Drop unused pages immediately

If a page is encountered that is only referenced by the migration code
then there is no reason to swap or migrate the page. Release
the page by calling move_to_lru().

Signed-off-by: Christoph Lameter <clameter@sgi.com>

Index: linux-2.6.15-rc1-mm1/mm/vmscan.c
===================================================================
--- linux-2.6.15-rc1-mm1.orig/mm/vmscan.c	2005-11-17 15:59:07.000000000 -0800
+++ linux-2.6.15-rc1-mm1/mm/vmscan.c	2005-11-17 16:05:18.000000000 -0800
@@ -700,6 +700,11 @@ redo:
 	list_for_each_entry_safe(page, page2, l, lru) {
 		cond_resched();
 
+		if (page_count(page) == 1) {
+			/* page was freed from under us. So we are done. */
+			move_to_lru(page);
+			continue;
+		}
 		/*
 		 * Skip locked pages during the first two passes to give the
 		 * functions holding the lock time to release the page. Later we