Stackably extensible template layer for file system development under Windows NT (Family)

This paper describes an architecture for stackably extending file functionality under Windows NT (Family) with minimal performance overhead and development cost. File systems often need to evolve and require many changes to support new features. Traditional file system development is difficult because most of the work is done in the kernel - a hostile development environment where progress is slow, debugging is difficult, and simple mistakes can crash systems. Kernel work also requires deep understanding of system internals, resulting in developers spending a lot of time becoming familiar with the system's details. Stackably extensible file systems promise to ease the development of file systems by offering a mechanism for incremental development. The Stackably Extensible Template Layer environment is an NT service-based COM (A. Rofail and Y. Shohoud, Mastering COM and COM+, SYBEX, San Francisco, USA, 2002) (component object model) server that seamlessly integrates with file system filter drivers (stacked modules that can be inserted anywhere in the drivers' calling hierarchy for intercepting file system operations) via the inverted call model supported in the Windows OS architecture and by sharing events between kernel and user mode. Stackably extensible template layer promises to speed file system development by providing an extensible file system interface. This extensibility allows new features to be added incrementally from the user mode.