Get rid of if(PageLocked())

This introduces another race condition since another process may have
locked the page. Simply relock the page after successfully calling
migratepages() and then retry.

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

Index: linux-2.6.17-rc2-mm1/mm/migrate.c
===================================================================
--- linux-2.6.17-rc2-mm1.orig/mm/migrate.c	2006-04-27 22:55:46.731119932 -0700
+++ linux-2.6.17-rc2-mm1/mm/migrate.c	2006-04-27 23:39:11.853319378 -0700
@@ -476,17 +476,20 @@
 			/* Someone else already triggered a write */
 			return -EAGAIN;
 
-		if (mapping->a_ops->writepage(page, &wbc) < 0)
+		rc = mapping->a_ops->writepage(page, &wbc);
+		if (rc < 0)
 			/* I/O Error writing */
 			return -EIO;
 
+		if (rc == AOP_WRITEPAGE_ACTIVATE)
+			return -EAGAIN;
+
+		lock_page(page);
 		/*
-		 * Retry if writepage() removed the lock or the page
-		 * is still dirty or undergoing writeback.
+		 * The lock was dropped by writepage() and so something
+		 * may have changed with the page.
 		 */
-		if (!PageLocked(page) ||
-			PageWriteback(page) || PageDirty(page))
-				return -EAGAIN;
+		return -EAGAIN;
 	}
 
 	/*
@@ -599,8 +602,7 @@
 
 		unlock_page(newpage);
 unlock_page:
-		if (PageLocked(page))	/* writepage() may unlock */
-			unlock_page(page);
+		unlock_page(page);
 
 next:
 		if (rc) {