I'll take this patch out of this series for the time being and let
other patches proceed while I think about this patch some more.
--mahesh..
> - Maciej
^ permalink raw reply [flat|nested] 6+ messages in thread
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2015-02-18 22:31 [PATCH next v5 2/6] bonding: implement bond_poll_controller() Mahesh Bandewar
2015-02-19 0:10 ` Nikolay Aleksandrov
2015-02-19 1:19 ` Mahesh Bandewar
2015-02-19 1:30 ` Mahesh Bandewar
2015-02-19 2:26 ` Maciej Żenczykowski
2015-02-19 5:06 ` Mahesh Bandewar
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