Commit 453742ba authored May 27, 2025 by Kairui Song Committed by Andrew Morton Jul 09, 2025

mm, list_lru: refactor the locking code

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

Link: https://lkml.kernel.org/r/20250526180638.14609-1-ryncsn@gmail.com


Signed-off-by: Kairui Song <kasong@tencent.com>
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Julia Lawall <julia.lawall@inria.fr>
Closes: https://lore.kernel.org/r/202505252043.pbT1tBHJ-lkp@intel.com/


Reviewed-by: Qi Zheng <zhengqi.arch@bytedance.com>
Reviewed-by: Muchun Song <muchun.song@linux.dev>
Reviewed-by: SeongJae Park <sj@kernel.org>
Cc: Chengming Zhou <zhouchengming@bytedance.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kairui Song <kasong@tencent.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

parent 3800d552

mm/list_lru.c

+19 −15

Original line number	Diff line number	Diff line
		@@ -60,31 +60,35 @@ 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;
		}
		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)) {
		if (likely(l) && lock_list_lru(l, irq)) {
		rcu_read_unlock();
		return l;
		}
		if (irq)
		spin_unlock_irq(&l->lock);
		else
		spin_unlock(&l->lock);
		}
		/*
		* Caller may simply bail out if raced with reparenting or
		* may iterate through the list_lru and expect empty slots.