Re: VFS mediator?

Pavel Machek (pavel@suse.cz)
Mon, 18 Mar 2002 23:38:27 +0100


Hi!

> >> * NFS (v2,v3): Portable. And that's the only good thing to say
> >> about it - it's stateless, it has messy semantics all over the
> >> place and implementing userland server requires a lot of glue.
>
> > Does not work... If you mount nfs server on localhost, you can
> > deadlock.
>
> Huh? Examples please? A hell of a lot of work has gone into ensuring
> that this cannot happen. I do most of my NFS client work on this sort
> of setup, so it had bloody well better work...

Okay, take userland nfs-server. (This thread was about userland
filesystems).

Then, make memory full of dirty pages. Imagine that nfs-server is
swapped-out by some bad luck. What you have is extremely nasty
deadlock, AFAICS. [To free memory you have to write out dirty data,
but you can't do that because you don't have enough memory for
nfs-server].
Pavel

-- 
Casualities in World Trade Center: ~3k dead inside the building,
cryptography in U.S.A. and free speech in Czech Republic.
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