mm, memcg: cg2 memory{.swap,}.peak write handlers

[David Finkel <davidf@vimeo.com>]

This is an update of a previous series[1] addressing Johannes' comments,
and rebasing on top of linus's master.

Unfortunately, linus's master doesn't seem to be bootable at the
moment, so I haven't re-run the tests on this change yet. I'll see about
re-running everything in the morning. (root= resolution seems to be
failing both for x86-64 (in qemu) and usermode linux)

 Documentation/admin-guide/cgroup-v2.rst          |  26 ++--
 include/linux/cgroup-defs.h                      |   5 +
 include/linux/cgroup.h                           |   3 +
 include/linux/memcontrol.h                       |   5 +
 include/linux/page_counter.h                     |   6 +-
 kernel/cgroup/cgroup-internal.h                  |   2 +
 kernel/cgroup/cgroup.c                           |   7 ++
 mm/memcontrol.c                                  | 117 ++++++++++++++++--
 mm/page_counter.c                                |  30 +++--
 tools/testing/selftests/cgroup/cgroup_util.c     |  22 ++++
 tools/testing/selftests/cgroup/cgroup_util.h     |   2 +
 tools/testing/selftests/cgroup/test_memcontrol.c | 226 ++++++++++++++++++++++++++++++++--
 12 files changed, 416 insertions(+), 35 deletions(-)


[1]: https://lore.kernel.org/cgroups/20240722235554.2911971-1-davidf@vimeo.com/T/


Thanks for all the constructive comments and discussion!

David Finkel
Senior Principal Engineer, Core Services
Vimeo Inc.