From: Lars Ellenberg <lars.ellenb...@linbit.com>
If in a two-primary scenario, we lost our peer, freeze IO,
and are still frozen (no UUID rotation) when the peer comes back
as Secondary after a hard crash, we will see identical UUIDs.
The "rule_nr = 40" chose to use the "CRASHED_PRIMARY" bit as
arbitration, but that would cause the still running (but frozen) Primary
to become SyncTarget (which it typically refuses), and the handshake is
declined.
Fix: check current roles.
If we have *one* current primary, the Primary wins.
(rule_nr = 41)
Since that is a protocol change, use the newly introduced DRBD_FF_WSAME
to determine if rule_nr = 41 can be applied.
Signed-off-by: Philipp Reisner <philipp.reis...@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenb...@linbit.com>
---
drivers/block/drbd/drbd_receiver.c | 47 +++++++++++++++++++++++++++++++++++---
1 file changed, 44 insertions(+), 3 deletions(-)
diff --git a/drivers/block/drbd/drbd_receiver.c
b/drivers/block/drbd/drbd_receiver.c
index 1320bb8..8e7afa3 100644
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -3181,7 +3181,8 @@ static void drbd_uuid_dump(struct drbd_device *device,
char *text, u64 *uuid,
-1091 requires proto 91
-1096 requires proto 96
*/
-static int drbd_uuid_compare(struct drbd_device *const device, int *rule_nr)
__must_hold(local)
+
+static int drbd_uuid_compare(struct drbd_device *const device, enum drbd_role
const peer_role, int *rule_nr) __must_hold(local)
{
struct drbd_peer_device *const peer_device = first_peer_device(device);
struct drbd_connection *const connection = peer_device ?
peer_device->connection : NULL;
@@ -3261,8 +3262,39 @@ static int drbd_uuid_compare(struct drbd_device *const
device, int *rule_nr) __m
* next bit (weight 2) is set when peer was primary */
*rule_nr = 40;
+ /* Neither has the "crashed primary" flag set,
+ * only a replication link hickup. */
+ if (rct == 0)
+ return 0;
+
+ /* Current UUID equal and no bitmap uuid; does not necessarily
+ * mean this was a "simultaneous hard crash", maybe IO was
+ * frozen, so no UUID-bump happened.
+ * This is a protocol change, overload DRBD_FF_WSAME as flag
+ * for "new-enough" peer DRBD version. */
+ if (device->state.role == R_PRIMARY || peer_role == R_PRIMARY) {
+ *rule_nr = 41;
+ if (!(connection->agreed_features & DRBD_FF_WSAME)) {
+ drbd_warn(peer_device, "Equivalent unrotated
UUIDs, but current primary present.\n");
+ return -(0x10000 | PRO_VERSION_MAX |
(DRBD_FF_WSAME << 8));
+ }
+ if (device->state.role == R_PRIMARY && peer_role ==
R_PRIMARY) {
+ /* At least one has the "crashed primary" bit
set,
+ * both are primary now, but neither has
rotated its UUIDs?
+ * "Can not happen." */
+ drbd_err(peer_device, "Equivalent unrotated
UUIDs, but both are primary. Can not resolve this.\n");
+ return -100;
+ }
+ if (device->state.role == R_PRIMARY)
+ return 1;
+ return -1;
+ }
+
+ /* Both are secondary.
+ * Really looks like recovery from simultaneous hard crash.
+ * Check which had been primary before, and arbitrate. */
switch (rct) {
- case 0: /* !self_pri && !peer_pri */ return 0;
+ case 0: /* !self_pri && !peer_pri */ return 0; /* already
handled */
case 1: /* self_pri && !peer_pri */ return 1;
case 2: /* !self_pri && peer_pri */ return -1;
case 3: /* self_pri && peer_pri */
@@ -3389,7 +3421,7 @@ static enum drbd_conns drbd_sync_handshake(struct
drbd_peer_device *peer_device,
drbd_uuid_dump(device, "peer", device->p_uuid,
device->p_uuid[UI_SIZE], device->p_uuid[UI_FLAGS]);
- hg = drbd_uuid_compare(device, &rule_nr);
+ hg = drbd_uuid_compare(device, peer_role, &rule_nr);
spin_unlock_irq(&device->ldev->md.uuid_lock);
drbd_info(device, "uuid_compare()=%d by rule %d\n", hg, rule_nr);
@@ -3398,6 +3430,15 @@ static enum drbd_conns drbd_sync_handshake(struct
drbd_peer_device *peer_device,
drbd_alert(device, "Unrelated data, aborting!\n");
return C_MASK;
}
+ if (hg < -0x10000) {
+ int proto, fflags;
+ hg = -hg;
+ proto = hg & 0xff;
+ fflags = (hg >> 8) & 0xff;
+ drbd_alert(device, "To resolve this both sides have to support
at least protocol %d and feature flags 0x%x\n",
+ proto, fflags);
+ return C_MASK;
+ }
if (hg < -1000) {
drbd_alert(device, "To resolve this both sides have to support
at least protocol %d\n", -hg - 1000);
return C_MASK;
--
1.9.1
