[PATCH] initialise page->private

From: Nathan Scott <nathans@sgi.com>

XFS wants to use page->private as a bitmap of uptodate indicators for
sub-page-sized blocks (which is one of the things ->provate was intended
for).

But someone needs to initialise ->private somewhere.  best to do it in the
page allocator, so the zeroness of a new page's ->private becomes a
system-wide thing.

mm/page_alloc.c

@@ -331,6 +331,7 @@ static void prep_new_page(struct page *page, int order)
 	page->flags &= ~(1 << PG_uptodate | 1 << PG_error |
 			1 << PG_referenced | 1 << PG_arch_1 |
 			1 << PG_checked | 1 << PG_mappedtodisk);
+	page->private = 0;
 	set_page_refs(page, order);
 }