Re: [PATCH net-next RFC 05/12] net: dsa: Add support for learning FDB through notification

[Nikolay Aleksandrov]

On 12/07/17 14:23, Arkadi Sharshevsky wrote:
> 
> 
> On 07/11/2017 06:05 PM, Nikolay Aleksandrov wrote:
>> On 11/07/17 13:26, Arkadi Sharshevsky wrote:
>>>
>>>
>>> On 07/10/2017 11:59 PM, Vivien Didelot wrote:
 Hi Arkadi,

 Arkadi Sharshevsky  writes:

>>> +   err = dsa_port_fdb_add(p->dp, fdb_info->addr, 
>>> fdb_info->vid);
>>> +   if (err) {
>>> +   netdev_dbg(dev, "fdb add failed err=%d\n", err);
>>> +   break;
>>> +   }
>>> +   call_switchdev_notifiers(SWITCHDEV_FDB_OFFLOADED, dev,
>>> +_info->info);
>>> +   break;
>>> +
>>> +   case SWITCHDEV_FDB_DEL_TO_DEVICE:
>>> +   fdb_info = _work->fdb_info;
>>> +   err = dsa_port_fdb_del(p->dp, fdb_info->addr, 
>>> fdb_info->vid);
>>> +   if (err)
>>> +   netdev_dbg(dev, "fdb del failed err=%d\n", err);
>>
>> OK I must have missed from the off-list discussion why we are not
>> calling the switchdev notifier here?
>
> We do not agree on it actually, that is why it was moved to the list.
> I think that delete should succeed, you should retry until succession.
>
> The deletion is done under spinlock in the bridge so you cannot block,
> thus delete cannot fail due to hardware failure. Calling it here doesn't
> make sense because the bridge probably already deleted this FDB.

 So as we discussed, the problem here is that if dsa_port_fdb_del fails
 for some probable reasons (MDIO timeout, weak GPIO lines, etc.), Linux
 bridge will delete the entry in software, dumping bridge fdb will show
 nothing, but the entry would still be programmed in hardware and the
 network can thus be inconsistent, unsupposedly switching frames.

 IMHO the correct way for bridge to use the notification chain is to make
 SWITCHDEV_FDB_DEL_TO_DEVICE symmetrical to SWITCHDEV_FDB_ADD_TO_DEVICE:
 if an entry has been marked as offloaded, bridge must mark the entry as
 to-be-deleted and do not delete the software entry until the driver
 notifies back the successful deletion.

 If that is hardly feasible due to some bridge limitations, we must
 explain this in a comment and use something more explosive than a simple
 netdev_dbg to warn the user about the broken network setup...


 Thanks,

 Vivien

>>>
>>> Hi Nikolay,
>>>
>>> Vivien raised inconsistency issue with the current switchdev
>>> notification chain in case of FDB del. In case of static FDB delete,
>>> notification will be sent to the driver, followed by deletion of the
>>> software entry without waiting for the hardware delete. In case of
>>> hardware deletion failure the consecutive FDB dump will not show the
>>> deleted entry, yet, the entry will stay in hardware.
>>>
>>> The deletion is done under lock thus the hardware deletion is deferred,
>>> and cannot fail due to hardware removal failure. Thus the above proposed
>>> solution by Vivien can lead to confusing situation:
>>>
>>> 1. User deletes the entry
>>> 2. Deletion succeed
>>> 3. User dumps FDB and still sees this entry due to hardware failure,
>>>what should he do? retry to delete until the FDB dump will not show
>>>the entry?
>>>
>>> Would like to hear you opinion about this solution.
>>>
>>> IMHO in this case the driver should retry to delete, in case of
>>> several retries the driver should maybe:
>>> 1. Trap the traffic to CPU (dint think it possible in case of DSA).
>>> 2. Disable the port (its more explosive then netdev_dbg).
>>>
>>> Thanks,
>>> Arkadi
>>>
>>>
>>
>> Hi,
>> Looking at the code - it would seem that retrying is the only current option
>> with the way these switchdev notifications are handled. They cannot fail, 
>> meaning
>> from the bridge POV these ops must always succeed and errors are ignored, so 
>> the
>> driver should do everything possible to stay in sync, and in case all fails
>> then disabling the port seems like the best option to me, to show that 
>> something is
>> clearly wrong and avoid further issues, but DSA maintainers can comment more
>> on how to handle failure.
>>
>> That being said:
>> This sounds a lot like the switchdev notifications vs callbacks discussions 
>> that we've
>> had in the past. Also what happened with the prepare+commit and all that ? 
>> If the hash_lock
>> is the main problem let's work towards improving that and making the fdb 
>> code handle
>> switchdev similar to the vlan code.
>>
>> Cheers,
>>  Nik
>>
> 
> Vlans can be only added by user under rtnl so its possible to sleep. On
> the other hand FDBs can be learned in atomic context, thus the
> notification chain is atomic. One Possible way I thought about doing it

Right, that's why I mentioned the hash_lock. :-)

> is to 

Re: [PATCH net-next RFC 05/12] net: dsa: Add support for learning FDB through notification

[Arkadi Sharshevsky]

On 07/11/2017 06:05 PM, Nikolay Aleksandrov wrote:
> On 11/07/17 13:26, Arkadi Sharshevsky wrote:
>>
>>
>> On 07/10/2017 11:59 PM, Vivien Didelot wrote:
>>> Hi Arkadi,
>>>
>>> Arkadi Sharshevsky  writes:
>>>
>> +err = dsa_port_fdb_add(p->dp, fdb_info->addr, 
>> fdb_info->vid);
>> +if (err) {
>> +netdev_dbg(dev, "fdb add failed err=%d\n", err);
>> +break;
>> +}
>> +call_switchdev_notifiers(SWITCHDEV_FDB_OFFLOADED, dev,
>> + _info->info);
>> +break;
>> +
>> +case SWITCHDEV_FDB_DEL_TO_DEVICE:
>> +fdb_info = _work->fdb_info;
>> +err = dsa_port_fdb_del(p->dp, fdb_info->addr, 
>> fdb_info->vid);
>> +if (err)
>> +netdev_dbg(dev, "fdb del failed err=%d\n", err);
>
> OK I must have missed from the off-list discussion why we are not
> calling the switchdev notifier here?

 We do not agree on it actually, that is why it was moved to the list.
 I think that delete should succeed, you should retry until succession.

 The deletion is done under spinlock in the bridge so you cannot block,
 thus delete cannot fail due to hardware failure. Calling it here doesn't
 make sense because the bridge probably already deleted this FDB.
>>>
>>> So as we discussed, the problem here is that if dsa_port_fdb_del fails
>>> for some probable reasons (MDIO timeout, weak GPIO lines, etc.), Linux
>>> bridge will delete the entry in software, dumping bridge fdb will show
>>> nothing, but the entry would still be programmed in hardware and the
>>> network can thus be inconsistent, unsupposedly switching frames.
>>>
>>> IMHO the correct way for bridge to use the notification chain is to make
>>> SWITCHDEV_FDB_DEL_TO_DEVICE symmetrical to SWITCHDEV_FDB_ADD_TO_DEVICE:
>>> if an entry has been marked as offloaded, bridge must mark the entry as
>>> to-be-deleted and do not delete the software entry until the driver
>>> notifies back the successful deletion.
>>>
>>> If that is hardly feasible due to some bridge limitations, we must
>>> explain this in a comment and use something more explosive than a simple
>>> netdev_dbg to warn the user about the broken network setup...
>>>
>>>
>>> Thanks,
>>>
>>> Vivien
>>>
>>
>> Hi Nikolay,
>>
>> Vivien raised inconsistency issue with the current switchdev
>> notification chain in case of FDB del. In case of static FDB delete,
>> notification will be sent to the driver, followed by deletion of the
>> software entry without waiting for the hardware delete. In case of
>> hardware deletion failure the consecutive FDB dump will not show the
>> deleted entry, yet, the entry will stay in hardware.
>>
>> The deletion is done under lock thus the hardware deletion is deferred,
>> and cannot fail due to hardware removal failure. Thus the above proposed
>> solution by Vivien can lead to confusing situation:
>>
>> 1. User deletes the entry
>> 2. Deletion succeed
>> 3. User dumps FDB and still sees this entry due to hardware failure,
>>what should he do? retry to delete until the FDB dump will not show
>>the entry?
>>
>> Would like to hear you opinion about this solution.
>>
>> IMHO in this case the driver should retry to delete, in case of
>> several retries the driver should maybe:
>> 1. Trap the traffic to CPU (dint think it possible in case of DSA).
>> 2. Disable the port (its more explosive then netdev_dbg).
>>
>> Thanks,
>> Arkadi
>>
>>
> 
> Hi,
> Looking at the code - it would seem that retrying is the only current option
> with the way these switchdev notifications are handled. They cannot fail, 
> meaning
> from the bridge POV these ops must always succeed and errors are ignored, so 
> the
> driver should do everything possible to stay in sync, and in case all fails
> then disabling the port seems like the best option to me, to show that 
> something is
> clearly wrong and avoid further issues, but DSA maintainers can comment more
> on how to handle failure.
> 
> That being said:
> This sounds a lot like the switchdev notifications vs callbacks discussions 
> that we've
> had in the past. Also what happened with the prepare+commit and all that ? If 
> the hash_lock
> is the main problem let's work towards improving that and making the fdb code 
> handle
> switchdev similar to the vlan code.
> 
> Cheers,
>  Nik
> 

Vlans can be only added by user under rtnl so its possible to sleep. On
the other hand FDBs can be learned in atomic context, thus the
notification chain is atomic. One Possible way I thought about doing it
is to maintain bridge internal ordered workqueue for the FDBs learned in
atomic context, furthermore the FDB table will be protected by mutex.
The STATIC entries are added in user context so the user will add

Re: [PATCH net-next RFC 05/12] net: dsa: Add support for learning FDB through notification

[Nikolay Aleksandrov]

On 11/07/17 13:26, Arkadi Sharshevsky wrote:
> 
> 
> On 07/10/2017 11:59 PM, Vivien Didelot wrote:
>> Hi Arkadi,
>>
>> Arkadi Sharshevsky  writes:
>>
> + err = dsa_port_fdb_add(p->dp, fdb_info->addr, fdb_info->vid);
> + if (err) {
> + netdev_dbg(dev, "fdb add failed err=%d\n", err);
> + break;
> + }
> + call_switchdev_notifiers(SWITCHDEV_FDB_OFFLOADED, dev,
> +  _info->info);
> + break;
> +
> + case SWITCHDEV_FDB_DEL_TO_DEVICE:
> + fdb_info = _work->fdb_info;
> + err = dsa_port_fdb_del(p->dp, fdb_info->addr, fdb_info->vid);
> + if (err)
> + netdev_dbg(dev, "fdb del failed err=%d\n", err);

 OK I must have missed from the off-list discussion why we are not
 calling the switchdev notifier here?
>>>
>>> We do not agree on it actually, that is why it was moved to the list.
>>> I think that delete should succeed, you should retry until succession.
>>>
>>> The deletion is done under spinlock in the bridge so you cannot block,
>>> thus delete cannot fail due to hardware failure. Calling it here doesn't
>>> make sense because the bridge probably already deleted this FDB.
>>
>> So as we discussed, the problem here is that if dsa_port_fdb_del fails
>> for some probable reasons (MDIO timeout, weak GPIO lines, etc.), Linux
>> bridge will delete the entry in software, dumping bridge fdb will show
>> nothing, but the entry would still be programmed in hardware and the
>> network can thus be inconsistent, unsupposedly switching frames.
>>
>> IMHO the correct way for bridge to use the notification chain is to make
>> SWITCHDEV_FDB_DEL_TO_DEVICE symmetrical to SWITCHDEV_FDB_ADD_TO_DEVICE:
>> if an entry has been marked as offloaded, bridge must mark the entry as
>> to-be-deleted and do not delete the software entry until the driver
>> notifies back the successful deletion.
>>
>> If that is hardly feasible due to some bridge limitations, we must
>> explain this in a comment and use something more explosive than a simple
>> netdev_dbg to warn the user about the broken network setup...
>>
>>
>> Thanks,
>>
>> Vivien
>>
> 
> Hi Nikolay,
> 
> Vivien raised inconsistency issue with the current switchdev
> notification chain in case of FDB del. In case of static FDB delete,
> notification will be sent to the driver, followed by deletion of the
> software entry without waiting for the hardware delete. In case of
> hardware deletion failure the consecutive FDB dump will not show the
> deleted entry, yet, the entry will stay in hardware.
> 
> The deletion is done under lock thus the hardware deletion is deferred,
> and cannot fail due to hardware removal failure. Thus the above proposed
> solution by Vivien can lead to confusing situation:
> 
> 1. User deletes the entry
> 2. Deletion succeed
> 3. User dumps FDB and still sees this entry due to hardware failure,
>what should he do? retry to delete until the FDB dump will not show
>the entry?
> 
> Would like to hear you opinion about this solution.
> 
> IMHO in this case the driver should retry to delete, in case of
> several retries the driver should maybe:
> 1. Trap the traffic to CPU (dint think it possible in case of DSA).
> 2. Disable the port (its more explosive then netdev_dbg).
> 
> Thanks,
> Arkadi
> 
> 

Hi,
Looking at the code - it would seem that retrying is the only current option
with the way these switchdev notifications are handled. They cannot fail, 
meaning
from the bridge POV these ops must always succeed and errors are ignored, so the
driver should do everything possible to stay in sync, and in case all fails
then disabling the port seems like the best option to me, to show that 
something is
clearly wrong and avoid further issues, but DSA maintainers can comment more
on how to handle failure.

That being said:
This sounds a lot like the switchdev notifications vs callbacks discussions 
that we've
had in the past. Also what happened with the prepare+commit and all that ? If 
the hash_lock
is the main problem let's work towards improving that and making the fdb code 
handle
switchdev similar to the vlan code.

Cheers,
 Nik

Re: [PATCH net-next RFC 05/12] net: dsa: Add support for learning FDB through notification

[Arkadi Sharshevsky]

On 07/10/2017 11:59 PM, Vivien Didelot wrote:
> Hi Arkadi,
> 
> Arkadi Sharshevsky  writes:
> 
 +  err = dsa_port_fdb_add(p->dp, fdb_info->addr, fdb_info->vid);
 +  if (err) {
 +  netdev_dbg(dev, "fdb add failed err=%d\n", err);
 +  break;
 +  }
 +  call_switchdev_notifiers(SWITCHDEV_FDB_OFFLOADED, dev,
 +   _info->info);
 +  break;
 +
 +  case SWITCHDEV_FDB_DEL_TO_DEVICE:
 +  fdb_info = _work->fdb_info;
 +  err = dsa_port_fdb_del(p->dp, fdb_info->addr, fdb_info->vid);
 +  if (err)
 +  netdev_dbg(dev, "fdb del failed err=%d\n", err);
>>>
>>> OK I must have missed from the off-list discussion why we are not
>>> calling the switchdev notifier here?
>>
>> We do not agree on it actually, that is why it was moved to the list.
>> I think that delete should succeed, you should retry until succession.
>>
>> The deletion is done under spinlock in the bridge so you cannot block,
>> thus delete cannot fail due to hardware failure. Calling it here doesn't
>> make sense because the bridge probably already deleted this FDB.
> 
> So as we discussed, the problem here is that if dsa_port_fdb_del fails
> for some probable reasons (MDIO timeout, weak GPIO lines, etc.), Linux
> bridge will delete the entry in software, dumping bridge fdb will show
> nothing, but the entry would still be programmed in hardware and the
> network can thus be inconsistent, unsupposedly switching frames.
> 
> IMHO the correct way for bridge to use the notification chain is to make
> SWITCHDEV_FDB_DEL_TO_DEVICE symmetrical to SWITCHDEV_FDB_ADD_TO_DEVICE:
> if an entry has been marked as offloaded, bridge must mark the entry as
> to-be-deleted and do not delete the software entry until the driver
> notifies back the successful deletion.
> 
> If that is hardly feasible due to some bridge limitations, we must
> explain this in a comment and use something more explosive than a simple
> netdev_dbg to warn the user about the broken network setup...
> 
> 
> Thanks,
> 
> Vivien
> 

Hi Nikolay,

Vivien raised inconsistency issue with the current switchdev
notification chain in case of FDB del. In case of static FDB delete,
notification will be sent to the driver, followed by deletion of the
software entry without waiting for the hardware delete. In case of
hardware deletion failure the consecutive FDB dump will not show the
deleted entry, yet, the entry will stay in hardware.

The deletion is done under lock thus the hardware deletion is deferred,
and cannot fail due to hardware removal failure. Thus the above proposed
solution by Vivien can lead to confusing situation:

1. User deletes the entry
2. Deletion succeed
3. User dumps FDB and still sees this entry due to hardware failure,
   what should he do? retry to delete until the FDB dump will not show
   the entry?

Would like to hear you opinion about this solution.

IMHO in this case the driver should retry to delete, in case of
several retries the driver should maybe:
1. Trap the traffic to CPU (dint think it possible in case of DSA).
2. Disable the port (its more explosive then netdev_dbg).

Thanks,
Arkadi

Re: [PATCH net-next RFC 05/12] net: dsa: Add support for learning FDB through notification

[Vivien Didelot]

Hi Arkadi,

Arkadi Sharshevsky  writes:

>>> +   err = dsa_port_fdb_add(p->dp, fdb_info->addr, fdb_info->vid);
>>> +   if (err) {
>>> +   netdev_dbg(dev, "fdb add failed err=%d\n", err);
>>> +   break;
>>> +   }
>>> +   call_switchdev_notifiers(SWITCHDEV_FDB_OFFLOADED, dev,
>>> +_info->info);
>>> +   break;
>>> +
>>> +   case SWITCHDEV_FDB_DEL_TO_DEVICE:
>>> +   fdb_info = _work->fdb_info;
>>> +   err = dsa_port_fdb_del(p->dp, fdb_info->addr, fdb_info->vid);
>>> +   if (err)
>>> +   netdev_dbg(dev, "fdb del failed err=%d\n", err);
>> 
>> OK I must have missed from the off-list discussion why we are not
>> calling the switchdev notifier here?
>
> We do not agree on it actually, that is why it was moved to the list.
> I think that delete should succeed, you should retry until succession.
>
> The deletion is done under spinlock in the bridge so you cannot block,
> thus delete cannot fail due to hardware failure. Calling it here doesn't
> make sense because the bridge probably already deleted this FDB.

So as we discussed, the problem here is that if dsa_port_fdb_del fails
for some probable reasons (MDIO timeout, weak GPIO lines, etc.), Linux
bridge will delete the entry in software, dumping bridge fdb will show
nothing, but the entry would still be programmed in hardware and the
network can thus be inconsistent, unsupposedly switching frames.

IMHO the correct way for bridge to use the notification chain is to make
SWITCHDEV_FDB_DEL_TO_DEVICE symmetrical to SWITCHDEV_FDB_ADD_TO_DEVICE:
if an entry has been marked as offloaded, bridge must mark the entry as
to-be-deleted and do not delete the software entry until the driver
notifies back the successful deletion.

If that is hardly feasible due to some bridge limitations, we must
explain this in a comment and use something more explosive than a simple
netdev_dbg to warn the user about the broken network setup...


Thanks,

Vivien

Re: [PATCH net-next RFC 05/12] net: dsa: Add support for learning FDB through notification

[Arkadi Sharshevsky]

On 07/05/2017 10:35 PM, Florian Fainelli wrote:
> On 07/05/2017 08:36 AM, Arkadi Sharshevsky wrote:
>> Add support for learning FDB through notification. The driver defers
>> the hardware update via ordered work queue. In case of a successful
>> FDB add a notification is sent back to bridge.
>>
>> Signed-off-by: Arkadi Sharshevsky 
>> ---
>>  net/dsa/slave.c | 124 
>> +++-
>>  1 file changed, 122 insertions(+), 2 deletions(-)
>>
>> diff --git a/net/dsa/slave.c b/net/dsa/slave.c
>> index 19395cc..d0592f2 100644
>> --- a/net/dsa/slave.c
>> +++ b/net/dsa/slave.c
>> @@ -1263,19 +1263,139 @@ static int dsa_slave_netdevice_event(struct 
>> notifier_block *nb,
>>  return NOTIFY_DONE;
>>  }
>>  
>> +struct dsa_switchdev_event_work {
>> +struct work_struct work;
>> +struct switchdev_notifier_fdb_info fdb_info;
>> +struct net_device *dev;
>> +unsigned long event;
>> +};
>> +
>> +static void dsa_switchdev_event_work(struct work_struct *work)
>> +{
>> +struct dsa_switchdev_event_work *switchdev_work =
>> +container_of(work, struct dsa_switchdev_event_work, work);
>> +struct net_device *dev = switchdev_work->dev;
>> +struct switchdev_notifier_fdb_info *fdb_info;
>> +struct dsa_slave_priv *p = netdev_priv(dev);
>> +int err;
>> +
>> +rtnl_lock();
>> +switch (switchdev_work->event) {
>> +case SWITCHDEV_FDB_ADD_TO_DEVICE:
>> +fdb_info = _work->fdb_info;
> 
> You could probably move this assignment outside of the switch()/case
> statement since it is repeated
> 

Yeah, but this cast is only correct for only this two cases. If in the
future it will be extended it will be weird getting it back inside the
switch.

Thanks for the review!

>> +err = dsa_port_fdb_add(p->dp, fdb_info->addr, fdb_info->vid);
>> +if (err) {
>> +netdev_dbg(dev, "fdb add failed err=%d\n", err);
>> +break;
>> +}
>> +call_switchdev_notifiers(SWITCHDEV_FDB_OFFLOADED, dev,
>> + _info->info);
>> +break;
>> +
>> +case SWITCHDEV_FDB_DEL_TO_DEVICE:
>> +fdb_info = _work->fdb_info;
>> +err = dsa_port_fdb_del(p->dp, fdb_info->addr, fdb_info->vid);
>> +if (err)
>> +netdev_dbg(dev, "fdb del failed err=%d\n", err);
> 
> OK I must have missed from the off-list discussion why we are not
> calling the switchdev notifier here?
> 

We do not agree on it actually, that is why it was moved to the list.
I think that delete should succeed, you should retry until succession.

The deletion is done under spinlock in the bridge so you cannot block,
thus delete cannot fail due to hardware failure. Calling it here doesn't
make sense because the bridge probably already deleted this FDB.

>> +break;
>> +}
>> +rtnl_unlock();
>> +
>> +kfree(switchdev_work->fdb_info.addr);
>> +kfree(switchdev_work);
>> +dev_put(dev);
>> +}
>> +
>> +static int
>> +dsa_slave_switchdev_fdb_work_init(struct dsa_switchdev_event_work *
>> +  switchdev_work,
>> +  const struct switchdev_notifier_fdb_info *
>> +  fdb_info)
>> +{
>> +memcpy(_work->fdb_info, fdb_info,
>> +   sizeof(switchdev_work->fdb_info));
>> +switchdev_work->fdb_info.addr = kzalloc(ETH_ALEN, GFP_ATOMIC);
>> +if (!switchdev_work->fdb_info.addr)
>> +return -ENOMEM;
> 
> Can't we have the fdb_info structure contain pre-allocated 6 bytes
> storage for address, it's really silly to do this here and every time we
> need to offload an FDB entry.
>

This fdb_info contains pointer to MAC which resides in the bridge's
internal fdb struct (struct net_bridge_fdb_entry). It has to be copied
at least once due to the async processing in the workqeue. Note that
no reference is taken on this struct, and while you process (async) the
add this struct can be already deleted followed by a del notification.

In case the fdb_info contains this 6 bytes, 2 copies would be performed:
1. Inside the bridge: from the net_bridge_fdb_entry to the fdb_info
   (which is allocated on the stack and used only during the
notification call)
2. Inside the driver: duplication of the fdb_info to the workqeue item

The current way only does one copy, so I think its better. We can do a
little optimization here by having the dsa_switchdev_event_work contain
the address itself instead of ptr to fdb_info. That way only one
allocation of the dsa_switchdev_event_work is done, but I think its not
that crucial.

>> +ether_addr_copy((u8 *)switchdev_work->fdb_info.addr,
>> +fdb_info->addr);
>> +return 0;
>> +}
>> +
>> +/* Called under rcu_read_lock() */
>> +static int dsa_slave_switchdev_event(struct notifier_block *unused,
>> + unsigned long 

Re: [PATCH net-next RFC 05/12] net: dsa: Add support for learning FDB through notification

[Florian Fainelli]

On 07/05/2017 08:36 AM, Arkadi Sharshevsky wrote:
> Add support for learning FDB through notification. The driver defers
> the hardware update via ordered work queue. In case of a successful
> FDB add a notification is sent back to bridge.
> 
> Signed-off-by: Arkadi Sharshevsky 
> ---
>  net/dsa/slave.c | 124 
> +++-
>  1 file changed, 122 insertions(+), 2 deletions(-)
> 
> diff --git a/net/dsa/slave.c b/net/dsa/slave.c
> index 19395cc..d0592f2 100644
> --- a/net/dsa/slave.c
> +++ b/net/dsa/slave.c
> @@ -1263,19 +1263,139 @@ static int dsa_slave_netdevice_event(struct 
> notifier_block *nb,
>   return NOTIFY_DONE;
>  }
>  
> +struct dsa_switchdev_event_work {
> + struct work_struct work;
> + struct switchdev_notifier_fdb_info fdb_info;
> + struct net_device *dev;
> + unsigned long event;
> +};
> +
> +static void dsa_switchdev_event_work(struct work_struct *work)
> +{
> + struct dsa_switchdev_event_work *switchdev_work =
> + container_of(work, struct dsa_switchdev_event_work, work);
> + struct net_device *dev = switchdev_work->dev;
> + struct switchdev_notifier_fdb_info *fdb_info;
> + struct dsa_slave_priv *p = netdev_priv(dev);
> + int err;
> +
> + rtnl_lock();
> + switch (switchdev_work->event) {
> + case SWITCHDEV_FDB_ADD_TO_DEVICE:
> + fdb_info = _work->fdb_info;

You could probably move this assignment outside of the switch()/case
statement since it is repeated

> + err = dsa_port_fdb_add(p->dp, fdb_info->addr, fdb_info->vid);
> + if (err) {
> + netdev_dbg(dev, "fdb add failed err=%d\n", err);
> + break;
> + }
> + call_switchdev_notifiers(SWITCHDEV_FDB_OFFLOADED, dev,
> +  _info->info);
> + break;
> +
> + case SWITCHDEV_FDB_DEL_TO_DEVICE:
> + fdb_info = _work->fdb_info;
> + err = dsa_port_fdb_del(p->dp, fdb_info->addr, fdb_info->vid);
> + if (err)
> + netdev_dbg(dev, "fdb del failed err=%d\n", err);

OK I must have missed from the off-list discussion why we are not
calling the switchdev notifier here?

> + break;
> + }
> + rtnl_unlock();
> +
> + kfree(switchdev_work->fdb_info.addr);
> + kfree(switchdev_work);
> + dev_put(dev);
> +}
> +
> +static int
> +dsa_slave_switchdev_fdb_work_init(struct dsa_switchdev_event_work *
> +   switchdev_work,
> +   const struct switchdev_notifier_fdb_info *
> +   fdb_info)
> +{
> + memcpy(_work->fdb_info, fdb_info,
> +sizeof(switchdev_work->fdb_info));
> + switchdev_work->fdb_info.addr = kzalloc(ETH_ALEN, GFP_ATOMIC);
> + if (!switchdev_work->fdb_info.addr)
> + return -ENOMEM;

Can't we have the fdb_info structure contain pre-allocated 6 bytes
storage for address, it's really silly to do this here and every time we
need to offload an FDB entry.

> + ether_addr_copy((u8 *)switchdev_work->fdb_info.addr,
> + fdb_info->addr);
> + return 0;
> +}
> +
> +/* Called under rcu_read_lock() */
> +static int dsa_slave_switchdev_event(struct notifier_block *unused,
> +  unsigned long event, void *ptr)
> +{
> + struct net_device *dev = switchdev_notifier_info_to_dev(ptr);
> + struct dsa_switchdev_event_work *switchdev_work;
> +
> + if (!dsa_slave_dev_check(dev))
> + return NOTIFY_DONE;
> +
> + switchdev_work = kzalloc(sizeof(*switchdev_work), GFP_ATOMIC);
> + if (!switchdev_work)
> + return NOTIFY_BAD;

Same here, can we try to re-use a heap allocated workqueue item and we
just re-initialize it when we have to?

> +
> + INIT_WORK(_work->work, dsa_switchdev_event_work);
> + switchdev_work->dev = dev;
> + switchdev_work->event = event;
> +
> + switch (event) {
> + case SWITCHDEV_FDB_ADD_TO_DEVICE: /* fall through */
> + case SWITCHDEV_FDB_DEL_TO_DEVICE:
> + if (dsa_slave_switchdev_fdb_work_init(switchdev_work,
> +   ptr))
> + goto err_fdb_work_init;
> + dev_hold(dev);
> + break;
> + default:
> + kfree(switchdev_work);
> + return NOTIFY_DONE;
> + }
> +
> + dsa_schedule_work(_work->work);
> + return NOTIFY_OK;
> +
> +err_fdb_work_init:
> + kfree(switchdev_work);
> + return NOTIFY_BAD;
> +}
> +
>  static struct notifier_block dsa_slave_nb __read_mostly = {
> - .notifier_call  = dsa_slave_netdevice_event,
> + .notifier_call  = dsa_slave_netdevice_event,
> +};
> +
> +static struct notifier_block dsa_slave_switchdev_notifier = {
> + .notifier_call = dsa_slave_switchdev_event,
>  };
>  
>  int