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Subject: Re: [PATCH] net: add APIs for manipulating skb page fragments.
From: Ian Campbell <Ian.Campbell@eu.citrix.com>
To: David Miller <davem@davemloft.net>
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Date: Sun, 21 Aug 2011 09:23:57 +0100
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On Sun, 2011-08-21 at 01:31 +0100, David Miller wrote:
> From: Ian Campbell <ian.campbell@citrix.com>
> Date: Fri, 19 Aug 2011 17:25:00 +0100
> 
> > The primary aim is to add skb_frag_(ref|unref) in order to remove the use of
> > bare get/put_page on SKB pages fragments and to isolate users from subsequent
> > changes to the skb_frag_t data structure.
> > 
> > Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
> 
> You're going to have to protect all of the things using the interfaces
> from linux/dma-mapping.h with CONFIG_HAS_DMA otherwise it won't build
> on platforms like S390.

s390 is one of the arches which I build tested and I initially saw this
issue too. I did add CONFIG_HAS_DMA but it turns out that
linux/dma-mapping.h takes care of this by including
asm-generic/dma-mapping-broken.h for you so I removed the #ifdef again.
The header defines the prototypes to allow building but causes a link
time failure if anything actually uses the interfaces.

I just tested a s390x defconfig build again and it appears to be fine.

Ian.