FiST: A language for stackable file systems

Traditional file system development is difficult. Stackable file systems promise to ease the development of file systems by offering a mechanism for incremental development. Unfortunately, existing methods often require writing complex low-level kernel code that is specific to a single operating system platform and also difficult to port. We propose a new language, FiST, to describe stackable file systems. FiST uses operations common to file system interfaces. From a single description, FiST’s compiler produces file system modules for multiple platforms. The generated code handles many kernel details, freeing developers to concentrate on the main issues of their file systems. This paper describes the design, implementation, and evaluation of FiST. We extended file system functionality in a portable way without changing existing kernels. We built several file systems using FiST on Solaris, FreeBSD, and Linux. Our experiences with these examples shows the following benefits of FiST: average code size over other stackable file systems is reduced ten times; average development time is reduced seven times; performance overhead of stacking is 1–2%.