Re: [PATCH net-next] net/8021q: create device with all possible features in wanted_features

[David Miller]

From: Andrei Vagin 
Date: Wed, 15 Mar 2017 17:41:14 -0700

> wanted_features is a set of features which have to be enabled if a
> hardware allows that.
> 
> Currently when a vlan device is created, its wanted_features is set to
> current features of its base device.
> 
> The problem is that the base device can get new features and they are
> not propagated to vlan-s of this device.
> 
> If we look at bonding devices, they doesn't have this problem and this
> patch suggests to fix this issue by the same way how it works for bonding
> devices.
> 
> We meet this problem, when we try to create a vlan device over a bonding
> device. When a system are booting, real devices require time to be
> initialized, so bonding devices created without slaves, then vlan
> devices are created and only then ethernet devices are added to the
> bonding device. As a result we have vlan devices with disabled
> scatter-gather.
> 
> * create a bonding device
>   $ ip link add bond0 type bond
>   $ ethtool -k bond0 | grep scatter
>   scatter-gather: off
>   tx-scatter-gather: off [requested on]
>   tx-scatter-gather-fraglist: off [requested on]
> 
> * create a vlan device
>   $ ip link add link bond0 name bond0.10 type vlan id 10
>   $ ethtool -k bond0.10 | grep scatter
>   scatter-gather: off
>   tx-scatter-gather: off
>   tx-scatter-gather-fraglist: off
> 
> * Add a slave device to bond0
>   $ ip link set dev eth0 master bond0
> 
> And now we can see that the bond0 device has got the scatter-gather
> feature, but the bond0.10 hasn't got it.
> [root@laptop linux-task-diag]# ethtool -k bond0 | grep scatter
> scatter-gather: on
>   tx-scatter-gather: on
>   tx-scatter-gather-fraglist: on
> [root@laptop linux-task-diag]# ethtool -k bond0.10 | grep scatter
> scatter-gather: off
>   tx-scatter-gather: off
>   tx-scatter-gather-fraglist: off
> 
> With this patch the vlan device will get all new features from the
> bonding device.
> 
> Here is a call trace how features which are set in this patch reach
> dev->wanted_features.
> 
> register_netdevice
>vlan_dev_init
>   ...
>   dev->hw_features = NETIF_F_HW_CSUM | NETIF_F_SG |
>  NETIF_F_FRAGLIST | NETIF_F_GSO_SOFTWARE |
>  NETIF_F_HIGHDMA | NETIF_F_SCTP_CRC |
>  NETIF_F_ALL_FCOE;
> 
>   dev->features |= dev->hw_features;
>   ...
> dev->wanted_features = dev->features & dev->hw_features;
> __netdev_update_features(dev);
> vlan_dev_fix_features
>  ...
> 
> Signed-off-by: Andrei Vagin 

Applied, thanks.

[PATCH net-next] net/8021q: create device with all possible features in wanted_features

[Andrei Vagin]

wanted_features is a set of features which have to be enabled if a
hardware allows that.

Currently when a vlan device is created, its wanted_features is set to
current features of its base device.

The problem is that the base device can get new features and they are
not propagated to vlan-s of this device.

If we look at bonding devices, they doesn't have this problem and this
patch suggests to fix this issue by the same way how it works for bonding
devices.

We meet this problem, when we try to create a vlan device over a bonding
device. When a system are booting, real devices require time to be
initialized, so bonding devices created without slaves, then vlan
devices are created and only then ethernet devices are added to the
bonding device. As a result we have vlan devices with disabled
scatter-gather.

* create a bonding device
  $ ip link add bond0 type bond
  $ ethtool -k bond0 | grep scatter
  scatter-gather: off
tx-scatter-gather: off [requested on]
tx-scatter-gather-fraglist: off [requested on]

* create a vlan device
  $ ip link add link bond0 name bond0.10 type vlan id 10
  $ ethtool -k bond0.10 | grep scatter
  scatter-gather: off
tx-scatter-gather: off
tx-scatter-gather-fraglist: off

* Add a slave device to bond0
  $ ip link set dev eth0 master bond0

And now we can see that the bond0 device has got the scatter-gather
feature, but the bond0.10 hasn't got it.
[root@laptop linux-task-diag]# ethtool -k bond0 | grep scatter
scatter-gather: on
tx-scatter-gather: on
tx-scatter-gather-fraglist: on
[root@laptop linux-task-diag]# ethtool -k bond0.10 | grep scatter
scatter-gather: off
tx-scatter-gather: off
tx-scatter-gather-fraglist: off

With this patch the vlan device will get all new features from the
bonding device.

Here is a call trace how features which are set in this patch reach
dev->wanted_features.

register_netdevice
   vlan_dev_init
...
dev->hw_features = NETIF_F_HW_CSUM | NETIF_F_SG |
   NETIF_F_FRAGLIST | NETIF_F_GSO_SOFTWARE |
   NETIF_F_HIGHDMA | NETIF_F_SCTP_CRC |
   NETIF_F_ALL_FCOE;

dev->features |= dev->hw_features;
...
dev->wanted_features = dev->features & dev->hw_features;
__netdev_update_features(dev);
vlan_dev_fix_features
   ...

Cc: Alexey Kuznetsov 
Cc: Patrick McHardy 
Cc: "David S. Miller" 
Signed-off-by: Andrei Vagin 
---
 net/8021q/vlan_dev.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/net/8021q/vlan_dev.c b/net/8021q/vlan_dev.c
index 10da6c5..b9ad2f8 100644
--- a/net/8021q/vlan_dev.c
+++ b/net/8021q/vlan_dev.c
@@ -562,8 +562,7 @@ static int vlan_dev_init(struct net_device *dev)
   NETIF_F_HIGHDMA | NETIF_F_SCTP_CRC |
   NETIF_F_ALL_FCOE;
 
-   dev->features |= real_dev->vlan_features | NETIF_F_LLTX |
-NETIF_F_GSO_SOFTWARE;
+   dev->features |= dev->hw_features | NETIF_F_LLTX;
dev->gso_max_size = real_dev->gso_max_size;
dev->gso_max_segs = real_dev->gso_max_segs;
if (dev->features & NETIF_F_VLAN_FEATURES)
-- 
2.9.3