Revision 1:
  When setting the size of a Device-Mapper device in the gendisk entry,
  also try to set the size of the corresponding block_device entry's
  inode. This is necessary to allow online device/filesystem resizing to
  work correctly.  [Kevin Corry]

Revision 2:
  The dm table size is always known in advance, so we can specify it in
  dm_table_create(), rather than relying on dynamic resizing.

Revision 3:
  Make the version-4 ioctl interface the default kernel configuration option.

Revision 4:
  Make sure that a target has a sensible set of default io restrictions.

Revision 5:
  You can no longer call dm_table_event() from interrupt context.