netdev - RE: [PATCH net-next-2.6] net: propagate NETIF_F

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Date:	Thu, 23 Sep 2010 09:30:03 -0700
From:	"Zou, Yi" <yi.zou@...el.com>
To:	Eric Dumazet <eric.dumazet@...il.com>,
	"Kirsher, Jeffrey T" <jeffrey.t.kirsher@...el.com>,
	David Miller <davem@...emloft.net>
CC:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"gospo@...hat.com" <gospo@...hat.com>,
	"bphilips@...ell.com" <bphilips@...ell.com>
Subject: RE: [PATCH net-next-2.6] 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@...il.com>
> ---
>  net/core/dev.c |    7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/net/core/dev.c b/net/core/dev.c
> index 2c7934f..e0c0b86 100644
> --- 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);
> 
Cool, thanks for taking care of this, Eric.

-yi