The Virtual Filesystem Interface in 4.4BSD.
Marshall Kirk McKusick · Computing systems · 1995
This paper describes the virtual filesys- tem interface found in 4.4BSD. This interface is de- signed around an object oriented virtual file node or data structure. The vnode structure is de- scribed along with its method for dynamically expand- ing its set of operations. These operations have been divided into two groups: those to manage the hierarchi- cal filesystem name space and those to manage the flat filestore. The translation of pathnames is described, as it requires a tight coupling between the virtual filesys- tem layer and the underþing filesystems through which the path traverses. This paper describes the filesystem services that are exported from the vnode interface to its clients, both local and remote. It also describes the set of services provided by the vnode layer to its client filesystems. The vnode interface has been generalized to allow multiple filesystems to be stacked together. After describing the stacking functionality, several examples of stacking filesystems are shown.