write-through dm-cache (lvmcache), dirty blocks

# bash lvmcache-stats.sh
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LVM Cache report of /dev/main/var
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- Cache Usage: 99.9% - Metadata Usage: .9%
- Read Hit Rate: 91.8% - Write Hit Rate: 98.5%
- Demotions/Promotions/Dirty: 3208/3219/583224
- Features in use: metadata2 writethrough no_discard_passdown 

# lvchange --cachesettings 'cleaner=1' main/var
  Logical volume main/var changed.
  WARNING: SMQ cache policy does not support "cleaner=1" setting, remove with 'lvchange --cachesettings "cleaner=default" ...'.
  WARNING: SMQ cache policy does not support "cleaner=1" setting, remove with 'lvchange --cachesettings "cleaner=default" ...'.