Memory controller had begun to print warning messages when using some
attributes that do no have a counterpart in its cgroup v2
implementation. This is informative to users who run (unwittingly) on v1
or to distros that run v1 (they can learn about such users or prepare
for disabling v1 configs).

I consider the deprecated files in three categories:
  - RE) replacement exists,
  - DN) dropped as non-ideal concept (e.g. non-hierarchical resources),
  - NE) not evaluated (yet).

For RE, I added the replacement into the warning message, DN have only a
plain deprecation message and I marked the commits with NE as RFC.
Also I'd be happy if you would point out some forgotten knobs that'd
deserve similar warnings.

The level of messages is info to avoid too much noise (may be increased
in future when there are fewer users). Some knobs from DN have warn
level.

The net_cls and net_prio controllers that only exist on v1 hierarchies
have no straightforward action for users (replacement would rely on net
NS or eBPF), so messages for their usage are omitted, although it'd be
good to eventually retire that code in favor of aforementioned.

At the end are some cleanup patches I encountered en route.

For the block related parts, as I'm assuming Tejun will pick this up:

Acked-by: Jens Axboe <axboe@kernel.dk>

-- 
Jens Axboe