We can't use self.put here since we need to force the use of the old _fhandle and _cachefile; update the db directly.
function update_db(p, stats, _cb) {
        var key = sprintf(FILES_KEY_FMT, p);
        var k1 = sprintf(FHANDLE_KEY_FMT, p);
        var k2 = sprintf(FNAME_KEY_FMT, stats._fhandle);

        self.db.batch()
            .put(key, stats)
            .put(k1, stats._fhandle)
            .put(k2, p)
            .write(function onBatchWrite(err2) {
                if (err2) {
                    log.error(err2, 'update_db(%s): failed', p);
                    _cb(errno(err2));
                } else {
                    log.trace('update_db(%s): done', p);
                    self.cache.set(key, stats);
                    _cb(null);
                }
            });
    }