mark_region
.mark_region = userspace_mark_region,
.mark_region = core_mark_region,
.mark_region = core_mark_region,
rh->log->type->mark_region(rh->log, reg->key);
mark_region(zorro_resource_start(z),
mark_region(m68k_memory[i].addr,
void (*mark_region)(struct dm_dirty_log *log, region_t region);