tools/ceph-objectstore-tool: split filestore directories offline to target hash level
Currently ceph-objectstore-tool can only split dirs that already meet the usual object number criteria. It won't reduce the cost of online split for those dirs that would meet the criteria online.
Following PR uses 'arg1' option for apply-layout-settings to specify the target hash level wants to split to. Then dirs will be split offline no matters how many objects they have. This also helps those pools that forgot to do pre-splitting at their creation time.
sudo ceph-objectstore-tool --data-path /data/lib/ceph/osd/ceph-0/ --op apply-layout-settings --pool "cephfs_data" --arg1 5
This will split all "cephfs_data" pool's PGs on OSD.0 offline to the 5th hash level no matter how many objects each dir has right now, to avoid potential costly online split.