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b=L4/VWeIAVDb1IzFKLYX1b/+IaSxpVI3jJNVNJK/KrLJj1lPqvsaKt6sIEY2jrpXAD 0EfamwAPKN09SBCxULADG0HVUsCF0rCS2HCanCVTd1rbWN143su7Q4lxoOygf/YdMG gmpMOt76dM4zHxEDdKyeESVM4cBRTLvsUYnLQrTs5DbU2kukNTkkXpAz/Gt/Tk/iuf posWqFnP4N94Pcj9WQq8u9pU/SVeZcqUb4cLlAw/5xtGWJIIaFqQ1tcwu+mIumfEtq gpRaupWOrLyBIin/QWtUIaX+F8bnqKaCnlPxNtRL4BXq1DJjFvA44j4ymwYecbm12j NWTei3CcBR+gg== From: "Barry Song (Xiaomi)" To: akpm@linux-foundation.org Cc: axelrasmussen@google.com, baohua@kernel.org, baoquan.he@linux.dev, david@kernel.org, hannes@cmpxchg.org, kasong@tencent.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, ljs@kernel.org, mhocko@kernel.org, qi.zheng@linux.dev, ridong.chen@linux.dev, shakeel.butt@linux.dev, weixugc@google.com, yuanchu@google.com, yuzhao@google.com, Chuanhua Han Subject: [PATCH] mm/mglru: restore accidentally removed seq < max_seq check Date: Tue, 15 Sep 2026 18:15:56 +0800 Message-Id: <20260915101556.50467-1-baohua@kernel.org> X-Mailer: git-send-email 2.39.3 (Apple Git-146) MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 55C0040008 X-Stat-Signature: a5o7tsz43yh8eezmd9gyd9ow8nxss6df X-HE-Tag: 1789467363-551850 X-HE-Meta: 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 kL9OHMZ2 GmqV9RYgWeywhGfNeK0afkHfA6heGhGgkImj7hPjiGZAFbxh3lqGIMqo0fZe2MFeQ4VojadKuRoWR5+JC2NvD4TN5bIVtJ+n0wEvR79AHp5qegew2Leih480dT3eafEcXXJycTWUIQtBxIXqZCw7HULRr74OGKfNsEsCQdRD3grbHx9cnw8S31iiqJoHUXJuzU8fam/yKoP3AL/s17+qE3XwFze7h6fPS5mU8g7xYy0uMeOL9AipP/qtl1Kmz2rFFbTdQiuX/7kMW3/8qmvzEJQeTVNDLatXCB9SXuIR/q1wEYHjHjB6QrQPcCQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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. Fixes: 798c0330c2ca ("mm/mglru: rework aging feedback") Reported-by: Chuanhua Han Signed-off-by: Barry Song (Xiaomi) --- mm/vmscan.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/mm/vmscan.c b/mm/vmscan.c index 5354eb8d3a07..18c4d3595749 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -5827,6 +5827,9 @@ static int run_aging(struct lruvec *lruvec, unsigned long seq, { DEFINE_MAX_SEQ(lruvec); + if (seq < max_seq) + return 0; + if (seq > max_seq) return -EINVAL; -- 2.39.3 (Apple Git-146)