[linux-cifs-client] Add support infrastructure for Named Pipe

[Christoph Hellwig]

On Fri, Oct 16, 2009 at 09:05:18AM -0400, Jeff Layton wrote:
> Well...all of this code seems to presuppose that there will be actual
> filesystem objects on which to operate. IOW, you can't call an ioctl on
> a non-existent filehandle.
> 
> Again, it's not at all clear from this patchset how userspace will
> actually use this code. How do you envision userspace programs actually
> making use of this?

Yeah.  I have no problem adding kernel support for the named pipes to
the kernel if we really need to, but:

 - please odn't shove it into a filesystem as that's a totally unrelated
   abstraction
 - write some proper code for it, not the thing that was submitted
   adding random ioctls dereferecing user pointers and similar.
   Incidentally moving it out of cifs will make that a lot easier as
   bad code doesn't really stick out in cifs.