[Deepin-Kernel-SIG] [linux 6.6.y] [Upstream] cleanups for lockless slab shrink

[opsiff]

https://lore.kernel.org/all/20230911092517.64141-1-zhengqi.arch@bytedance.com/

Hi all,

This series is some cleanups for lockless slab shrink, I dropped the
[PATCH v2 5/5] which is more related to the main lockless patch.

This series is based on the v6.6-rc1.

Comments and suggestions are welcome.

Thanks,
Qi

Changlog in v3 -> v4:

• rebase onto the v6.6-rc1

Changlog in part 1 v2 -> part 1 v3:

• drop [PATCH v2 5/5]
• collect Acked-by
• rebase onto the next-20230823

Changlog in part 1 v1 -> part 1 v2:

• fix compilation warning in [PATCH 1/5]
• rename synchronize_shrinkers() to ttm_pool_synchronize_shrinkers()
  (pointed by Christian König)
• collect Reviewed-by

Changlog in v4 -> part 1 v1:

• split from the previous large patchset
• fix comment format in [PATCH v4 01/48] (pointed by Muchun Song)
• change to use kzalloc_node() and fix typo in [PATCH v4 44/48]
  (pointed by Dave Chinner)
• collect Reviewed-bys
• rebase onto the next-20230815

Qi Zheng (4):
mm: move some shrinker-related function declarations to mm/internal.h
mm: vmscan: move shrinker-related code into a separate file
mm: shrinker: remove redundant shrinker_rwsem in debugfs operations
drm/ttm: introduce pool_shrink_rwsem

drivers/gpu/drm/ttm/ttm_pool.c | 17 +-
include/linux/shrinker.h | 20 -
mm/Makefile | 4 +-
mm/internal.h | 28 ++
mm/shrinker.c | 694 ++++++++++++++++++++++++++++++++
mm/shrinker_debug.c | 18 +-
mm/vmscan.c | 701 ---------------------------------
7 files changed, 743 insertions(+), 739 deletions(-)
create mode 100644 mm/shrinker.c

--
2.30.2

Summary by Sourcery

Refactor shrinker and slab-shrinking infrastructure into a dedicated mm/shrinker.c unit and adjust users to support lockless slab shrink cleanups.

Enhancements:

• Move shrinker core logic and slab shrinking paths from vmscan.c into a new mm/shrinker.c compilation unit and wire it into the mm build.
• Relocate shrinker- and debugfs-related declarations from public headers into mm/internal.h to narrow exposure of internal MM interfaces.
• Simplify shrinker debugfs count/scan operations to avoid taking the global shrinker_rwsem in debug paths, improving decoupling from core shrinker locking.
• Introduce a dedicated pool_shrink_rwsem and local ttm_pool_synchronize_shrinkers() in TTM so pool teardown no longer depends on the global shrinker synchronization primitive.

[sourcery-ai]

Reviewer's Guide

Refactors shrinker-related VM code out of vmscan into a new mm/shrinker.c translation unit, tightens debugfs shrinker usage to avoid taking the global shrinker_rwsem where unnecessary, and introduces a TTM-local rwsem to synchronize pool shrink operations instead of using the global shrinker synchronization primitive.

Sequence diagram for TTM pool shrink and fini synchronization

sequenceDiagram
    participant Reclaim as ttm_pool_shrink
    participant Fini as ttm_pool_fini
    participant Sync as ttm_pool_synchronize_shrinkers
    participant RW as pool_shrink_rwsem
    participant SL as shrinker_lock

    Reclaim->>RW: down_read(pool_shrink_rwsem)
    Reclaim->>SL: spin_lock(shrinker_lock)
    Reclaim->>SL: list_first_entry / list_move_tail
    Reclaim->>SL: spin_unlock(shrinker_lock)
    Reclaim->>RW: up_read(pool_shrink_rwsem)

    Fini->>Sync: ttm_pool_synchronize_shrinkers()
    Sync->>RW: down_write(pool_shrink_rwsem)
    Sync-->>RW: up_write(pool_shrink_rwsem)
    Fini->>SL: spin_lock(shrinker_lock)
    Fini->>SL: list_del(&pool_type->shrinker_list)
    Fini-->>SL: spin_unlock(shrinker_lock)

Loading

File-Level Changes

Change	Details	Files
Move all shrinker core logic from vmscan into a dedicated mm/shrinker.c and adjust build and internal interfaces.	Remove shrinker list, rwsem, and all shrink_slab/do_shrink_slab and memcg shrinker helpers from vmscan.c Introduce new mm/shrinker.c file containing the shrinker list, shrinker_rwsem, NUMA and memcg-aware deferred accounting, shrink_slab implementation, and shrinker registration/preallocation helpers Export shrink_slab and shrinker registration APIs from mm/shrinker.c and wire them via mm/internal.h Update mm/Makefile to compile the new shrinker.c object and keep vmscan focused on reclaim logic	mm/vmscan.c mm/shrinker.c mm/Makefile mm/internal.h
Reorganize shrinker headers so core APIs stay in include/linux/shrinker.h and internal helpers move to mm/internal.h.	Remove synchronize_shrinkers() declaration and debugfs helper declarations from include/linux/shrinker.h, leaving only the public shrinker registration APIs and debugfs rename helper Add shrink_slab() prototype and shrinker debugfs helper declarations or stubs into mm/internal.h so shrinker.c and mm/shrinker_debug.c can share them without exposing them globally	include/linux/shrinker.h mm/internal.h
Decouple shrinker debugfs operations from the global shrinker_rwsem to avoid unnecessary locking when inspecting or manually invoking shrinkers.	Include mm/internal.h in shrinker_debug.c to access internal helpers Drop down_read_killable()/up_read() around shrinker_debugfs_count_show and rely on RCU and existing synchronization for safe iteration over shrinkers and memcgs Similarly remove shrinker_rwsem usage from shrinker_debugfs_scan_write, calling the shrinker scan callback under RCU and memcg reference handling only	mm/shrinker_debug.c
Introduce a TTM-specific pool_shrink_rwsem and local synchronize helper instead of using the global synchronize_shrinkers().	Define a new pool_shrink_rwsem protecting the TTM pool shrinker LRU and operations Wrap ttm_pool_shrink() with down_read()/up_read() on pool_shrink_rwsem around the shrinker list rotation and page freeing Add a private ttm_pool_synchronize_shrinkers() that takes and releases pool_shrink_rwsem in write mode to wait for in-flight shrink operations Change ttm_pool_fini() to call ttm_pool_synchronize_shrinkers() instead of the removed global synchronize_shrinkers()	drivers/gpu/drm/ttm/ttm_pool.c

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[sourcery-ai]

Hey - I've left some high level feedback:

• In shrinker_debug.c the comment and externs still reference shrinker_rwsem and shrinker_list as being defined in vmscan.c; now that these live in shrinker.c, consider exposing them via mm/internal.h or updating the comment/externs to avoid stale cross-unit assumptions.
• Now that shrinker_debugfs paths no longer take shrinker_rwsem, it would be worth double-checking and documenting the expected lifetime/ownership rules of struct shrinker in these debugfs callbacks, since they can now race with unregister_shrinker() without explicit locking.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- In shrinker_debug.c the comment and externs still reference `shrinker_rwsem` and `shrinker_list` as being defined in vmscan.c; now that these live in shrinker.c, consider exposing them via mm/internal.h or updating the comment/externs to avoid stale cross-unit assumptions.
- Now that shrinker_debugfs paths no longer take `shrinker_rwsem`, it would be worth double-checking and documenting the expected lifetime/ownership rules of `struct shrinker` in these debugfs callbacks, since they can now race with `unregister_shrinker()` without explicit locking.

---

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[Avenger-285714]

why sw_64 ci always fail now?

[Copilot]

Pull request overview

This PR refactors the core shrinker/slab-shrinking infrastructure to support the “lockless slab shrink” cleanup series by moving shrinker code out of mm/vmscan.c into a dedicated mm/shrinker.c, tightening header exposure, and adjusting affected users (notably TTM).

Changes:

• Move shrinker core logic (registration, memcg shrinker infrastructure, shrink_slab()) from mm/vmscan.c into the new mm/shrinker.c and hook it into the MM build.
• Narrow public API surface by moving shrinker debugfs helper declarations from include/linux/shrinker.h into mm/internal.h.
• Update TTM pool teardown to synchronize against pool shrink activity via a dedicated pool_shrink_rwsem instead of the global synchronize_shrinkers().

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
mm/vmscan.c	Removes shrinker infrastructure that has been relocated into mm/shrinker.c.
mm/shrinker.c	New compilation unit containing the moved shrinker core + memcg shrinker logic.
mm/shrinker_debug.c	Adjusts shrinker debugfs code; drops shrinker_rwsem usage in debugfs ops (problematic).
mm/Makefile	Adds shrinker.o to the mm build.
mm/internal.h	Adds internal-only declarations for shrink_slab() and shrinker debugfs helpers.
include/linux/shrinker.h	Removes public declarations (incl. synchronize_shrinkers()).
drivers/gpu/drm/ttm/ttm_pool.c	Adds pool_shrink_rwsem + local synchronize helper for safe pool teardown.

---

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[opsiff]

why sw_64 ci always fail now?

fix pending #1818

[Avenger-285714]

/approve

[deepin-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Avenger-285714

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