[merged mm-stable] mm-mglru-restore-accidentally-removed-seq-max_seq-check.patch removed from -mm tree

[merged mm-stable] mm-mglru-restore-accidentally-removed-seq-max_seq-check.patch removed from -mm tree

[Andrew Morton]

The quilt patch titled
     Subject: mm/mglru: restore accidentally removed seq < max_seq check
has been removed from the -mm tree.  Its filename was
     mm-mglru-restore-accidentally-removed-seq-max_seq-check.patch

This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: "Barry Song (Xiaomi)" <baohua@kernel.org>
Subject: mm/mglru: restore accidentally removed seq < max_seq check
Date: Tue, 15 Sep 2026 18:15:56 +0800

Since commit 798c0330c2ca ("mm/mglru: rework aging feedback"), the
following sanity check was accidentally removed:

       if (seq < max_seq)
               return 0;

That means we can perform aging for any value less than or equal to
max_gen_nr.

This has been inconsistent with
Documentation/admin-guide/mm/multigen_lru.rst, which states:

 Users can write the following command to ``lru_gen`` to create a new
 generation ``max_gen_nr+1``:

     ``+ memcg_id node_id max_gen_nr [can_swap [force_scan]]``

The correct semantics are that writing a value smaller than max_gen_nr
should return 0, since the requested generation already exists.

Link: https://lore.kernel.org/20260915101556.50467-1-baohua@kernel.org
Fixes: 798c0330c2ca ("mm/mglru: rework aging feedback")
Signed-off-by: Barry Song (Xiaomi) <baohua@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reported-by: Chuanhua Han <hanchuanhua802@gmail.com>
Reviewed-by: Kairui Song <kasong@tencent.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Baoquan He <baoquan.he@linux.dev>
Cc: David Hildenbrand <david@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Wei Xu <weixugc@google.com>
Cc: Yuanchu Xie <yuanchu@google.com>
Cc: Yu Zhao <yuzhao@google.com>
---

 mm/vmscan.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/mm/vmscan.c~mm-mglru-restore-accidentally-removed-seq-max_seq-check
+++ a/mm/vmscan.c
@@ -5839,6 +5839,9 @@ static int run_aging(struct lruvec *lruv
 {
 	DEFINE_MAX_SEQ(lruvec);
 
+	if (seq < max_seq)
+		return 0;
+
 	if (seq > max_seq)
 		return -EINVAL;
 
_

Patches currently in -mm which might be from baohua@kernel.org are