net: propagate NETIF_F_HIGHDMA to vlans

Automatically allows vlans to get NETIF_F_HIGHDMA if underlying device
supports it.

On 32bit arches (and more precisely if CONFIG_HIGHMEM is enabled), it
can help to reduce cost of illegal_highdma() and __skb_linearize()
calls.

Tested on tg3 , bnx2, bonding, this worked very well.

This is a generalization of a patch provided by Yi Zou & Jeff Kirsher.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/core/dev.c b/net/core/dev.c
index 2c7934f8cf3ec15ca57fbcb6758fc30ebc4b947f..e0c0b86f57a1642a3036204af0bf39e1c444d624 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -5058,10 +5058,11 @@ int register_netdevice(struct net_device *dev)
        if (dev->features & NETIF_F_SG)
                dev->features |= NETIF_F_GSO;
 
-       /* Enable GRO for vlans by default if dev->features has GRO also.
-        * vlan_dev_init() will do the dev->features check.
+       /* Enable GRO and NETIF_F_HIGHDMA for vlans by default,
+        * vlan_dev_init() will do the dev->features check, so these features
+        * are enabled only if supported by underlying device.
         */
-       dev->vlan_features |= NETIF_F_GRO;
+       dev->vlan_features |= (NETIF_F_GRO | NETIF_F_HIGHDMA);
 
        ret = call_netdevice_notifiers(NETDEV_POST_INIT, dev);
        ret = notifier_to_errno(ret);