On Thu, Apr 08, 2010 at 07:09:48PM +0200, Andrea Arcangeli wrote:
> + if (PageTransCompound(page)) {
> + low_pfn += (1 << page_order(page)) - 1;
> + continue;
> + }
Thinking again the low_pfn += I'll have to remove it even from the
hugepage case, because this could be a compound page that doesn't
belong to transparent hugepage support, so it could go away from under
us and make the order-reading invalid despite we hold the lru_lock.
Unless we mark the transparent hugepages with a special bit in the
page->flags we can't retain this optimization.
This would have been safe if we used compound_order and we knew it was
owned by transparent hugepage support. Given how short we are in
page->flags (I already had to remove the PG_buddy) it's unlikely we
can mark it specially and retain this.
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