Patch "net/8021q: create device with all possible features in wanted_features" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

net/8021q: create device with all possible features in wanted_features

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
net-8021q-create-device-with-all-possible-features-in-wanted_features.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Andrey Vagin <[email protected]>
Date: Wed, 15 Mar 2017 17:41:14 -0700
Subject: net/8021q: create device with all possible features in wanted_features

From: Andrey Vagin <[email protected]>

[ Upstream commit 88997e4208aea117627898e5f6f9801cf3cd42d2 ]

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
	   ...

---
 net/8021q/vlan_dev.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

@@ -562,8 +562,7 @@ static int vlan_dev_init(struct net_devi
 			   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)

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/net-8021q-create-device-with-all-possible-features-in-wanted_features.patch