The trick with utilizing space in cgroup_root for cgroup::ancetors flex
array was an obstacle for kernel reworks for
-Wflex-array-member-not-at-end.

The first patch fixes that, then I wanted to utilize __counted_by for
this flex array which required some more rework how cgroup level is
evaluated.

Similar flex array is also in struct ioc_gq where it was tempting to
simply use __counted_by(level), however, this would be off-by-one as it
has semantics like cgroup's level (0 == root).
Proper adjustment for __counted_by() would either need similar
level/ancestor helpers or abstracted macros for ancestors up/down
iterations.

I only made a simple comment fixup since I'm not sure about benefit of
__counted_by for structs that aren't sized based on direct user input.

Michal Koutný (4):
  cgroup: Eliminate cgrp_ancestor_storage in cgroup_root
  cgroup: Introduce cgroup_level() helper
  cgroup: Use __counted_by for cgroup::ancestors
  blk-iocost: Correct comment ioc_gq::level

 block/bfq-iosched.c           |  2 +-
 block/blk-iocost.c            |  6 ++---
 include/linux/cgroup-defs.h   | 43 +++++++++++++++++++----------------
 include/linux/cgroup.h        | 18 ++++++++++++---
 include/trace/events/cgroup.h |  8 +++----
 kernel/bpf/helpers.c          |  2 +-
 kernel/cgroup/cgroup.c        |  9 ++++----
 net/netfilter/nft_socket.c    |  2 +-
 8 files changed, 53 insertions(+), 37 deletions(-)


base-commit: 8f0b4cce4481fb22653697cced8d0d04027cb1e8
-- 
2.52.0