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SubjectRe: [PATCH] Fix __pfn_to_page(pfn) for CONFIG_DISCONTIGMEM=y
Date
On Saturday, 8 of November 2008, Pavel Machek wrote:
> Hi!
>
> > This would be good to have in .28 IMO.
>
> Actually, this makes sense even for .27-stable, AFAICT.

Yes, it does, but it has to be merged first. :-)

> > From: Rafael J. Wysocki <rjw@sisk.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?

Oh, I mean __pfn_to_page(a_function(something)), where a_function() does more
than just computing the result.

> > 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@sisk.pl>
> > Cc: Pavel Machek <pavel@suse.cz>
>
> Acked-by: Pavel Machek <pavel@suse.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);\
> > })

Thanks,
Rafael


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