``Stacking'' Vnodes: A Progress Report
Glenn C. Skinner and Thomas K. Wong
SunSoft Inc.
2550 Garcia Avenue
Mountain View, Ca 94043
Abstract
People are dissatisfied with the file system services that come with
their UNIX systems. They want to add new and better features. At
present they have two choices: express their service as a user-level
NFS server, or use the vnode/VFS interface to build at least part of
it into the kernel. Although the vnode/VFS interface has been
remarkably successful as a kernel structuring concept, it has failed
to provide source portability between UNIX versions or even binary
compatibility between releases of the same UNIX version. It has been
obvious for some time that a redesign of the vnode/VFS interface that
allowed file systems to be shipped as binary kernel modules that
survive from release to release is needed. We describe a prototype
kernel with a vnode/VFS interface that would allow this. It is based
on earlier work on ``stacking'' vnodes at Sun and at UCLA, but it
replaces the stacking concept by a more strictly object-oriented
concept of interposition.
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