ceph: fix divide-by-zero in __validate_layout()

The 'stripe_unit' field is 64 bits, casting it to 32 bits can result zero.
Signed-off-by: NYan, Zheng <zyan@redhat.com>

fs/ceph/ioctl.c

@@ -41,7 +41,7 @@ static long __validate_layout(struct ceph_mds_client *mdsc,
 	/* validate striping parameters */
 	if ((l->object_size & ~PAGE_MASK) ||
 	    (l->stripe_unit & ~PAGE_MASK) ||
-	    (l->stripe_unit != 0 &&
+	    ((unsigned)l->stripe_unit != 0 &&
 	     ((unsigned)l->object_size % (unsigned)l->stripe_unit)))
 		return -EINVAL;