linux-kernel - Re: [PATCH] Fix __pfn_to_page(pfn) for CONFIG

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Date:	Sat, 8 Nov 2008 13:59:52 +0100
From:	Pavel Machek <pavel@...e.cz>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	pm list <linux-pm@...ts.linux-foundation.org>
Subject: Re: [PATCH] Fix __pfn_to_page(pfn) for CONFIG_DISCONTIGMEM=y

Hi!

> This would be good to have in .28 IMO.

Actually, this makes sense even for .27-stable, AFAICT.

> From: Rafael J. Wysocki <rjw@...k.pl>
> Subject: Fix __pfn_to_page(pfn) for CONFIG_DISCONTIGMEM=y
> 
> Fix macro __pfn_to_page(pfn) so that it doesn't evaluate its
> argument twice in the CONFIG_DISCONTIGMEM=y case, because 'pfn' may
> be a result of a funtion call having side effects.

function call?

> For example, the hibernation code applies pfn_to_page(pfn) to the
> result of a function returning the pfn corresponding to the next set
> bit in a bitmap and the current bit position is modified on each
> call.  This leads to "interesting" failures for CONFIG_DISCONTIGMEM=y
> due to the current behavior of __pfn_to_page(pfn).
> 
> Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>
> Cc: Pavel Machek <pavel@...e.cz>

Acked-by: Pavel Machek <pavel@...e.cz>


>  include/asm-generic/memory_model.h |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> Index: linux-2.6/include/asm-generic/memory_model.h
> ===================================================================
> --- linux-2.6.orig/include/asm-generic/memory_model.h
> +++ linux-2.6/include/asm-generic/memory_model.h
> @@ -34,7 +34,7 @@
>  
>  #define __pfn_to_page(pfn)			\
>  ({	unsigned long __pfn = (pfn);		\
> -	unsigned long __nid = arch_pfn_to_nid(pfn);  \
> +	unsigned long __nid = arch_pfn_to_nid(__pfn);  \
>  	NODE_DATA(__nid)->node_mem_map + arch_local_page_offset(__pfn, __nid);\
>  })
>  

-- 
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