netdev - Re: [patch net-next v5 5/8] switchdev: introduce possibility to defer obj

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Date:	Mon, 19 Oct 2015 10:24:01 +0200
From:	Jiri Pirko <jiri@...nulli.us>
To:	Scott Feldman <sfeldma@...il.com>
Cc:	Netdev <netdev@...r.kernel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Ido Schimmel <idosch@...lanox.com>,
	Elad Raz <eladr@...lanox.com>,
	Florian Fainelli <f.fainelli@...il.com>,
	Guenter Roeck <linux@...ck-us.net>,
	Vivien Didelot <vivien.didelot@...oirfairelinux.com>,
	"andrew@...n.ch" <andrew@...n.ch>,
	john fastabend <john.fastabend@...il.com>,
	David Laight <David.Laight@...lab.com>,
	"stephen@...workplumber.org" <stephen@...workplumber.org>
Subject: Re: [patch net-next v5 5/8] switchdev: introduce possibility to
 defer obj_add/del

Mon, Oct 19, 2015 at 09:55:59AM CEST, sfeldma@...il.com wrote:
>On Wed, Oct 14, 2015 at 10:40 AM, 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>
>> ---
>>  include/net/switchdev.h   |   1 +
>>  net/switchdev/switchdev.c | 100 ++++++++++++++++++++++++++++++++++++----------
>>  2 files changed, 81 insertions(+), 20 deletions(-)
>>
>> diff --git a/include/net/switchdev.h b/include/net/switchdev.h
>> index f8672d7..bc865e2 100644
>> --- a/include/net/switchdev.h
>> +++ b/include/net/switchdev.h
>> @@ -69,6 +69,7 @@ enum switchdev_obj_id {
>>
>>  struct switchdev_obj {
>>         enum switchdev_obj_id id;
>> +       u32 flags;
>>  };
>>
>>  /* SWITCHDEV_OBJ_ID_PORT_VLAN */
>> diff --git a/net/switchdev/switchdev.c b/net/switchdev/switchdev.c
>> index 5963d7a..eac68c4 100644
>> --- a/net/switchdev/switchdev.c
>> +++ b/net/switchdev/switchdev.c
>> @@ -362,21 +362,8 @@ static int __switchdev_port_obj_add(struct net_device *dev,
>>         return err;
>>  }
>>
>> -/**
>> - *     switchdev_port_obj_add - Add port object
>> - *
>> - *     @dev: port device
>> - *     @id: object ID
>> - *     @obj: object to add
>> - *
>> - *     Use a 2-phase prepare-commit transaction model to ensure
>> - *     system is not left in a partially updated state due to
>> - *     failure from driver/device.
>> - *
>> - *     rtnl_lock must be held.
>> - */
>> -int switchdev_port_obj_add(struct net_device *dev,
>> -                          const struct switchdev_obj *obj)
>> +static int switchdev_port_obj_add_now(struct net_device *dev,
>> +                                     const struct switchdev_obj *obj)
>>  {
>>         struct switchdev_trans trans;
>>         int err;
>> @@ -418,18 +405,53 @@ int switchdev_port_obj_add(struct net_device *dev,
>>
>>         return err;
>>  }
>> -EXPORT_SYMBOL_GPL(switchdev_port_obj_add);
>> +
>> +static void switchdev_port_obj_add_deferred(struct net_device *dev,
>> +                                           const void *data)
>> +{
>> +       const struct switchdev_obj *obj = data;
>> +       int err;
>> +
>> +       err = switchdev_port_obj_add_now(dev, obj);
>> +       if (err && err != -EOPNOTSUPP)
>> +               netdev_err(dev, "failed (err=%d) to add object (id=%d)\n",
>> +                          err, obj->id);
>> +}
>> +
>> +static int switchdev_port_obj_add_defer(struct net_device *dev,
>> +                                       const struct switchdev_obj *obj)
>> +{
>> +       return switchdev_deferred_enqueue(dev, obj, sizeof(*obj),
>> +                                         switchdev_port_obj_add_deferred);
>> +}
>
>Hi Jiri,
>
>I think there is a problem here with this patch.  When we defer adding
>an obj, we're only copying the inner struct switchdev_obj.  The rest
>of the containing obj is lost.  So when
>switchdev_port_obj_add_deferred() runs, we're up casting to garbage.
>So if this FDB obj was deferred, the addr, vid, and ndm_state members
>would be garbage:

Right, we should pass correct size. I'll fix this in a moment. Thanks

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