ceph: ignore preferred_osd field

Old users may not expect EINVAL, and there is no clear user-visibile
behavior change now that we ignore it.

Signed-off-by: Sage Weil <sage@inktank.com>
Reviewed-by: Alex Elder <elder@inktank.com>

fs/ceph/ioctl.c

@@ -39,10 +39,6 @@ static long __validate_layout(struct ceph_mds_client *mdsc,
 {
 	int i, err;
 
-	/* preferred_osd is no longer supported */
-	if (l->preferred_osd != -1)
-		return -EINVAL;
-
 	/* validate striping parameters */
 	if ((l->object_size & ~PAGE_MASK) ||
 	    (l->stripe_unit & ~PAGE_MASK) ||