Commit f2d3d75b authored by Lars Ellenberg's avatar Lars Ellenberg Committed by Jens Axboe

drbd: sync_handshake: handle identical uuids with current (frozen) Primary

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: default avatarPhilipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: default avatarLars Ellenberg <lars.ellenberg@linbit.com>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent 9104d31a
...@@ -3194,7 +3194,8 @@ static void drbd_uuid_dump(struct drbd_device *device, char *text, u64 *uuid, ...@@ -3194,7 +3194,8 @@ static void drbd_uuid_dump(struct drbd_device *device, char *text, u64 *uuid,
-1091 requires proto 91 -1091 requires proto 91
-1096 requires proto 96 -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_peer_device *const peer_device = first_peer_device(device);
struct drbd_connection *const connection = peer_device ? peer_device->connection : NULL; struct drbd_connection *const connection = peer_device ? peer_device->connection : NULL;
...@@ -3274,8 +3275,39 @@ static int drbd_uuid_compare(struct drbd_device *const device, int *rule_nr) __m ...@@ -3274,8 +3275,39 @@ static int drbd_uuid_compare(struct drbd_device *const device, int *rule_nr) __m
* next bit (weight 2) is set when peer was primary */ * next bit (weight 2) is set when peer was primary */
*rule_nr = 40; *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) { 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 1: /* self_pri && !peer_pri */ return 1;
case 2: /* !self_pri && peer_pri */ return -1; case 2: /* !self_pri && peer_pri */ return -1;
case 3: /* self_pri && peer_pri */ case 3: /* self_pri && peer_pri */
...@@ -3402,7 +3434,7 @@ static enum drbd_conns drbd_sync_handshake(struct drbd_peer_device *peer_device, ...@@ -3402,7 +3434,7 @@ static enum drbd_conns drbd_sync_handshake(struct drbd_peer_device *peer_device,
drbd_uuid_dump(device, "peer", device->p_uuid, drbd_uuid_dump(device, "peer", device->p_uuid,
device->p_uuid[UI_SIZE], device->p_uuid[UI_FLAGS]); 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); spin_unlock_irq(&device->ldev->md.uuid_lock);
drbd_info(device, "uuid_compare()=%d by rule %d\n", hg, rule_nr); drbd_info(device, "uuid_compare()=%d by rule %d\n", hg, rule_nr);
...@@ -3411,6 +3443,15 @@ static enum drbd_conns drbd_sync_handshake(struct drbd_peer_device *peer_device, ...@@ -3411,6 +3443,15 @@ static enum drbd_conns drbd_sync_handshake(struct drbd_peer_device *peer_device,
drbd_alert(device, "Unrelated data, aborting!\n"); drbd_alert(device, "Unrelated data, aborting!\n");
return C_MASK; 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) { if (hg < -1000) {
drbd_alert(device, "To resolve this both sides have to support at least protocol %d\n", -hg - 1000); drbd_alert(device, "To resolve this both sides have to support at least protocol %d\n", -hg - 1000);
return C_MASK; return C_MASK;
......
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