netdev - Re: [patch net-next RFC 3/3] switchdev: introduce deferred variants of obj

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Date:	Thu, 8 Oct 2015 15:09:11 +0200
From:	Jiri Pirko <jiri@...nulli.us>
To:	Or Gerlitz <gerlitz.or@...il.com>
Cc:	Linux Netdev List <netdev@...r.kernel.org>,
	David Miller <davem@...emloft.net>, idosch@...lanox.com,
	Elad Raz <eladr@...lanox.com>,
	Scott Feldman <sfeldma@...il.com>,
	Florian Fainelli <f.fainelli@...il.com>,
	Guenter Roeck <linux@...ck-us.net>,
	Vivien Didelot <vivien.didelot@...oirfairelinux.com>,
	Andrew Lunn <andrew@...n.ch>,
	john fastabend <john.fastabend@...il.com>,
	David Laight <David.Laight@...lab.com>
Subject: Re: [patch net-next RFC 3/3] switchdev: introduce deferred variants
 of obj_add/del helpers

Thu, Oct 08, 2015 at 10:28:58AM CEST, jiri@...nulli.us wrote:
>Thu, Oct 08, 2015 at 08:45:58AM CEST, gerlitz.or@...il.com wrote:
>>On Wed, Oct 7, 2015 at 9:30 PM, Jiri Pirko <jiri@...nulli.us> wrote:
>>> From: Jiri Pirko <jiri@...lanox.com>
>>>
>>> Similar to the attr usecase, the caller knows if he is holding RTNL and is
>>> in atomic section. So let the called to decide the correct call variant.
>>>
>>> This allows drivers to sleep inside their ops and wait for hw to get the
>>> operation status. Then the status is propagated into switchdev core.
>>> This avoids silent errors in drivers.
>>>
>>> Signed-off-by: Jiri Pirko <jiri@...lanox.com>
>>
>>> diff --git a/net/bridge/br_fdb.c b/net/bridge/br_fdb.c
>>> index 7f7d551..2086767 100644
>>> --- a/net/bridge/br_fdb.c
>>> +++ b/net/bridge/br_fdb.c
>>> @@ -139,7 +139,7 @@ static void fdb_del_external_learn(struct net_bridge_fdb_entry *f)
>>>                 .vid = f->vlan_id,
>>>         };
>>>
>>> -       switchdev_port_obj_del(f->dst->dev, &fdb.obj);
>>> +       switchdev_port_obj_del_deferred(f->dst->dev, &fdb.obj);
>>>  }
>>
>>
>>>  static void fdb_delete(struct net_bridge *br, struct net_bridge_fdb_entry *f)
>>> diff --git a/net/switchdev/switchdev.c b/net/switchdev/switchdev.c
>>> index c29f4ee..49e6e6f 100644
>>> --- a/net/switchdev/switchdev.c
>>> +++ b/net/switchdev/switchdev.c
>>> @@ -362,6 +362,75 @@ int switchdev_port_obj_add(struct net_device *dev,
>>>  }
>>>  EXPORT_SYMBOL_GPL(switchdev_port_obj_add);
>>>
>>> +struct switchdev_obj_work {
>>> +       struct work_struct work;
>>> +       struct net_device *dev;
>>> +       struct switchdev_obj obj;
>>> +       bool add; /* add of del */
>>> +};
>>> +
>>> +static void switchdev_port_obj_work(struct work_struct *work)
>>> +{
>>> +       struct switchdev_obj_work *ow =
>>> +                       container_of(work, struct switchdev_obj_work, work);
>>> +       int err;
>>> +
>>> +       rtnl_lock();
>>> +       if (ow->add)
>>> +               err = switchdev_port_obj_add(ow->dev, &ow->obj);
>>> +       else
>>> +               err = switchdev_port_obj_del(ow->dev, &ow->obj);
>>> +       if (err && err != -EOPNOTSUPP)
>>> +               netdev_err(ow->dev, "failed (err=%d) to %s object (id=%d)\n",
>>> +                          err, ow->add ? "add" : "del", ow->obj.id);
>>
>>This introduced a regression to the 2-phase commit scheme, since the
>>prepare commit can fail
>>and that would go un-noticed toward the upper layer, agree?
>
>Well, no. This still does the transaction for all lower devices in one
>go. No change in that.
>
Now I get it, yes you are right. But currently there is no code in
kernel which would control retval of deferred attr_set or obj_add/del
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