o vn_open() fails to call VOP_CLOSE() if vfs_object_create fails. Ideally

all successful calls to VOP_OPEN() might be reflected in a call to
  VOP_CLOSE().  For now, simply add a comment reflecting this problem;
  this should be fixed at some point.

sys/kern/vfs_vnops.c

@@ -188,6 +188,7 @@ vn_open(ndp, flagp, cmode)
 	 */
 	if (vn_canvmio(vp) == TRUE) {
 		if ((error = vfs_object_create(vp, td, cred)) != 0)
+			/* XXX: Should VOP_CLOSE() again here. */
 			goto bad;
 	}