The remote procedure call (a.k.a. RPC) latency becomes increasingly significant in a distributed file system. We propose BuffetFS, a user-level file system that optimizes I/O performance by eliminating the RPCs caused by \texttt{open()} operation. By leveraging \texttt{open()} from file servers to clients, BuffetFS can restrain the procedure calls for permission checks locally, hence avoid RPCs during the initial stage to access a file. BuffetFS can further reduce response time when users are accessing a large number of small files. We implement a BuffetFS prototype and integrate it into a storage cluster. Our preliminary evaluation results show that BuffetFS can offer up to 70\% performance gain compared to the Lustre file system.