Ceph

Hi all,
recently i read the source code and paper, and i have some questions about the data movement:
1. when OSD's add or removal, how Ceph do this data migration and rebalance the crush map? is it the rados modify the crush map or cluster map, and the primary OSD does the data movement according to the cluster map? how to found it in the source code?

2. when OSD's down or failed, how Ceph recover the data in other OSDs? is it the primary OSD copy the PG to the new located OSD?

3. the OSD has 4 status bits: up,down,in,out. But i can't found the defined status-- CEPH_OSD_DOWN, is it the OSD call the function mark_osd_down() to modify the OSD status in OSDMap?

Very appreciate ur kindly reply!
Thx!