When vn_open() is failing because it cannot allocate a vm object, call

VOP_CLOSE() on the vnode, so that VOP_OPEN() and VOP_CLOSE() calls
are symmetric in all failure cases.  This prevents an 'open' reference
from being leaked in that unlikely failure scenario.

sys/kern/vfs_vnops.c

@@ -199,7 +199,7 @@ vn_open_cred(ndp, flagp, cmode, cred)
 	 */
 	if (vn_canvmio(vp) == TRUE) {
 		if ((error = vfs_object_create(vp, td, cred)) != 0)
-			/* XXX: Should VOP_CLOSE() again here. */
+			VOP_CLOSE(vp, fmode, cred, td);
 			goto bad;
 	}