ITS#7789 Fix resize vs MDB_NOMETASYNC, and a comment.

libraries/liblmdb/lmdb.h

@@ -411,7 +411,7 @@ typedef enum MDB_cursor_op {
 #define MDB_CURSOR_FULL	(-30787)
 	/** Page has not enough space - internal error */
 #define MDB_PAGE_FULL	(-30786)
-	/** Database contents grew beyond environment mapsize */
+	/** Environment mapsize was changed by another process */
 #define MDB_MAP_RESIZED	(-30785)
 	/** MDB_INCOMPATIBLE: Operation and DB incompatible, or DB flags changed */
 #define MDB_INCOMPATIBLE	(-30784)

libraries/liblmdb/mdb.c

@@ -3323,7 +3323,6 @@ mdb_txn_commit(MDB_txn *txn)
 #endif
 
 	if ((rc = mdb_page_flush(txn, 0)) ||
-		(rc = mdb_env_sync(env, 0)) ||
 		(rc = mdb_env_write_meta(txn)))
 		goto fail;
 
@@ -3480,7 +3479,7 @@ mdb_env_init_meta(MDB_env *env, MDB_meta *meta)
 static int
 mdb_env_write_meta(MDB_txn *txn)
 {
-	MDB_env *env;
+	MDB_env *env = txn->mt_env;
 	MDB_meta	meta, metab, *mp;
 	off_t off;
 	int rc, len, toggle;
@@ -3492,11 +3491,14 @@ mdb_env_write_meta(MDB_txn *txn)
 	int r2;
 #endif
 
+	/* Sync data and previous metapage before writing a new metapage */
+	if ((rc = mdb_env_sync(env, 0)) != MDB_SUCCESS)
+		return rc;
+
 	toggle = txn->mt_txnid & 1;
 	DPRINTF(("writing meta page %d for root page %"Z"u",
 		toggle, txn->mt_dbs[MAIN_DBI].md_root));
 
-	env = txn->mt_env;
 	mp = env->me_metas[toggle];
 
 	if (env->me_flags & MDB_WRITEMAP) {