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Tue, 11 May 2021 03:51:22 -0700 (PDT) Received: from localhost.localdomain ([139.177.225.240]) by smtp.gmail.com with ESMTPSA id n18sm13501952pgj.71.2021.05.11.03.51.15 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Tue, 11 May 2021 03:51:22 -0700 (PDT) From: Muchun Song To: willy@infradead.org, akpm@linux-foundation.org, hannes@cmpxchg.org, mhocko@kernel.org, vdavydov.dev@gmail.com, shakeelb@google.com, guro@fb.com, shy828301@gmail.com, alexs@kernel.org, richard.weiyang@gmail.com, david@fromorbit.com, trond.myklebust@hammerspace.com, anna.schumaker@netapp.com Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-nfs@vger.kernel.org, zhengqi.arch@bytedance.com, duanxiongchun@bytedance.com, fam.zheng@bytedance.com, Muchun Song Subject: [PATCH 01/17] mm: list_lru: fix list_lru_count_one() return value Date: Tue, 11 May 2021 18:46:31 +0800 Message-Id: <20210511104647.604-2-songmuchun@bytedance.com> X-Mailer: git-send-email 2.21.0 (Apple Git-122) In-Reply-To: <20210511104647.604-1-songmuchun@bytedance.com> References: <20210511104647.604-1-songmuchun@bytedance.com> MIME-Version: 1.0 Authentication-Results: imf20.hostedemail.com; dkim=pass header.d=bytedance-com.20150623.gappssmtp.com header.s=20150623 header.b=qqcBn0jk; dmarc=pass (policy=none) header.from=bytedance.com; spf=pass (imf20.hostedemail.com: domain of songmuchun@bytedance.com designates 209.85.214.175 as permitted sender) smtp.mailfrom=songmuchun@bytedance.com X-Stat-Signature: 8s6e7tw3qjp3rfnqf9ux8xrj8itjdfmd X-Rspamd-Queue-Id: 42534138 X-Rspamd-Server: rspam02 Received-SPF: none (bytedance.com>: No applicable sender policy available) receiver=imf20; identity=mailfrom; envelope-from=""; helo=mail-pl1-f175.google.com; client-ip=209.85.214.175 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1620730283-501243 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Since commit 2788cf0c401c ("memcg: reparent list_lrus and free kmemcg_id on css offline"), the ->nr_items can be negative during memory cgroup reparenting. In this case, list_lru_count_one() returns an unusual and huge value. Ii can surprise users. So let it return zero when ->nr_items is negative. Signed-off-by: Muchun Song --- mm/list_lru.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/mm/list_lru.c b/mm/list_lru.c index cd58790d0fb3..4962d48d4410 100644 --- a/mm/list_lru.c +++ b/mm/list_lru.c @@ -176,13 +176,16 @@ unsigned long list_lru_count_one(struct list_lru *l= ru, { struct list_lru_node *nlru =3D &lru->node[nid]; struct list_lru_one *l; - unsigned long count; + long count; =20 rcu_read_lock(); l =3D list_lru_from_memcg_idx(nlru, memcg_cache_id(memcg)); count =3D READ_ONCE(l->nr_items); rcu_read_unlock(); =20 + if (unlikely(count < 0)) + count =3D 0; + return count; } EXPORT_SYMBOL_GPL(list_lru_count_one); --=20 2.11.0