drbd: Turn no-disk-drain into disk-drain={yes|no}

Change the --no-disk-drain drbdsetup command line option as well as
the no_disk_drain netlink packet.
Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>

drivers/block/drbd/drbd_receiver.c

@@ -1181,7 +1181,7 @@ void drbd_bump_write_ordering(struct drbd_conf *mdev, enum write_ordering_e wo)
 
 	if (wo == WO_bdev_flush && !dc->disk_flushes)
 		wo = WO_drain_io;
-	if (wo == WO_drain_io && dc->no_disk_drain)
+	if (wo == WO_drain_io && !dc->disk_drain)
 		wo = WO_none;
 	rcu_read_unlock();
 	mdev->write_ordering = wo;

include/linux/drbd_genl.h

@@ -124,7 +124,7 @@ GENL_struct(DRBD_NLA_DISK_CONF, 3, disk_conf,
 
 	__flg_field_def(16, GENLA_F_MANDATORY,	disk_barrier, 1)
 	__flg_field_def(17, GENLA_F_MANDATORY,	disk_flushes, 1)
-	__flg_field_def(18, GENLA_F_MANDATORY,	no_disk_drain, 0)
+	__flg_field_def(18, GENLA_F_MANDATORY,	disk_drain, 1)
 	__flg_field_def(19, GENLA_F_MANDATORY,	no_md_flush, 0)
 )