From f2d3d75b66fc80c69ae2813cba72c2b5ad755f3e Mon Sep 17 00:00:00 2001 From: Lars Ellenberg Date: Tue, 14 Jun 2016 00:26:32 +0200 Subject: [PATCH] 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: Philipp Reisner Signed-off-by: Lars Ellenberg Signed-off-by: Jens Axboe --- 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 b25600e23ec2..577a1872da48 100644 --- a/drivers/block/drbd/drbd_receiver.c +++ b/drivers/block/drbd/drbd_receiver.c @@ -3194,7 +3194,8 @@ 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; @@ -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 */ *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 */ @@ -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, 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); @@ -3411,6 +3443,15 @@ 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; -- 2.11.0