drbd: Move the CREATE_BARRIER flag from connection to device

That is necessary since the whole transfer log is per connection(tconn)
and not per device(mdev).

This bug caused list corruption on the worker list. When a barrier is queued
for sending in the context of one device, another device did not see the
CREATE_BARRIER bit, and queued the same object again -> list corruption.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index 3177e3e..e391330 100644
--- a/drivers/block/drbd/drbd_int.h
+++ b/drivers/block/drbd/drbd_int.h
@@ -670,7 +670,6 @@
 
 /* flag bits per mdev */
 enum {
-	CREATE_BARRIER,		/* next P_DATA is preceded by a P_BARRIER */
 	UNPLUG_QUEUED,		/* only relevant with kernel 2.4 */
 	UNPLUG_REMOTE,		/* sending a "UnplugRemote" could help */
 	MD_DIRTY,		/* current uuids and flags not yet on disk */
@@ -813,6 +812,7 @@
 	CONN_WD_ST_CHG_OKAY,
 	CONN_WD_ST_CHG_FAIL,
 	CONN_DRY_RUN,		/* Expect disconnect after resync handshake. */
+	CREATE_BARRIER,		/* next P_DATA is preceded by a P_BARRIER */
 };
 
 struct drbd_tconn {			/* is a resource from the config file */