From: Vladimír Čunát <vladimir.cunat@nic.cz>
Date: Mon, 4 Sep 2017 12:48:41 +0000 (+0200)
Subject: cache.clear() on LMDB: be more strict about transactions
X-Git-Tag: v1.4.0~9^2~2
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=10691bf05127b815ef832e5f8d8df682e7e4c618;p=thirdparty%2Fknot-resolver.git

cache.clear() on LMDB: be more strict about transactions

In particular, don't keep even a reset read-only transaction.
This doesn't help with that MDB_BAD_TXN, but still it seems better.
---

diff --git a/lib/cdb_lmdb.c b/lib/cdb_lmdb.c
index 23e2850ac..040ef44b1 100644
--- a/lib/cdb_lmdb.c
+++ b/lib/cdb_lmdb.c
@@ -326,9 +326,6 @@ static int cdb_count(knot_db_t *db)
 static int cdb_clear(knot_db_t *db)
 {
 	struct lmdb_env *env = db;
-	/* Always attempt to commit write transactions in-flight. */
-	(void) cdb_sync(db);
-
 	/* First try mdb_drop() to clear the DB; this may fail with ENOSPC. */
 	{
 		MDB_txn *txn = NULL;
@@ -345,6 +342,13 @@ static int cdb_clear(knot_db_t *db)
 		kr_log_info("[cache] clearing error, falling back\n");
 	}
 
+	/* We are about to switch to a different file, so end all txns, to be sure. */
+	(void) cdb_sync(db);
+	if (env->txn.ro) {
+		mdb_txn_abort(env->txn.ro);
+		env->txn.ro = NULL;
+	}
+
 	/* Since there is no guarantee that there will be free
 	 * pages to hold whole dirtied db for transaction-safe clear,
 	 * we simply remove the database files and reopen.