Remove another check for mapping

The mapping never changes for a locked page. Remove two more
checks for mapping being NULL.

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

Index: linux-2.6.17-rc3/mm/migrate.c
===================================================================
--- linux-2.6.17-rc3.orig/mm/migrate.c	2006-04-30 22:45:53.794977846 -0700
+++ linux-2.6.17-rc3/mm/migrate.c	2006-05-03 21:49:52.957619975 -0700
@@ -291,7 +291,7 @@
 
 	if (!mapping) {
 		/* Anonymous page */
-		if (page_count(page) != 1 || !page->mapping)
+		if (page_count(page) != 1)
 			return -EAGAIN;
 		return 0;
 	}
@@ -302,8 +302,7 @@
 						&mapping->page_tree,
 						page_index(page));
 
-	if (!page_mapping(page) ||
-			page_count(page) != 2 + !!PagePrivate(page) ||
+	if (page_count(page) != 2 + !!PagePrivate(page) ||
 			*radix_pointer != page) {
 		write_unlock_irq(&mapping->tree_lock);
 		return -EAGAIN;