FiST: A Language for Stackable File Systems

Erez Zadok, Jason Nieh

Department of Computer Science, Columbia University Technical Report , CUCS-034-99, December 1999

Abstract

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 sys- tem interfaces differ from system to system and they sup- port extensibility poorly. Consequently, extending file sys- tem 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 pro- duces file system modules for multiple platforms. The gen- erated code handles many kernel details, freeing developers to concentrate on the main issues of their file systems. This paper describes the design, implementation, and eval- uation 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 fol- lowing benefits of FiST: average code size over other stack- able file systems is reduced ten times; average development time is reduced seven times; performance overhead of stack- ing is 1–2%.

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cucs:034:99

Columbia University Department of Computer Science