drbd: Implemented two new connection states Ahead/Behind

In this connection mode, the ahead node no longer replicates
application IO. The behind's disk becomes out dated.

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

6 files changed, 45 insertions, 3 deletions

diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index c804e44b9455..21b7439438cd 100644
--- a/drivers/block/drbd/drbd_int.h
+++ b/drivers/block/drbd/drbd_int.h
@@ -2217,6 +2217,8 @@ static inline int drbd_state_is_stable(union drbd_state s)
         case C_VERIFY_T:
         case C_PAUSED_SYNC_S:
         case C_PAUSED_SYNC_T:
+        case C_AHEAD:
+        case C_BEHIND:
                 /* maybe stable, look at the disk state */
                 break;
 
diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index e81d009dd061..46f27d6c0b21 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -871,16 +871,19 @@ static union drbd_state sanitize_state(struct drbd_conf *mdev, union drbd_state
 
         if (ns.conn >= C_CONNECTED &&
             ((ns.disk == D_CONSISTENT || ns.disk == D_OUTDATED) ||
-             (ns.disk == D_NEGOTIATING && ns.conn == C_WF_BITMAP_T))) {
+             (ns.disk == D_NEGOTIATING && ns.conn == C_WF_BITMAP_T) ||
+             ns.conn >= C_AHEAD)) {
                 switch (ns.conn) {
                 case C_WF_BITMAP_T:
                 case C_PAUSED_SYNC_T:
+                case C_BEHIND:
                         ns.disk = D_OUTDATED;
                         break;
                 case C_CONNECTED:
                 case C_WF_BITMAP_S:
                 case C_SYNC_SOURCE:
                 case C_PAUSED_SYNC_S:
+                case C_AHEAD:
                         ns.disk = D_UP_TO_DATE;
                         break;
                 case C_SYNC_TARGET:
@@ -893,16 +896,18 @@ static union drbd_state sanitize_state(struct drbd_conf *mdev, union drbd_state
         }
 
         if (ns.conn >= C_CONNECTED &&
-            (ns.pdsk == D_CONSISTENT || ns.pdsk == D_OUTDATED)) {
+            (ns.pdsk == D_CONSISTENT || ns.pdsk == D_OUTDATED || ns.conn >= C_AHEAD)) {
                 switch (ns.conn) {
                 case C_CONNECTED:
                 case C_WF_BITMAP_T:
                 case C_PAUSED_SYNC_T:
                 case C_SYNC_TARGET:
+                case C_BEHIND:
                         ns.pdsk = D_UP_TO_DATE;
                         break;
                 case C_WF_BITMAP_S:
                 case C_PAUSED_SYNC_S:
+                case C_AHEAD:
                         /* remap any consistent state to D_OUTDATED,
                          * but disallow "upgrade" of not even consistent states.
                          */
@@ -1374,6 +1379,9 @@ static void after_state_ch(struct drbd_conf *mdev, union drbd_state os,
         if (os.conn == C_WF_REPORT_PARAMS && ns.conn >= C_CONNECTED)
                 drbd_send_state(mdev);
 
+        if (os.conn != C_AHEAD && ns.conn == C_AHEAD)
+                drbd_send_state(mdev);
+
         /* We are in the progress to start a full sync... */
         if ((os.conn != C_STARTING_SYNC_T && ns.conn == C_STARTING_SYNC_T) ||
             (os.conn != C_STARTING_SYNC_S && ns.conn == C_STARTING_SYNC_S))
diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
index f3052d871d31..b19e8b2c4ce5 100644
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -3179,6 +3179,9 @@ static int receive_state(struct drbd_conf *mdev, enum drbd_packets cmd, unsigned
         if (ns.conn == C_WF_REPORT_PARAMS)
                 ns.conn = C_CONNECTED;
 
+        if (peer_state.conn == C_AHEAD)
+                ns.conn = C_BEHIND;
+
         if (mdev->p_uuid && peer_state.disk >= D_NEGOTIATING &&
             get_ldev_if_state(mdev, D_NEGOTIATING)) {
                 int cr; /* consider resync */
diff --git a/drivers/block/drbd/drbd_req.c b/drivers/block/drbd/drbd_req.c
index 5c60d77d447c..60288fb3c4d7 100644
--- a/drivers/block/drbd/drbd_req.c
+++ b/drivers/block/drbd/drbd_req.c
@@ -948,6 +948,29 @@ allocate_barrier:
                                 ? queue_for_net_write
                                 : queue_for_net_read);
         }
+
+        if (remote && mdev->net_conf->on_congestion != OC_BLOCK) {
+                int congested = 0;
+
+                if (mdev->net_conf->cong_fill &&
+                    atomic_read(&mdev->ap_in_flight) >= mdev->net_conf->cong_fill) {
+                        dev_info(DEV, "Congestion-fill threshold reached\n");
+                        congested = 1;
+                }
+
+                if (mdev->act_log->used >= mdev->net_conf->cong_extents) {
+                        dev_info(DEV, "Congestion-extents threshold reached\n");
+                        congested = 1;
+                }
+
+                if (congested) {
+                        if (mdev->net_conf->on_congestion == OC_PULL_AHEAD)
+                                _drbd_set_state(_NS(mdev, conn, C_AHEAD), 0, NULL);
+                        else  /*mdev->net_conf->on_congestion == OC_DISCONNECT */
+                                _drbd_set_state(_NS(mdev, conn, C_DISCONNECTING), 0, NULL);
+                }
+        }
+
         spin_unlock_irq(&mdev->req_lock);
         kfree(b); /* if someone else has beaten us to it... */
 
diff --git a/drivers/block/drbd/drbd_strings.c b/drivers/block/drbd/drbd_strings.c
index 85179e1fb50a..5b970adc3b6f 100644
--- a/drivers/block/drbd/drbd_strings.c
+++ b/drivers/block/drbd/drbd_strings.c
@@ -48,6 +48,8 @@ static const char *drbd_conn_s_names[] = {
         [C_PAUSED_SYNC_T]    = "PausedSyncT",
         [C_VERIFY_S]         = "VerifyS",
         [C_VERIFY_T]         = "VerifyT",
+        [C_AHEAD]            = "Ahead",
+        [C_BEHIND]           = "Behind",
 };
 
 static const char *drbd_role_s_names[] = {
@@ -92,7 +94,7 @@ static const char *drbd_state_sw_errors[] = {
 const char *drbd_conn_str(enum drbd_conns s)
 {
         /* enums are unsigned... */
-        return s > C_PAUSED_SYNC_T ? "TOO_LARGE" : drbd_conn_s_names[s];
+        return s > C_BEHIND ? "TOO_LARGE" : drbd_conn_s_names[s];
 }
 
 const char *drbd_role_str(enum drbd_role s)
diff --git a/include/linux/drbd.h b/include/linux/drbd.h
index 03a08baabf11..23f31be6f00d 100644
--- a/include/linux/drbd.h
+++ b/include/linux/drbd.h
@@ -206,6 +206,10 @@ enum drbd_conns {
         C_VERIFY_T,
         C_PAUSED_SYNC_S,
         C_PAUSED_SYNC_T,
+
+        C_AHEAD,
+        C_BEHIND,
+
         C_MASK = 31
 };