netdev - Re: [PATCH 05/10] net: Disable NOCACHE

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Message-ID: <CA+mtBx-zKBV+gd-1gNJTV4SBZtcQUpoYbxvOKn0eeOO36hoMpg@mail.gmail.com>
Date:	Wed, 13 Jul 2011 17:44:44 -0700
From:	Tom Herbert <therbert@...gle.com>
To:	Michał Mirosław <mirq-linux@...e.qmqm.pl>
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH 05/10] net: Disable NOCACHE_COPY by default

On Wed, Jul 13, 2011 at 5:10 PM, Michał Mirosław
<mirq-linux@...e.qmqm.pl> wrote:
>
> Disable NOCACHE_COPY by default as there's no reliable way to tell
> in advance what device(s) will take the packet. Also, allow the
> setting to be inherited by VLAN devices.
>

What problem is this addressing?  Is this just to get rid of the
NETIF_NO_CSUM bit, or is there an issue with nocachecopy being enabled
by default?

Tom

> This is the last use of NETIF_F_NO_CSUM.
>
> Signed-off-by: Michał Mirosław <mirq-linux@...e.qmqm.pl>
> ---
>  net/core/dev.c |   11 +++++------
>  1 files changed, 5 insertions(+), 6 deletions(-)
>
> diff --git a/net/core/dev.c b/net/core/dev.c
> index e57be02..7b9e2f4 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -5480,13 +5480,12 @@ int register_netdevice(struct net_device *dev)
>        dev->features |= NETIF_F_SOFT_FEATURES;
>        dev->wanted_features = dev->features & dev->hw_features;
>
> -       /* Turn on no cache copy if HW is doing checksum */
> +       /* Allow changing no-cache copy but disable it by default
> +        * as there's no reliable way to tell what device(s) will take
> +        * the packet. Allow the setting to be inherited to VLANs.
> +        */
>        dev->hw_features |= NETIF_F_NOCACHE_COPY;
> -       if ((dev->features & NETIF_F_ALL_CSUM) &&
> -           !(dev->features & NETIF_F_NO_CSUM)) {
> -               dev->wanted_features |= NETIF_F_NOCACHE_COPY;
> -               dev->features |= NETIF_F_NOCACHE_COPY;
> -       }
> +       dev->vlan_features |= NETIF_F_NOCACHE_COPY;
>
>        /* Make NETIF_F_HIGHDMA inheritable to VLAN devices.
>         */
> --
> 1.7.5.4
>
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