linux-kernel - [PATCH v9 0/2] mm/vmscan: fix demotion targets checks in reclaim/demotion

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Message-ID: <20260114205305.2869796-1-bingjiao@google.com>
Date: Wed, 14 Jan 2026 20:53:01 +0000
From: Bing Jiao <bingjiao@...gle.com>
To: bingjiao@...gle.com
Cc: Andrew Morton <akpm@...ux-foundation.org>, David Hildenbrand <david@...nel.org>, 
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, "Liam R. Howlett" <Liam.Howlett@...cle.com>, 
	Vlastimil Babka <vbabka@...e.cz>, Mike Rapoport <rppt@...nel.org>, Suren Baghdasaryan <surenb@...gle.com>, 
	Michal Hocko <mhocko@...e.com>, Axel Rasmussen <axelrasmussen@...gle.com>, 
	Yuanchu Xie <yuanchu@...gle.com>, Wei Xu <weixugc@...gle.com>, 
	Johannes Weiner <hannes@...xchg.org>, Qi Zheng <zhengqi.arch@...edance.com>, 
	Shakeel Butt <shakeel.butt@...ux.dev>, Gregory Price <gourry@...rry.net>, 
	Joshua Hahn <joshua.hahnjy@...il.com>, muchun.song@...ux.dev, roman.gushchin@...ux.dev, 
	tj@...nel.org, longman@...hat.com, chenridong@...weicloud.com, 
	linux-mm@...ck.org, linux-kernel@...r.kernel.org, cgroups@...r.kernel.org
Subject: [PATCH v9 0/2] mm/vmscan: fix demotion targets checks in reclaim/demotion

This patch series addresses two issues in demote_folio_list(),
can_demote(), and next_demotion_node() in reclaim/demotion.

1. demote_folio_list() and can_demote() do not correctly check demotion
   target against cpuset.mems_effective, which will cause (a) pages are
   demoted to not-allowed nodes and (b) pages are failed to demote even
   if the system still have allowed demotion nodes.

   Patch 1 fixes this bug by update cpuset_node_allowed() and
   mem_cgroup_node_allowed() to return effective_mems, allowing directly
   logic-and operation against demotion targets.

2. next_demotion_node() returns a preferred demotion target, but it does
   check the node against allowed nodes.

   Patch 2 ensures that next_demotion_node() filters against the allowed
   node mask and selects the closest demotion target to the source node.

===

Hi Andrew,

Sorry for the extra noise in your inbox.

I’m resubmitting the full refreshed patch series together this time.
I just realized it is better to include the unmodified patches alongside
the modified ones to ensure compatibility with upstream automated tools
and to simplify your review process.

The refreshed patch series replaces some commits in mm-untable,
including:

  - Commit 809cc3db1831 ("mm/vmscan: fix demotion targets checks in
    reclaim/demotion")
  - Commit fd8cb9a8cedc ("mm/vmscan: select the closest preferred node
    in demote_folio_list()")
  - Commit 127714c76c46 ("mm/vmscan: fix uninitialized variable in
    demote_folio_list()")

Thanks!

Best regards,
Bing

Bing Jiao (2):
  mm/vmscan: fix demotion targets checks in reclaim/demotion
  mm/vmscan: select the closest perferred node in demote_folio_list()

 include/linux/cpuset.h       |  6 ++--
 include/linux/memcontrol.h   |  6 ++--
 include/linux/memory-tiers.h |  6 ++--
 kernel/cgroup/cpuset.c       | 54 ++++++++++++++++++++++++------------
 mm/memcontrol.c              | 16 +++++++++--
 mm/memory-tiers.c            | 21 ++++++++++----
 mm/vmscan.c                  | 31 +++++++++++++--------
 7 files changed, 95 insertions(+), 45 deletions(-)

--
2.52.0.457.g6b5491de43-goog