1999 Reports

FiST: A Language for Stackable File Systems

Zadok, Erez; Nieh, Jason

Stackable file systems promise to ease the development of file systems. Operating system vendors, however,resist making extensive changes to support stacking, because of the impact on performance and stability. Existing file system interfaces differ from system to system and they support extensibility poorly. Consequently, extending file system functionality across platforms is difficult. 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\%.