[PATCH] SwapMig: Drop unused pages immediately

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: NChristoph Lameter <clameter@sgi.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

mm/vmscan.c

@@ -689,6 +689,11 @@ int migrate_pages(struct list_head *l, struct list_head *t)
 	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