From mboxrd@z Thu Jan  1 00:00:00 1970
From: David Miller <davem@davemloft.net>
Subject: Re: [PATCH v3] net: Allow no-cache copy from user on transmit
Date: Sun, 03 Apr 2011 22:23:41 -0700 (PDT)
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From: David Miller <davem@davemloft.net>
Date: Sun, 03 Apr 2011 22:03:05 -0700 (PDT)

> From: Tom Herbert <therbert@google.com>
> Date: Sun, 3 Apr 2011 21:56:17 -0700 (PDT)
> 
>> This patch uses __copy_from_user_nocache on transmit to bypass data
>> cache for a performance improvement.  skb_add_data_nocache and
>> skb_copy_to_page_nocache can be called by sendmsg functions to use
>> this feature, initial support is in tcp_sendmsg.  This functionality is
>> configurable per device using ethtool.
>  ...
>> Signed-off-by: Tom Herbert <therbert@google.com>
> 
> Applied, thanks Tom.

Actually, I'm sorry, I have to kick this back to you again Tom.

The original problem is that "linux/uaccess.h" has not been included
in the spot where you try to invoke the nocache copies.

linux/uaccess.h, when ARCH_HAS_NOCACHE_UACCESS is defined, provides
dummy routines.

So it's not correct to use ARCH_HAS_NOCACHE_UACCESS to conditionalize
things in the networking, just make sure linux/uaccess.h is included
at the call sites.

Thanks.