On Wed, Jul 04, 2007 at 03:37:01PM +1000, Timothy Shimmin wrote:

We use this capability in XFS at the moment.
I think this is mainly for DMF (HSM) but is done via the xfs handle 
interface
(xfs_open_by_handle) AFAICT.

You're not :)  You're using an O_INVIBLE equivalent (as described below),
which would be a useful thing to have at the VFS level, but adding hacks
to some system calls only wouldn't help any HSM system.  It's just useless
API clutter.