drbd: Do not allow a fencing-policy of resource-and-stonith with protocol A

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

drivers/block/drbd/drbd_nl.c

@@ -806,6 +806,15 @@ static int drbd_nl_disk_conf(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp
 		goto fail;
 	}
 
+	if (get_net_conf(mdev)) {
+		int prot = mdev->net_conf->wire_protocol;
+		put_net_conf(mdev);
+		if (nbc->dc.fencing == FP_STONITH && prot == DRBD_PROT_A) {
+			retcode = ERR_STONITH_AND_PROT_A;
+			goto fail;
+		}
+	}
+
 	nbc->lo_file = filp_open(nbc->dc.backing_dev, O_RDWR, 0);
 	if (IS_ERR(nbc->lo_file)) {
 		dev_err(DEV, "open(\"%s\") failed with %ld\n", nbc->dc.backing_dev,
@@ -1238,7 +1247,16 @@ static int drbd_nl_net_conf(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
 	    && (new_conf->wire_protocol != DRBD_PROT_C)) {
 		retcode = ERR_NOT_PROTO_C;
 		goto fail;
-	};
+	}
+
+	if (get_ldev(mdev)) {
+		enum drbd_fencing_p fp = mdev->ldev->dc.fencing;
+		put_ldev(mdev);
+		if (new_conf->wire_protocol == DRBD_PROT_A && fp == FP_STONITH) {
+			retcode = ERR_STONITH_AND_PROT_A;
+			goto fail;
+		}
+	}
 
 	if (mdev->state.role == R_PRIMARY && new_conf->want_lose) {
 		retcode = ERR_DISCARD;

drivers/block/drbd/drbd_req.c

@@ -660,7 +660,7 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
 
 	case resend:
 		/* If RQ_NET_OK is already set, we got a P_WRITE_ACK or P_RECV_ACK
-		   before the connection loss; only P_BARRIER_ACK was missing.
+		   before the connection loss (B&C only); only P_BARRIER_ACK was missing.
 		   Trowing them out of the TL here by pretending we got a BARRIER_ACK
 		   TODO: Either resync them, or ensure peer was not rebooted. */
 		if (!(req->rq_state & RQ_NET_OK)) {

include/linux/drbd.h

@@ -145,6 +145,7 @@ enum drbd_ret_codes {
 	ERR_CONNECTED		= 151, /* DRBD 8.3 only */
 	ERR_PERM		= 152,
 	ERR_NEED_APV_93		= 153,
+	ERR_STONITH_AND_PROT_A  = 154,
 
 	/* insert new ones above this line */
 	AFTER_LAST_ERR_CODE