This is the seventh patch to the NBD driver and it's meant to add 
backward compatibility with the previous ioctl user interface while 
maintaining the better resource locking (ie. make NBD_SET_SOCK, 
NBD_DO_IT, NBD_CLEAR_SOCK all functional again as they were before patch 
6). It also re-orders code more, adds a new ioctl called NBD_RUN_SOCK 
(to be used like NBD_DO_IT in and only in patch 6), and a few other 
things. This patch can be applied sequentially with my other patches 
against 2.5.73 or this patch can alternatively just solely be applied 
against Andrew's 2.5.73-mm2 sources.

Unfortunately, with this patch I've also realized some things that I'm 
not pleased about:

   1. I don't like compatibility enough in this case to justify it (even
      though I've implemented it).
   2. This patch adds some new uglies (albiet not so bad as without the
      resource locking fixes of patch 6).
   3. The previous nbd resource locking problems are too time consuming
      for me to properly explain.
   4. It's best going forward for me to entirely fork my work on the nbd
      driver rather than to try making so many little changes to the
      mainstream this quickly. This will allow tighter integration with
      any required user space tools and also facilitate concentrating on
      the changes I'm most interested in. If you'd like to follow my
      future forked work, please do so at
      <http://freshmeat.net/projects/anbd/>.