drbd: Delay/reject other state changes while establishing a connection

Changes to the role and disk state should be delayed or rejected
while we establish a connection.

This is necessary, since the peer will base its resync decision
on the UUIDs and the state we sent in the drbd_connect() function.

The most prominent example for this race is becoming primary after
sending state and UUIDs and before the state changes to C_WF_CONNECTION.

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

drivers/block/drbd/drbd_int.h

@@ -808,6 +808,7 @@ enum {
 	CONN_WD_ST_CHG_FAIL,
 	CONN_DRY_RUN,		/* Expect disconnect after resync handshake. */
 	CREATE_BARRIER,		/* next P_DATA is preceded by a P_BARRIER */
+	STATE_SENT,		/* Do not change state/UUIDs while this is set */
 };
 
 struct drbd_tconn {			/* is a resource from the config file */

drivers/block/drbd/drbd_nl.c

@@ -502,7 +502,7 @@ bool conn_try_outdate_peer(struct drbd_tconn *tconn)
 	   here, because we might were able to re-establish the connection in the
 	   meantime. */
 	spin_lock_irq(&tconn->req_lock);
-	if (tconn->cstate < C_WF_REPORT_PARAMS)
+	if (tconn->cstate < C_WF_REPORT_PARAMS && !test_bit(STATE_SENT, &tconn->flags))
 		_conn_request_state(tconn, mask, val, CS_VERBOSE);
 	spin_unlock_irq(&tconn->req_lock);
 

drivers/block/drbd/drbd_receiver.c

@@ -848,6 +848,7 @@ static int conn_connect(struct drbd_tconn *tconn)
 	struct net_conf *nc;
 	int vnr, timeout, try, h, ok;
 	bool discard_my_data;
+	enum drbd_state_rv rv;
 
 	if (conn_request_state(tconn, NS(conn, C_WF_CONNECTION), CS_VERBOSE) < SS_SUCCESS)
 		return -2;
@@ -1008,6 +1009,8 @@ retry:
 	if (drbd_send_protocol(tconn) == -EOPNOTSUPP)
 		return -1;
 
+	set_bit(STATE_SENT, &tconn->flags);
+
 	rcu_read_lock();
 	idr_for_each_entry(&tconn->volumes, mdev, vnr) {
 		kref_get(&mdev->kref);
@@ -1024,8 +1027,11 @@ retry:
 	}
 	rcu_read_unlock();
 
-	if (conn_request_state(tconn, NS(conn, C_WF_REPORT_PARAMS), CS_VERBOSE) < SS_SUCCESS)
+	rv = conn_request_state(tconn, NS(conn, C_WF_REPORT_PARAMS), CS_VERBOSE);
+	if (rv < SS_SUCCESS) {
+		clear_bit(STATE_SENT, &tconn->flags);
 		return 0;
+	}
 
 	drbd_thread_start(&tconn->asender);
 

drivers/block/drbd/drbd_state.c

@@ -53,7 +53,7 @@ static int w_after_state_ch(struct drbd_work *w, int unused);
 static void after_state_ch(struct drbd_conf *mdev, union drbd_state os,
 			   union drbd_state ns, enum chg_state_flags flags);
 static enum drbd_state_rv is_valid_state(struct drbd_conf *, union drbd_state);
-static enum drbd_state_rv is_valid_soft_transition(union drbd_state, union drbd_state);
+static enum drbd_state_rv is_valid_soft_transition(union drbd_state, union drbd_state, struct drbd_tconn *);
 static enum drbd_state_rv is_valid_transition(union drbd_state os, union drbd_state ns);
 static union drbd_state sanitize_state(struct drbd_conf *mdev, union drbd_state ns,
 				       enum sanitize_state_warnings *warn);
@@ -267,7 +267,7 @@ _req_st_cond(struct drbd_conf *mdev, union drbd_state mask,
 	if (rv == SS_UNKNOWN_ERROR) {
 		rv = is_valid_state(mdev, ns);
 		if (rv == SS_SUCCESS) {
-			rv = is_valid_soft_transition(os, ns);
+			rv = is_valid_soft_transition(os, ns, mdev->tconn);
 			if (rv == SS_SUCCESS)
 				rv = SS_UNKNOWN_ERROR; /* cont waiting, otherwise fail. */
 		}
@@ -313,7 +313,7 @@ drbd_req_state(struct drbd_conf *mdev, union drbd_state mask,
 	if (cl_wide_st_chg(mdev, os, ns)) {
 		rv = is_valid_state(mdev, ns);
 		if (rv == SS_SUCCESS)
-			rv = is_valid_soft_transition(os, ns);
+			rv = is_valid_soft_transition(os, ns, mdev->tconn);
 		spin_unlock_irqrestore(&mdev->tconn->req_lock, flags);
 
 		if (rv < SS_SUCCESS) {
@@ -569,7 +569,7 @@ is_valid_state(struct drbd_conf *mdev, union drbd_state ns)
  * @os:		old state.
  */
 static enum drbd_state_rv
-is_valid_soft_transition(union drbd_state os, union drbd_state ns)
+is_valid_soft_transition(union drbd_state os, union drbd_state ns, struct drbd_tconn *tconn)
 {
 	enum drbd_state_rv rv = SS_SUCCESS;
 
@@ -595,6 +595,13 @@ is_valid_soft_transition(union drbd_state os, union drbd_state ns)
 	/* if (ns.conn == os.conn && ns.conn == C_WF_REPORT_PARAMS)
 	   rv = SS_IN_TRANSIENT_STATE; */
 
+	/* While establishing a connection only allow cstate to change.
+	   Delay/refuse role changes, detach attach etc... */
+	if (test_bit(STATE_SENT, &tconn->flags) &&
+	    !(os.conn == C_WF_REPORT_PARAMS ||
+	      (ns.conn == C_WF_REPORT_PARAMS && os.conn == C_WF_CONNECTION)))
+		rv = SS_IN_TRANSIENT_STATE;
+
 	if ((ns.conn == C_VERIFY_S || ns.conn == C_VERIFY_T) && os.conn < C_CONNECTED)
 		rv = SS_NEED_CONNECTION;
 
@@ -927,9 +934,9 @@ __drbd_set_state(struct drbd_conf *mdev, union drbd_state ns,
 			   this happen...*/
 
 			if (is_valid_state(mdev, os) == rv)
-				rv = is_valid_soft_transition(os, ns);
+				rv = is_valid_soft_transition(os, ns, mdev->tconn);
 		} else
-			rv = is_valid_soft_transition(os, ns);
+			rv = is_valid_soft_transition(os, ns, mdev->tconn);
 	}
 
 	if (rv < SS_SUCCESS) {
@@ -1393,6 +1400,12 @@ static void after_state_ch(struct drbd_conf *mdev, union drbd_state os,
 	if (os.disk < D_UP_TO_DATE && os.conn >= C_SYNC_SOURCE && ns.conn == C_CONNECTED)
 		drbd_send_state(mdev, ns);
 
+	/* Wake up role changes, that were delayed because of connection establishing */
+	if (os.conn == C_WF_REPORT_PARAMS && ns.conn != C_WF_REPORT_PARAMS) {
+		if (test_and_clear_bit(STATE_SENT, &mdev->tconn->flags))
+			wake_up(&mdev->state_wait);
+	}
+
 	/* This triggers bitmap writeout of potentially still unwritten pages
 	 * if the resync finished cleanly, or aborted because of peer disk
 	 * failure, or because of connection loss.
@@ -1565,9 +1578,9 @@ conn_is_valid_transition(struct drbd_tconn *tconn, union drbd_state mask, union
 			rv = is_valid_state(mdev, ns);
 			if (rv < SS_SUCCESS) {
 				if (is_valid_state(mdev, os) == rv)
-					rv = is_valid_soft_transition(os, ns);
+					rv = is_valid_soft_transition(os, ns, tconn);
 			} else
-				rv = is_valid_soft_transition(os, ns);
+				rv = is_valid_soft_transition(os, ns, tconn);
 		}
 		if (rv < SS_SUCCESS)
 			break;