peter's code works for me, and the 40-odd people who download
the -mm patches.  Anton has tested it on ppc64 and I presume that
Peter has tested it on ia64.  I use gcc-2.91.66 and others use
later compilers.  I expect that any remaining problems will
mainly be caught by the compiler.  And compiler bugs can be
detected by turning off the option in config and seeing if things
get better.

From Peter Chubb

 - do_request() function takes sector_t not unsigned long as the
   block number to operate on.
 - Various casts to long where the underlying device can never get
   big enough to warrant a 64-bit sector offset.
 - Cast sector_t to unsigned long long when printing.