Linus Torvalds wrote:

On Fri, 23 May 2008, Jeremy Fitzhardinge wrote:
  

quoted

Well, you could use it to update the page and protection bits while preserving
the AD bits, but I don't think that's very useful.
    

It's not that it's not "very useful" - it's that it would be TOTALLY 
WRONG.
  

Sorry, I was using ironic understatement.  I meant "...while preserving 
the AD bits, but I think that would be totally fucking stupid".

    J