[PATCH -v4 0/2] mm: vmscan: fix node reclaim ignoring swappiness parameter

From: Ridong Chen <[email protected]>

The per-node proactive reclaim interface
(/sys/devices/system/node/nodeX/reclaim) accepts a swappiness parameter,
but it is silently ignored when CONFIG_MEMCG is disabled. The root cause
is that sc_swappiness() has separate implementations for CONFIG_MEMCG and
!CONFIG_MEMCG, and the latter never checks proactive_swappiness.

Patch 1 moves mem_cgroup_swappiness() and vm_swappiness out of the public
include/linux/swap.h into the mm-private mm/swap.h, and makes the helper
handle both CONFIG_MEMCG and !CONFIG_MEMCG in a single inline function.
This is a prerequisite for unifying sc_swappiness().

Patch 2 consolidates sc_swappiness() into a single definition that works
regardless of CONFIG_MEMCG, fixing the node reclaim swappiness bug.

---

v3 -> v4:
 - READ_ONCE() was missed when reading memcg->swappiness, add it back.

v2 -> v3:
 - Simplify mem_cgroup_swappiness as suggested by Johannes.  
 - Rebase on the next-20260722

v1 -> v2:
 - Move mem_cgroup_swappiness() and vm_swappiness to mm/swap.h instead of
   include/linux/memcontrol.h. Suggested by Barry Song.
 - Correct fix tag for patch 2.

v1: https://lore.kernel.org/all/[email protected]/

Ridong Chen (2):
  memcg: move mem_cgroup_swappiness and vm_swappiness to mm/swap.h
  mm: vmscan: fix node reclaim ignoring swappiness parameter

 include/linux/memcontrol.h |  4 ++--
 include/linux/swap.h       | 19 -------------------
 mm/memcontrol.c            |  4 ++--
 mm/swap.h                  | 13 +++++++++++++
 mm/vmscan.c                | 19 +++++++------------
 5 files changed, 24 insertions(+), 35 deletions(-)

-- 
2.34.1