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Re: NFS -- Hurd

Allover Stripes <allover@hedgehog.dyn.ez-ip.net> writes:

> > If you look at the implementation of the NFS lookup call in the Hurd
> > nfsd (hurd/nfsd/ops.c:op_lookup) you will see that the server uses
> > O_NOTRANS to prevent such activation.

> Hmmm.  Is this really a good idea?  Won't this cause problems if, for
> example, there's a "mount point" in the filesystem being served?  What
> if the server really does want to run translators?  

Well, this is the current behavior of Sun NFS and most others; it
would have to be a configuration option for the server which way you
wanted it to run.

> Say, it wants to export via NFS its BSD filesystem; would it then
> send raw disk blocks across the network for the client to translate?

I can't understand at all what you mean.  Why does the fact that it's
a BSD filesystem have anything to do with it?  The point is that the
nfsd doesn't ever cross translator linkages (== mount points).

> That wasn't very clear.  Suppose I have the following: antelope is
> running an NFS server. It exports /visible and everything under it.
> caribou is running an NFS client, importing the tree as /nfs.  Now
> suppose the following occur: antelope:/visible/bsd has a translator
> set to "/bin/ufs /dev/hd0s3".  Then if caribou tries to read and write
> caribou:/nfs/bsd, it starts a translator trying to read and write
> caribou's /dev/hd0s3.  

Yes, that's right.  This is thus a little more live than the Sun NFS
(for which the client doesn't see a mount at all).  A server option
could usefully set whether the client ever sees a translator.

> At best it returns an error message; at worst severe lossage occurs.
> Alternatively, suppose antelope:/visible/foo has its translator set
> as /visible/bar. Then caribou:/nfs/foo apparently has its translator
> set to teh nonexistent /visible/bar.  If you then set
> caribou:/nfs/foo's translator to /nfs/bar, reading the file works on
> caribou but not on antelope.

Yep, that's right.

> Some nightmares are to be expected when using NFS; but is this really
> the Right Thing?

Possibly not.  NFS handles mount points poorly, and the flexibility of
translators makes it even harder to decide just what the Right Thing
is.  The best I can think of is a plethora of server options so users
can pick which form of confusion they prefer.


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