[linux-lvm] Howto change cachepolicy on cached thinpool devices?

[Oliver Rath]

Hi list,

caching the _tdata part of a thinpool works fine now. Unfortunatly with
lvchange it is not possible to change the policy (vg:dmivg,
cachepool:dmipool,thinpool:winthinpool):

# lvchange --cachepolicy cleaner dmivg/dmicache
  Operation not permitted on hidden LV dmivg/dmicache.

# lvchange --cachepolicy cleaner /dev/mapper/dmivg-winthinpool_tdata
  Operation not permitted on hidden LV dmivg/winthinpool_tdata.

# lvchange --cachepolicy cleaner dmivg/winthinpool
  Command on LV dmivg/winthinpool does not accept LV type thinpool.
Required LV types are cache cachepool .
  Command not permitted on LV dmivg/winthinpool.

The only possibility at the moment seems to change it via lowlewel
dmsetup command.

# dmsetup status dmivg-winthinpool_tdata
0 7730954240 cache 8 1458/9216 128 720896/720896 4608761 7143953 1177059
5866353 40700 761596 2993 2 metadata2 writeback 2 migration_threshold
2048 smq 0 rw -

...

How can this be done with lv*?

Tfh!
Oliver