[Gnu-arch-users] [OT] GNU Hurd

[Ludovic Courtès]

Hi,

Haakon Riiser <address@hidden> writes:

> Could you please explain how FUSE is broken?  (I have no experience
> with it yet, I've only skimmed through the implementation notes.)

The Hurd is designed from the ground up to have filesystems implemented
in user-space.  In fact, it considers filesystems as "normal
applications", which they are, indeed.  The number of libraries/programs
that implement their own VFS actually proves that filesystems ought to
be treated as applications.

OTOH, Linux considers file systems as integral parts of the kernel, part
of the trusted computing base (TCB).  This typically precludes the
implementation of filesystems such as tar+gz, or other complex file
systems that need a lot of code and may not reasonably be audited the
way regular kernel code is.

Therefore, FUSE had to work around this assumption (filesystems being
in-kernel) by implementing in-kernel glue code that would just forward
I/O syscalls to some user-level application.  Compared to the Hurd's
design, it looks quite hackish.

You might want to look at:
http://www.gnu.org/software/hurd/hurd-paper.html .

Note that Plan 9 has a similar approach to file systems.

Thanks,
Ludovic.