Revision 1:
  -mm1

Revision 2:
  Add an endio method to targets.  This method is allowed to request
  another shot at failed ios (think multipath).  Context can be passed
  between the map method and the endio method.

Revision 3:
  Remove the version-1 ioctl interface.

Revision 4:
  Audit for list_for_each_*entry*

Revision 5:
  Fill in missing queue limitations when table is complete instead of
  enforcing the "default" limits on every dm device.
  Problem noticed by Mike Christie.
  
  [Christophe Saout]

Revision 6:
  List targets ioctl.  [Patrick Caulfield]

Revision 7:
  Multipath target

Revision 8:
  dm-io

Revision 9:
  kcopyd

Revision 10:
  Snapshot target

Revision 11:
  Mirror target

Revision 12:
  Flakey target