drbd: Do not full sync if a P_SYNC_UUID packet gets lost

See also commit from 2009-08-15
"drbd_uuid_compare(): Do not full sync in case a P_SYNC_UUID packet gets lost."

We saw cases where the History UUIDs where not as expected. So the
detection of the special case did not trigger. With the sync UUID
no longer being a random number, but deducible from the previous
bitmap UUID, the detection of this special case becomes more
reliable.

The SyncUUID now is the previous bitmap UUID + 0x1000000000000.

Rule 5a:
Cs = H1p & H1p + Offset = Bp
  Connection was lost before SyncUUID Packet came through.
  Corrent (peer) UUIDs:
   Bp = H1p
   H1p = H2p
   H2p = 0
  Become Sync target.

Rule 7a:
Cp = H1s & H1s + Offset = Bs
  Connection was lost before SyncUUID Packet came through.
  Correct (own) UUIDs:
   Bs = H1s
   H1s = H2s
   H2s = 0
  Become Sync source.

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

diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index 84b4575fdf432eea9b7f89325f5dc568880c5539..3c8eecd9666d86dc43e8ec3ea41286299d817bd3 100644 (file)
--- a/drivers/block/drbd/drbd_int.h
+++ b/drivers/block/drbd/drbd_int.h
@@ -97,6 +97,7 @@ extern char usermode_helper[];
 #define ID_SYNCER (-1ULL)
 #define ID_VACANT 0
 #define is_syncer_block_id(id) ((id) == ID_SYNCER)
+#define UUID_NEW_BM_OFFSET ((u64)0x0001000000000000ULL)
 
 struct drbd_conf;
 

diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index da98bff7c33359592708e8e40d1f3db29c15009d..b3b6d3190f652f15b439ba7cda0551d8f1597192 100644 (file)
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -2022,7 +2022,7 @@ int drbd_gen_and_send_sync_uuid(struct drbd_conf *mdev)
 
        D_ASSERT(mdev->state.disk == D_UP_TO_DATE);
 
-       get_random_bytes(&uuid, sizeof(u64));
+       uuid = mdev->ldev->md.uuid[UI_BITMAP] + UUID_NEW_BM_OFFSET;
        drbd_uuid_set(mdev, UI_BITMAP, uuid);
        drbd_md_sync(mdev);
        p.uuid = cpu_to_be64(uuid);

diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
index fd0957f9c230546b3ab8349d1e796a1ea72d399d..7991183749e382f8cafc4e8dcaa98d190b6359a2 100644 (file)
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -2293,6 +2293,8 @@ static void drbd_uuid_dump(struct drbd_conf *mdev, char *text, u64 *uuid,
    -2  C_SYNC_TARGET set BitMap
  -100  after split brain, disconnect
 -1000  unrelated data
+-1091   requires proto 91
+-1096   requires proto 96
  */
 static int drbd_uuid_compare(struct drbd_conf *mdev, int *rule_nr) __must_hold(local)
 {
@@ -2322,7 +2324,7 @@ static int drbd_uuid_compare(struct drbd_conf *mdev, int *rule_nr) __must_hold(l
                if (mdev->p_uuid[UI_BITMAP] == (u64)0 && mdev->ldev->md.uuid[UI_BITMAP] != (u64)0) {
 
                        if (mdev->agreed_pro_version < 91)
-                               return -1001;
+                               return -1091;
 
                        if ((mdev->ldev->md.uuid[UI_BITMAP] & ~((u64)1)) == (mdev->p_uuid[UI_HISTORY_START] & ~((u64)1)) &&
                            (mdev->ldev->md.uuid[UI_HISTORY_START] & ~((u64)1)) == (mdev->p_uuid[UI_HISTORY_START + 1] & ~((u64)1))) {
@@ -2343,7 +2345,7 @@ static int drbd_uuid_compare(struct drbd_conf *mdev, int *rule_nr) __must_hold(l
                if (mdev->ldev->md.uuid[UI_BITMAP] == (u64)0 && mdev->p_uuid[UI_BITMAP] != (u64)0) {
 
                        if (mdev->agreed_pro_version < 91)
-                               return -1001;
+                               return -1091;
 
                        if ((mdev->ldev->md.uuid[UI_HISTORY_START] & ~((u64)1)) == (mdev->p_uuid[UI_BITMAP] & ~((u64)1)) &&
                            (mdev->ldev->md.uuid[UI_HISTORY_START + 1] & ~((u64)1)) == (mdev->p_uuid[UI_HISTORY_START] & ~((u64)1))) {
@@ -2388,17 +2390,22 @@ static int drbd_uuid_compare(struct drbd_conf *mdev, int *rule_nr) __must_hold(l
        *rule_nr = 51;
        peer = mdev->p_uuid[UI_HISTORY_START] & ~((u64)1);
        if (self == peer) {
-               self = mdev->ldev->md.uuid[UI_HISTORY_START] & ~((u64)1);
-               peer = mdev->p_uuid[UI_HISTORY_START + 1] & ~((u64)1);
-               if (self == peer) {
+               if (mdev->agreed_pro_version < 96 ?
+                   (mdev->ldev->md.uuid[UI_HISTORY_START] & ~((u64)1)) ==
+                   (mdev->p_uuid[UI_HISTORY_START + 1] & ~((u64)1)) :
+                   peer + UUID_NEW_BM_OFFSET == (mdev->p_uuid[UI_BITMAP] & ~((u64)1))) {
                        /* The last P_SYNC_UUID did not get though. Undo the last start of
                           resync as sync source modifications of the peer's UUIDs. */
 
                        if (mdev->agreed_pro_version < 91)
-                               return -1001;
+                               return -1091;
 
                        mdev->p_uuid[UI_BITMAP] = mdev->p_uuid[UI_HISTORY_START];
                        mdev->p_uuid[UI_HISTORY_START] = mdev->p_uuid[UI_HISTORY_START + 1];
+
+                       dev_info(DEV, "Did not got last syncUUID packet, corrected:\n");
+                       drbd_uuid_dump(mdev, "peer", mdev->p_uuid, mdev->p_uuid[UI_SIZE], mdev->p_uuid[UI_FLAGS]);
+
                        return -1;
                }
        }
@@ -2420,20 +2427,20 @@ static int drbd_uuid_compare(struct drbd_conf *mdev, int *rule_nr) __must_hold(l
        *rule_nr = 71;
        self = mdev->ldev->md.uuid[UI_HISTORY_START] & ~((u64)1);
        if (self == peer) {
-               self = mdev->ldev->md.uuid[UI_HISTORY_START + 1] & ~((u64)1);
-               peer = mdev->p_uuid[UI_HISTORY_START] & ~((u64)1);
-               if (self == peer) {
+               if (mdev->agreed_pro_version < 96 ?
+                   (mdev->ldev->md.uuid[UI_HISTORY_START + 1] & ~((u64)1)) ==
+                   (mdev->p_uuid[UI_HISTORY_START] & ~((u64)1)) :
+                   self + UUID_NEW_BM_OFFSET == (mdev->ldev->md.uuid[UI_BITMAP] & ~((u64)1))) {
                        /* The last P_SYNC_UUID did not get though. Undo the last start of
                           resync as sync source modifications of our UUIDs. */
 
                        if (mdev->agreed_pro_version < 91)
-                               return -1001;
+                               return -1091;
 
                        _drbd_uuid_set(mdev, UI_BITMAP, mdev->ldev->md.uuid[UI_HISTORY_START]);
                        _drbd_uuid_set(mdev, UI_HISTORY_START, mdev->ldev->md.uuid[UI_HISTORY_START + 1]);
 
-                       dev_info(DEV, "Undid last start of resync:\n");
-
+                       dev_info(DEV, "Last syncUUID did not get through, corrected:\n");
                        drbd_uuid_dump(mdev, "self", mdev->ldev->md.uuid,
                                       mdev->state.disk >= D_NEGOTIATING ? drbd_bm_total_weight(mdev) : 0, 0);
 
@@ -2496,8 +2503,8 @@ static enum drbd_conns drbd_sync_handshake(struct drbd_conf *mdev, enum drbd_rol
                dev_alert(DEV, "Unrelated data, aborting!\n");
                return C_MASK;
        }
-       if (hg == -1001) {
-               dev_alert(DEV, "To resolve this both sides have to support at least protocol 91\n");
+       if (hg < -1000) {
+               dev_alert(DEV, "To resolve this both sides have to support at least protocol %d\n", -hg - 1000);
                return C_MASK;
        }