The work includes:

• using llapi_layout_* interfaces to get or set the composite layout parameters (stripe count, stripe size) correctly
• improving the following I/O redistribution algorithm with PFL feature:
  • Stripe-contiguous: use the LCM(lowest common multiple) of different component stripe count to calculate available cb nodes, and try to make sure each I/O write among MPI procs happens in the same component extent
  • File-contiguous: use the max. or LCM of component stripe size as the common stripe size to keep the stripe alignment in each write.

The patch will be submitted to MPICH finally.