ND_REGION_ASYNC
set_bit(ND_REGION_ASYNC, &ndr_desc.flags);
if (test_bit(ND_REGION_ASYNC, &nd_region->flags) && nd_region->flush)
!test_bit(ND_REGION_ASYNC, &nd_region->flags);
set_bit(ND_REGION_ASYNC, &ndr_desc.flags);