Re: [PATCH] fix posix lock on NFS

[Peter Staubach]

Trond Myklebust wrote:

> On Tue, 2006-01-03 at 15:09 -0500, Peter Staubach wrote:
>  
>
> > Matthew Wilcox wrote:
> >    
> >
> > > Mandatory locks aren't mandatory for other clients.
> > >
> > >
> > >      
> > So?
> >
> > I guess that I don't understand this response.
> >
> > The server is responsible for keeping itself from attempting to access
> > a mandatory lock file.  The client is not responsible for doing so and
> > trying to help the server is kind of a waste of time, mostly.
> >
> > The mandatory lock mode bits really only come into play when attempting
> > to read or write the file.  In this case, the system will automatically
> > try to take a lock for the process, if that process does not already
> > have a lock.  The server should prevent itself from trying to access
> > files like this in order to avoid DoS attacks.
> >
> > The NFS client does not support mandatory locking, mostly due to the
> > possibility of DoS attacks and also due to the locking and NFS protocols
> > not being sufficiently aware of each other.  NFSv4 can be used to address
> > this latter problem, but probably not the former.
> >
> > So, why deny lock requests for such files?  Especially on the client?
> >    
>
> I agree, however that would have been a change in behaviour that would
> have been hard to find time to test properly in an -rc6(?) release, so
> we went for the quick and dirty fix.

Okay.

Are we going to be able to fix this properly once things open up a bit then?

   Thanx...

      ps
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