you may find an article about file systems. It is very light weight and,
most importantly, 9fs is not menitoned.
I am posting this if somebody with an account at Ars would like to use the
comments to correct this omission.

Those were the days...
EPO guidelines 1978: "If the contribution to the known art resides
solely in a computer program then the subject matter is not
patentable in whatever manner it may be presented in the claims."