Re: [PATCH] nfs_unlink() race (was: nfs_refresh_inode: inode number mismatch)

[viro@parcelfarce.linux.theplanet.co.uk]

On Tue, Jun 10, 2003 at 07:43:33PM -0700, Frank Cusack wrote:
> On Wed, Jun 11, 2003 at 03:27:54AM +0100, viro@parcelfarce.linux.theplanet.co.uk wrote:
> > On Wed, Jun 11, 2003 at 03:59:10AM +0200, Trond Myklebust wrote:
> > > IOW we just want to prevent VFS from unhashing the dentry in the first
> > > place: dentry aliasing cannot work together with sillyrename.
> > 
> > Aliasing could be dealt with.  They would have the same inode, so it's
> > easy to detect.
> 
> dentry only contains the inode, not the fh.  On the server, the inode
> can go away and come back as a new fh, but with the same inode.  Is
> that detectable (would comparison hooks have to be added?)?  Although,
> I guess the inode is enough; you can do an NFS_I(inode)->fh to get
> the fh, but I wouldn't guess you'd want that in the VFS.  Bah, here
> I go again ... forgive me if that's nonsense.

You wouldn't need to do that anywhere near VFS - all relevant code is
inside NFS and yes, there we _are_ allowed to look at ->fh ;-)

FWIW, we could probably simply do the following: have nfs_lookup()
return ERR_PTR(-EINVAL) if it notices that it's about to give us
such alias.  IOW, no access to such guys at all - if it's going
to die, we refuse to do anything with it.  I'll try to do that
variant when I get some sleep - I'd rather not mess with anything
in that area until I'm completely awake...