drbd: --dry-run option for drbdsetup net ( drbdadm -- --dry-run connect <res> )

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_receiver.c b/drivers/block/drbd/drbd_receiver.c
index d065c64..8bcde4a 100644
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -2538,6 +2538,16 @@
 		}
 	}
 
+	if (mdev->net_conf->dry_run || test_bit(CONN_DRY_RUN, &mdev->flags)) {
+		if (hg == 0)
+			dev_info(DEV, "dry-run connect: No resync, would become Connected immediately.\n");
+		else
+			dev_info(DEV, "dry-run connect: Would become %s, doing a %s resync.",
+				 drbd_conn_str(hg > 0 ? C_SYNC_SOURCE : C_SYNC_TARGET),
+				 abs(hg) >= 2 ? "full" : "bit-map based");
+		return C_MASK;
+	}
+
 	if (abs(hg) >= 2) {
 		dev_info(DEV, "Writing the whole bitmap, full sync required after drbd_sync_handshake.\n");
 		if (drbd_bitmap_io(mdev, &drbd_bmio_set_n_write, "set_n_write from sync_handshake"))
@@ -2585,7 +2595,7 @@
 	struct p_protocol *p = (struct p_protocol *)h;
 	int header_size, data_size;
 	int p_proto, p_after_sb_0p, p_after_sb_1p, p_after_sb_2p;
-	int p_want_lose, p_two_primaries;
+	int p_want_lose, p_two_primaries, cf;
 	char p_integrity_alg[SHARED_SECRET_MAX] = "";
 
 	header_size = sizeof(*p) - sizeof(*h);
@@ -2598,8 +2608,14 @@
 	p_after_sb_0p	= be32_to_cpu(p->after_sb_0p);
 	p_after_sb_1p	= be32_to_cpu(p->after_sb_1p);
 	p_after_sb_2p	= be32_to_cpu(p->after_sb_2p);
-	p_want_lose	= be32_to_cpu(p->want_lose);
 	p_two_primaries = be32_to_cpu(p->two_primaries);
+	cf		= be32_to_cpu(p->conn_flags);
+	p_want_lose = cf & CF_WANT_LOSE;
+
+	clear_bit(CONN_DRY_RUN, &mdev->flags);
+
+	if (cf & CF_DRY_RUN)
+		set_bit(CONN_DRY_RUN, &mdev->flags);
 
 	if (p_proto != mdev->net_conf->wire_protocol) {
 		dev_err(DEV, "incompatible communication protocols\n");
@@ -3125,6 +3141,8 @@
 				dev_err(DEV, "Disk attach process on the peer node was aborted.\n");
 				peer_state.disk = D_DISKLESS;
 			} else {
+				if (test_and_clear_bit(CONN_DRY_RUN, &mdev->flags))
+					return FALSE;
 				D_ASSERT(oconn == C_WF_REPORT_PARAMS);
 				drbd_force_state(mdev, NS(conn, C_DISCONNECTING));
 				return FALSE;