drbd: Allow online change of replication protocol only with agreed_pv >= 100

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>

drivers/block/drbd/drbd_nl.c

@@ -1671,6 +1671,11 @@ check_net_options(struct drbd_tconn *tconn, struct net_conf *new_conf)
 	struct drbd_conf *mdev;
 	int i;
 
+	if (tconn->net_conf && tconn->agreed_pro_version < 100 &&
+	    tconn->cstate == C_WF_REPORT_PARAMS &&
+	    new_conf->wire_protocol != tconn->net_conf->wire_protocol)
+		return ERR_NEED_APV_100;
+
 	if (new_conf->two_primaries &&
 	    (new_conf->wire_protocol != DRBD_PROT_C))
 		return ERR_NOT_PROTO_C;

include/linux/drbd.h

@@ -160,6 +160,7 @@ enum drbd_ret_code {
 	ERR_MINOR_CONFIGURED    = 160,
 	ERR_MINOR_EXISTS	= 161,
 	ERR_INVALID_REQUEST	= 162,
+	ERR_NEED_APV_100	= 163,
 
 	/* insert new ones above this line */
 	AFTER_LAST_ERR_CODE