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b=edYTmbc6yots7d1MpDd90TgP/YEipvQ1EZRV6+QhTPE9ReH1dTfzCqhS6hh0fSP4M H9j7wZfWxwtvBc+sCgw4jAEusxZrT5V0sPB1oxGeaTwbTi55VV+k3YbWs2wHxB6cMe qpz4VZGkqE36bFbPio6C7GYZM84jaBAPZ35HTnpYS4bPdazxcUh0Tnsvohi7XQvRJq j3hq+zfihH7GyOfjiyRx3UxG/9QgtA+ylU18Bx4OMG26HwuZNGYDGDxRipZe/5BQs9 XOOk+UtWgfJtNQtosuyneNvvohr3ohy8dhDMCooyJT4iqcfkHgNBsXbd95HQg1HjJ4 1Rvz3HFTnGgBg== From: SeongJae Park To: Kairui Song Cc: SeongJae Park , linux-mm@kvack.org, 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: Re: [PATCH] mm, list_lru: refactor the locking code Date: Tue, 27 May 2025 12:25:55 -0700 Message-Id: <20250527192555.12838-1-sj@kernel.org> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20250526180638.14609-1-ryncsn@gmail.com> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 374EE100010 X-Stat-Signature: 6784cmb7xs4y61ummrtp449ixy9f6kmb X-Rspam-User: X-HE-Tag: 1748373959-947576 X-HE-Meta: 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 6TNNgreS QVFj3jAYwYhY2jv/7Sfbm1MyXR4uPkLodkOFo8bopZ5eEjOjR6jGDLciSA9jyit2pN4vxfuMaxhkC258bP5nIeXoLxhV8bK6j1ufV77XmNOiFkExVkdnH81832UTUG25UUWVbdVu7vwtF7JPp+FJeOwtLqsQIB2UQJOiasIVUQeq0A0dnFQKN5JzTdn77b16QEQcT2EL7DbQthyuU0sK0CdldJOhTExYFD3hVXI0LQkOTkcVg0sgq0qkhDzuAYYRlPfjKqkHZ09fOPgV0FGUgINgS7h+LB4ISzbtOgwJI0Un4YFA9v3crHxNXrTVzXC+saOI4nALVKhKF093PsvSi4bhjHjpvaHwo2HqM 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: List-Subscribe: List-Unsubscribe: Hi Kairui, On Tue, 27 May 2025 02:06:38 +0800 Kairui Song wrote: > 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: 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; > } > > +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) == LONG_MIN)) { > + if (irq) > + spin_unlock_irq(&l->lock); > + else > + spin_unlock(&l->lock); > + return false; > + } I'd prefer 'if (likely(...)) return true;' to reduce indentation and stop wondering what goes to the likely case earlier. But that's my personal preferrence that shouldn't block this. > + return true; > +} > + > static inline struct list_lru_one * > lock_list_lru_of_memcg(struct list_lru *lru, int nid, struct mem_cgroup *memcg, > bool irq, bool skip_empty) > { > struct list_lru_one *l; > - long nr_items; > > rcu_read_lock(); > again: > l = 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 = READ_ONCE(l->nr_items); > - if (likely(nr_items != 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; > } Much easier to read, indeed :) > /* > * Caller may simply bail out if raced with reparenting or > -- > 2.49.0 Thanks, SJ [...]