[Linux-cachefs] Re: [PATCH 0/7] Permit filesystem local caching and NFS superblock sharing [try #13]

[Trond Myklebust]

On Wed, 2006-09-06 at 10:51 +0100, David Howells wrote:
> Ian Kent <raven at themaw.net> wrote:
> 
> > > Not if you've already caused the NFS filesystem to create a "dummy" dentry
> > > that's a directory because you couldn't see that what that name
> > > corresponds to on the server is actually a symlink.
> > 
> > Shouldn't stat tell me if this is a symlink?
> 
> You may not be able to find out from the server what it is you're trying to
> deal with because you may not have permission to do so, or because whatever it
> is may not be exported.  The first may be the trickiest to deal with because
> the MOUNT service for NFS2 and NFS3 can jump you over bits of the path you
> can't otherwise access.
> 
> The problem actually comes when the conditions on the server change; perhaps an
> intermediate directory is made accessible on the server and suddenly the client
> can see inside of it.  It may then find out that what it had assumed to be
> directories, and what it had set dummy directory dentries up for, aren't.

It really doesn't matter whether there is a symlink or not. automounters
should _not_ be trying to create directories on any filesystem other
than the autofs filesystem itself.