Hi Kai,

As far as the docs tell, bcache is designed to shut down unclean. So
this is expected behavior in write-back mode.

Yes, I also read it - but since I got a few btrfs fs errors when
running btrfs check (mostly space-cache related) I became a bit
alarmed.
As all csums are ok, so I don't think the backing/caching devices are
corrupt in any way.

To cleanly detach a bcache, you would need to first put it in
write-through or write-around mode and wait for write-back to finish.
In turn, this mode should also avoid these messages at boot.

This is exactly what I do now before each shutdown: switch to
writethrough and wait in a bash-loop until state="clean" - sorrounded
by two calls to sync.
However, I still get the journal replay messages at bootup:

[    2.590615] bcache: bch_journal_replay() journal replay done, 827
keys in 37 entries, seq 145717


Br, Clemens