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Subject: Re: [PATCH 2/9] mm: alloc_contig_freed_pages() added
From: Dave Hansen <dave@linux.vnet.ibm.com>
To: Michal Nazarewicz <mina86@mina86.com>
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Date: Tue, 18 Oct 2011 10:48:46 -0700
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On Tue, 2011-10-18 at 10:26 -0700, Michal Nazarewicz wrote:
> > You can do this in a more general fashion by checking the
> > zone boundaries and resolving the pfn->page every MAX_ORDER_NR_PAGES.
> > That will not be SPARSEMEM specific.
> 
> I've tried doing stuff that way but it ended up with much more code.

I guess instead of:

>> +static inline bool zone_pfn_same_memmap(unsigned long pfn1, unsigned long pfn2)
>> +{
>> +    return pfn_to_section_nr(pfn1) == pfn_to_section_nr(pfn2);
>> +}

You could do:

static inline bool zone_pfn_same_maxorder(unsigned long pfn1, unsigned long pfn2)
{
	unsigned long mask = MAX_ORDER_NR_PAGES-1;
	return (pfn1 & mask) == (pfn2 & mask);
}

I think that works.  Should be the same code you have now, basically.

-- Dave