Re: Union mounts, NFS, and locking

[Valerie Aurora <vaurora@redhat.com>]

On Wed, Jul 15, 2009 at 01:27:59PM -0400, J. Bruce Fields wrote:
> On Tue, Jul 14, 2009 at 06:05:16PM -0400, Valerie Aurora wrote:
> > On Tue, Jul 14, 2009 at 04:36:40PM -0400, Erez Zadok wrote:
> > > In message <20090714201940.GF27582@shell>, Valerie Aurora writes:
> > >
> > > > Okay, so my best idea for a solution is to introduce a new NFS mount
> > > > option that means the server promises that the exported file system is
> > > > read-only (using superblock read-only count scheme locally).  E.g.:
> 
> Language nitpick: the term "read-only" is confusing.  Files
> (/proc/mounts) and filesystems (nfs) that are "read-only" can still
> change.
> 
> I'd be happier with "unchanging" or "constant" or "static".

What about "immutable"?  It should be familiar from inode attributes.

> The mount options aren't really in the protocol--so it'd probably take
> the form of a filesystem-granularity attribute that the client could
> query (and then fail the mount if the client didn't like the answer).
> 
> But even then: the fact is that someone will want to update the
> filesystem some day.  And there's no way to force every client
> administrator to remount.  So we'd have to decide how to handle that
> case.

Agreed.  I'm no NFS expert, but I think that treating it as if the NFS
server had stopped responding might be a start?

-VAL