On Tue, 18 Oct 2011 10:48:46 -0700, Dave Hansen [off-list ref] wrote:

On Tue, 2011-10-18 at 10:26 -0700, Michal Nazarewicz wrote:

quoted

quoted

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:

quoted

quoted

+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.

Makes sense.  It'd require calling pfn_to_page() every MAX_ORDER_NR_PAGES even
in memory models that have linear mapping of struct page, but I guess that's
not that bad.

-- 
Best regards,                                         _     _
.o. | Liege of Serenely Enlightened Majesty of      o' \,=./ `o
..o | Computer Science,  Micha? ?mina86? Nazarewicz    (o o)
ooo +----<email/xmpp: mpn@google.com>--------------ooO--(_)--Ooo--