[PATCH v2 0/8] memcg: remove the v1 soft limit

[Shakeel Butt]

The v1 soft limit was deprecated in v6.12 by commit 569c4f62d84a ("memcg:
initiate deprecation of v1 soft limit") and nobody has reported depending
on it in the ~21 months since. memory.low and memory.min in v2 have
covered the same ground for far longer.

The knob has since been made inert by "memcg: make the v1 soft limit knob
inert", already queued in mm-hotfixes as a backportable fix for a syzbot
report [1]. Nothing can enter the soft limit rbtree anymore, so this
series just deletes the machinery that is now dead: the reclaim pass in
kswapd and direct reclaim, mem_cgroup_shrink_node() and its tracepoints,
the per-node rbtree, lru_gen_soft_reclaim() and the MEMCG_LRU_HEAD op, the
per-node tree fields, mem_cgroup->soft_limit, and finally the v1 event
ratelimiting which is now down to a single target.

memory.soft_limit_in_bytes itself is untouched: writes stay ignored and
reads keep returning the maximum value.

Changes since v1 [2]:
- Dropped "memcg: make the v1 soft limit knob inert" (1/9 in v1), which is
  already queued in mm-hotfixes, making this an 8-patch series.
- Collected the acks and review tags. No code changes.

Sashiko's v1 review [3] asked whether the softlimit tracepoints,
lru_gen_soft_reclaim(), the per-node tree fields and the
MEM_CGROUP_TARGET_SOFTLIMIT ratelimiting could go too. They all can and
they all do, in patches 3/8, 5/8, 6/8 and 8/8 of this same series.

[1] https://lore.kernel.org/all/6a7a6929.b50370da.49fe0.005e.GAE@xxxxxxxxxx/
[2] https://lore.kernel.org/all/20260811203203.3456029-1-shakeel.butt@xxxxxxxxx/
[3] https://sashiko.dev/#/patchset/20260811203203.3456029-1-shakeel.butt@xxxxxxxxx

Shakeel Butt (8):
  memcg: remove v1 soft limit reclaim
  memcg: remove mem_cgroup_shrink_node()
  memcg: remove the soft limit reclaim tracepoints
  memcg: remove the soft limit rbtree
  memcg: remove lru_gen_soft_reclaim()
  memcg: remove the per-node soft limit tree fields
  memcg: remove mem_cgroup->soft_limit
  memcg: simplify v1 event ratelimiting

 include/linux/memcontrol.h    |  27 ---
 include/linux/mmzone.h        |  30 +--
 include/trace/events/vmscan.h |  14 --
 mm/internal.h                 |   4 -
 mm/memcontrol-v1.c            | 392 ++--------------------------------
 mm/memcontrol-v1.h            |  12 +-
 mm/memcontrol.c               |   7 +-
 mm/vmscan.c                   |  96 +--------
 8 files changed, 34 insertions(+), 548 deletions(-)

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