Re: [PATCH] Fix crash with FLAT_MEMORY and ARCH_PFN_OFFSET != 0

[tsbogend@alpha.franken.de (Thomas Bogendoerfer)]

On Tue, Dec 18, 2007 at 04:24:04AM -0800, Andrew Morton wrote:
> On Tue, 18 Dec 2007 13:03:00 +0100 (CET) Thomas Bogendoerfer <tsbogend@alpha.franken.de> wrote:
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -3427,7 +3427,7 @@ static void __init_refok alloc_node_mem_map(struct pglist_data *pgdat)
> >  		mem_map = NODE_DATA(0)->node_mem_map;
> >  #ifdef CONFIG_ARCH_POPULATES_NODE_MAP
> >  		if (page_to_pfn(mem_map) != pgdat->node_start_pfn)
> > -			mem_map -= pgdat->node_start_pfn;
> > +			mem_map -= (pgdat->node_start_pfn - ARCH_PFN_OFFSET);
> >  #endif /* CONFIG_ARCH_POPULATES_NODE_MAP */
> >  	}
> >  #endif
> 
> hm.  It's rather non-trivial to verify that this will compile OK on all
> architectures.

I grepped through include/asm-* and found:

#if defined(CONFIG_FLATMEM)

#ifndef ARCH_PFN_OFFSET
#define ARCH_PFN_OFFSET         (0UL)
#endif

in include/asm-generic/memory_model.h. So I'm still confident, that
this works on all architectures. It's tested on MIPS.

Thomas.

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