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mm, list_lru: refactor the locking code

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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>
This commit is contained in:
Kairui Song 2025-05-27 02:06:38 +08:00 committed by Andrew Morton
parent 3800d55250
commit 453742ba5b
1 changed files with 19 additions and 15 deletions
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34
mm/list_lru.c
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@ -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;
}
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;
}
/*
* Caller may simply bail out if raced with reparenting or