[PATCH v4 0/6] mm/mglru: clean up folio counters and flag usage

[Kairui Song via B4 Relay <devnull+kasong.tencent.com@kernel.org>]

This is a cleanup series separated out from the MGLRU-FG series [1]. As
that series is getting too long in following updates, seperate out the
clean up part for easier review and merge.

No feature change is intended, except one bugfix. It mostly replaces
the open-coded bit operations scattered throughout the MGLRU code with
new helpers, with proper kdocs, sanity debug checks, and hardens a few
MGLRU functions.

A subtle generation counter leak is also found during the refactoring
and the fix is included.

Also collected review feedbacks on the cleanup part from the posted
series.

Link: https://lore.kernel.org/linux-mm/20260804-mglru-fg-v1-0-4d8dad39dad6@tencent.com/ [1]
Signed-off-by: Kairui Song <kasong@tencent.com>
---
Changes in v4:
- Rename lru_gen_set_flags/lru_gen_from_flags to
  lru_set_gen_flags/lru_get_gen_flags, similiar with lru refs helpers,
  as suggested by [ Barry Song ].
- Added some comments to cover concerned raised by [ Barry Song ] and [
  Baolin Wang ].
- A little code shuffling and better sanity check for concerns raised by 
  [ Ridong Chen ].
- Collect tags.
- Link to v3: https://patch.msgid.link/20260826-mglru-flags-cleanup-v3-0-d9f1c75549c8@tencent.com

Changes in v3:
- Set PG_workingset before setting LRU refs bit to avoid any potential
  under report of folio tier.
- Migrate folio's referenced status before PG_update so lockless readers
  won't set stale referenced status.
- Link to v2: https://patch.msgid.link/20260824-mglru-flags-cleanup-v2-0-0104132114ae@tencent.com

Changes in v2:
- Dropped the redundant LRU_GEN_MAX macro.
- Renamed folio_migrate_refs() to folio_migrate_lru_refs() and reworded
  its commit message to describe the referenced state being transferred.
- Rewrote patch 6's commit message with a detailed analysis of the
  anon/file accounting race.
- Dropped patch 7, it doesn't really fix anything, and might be in
  conflict with other updating series.
- Collected Reviewed-by tags.
- Link to v1: https://patch.msgid.link/20260818-mglru-flags-cleanup-v1-0-8dbbdac0d28c@tencent.com

---
Kairui Song (6):
      mm/memcontrol: make lru_zone_size atomic and simplify sanity check
      mm/mglru: introduce helpers for manipulating gen and refs flags
      mm/migrate: copy all referenced state via folio_migrate_lru_refs
      mm/mglru: move max_seq read into walk_update_folio
      mm/mglru: use explicit tier range in read_ctrl_pos()
      mm/mglru: fix potential generation folio number leak

 include/linux/memcontrol.h |   9 +++-
 include/linux/mm_inline.h  | 111 ++++++++++++++++++++++++++++++++++++------
 include/linux/mmzone.h     |   3 ++
 mm/folio.c                 |  19 ++++----
 mm/memcontrol.c            |  18 +------
 mm/migrate.c               |   6 +--
 mm/vmscan.c                | 117 +++++++++++++++++++++++----------------------
 7 files changed, 183 insertions(+), 100 deletions(-)
---
base-commit: aeddb4d52acfcc5ce5e988acd48f2906fe966ca3
change-id: 20260818-mglru-flags-cleanup-cc49cfad654f

Best regards,
--  
Kairui Song <kasong@tencent.com>