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>

3 files changed, 41 insertions, 5 deletions

diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index 2bf3a6ef3684..1aae724e37fb 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 ab871e00ffc5..b2d347d18c7d 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 d065c646b35a..8bcde4a9632b 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;