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Mon, 26 May 2025 11:06:58 -0700 (PDT) Received: from KASONG-MC4.tencent.com ([101.32.222.185]) by smtp.gmail.com with ESMTPSA id af79cd13be357-7cd467f0c43sm1587627385a.54.2025.05.26.11.06.54 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Mon, 26 May 2025 11:06:57 -0700 (PDT) From: Kairui Song To: linux-mm@kvack.org Cc: Andrew Morton , Johannes Weiner , Roman Gushchin , Chengming Zhou , Qi Zheng , Muchun Song , linux-kernel@vger.kernel.org, Kairui Song , kernel test robot , Julia Lawall Subject: [PATCH] mm, list_lru: refactor the locking code Date: Tue, 27 May 2025 02:06:38 +0800 Message-ID: <20250526180638.14609-1-ryncsn@gmail.com> X-Mailer: git-send-email 2.49.0 Reply-To: Kairui Song Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Kairui Song Cocci is confused by the try lock then release RCU and return logic here. So separate the try lock part out into a standalone helper. The code is easier to follow too. No feature change, fixes: cocci warnings: (new ones prefixed by >>) >> mm/list_lru.c:82:3-9: preceding lock on line 77 >> mm/list_lru.c:82:3-9: preceding lock on line 77 mm/list_lru.c:82:3-9: preceding lock on line 75 mm/list_lru.c:82:3-9: preceding lock on line 75 Reported-by: kernel test robot Reported-by: Julia Lawall Closes: https://lore.kernel.org/r/202505252043.pbT1tBHJ-lkp@intel.com/ Signed-off-by: Kairui Song Reviewed-by: Muchun Song Reviewed-by: Qi Zheng Reviewed-by: SeongJae Park --- mm/list_lru.c | 34 +++++++++++++++++++--------------- 1 file changed, 19 insertions(+), 15 deletions(-) diff --git a/mm/list_lru.c b/mm/list_lru.c index 490473af3122..ec48b5dadf51 100644 --- a/mm/list_lru.c +++ b/mm/list_lru.c @@ -60,30 +60,34 @@ list_lru_from_memcg_idx(struct list_lru *lru, int nid, = int idx) return &lru->node[nid].lru; } =20 +static inline bool lock_list_lru(struct list_lru_one *l, bool irq) +{ + if (irq) + spin_lock_irq(&l->lock); + else + spin_lock(&l->lock); + if (unlikely(READ_ONCE(l->nr_items) =3D=3D LONG_MIN)) { + if (irq) + spin_unlock_irq(&l->lock); + else + spin_unlock(&l->lock); + return false; + } + return true; +} + static inline struct list_lru_one * lock_list_lru_of_memcg(struct list_lru *lru, int nid, struct mem_cgroup *m= emcg, bool irq, bool skip_empty) { struct list_lru_one *l; - long nr_items; =20 rcu_read_lock(); again: l =3D list_lru_from_memcg_idx(lru, nid, memcg_kmem_id(memcg)); - if (likely(l)) { - if (irq) - spin_lock_irq(&l->lock); - else - spin_lock(&l->lock); - nr_items =3D READ_ONCE(l->nr_items); - if (likely(nr_items !=3D LONG_MIN)) { - rcu_read_unlock(); - return l; - } - if (irq) - spin_unlock_irq(&l->lock); - else - spin_unlock(&l->lock); + if (likely(l) && lock_list_lru(l, irq)) { + rcu_read_unlock(); + return l; } /* * Caller may simply bail out if raced with reparenting or --=20 2.49.0