Re: [9fans] Plan 9

[Alexander Viro <viro@math.psu.edu>]

On Mon, 5 Nov 2001, Wladimir Mutel wrote:

> 	VFS is a kernel module interface to support different filesystems. It
> 	describes protocol similar (to some degree) to 9P. Plan9 has some
> 	in-kernel modules (device drivers) working by 9P, but it supports FAT
> 	and EXT2 filesystems by fileservers that are processes. Similar

Not exactly.  You are confusing 9P with set of methods provided by
filesystems.  There is _one_ in-kernel fs that speaks 9P - mnt.
Nothing stops you from doing similar under Linux/*BSD/whatever,
but result will be VFS->9pfs->fileservers, same as with Plan 9.

IOW, it's not a replacement for VFS code - you still have a part
that translates system calls into sequence of method calls +
part that uses 9P to provide such set of methods.  Notice that there
is a _lot_ of filesystems that belong to kernel - see /sys/man/3 for
the list of Plan 9 ones.  So separating 9P-speaking layer from
the VFS logics is a Good Thing(tm).

BTW, a lot of Unices (Linux included) _do_ support userland fileservers.
And I'm not talking about "make it look like NFS" schemes.  CODA actually
allows to do userland filesystems, but its intended use is for heavy
caching stuff and that shows (you still can do more RPC-style fileservers,
but overhead won't be pretty).

As for the Hurd...  I'd rather avoid commenting on Hurd "architecture" -
I'm not interested in that flamewar and this is not the place for it
anyway.  I'm not saying that all GNU folks are tasteless wankers, but
the culture and design philosophy of GNU in general...  Sigh.