Re: [TUHS] VFS prior to 1984

[Norman Wilson <norman@oclsc.org>]

Rob Pike:

  For my taste, the various Unix file system switches that I've seen are too
  firmly tied to the idea of blocks and disks and all that, making them less
  flexible than they should have been. That's why the Plan 9 version is about
  names and byte streams, to make it as general as possible.

=====

The only file-system switch I know well is that in the later
Research systems.  It has nothing to do with disks or blocks.
It is about names and inodes: turn name to struct inode, read
arbitrary chunk of data, write arbitrary chunk of data, create
file, unlink file, abominable ill-defined system call that just
wouldn't die erm I mean ioctl, and so on.

It was certainly a cheap hack (as its author cheerfully admitted)
but it really was about I/O operations, not about simulating
disks.  That's why it so easily supported /proc (the one that
was just about processes, not the misnamed Linux one that
is really about all things in the kernel so you don't need
/dev/kmem).

I don't know a lot about later VFSes like those in SunOS or
Linux or the BSDs.  Blockiness might well have crept in in
support of memory-mapped I/O or in collaboration with the
buffer-cache implementation.  The Research version was never
used directly to support different on-disk file system formats
(we did a different pjw cheap hack for the one case that
mattered in the kernel, and used the idea later developed
more by FUSE for other cases because speed didn't matter).

Norman Wilson
Toronto ON