Index: vfs_lookup.c
===================================================================
RCS file: /zoo/pjd/repo/src/sys/kern/vfs_lookup.c,v
retrieving revision 1.101
diff -u -p -r1.101 vfs_lookup.c
--- vfs_lookup.c	27 May 2007 20:50:23 -0000	1.101
+++ vfs_lookup.c	6 Jun 2007 18:58:07 -0000
@@ -495,6 +495,11 @@ dirloop:
 
 		if (!(cnp->cn_flags & (LOCKPARENT | LOCKLEAF)))
 			VOP_UNLOCK(dp, 0, td);
+		else if ((cnp->cn_flags & (ISLASTCN|LOCKSHARED|LOCKLEAF)) ==
+		    (ISLASTCN|LOCKLEAF)) {
+			if (VOP_ISLOCKED(dp, td) != LK_EXCLUSIVE)
+				vn_lock(dp, LK_UPGRADE | LK_RETRY, td);
+		}
 		/* XXX This should probably move to the top of function. */
 		if (cnp->cn_flags & SAVESTART)
 			panic("lookup: SAVESTART");