bugfix. add WQ_UNBOUND to alloc_workqueue(). WQ_UNBOUND flag is needed to create singlethreaded workqueue.
add dm_sync_io_retry. dm_sync_io has argument thread :: bool now.
flourish dm_safe_io_retry. complex fio passed. once fail but ok afterall confirmed.
change to INIT_WORK_ONSTACK
add status(id=0). add packed to metablock