[Tarantool-patches] [PATCH v14 2/6] qsync: update confirmed lsn on initial promote request

[Cyrill Gorcunov via Tarantool-patches <tarantool-patches@dev.tarantool.org>]

When promote request is handled we drop last confirmed
lsn to zero because its value make sense for sync queue
owner only. Still the case where we become queue owner
for the first time is special - we need to fetch the
obtained lsn from the request and remember it so we
will be able to filter any next malformed requests
with wrong lsn numbers (see queue filtering procedure
in next patch).

Part-of #6036

Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
---
 src/box/txn_limbo.c | 8 +++++++-
 src/box/txn_limbo.h | 6 ++++++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/src/box/txn_limbo.c b/src/box/txn_limbo.c
index cca2ce493..08463219d 100644
--- a/src/box/txn_limbo.c
+++ b/src/box/txn_limbo.c
@@ -50,6 +50,7 @@ txn_limbo_create(struct txn_limbo *limbo)
 	limbo->confirmed_lsn = 0;
 	limbo->rollback_count = 0;
 	limbo->is_in_rollback = false;
+	limbo->has_initial_promote = false;
 }
 
 bool
@@ -521,8 +522,13 @@ txn_limbo_read_promote(struct txn_limbo *limbo, uint32_t replica_id,
 	txn_limbo_read_rollback(limbo, lsn + 1);
 	assert(txn_limbo_is_empty(&txn_limbo));
 	limbo->owner_id = replica_id;
+	if (likely(limbo->has_initial_promote)) {
+		limbo->confirmed_lsn = 0;
+	} else {
+		limbo->confirmed_lsn = lsn;
+		limbo->has_initial_promote = true;
+	}
 	box_update_ro_summary();
-	limbo->confirmed_lsn = 0;
 }
 
 void
diff --git a/src/box/txn_limbo.h b/src/box/txn_limbo.h
index 53e52f676..e0d17de4b 100644
--- a/src/box/txn_limbo.h
+++ b/src/box/txn_limbo.h
@@ -179,6 +179,12 @@ struct txn_limbo {
 	 * by the 'reversed rollback order' rule - contradiction.
 	 */
 	bool is_in_rollback;
+	/**
+	 * Whether the limbo received initial PROMOTE request. It is needed to
+	 * update confirmed_lsn appropriately and pass packet validation/filtering
+	 * procedure.
+	 */
+	bool has_initial_promote;
 };
 
 /**
-- 
2.31.1