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>

4 files changed, 24 insertions, 2 deletions

diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index 746f7933bf86..f215ad430bb8 100644
--- a/drivers/block/drbd/drbd_int.h
+++ b/drivers/block/drbd/drbd_int.h
@@ -850,6 +850,7 @@ enum {
         NEW_CUR_UUID,           /* Create new current UUID when thawing IO */
         AL_SUSPENDED,           /* Activity logging is currently suspended. */
         AHEAD_TO_SYNC_SOURCE,   /* Ahead -> SyncSource queued */
+        STATE_SENT,             /* Do not change state/UUIDs while this is set */
 };
 
 struct drbd_bitmap; /* opaque for drbd_conf */
diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index 519f286a4299..deccff3af774 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -841,6 +841,13 @@ is_valid_state_transition(struct drbd_conf *mdev, 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, &mdev->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;
 
@@ -1668,6 +1675,12 @@ 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) {
+                clear_bit(STATE_SENT, &mdev->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.
diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index 1bbbad302ae7..308beb8c0c1e 100644
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -289,7 +289,7 @@ static int _try_outdate_peer_async(void *data)
         */
         spin_lock_irq(&mdev->req_lock);
         ns = mdev->state;
-        if (ns.conn < C_WF_REPORT_PARAMS) {
+        if (ns.conn < C_WF_REPORT_PARAMS && !test_bit(STATE_SENT, &mdev->flags)) {
                 ns.pdsk = nps;
                 _drbd_set_state(mdev, ns, CS_VERBOSE, NULL);
         }
diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
index d601501c336a..9db93ff11c02 100644
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -751,6 +751,7 @@ static int drbd_connect(struct drbd_conf *mdev)
 {
         struct socket *s, *sock, *msock;
         int try, h, ok;
+        enum drbd_state_rv rv;
 
         D_ASSERT(!mdev->data.socket);
 
@@ -897,6 +898,7 @@ retry:
 
         if (drbd_send_protocol(mdev) == -1)
                 return -1;
+        set_bit(STATE_SENT, &mdev->flags);
         drbd_send_sync_param(mdev, &mdev->sync_conf);
         drbd_send_sizes(mdev, 0, 0);
         drbd_send_uuids(mdev);
@@ -904,7 +906,13 @@ retry:
         clear_bit(USE_DEGR_WFC_T, &mdev->flags);
         clear_bit(RESIZE_PENDING, &mdev->flags);
 
-        if (drbd_request_state(mdev, NS(conn, C_WF_REPORT_PARAMS)) < SS_SUCCESS)
+        spin_lock_irq(&mdev->req_lock);
+        rv = _drbd_set_state(_NS(mdev, conn, C_WF_REPORT_PARAMS), CS_VERBOSE, NULL);
+        if (mdev->state.conn != C_WF_REPORT_PARAMS)
+                clear_bit(STATE_SENT, &mdev->flags);
+        spin_unlock_irq(&mdev->req_lock);
+
+        if (rv < SS_SUCCESS)
                 return 0;
 
         drbd_thread_start(&mdev->asender);