netdev - Re: [patch net-next 3/6] net: add netif_is_ovs_master helper with IFF

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Date:	Wed, 26 Aug 2015 23:23:13 -0700
From:	Scott Feldman <sfeldma@...il.com>
To:	Jiri Pirko <jiri@...nulli.us>
Cc:	Netdev <netdev@...r.kernel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Ido Schimmel <idosch@...lanox.com>, eladr@...lanox.com,
	"simon.horman@...ronome.com" <simon.horman@...ronome.com>,
	Jiri Pirko <jiri@...lanox.com>
Subject: Re: [patch net-next 3/6] net: add netif_is_ovs_master helper with
 IFF_OPENVSWITCH private flag

On Wed, Aug 26, 2015 at 10:43 PM, Jiri Pirko <jiri@...nulli.us> wrote:
> Wed, Aug 26, 2015 at 07:43:18PM CEST, sfeldma@...il.com wrote:
>>On Wed, Aug 26, 2015 at 9:36 AM, Jiri Pirko <jiri@...nulli.us> wrote:
>>> From: Jiri Pirko <jiri@...lanox.com>
>>>
>>> Add this helper so code can easily figure out if netdev is openswitch.
>>>
>>> Signed-off-by: Jiri Pirko <jiri@...lanox.com>
>>> ---
>>>  include/linux/netdevice.h            | 8 ++++++++
>>>  net/openvswitch/vport-internal_dev.c | 2 +-
>>>  2 files changed, 9 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
>>> index be625f4..0a884e6 100644
>>> --- a/include/linux/netdevice.h
>>> +++ b/include/linux/netdevice.h
>>> @@ -1264,6 +1264,7 @@ struct net_device_ops {
>>>   * @IFF_MACVLAN: Macvlan device
>>>   * @IFF_VRF_MASTER: device is a VRF master
>>>   * @IFF_NO_QUEUE: device can run without qdisc attached
>>> + * @IFF_VRF_OPENVSWITCH: device is a Open vSwitch master
>>>   */
>>>  enum netdev_priv_flags {
>>>         IFF_802_1Q_VLAN                 = 1<<0,
>>> @@ -1293,6 +1294,7 @@ enum netdev_priv_flags {
>>>         IFF_IPVLAN_SLAVE                = 1<<24,
>>>         IFF_VRF_MASTER                  = 1<<25,
>>>         IFF_NO_QUEUE                    = 1<<26,
>>> +       IFF_OPENVSWITCH                 = 1<<27,
>>>  };
>>>
>>>  #define IFF_802_1Q_VLAN                        IFF_802_1Q_VLAN
>>> @@ -1322,6 +1324,7 @@ enum netdev_priv_flags {
>>>  #define IFF_IPVLAN_SLAVE               IFF_IPVLAN_SLAVE
>>>  #define IFF_VRF_MASTER                 IFF_VRF_MASTER
>>>  #define IFF_NO_QUEUE                   IFF_NO_QUEUE
>>> +#define IFF_OPENVSWITCH                        IFF_OPENVSWITCH
>>>
>>>  /**
>>>   *     struct net_device - The DEVICE structure.
>>> @@ -3853,6 +3856,11 @@ static inline bool netif_is_bridge_master(const struct net_device *dev)
>>>         return dev->priv_flags & IFF_EBRIDGE;
>>>  }
>>>
>>> +static inline bool netif_is_ovs_master(const struct net_device *dev)
>>> +{
>>> +       return dev->priv_flags & IFF_OPENVSWITCH;
>>> +}
>>
>>We're going to run out of priv_flags bits.  This flag doesn't seem
>>like something that will be checked lots of places.  How about using
>>rtnl_link_ops->kind to save a bit in priv_flags?
>>
>>static inline bool netif_is_ovs_master(const struct net_device *dev)
>>{
>>    return !strcmp(dev->rtnl_link_ops->kind, "openvswitch"));
>>}
>
> There are lot of helpers like this for other soft-devices. I think that
> is okay to have it this way. The thing is that sometimes you need to use
> thi helper in fast path and in that case, you do not want to strcmp.
>
> There is plenty of priv_flags bits for now when I killed the bonding
> stuff.

Ya, but think about the bit: you (and others) used a bit in priv_flags
to indicate the netdev type.  Can you add an enum field to
rtnl_link_ops->type to indicate link type?  Then it's not a strcmp.
You can write your helper using strcmp first, and then later migrate
to using rtnl_link_ops->type.
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