[RFC] Non-repeating file_service_type: roundrobin1 and random1

[koct9i]

These servicing modes does not repeat file until completion previous operation.

( i.e. when nrfiles > iodepth fio should chose files which has no in-flight I/O )

Streaming IO-engines might not handle several requests to one "file" at once.
Or such workload might not match any real scenarios.

Signed-off-by: Konstantin Khlebnikov koct9i@gmail.com

Reminders:

1. If you modify struct thread_options, also make corresponding changes in
   cconv.c and bump FIO_SERVER_VER in server.h
2. If you change the ioengine interface (hooks, flags, etc), remember to bump
   FIO_IOOPS_VERSION in ioengines.h.

// Ok, will do later if this change is ok

[vincentkfu]

I think the general idea is fine. I will take a closer look later but here are some general comments:

• Documentation needs to be updated
• Please choose better names than random1 and roundrobin1
• With these options it does not make sense to have iodepth > nrfiles. Perhaps fio should emit an error message in this situation. This could be added in fixup_options().
• The code would be more readable to have a helper to check service_type == RANDOM || service_type == RANDOM1