3 files changed, 41 insertions, 5 deletions

diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index 2bf3a6e..1aae724 100644
--- a/drivers/block/drbd/drbd_int.h
+++ b/drivers/block/drbd/drbd_int.h
@@ -443,13 +443,18 @@ struct p_rs_param_89 {
 	char csums_alg[SHARED_SECRET_MAX];
 } __packed;
 
+enum drbd_conn_flags {
+	CF_WANT_LOSE = 1,
+	CF_DRY_RUN = 2,
+};
+
 struct p_protocol {
 	struct p_header head;
 	u32 protocol;
 	u32 after_sb_0p;
 	u32 after_sb_1p;
 	u32 after_sb_2p;
-	u32 want_lose;
+	u32 conn_flags;
 	u32 two_primaries;
 
               /* Since protocol version 87 and higher. */
@@ -791,6 +796,7 @@ enum {
 				 * while this is set. */
 	RESIZE_PENDING,		/* Size change detected locally, waiting for the response from
 				 * the peer, if it changed there as well. */
+	CONN_DRY_RUN,		/* Expect disconnect after resync handshake. */
 };
 
 struct drbd_bitmap; /* opaque for drbd_conf */
diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index ab871e0..b2d347d 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -1668,7 +1668,7 @@ int drbd_send_sync_param(struct drbd_conf *mdev, struct syncer_conf *sc)
 int drbd_send_protocol(struct drbd_conf *mdev)
 {
 	struct p_protocol *p;
-	int size, rv;
+	int size, cf, rv;
 
 	size = sizeof(struct p_protocol);
 
@@ -1685,9 +1685,21 @@ int drbd_send_protocol(struct drbd_conf *mdev)
 	p->after_sb_0p   = cpu_to_be32(mdev->net_conf->after_sb_0p);
 	p->after_sb_1p   = cpu_to_be32(mdev->net_conf->after_sb_1p);
 	p->after_sb_2p   = cpu_to_be32(mdev->net_conf->after_sb_2p);
-	p->want_lose     = cpu_to_be32(mdev->net_conf->want_lose);
 	p->two_primaries = cpu_to_be32(mdev->net_conf->two_primaries);
 
+	cf = 0;
+	if (mdev->net_conf->want_lose)
+		cf |= CF_WANT_LOSE;
+	if (mdev->net_conf->dry_run) {
+		if (mdev->agreed_pro_version >= 92)
+			cf |= CF_DRY_RUN;
+		else {
+			dev_err(DEV, "--dry-run is not supported by peer");
+			return 0;
+		}
+	}
+	p->conn_flags    = cpu_to_be32(cf);
+
 	if (mdev->agreed_pro_version >= 87)
 		strcpy(p->integrity_alg, mdev->net_conf->integrity_alg);
 
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 @@ static enum drbd_conns drbd_sync_handshake(struct drbd_conf *mdev, enum drbd_rol
 		}
 	}
 
+	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 @@ static int receive_protocol(struct drbd_conf *mdev, struct p_header *h)
 	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 @@ static int receive_protocol(struct drbd_conf *mdev, struct p_header *h)
 	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 @@ static int receive_state(struct drbd_conf *mdev, struct p_header *h)
 				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;