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Date: Fri, 8 Feb 2008 14:05:55 -0800
From: Andrew Morton <akpm@linux-foundation.org>
To: Matt Mackall <mpm@selenic.com>
Cc: vapier@gentoo.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] stub out is_swap_pte for !MMU
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On Fri, 08 Feb 2008 15:41:42 -0600
Matt Mackall <mpm@selenic.com> wrote:

> Fix compile error on nommu for is_swap_pte
> 
> Does it ever make sense to ask "is this pte a swap entry?" on a machine
> with no MMU? Presumably this also means it has no ptes too, right? In
> which case, it's better to comment the whole function out. Then when
> someone tries to ask the above meaningless question, they get a compile
> error rather than a meaningless answer.
> 
> Signed-off-by: Matt Mackall <mpm@selenic.com>
> 
> diff -r 50a6e531a9f2 include/linux/swapops.h
> --- a/include/linux/swapops.h	Mon Feb 04 20:23:02 2008 -0600
> +++ b/include/linux/swapops.h	Fri Feb 08 15:38:01 2008 -0600
> @@ -42,11 +42,13 @@
>  	return entry.val & SWP_OFFSET_MASK(entry);
>  }
>  
> +#ifdef CONFIG_MMU
>  /* check whether a pte points to a swap entry */
>  static inline int is_swap_pte(pte_t pte)
>  {
>  	return !pte_none(pte) && !pte_present(pte) && !pte_file(pte);
>  }
> +#endif
>  

Seems contradictory.  Is there _really_ a compilation error at present? 
The changelog seems to imply otherwise and no compiler error output is
quoted and it all compiled OK for me on nommu superh.