linux-kernel - [PATCH v2 00/11] cgroup v1 deprecation messages

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Message-ID: <20250311123640.530377-1-mkoutny@suse.com>
Date: Tue, 11 Mar 2025 13:36:17 +0100
From: Michal Koutný <mkoutny@...e.com>
To: cgroups@...r.kernel.org,
	linux-block@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-doc@...r.kernel.org,
	linux-mm@...ck.org
Cc: Michal Koutný <mkoutny@...e.com>,
	Josef Bacik <josef@...icpanda.com>,
	Waiman Long <longman@...hat.com>,
	Jonathan Corbet <corbet@....net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Shakeel Butt <shakeel.butt@...ux.dev>,
	Roman Gushchin <roman.gushchin@...ux.dev>,
	Johannes Weiner <hannes@...xchg.org>,
	Tejun Heo <tj@...nel.org>,
	Muchun Song <muchun.song@...ux.dev>,
	Michal Hocko <mhocko@...nel.org>,
	Jens Axboe <axboe@...nel.dk>
Subject: [PATCH v2 00/11] cgroup v1 deprecation messages

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.

Changes from v1 (https://lore.kernel.org/r/20250304153801.597907-1-mkoutny@suse.com/)
- cpuset load_balance/pressure warn wording (Waiman)
- comment typo (Waiman)
- collect Acks
- drop bouncing Cc: and respective RFC (self)
- change level warn -> info, except for spread slab (Tejun)
- add memory.swappiness (self)
- add legacy freezer message (self)
- update cover wrt net* controllers (self)

Michal Koutný (11):
  cgroup/cpuset-v1: Add deprecation messages to sched_load_balance and
    memory_pressure_enabled
  cgroup/cpuset-v1: Add deprecation messages to memory_spread_page and
    memory_spread_slab
  cgroup/blkio: Add deprecation messages to reset_stats
  cgroup: Print message when /proc/cgroups is read on v2-only system
  cgroup/cpuset-v1: Add deprecation messages to mem_exclusive and
    mem_hardwall
  cgroup/cpuset-v1: Add deprecation messages to memory_migrate
  RFC cgroup/cpuset-v1: Add deprecation messages to
    sched_relax_domain_level
  mm: Add transformation message for per-memcg swappiness
  cgroup: Add deprecation message to legacy freezer controller
  cgroup: Update file naming comment
  blk-cgroup: Simplify policy files registration

 .../cgroup-v1/freezer-subsystem.rst           |  4 ++++
 .../admin-guide/cgroup-v1/memory.rst          |  1 +
 block/blk-cgroup.c                            |  8 +++++--
 block/blk-ioprio.c                            | 23 ++++++-------------
 include/linux/cgroup-defs.h                   |  5 ++--
 include/linux/cgroup.h                        |  1 +
 kernel/cgroup/cgroup-internal.h               |  1 +
 kernel/cgroup/cgroup-v1.c                     |  7 ++++++
 kernel/cgroup/cgroup.c                        |  4 ++--
 kernel/cgroup/cpuset-v1.c                     |  8 +++++++
 kernel/cgroup/legacy_freezer.c                |  6 +++--
 mm/memcontrol-v1.c                            |  6 +++--
 12 files changed, 47 insertions(+), 27 deletions(-)


base-commit: 80e54e84911a923c40d7bee33a34c1b4be148d7a
-- 
2.48.1