mm/mglru: restore accidentally removed seq < max_seq check

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>

0 files changed, 0 insertions, 0 deletions