Re: assert/crash in __rmqueue() when enabling CONFIG_NUMA

[Dave Hansen <haveblue@us.ibm.com>]

On Fri, 2006-05-05 at 09:55 -0400, Bob Picco wrote:
> -               if (!page_is_buddy(buddy, order))
> +               if (page_in_zone_hole(buddy))
> +                       break;
> +               else if (page_zonenum(buddy) != page_zonenum(page))
> +                       break;
> +               else if (!page_is_buddy(buddy, order))
>                         break;          /* Move the buddy up one level. */ 

The page_zonenum() checks look good, but I'm not sure I understand the
page_in_zone_hole() part.  If a page is in a hole in a zone, it will
still have a valid mem_map entry, right?  It should also never have been
put into the allocator, so it also won't ever be coalesced.  

I'm a bit confused. :(

BTW, I like the idea of just aligning HIGHMEM's start because it has no
runtime cost.  Buuuuut, it is still just a shift and compare of the two
page->flags, which should already be (or will soon anyway be) in the
cache.

-- Dave

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