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mm: list_lru: remove holding lru lock

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Since commit e5bc3af773 ("rcu: Consolidate PREEMPT and !PREEMPT
synchronize_rcu()"), the critical section of spin lock can serve as an
RCU read-side critical section which already allows readers that hold
nlru->lock to avoid taking rcu lock.  So just remove holding lock.

Link: https://lkml.kernel.org/r/20211025124534.56345-1-songmuchun@bytedance.com
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: Shakeel Butt <shakeelb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Muchun Song 2021-11-05 13:37:47 -07:00 committed by Linus Torvalds
parent 58056f7750
commit 60ec6a48ee
1 changed files with 0 additions and 11 deletions
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11
mm/list_lru.c
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@ -398,18 +398,7 @@ static int memcg_update_list_lru_node(struct list_lru_node *nlru,
}
memcpy(&new->lru, &old->lru, flex_array_size(new, lru, old_size));
/*
* The locking below allows readers that hold nlru->lock avoid taking
* rcu_read_lock (see list_lru_from_memcg_idx).
*
* Since list_lru_{add,del} may be called under an IRQ-safe lock,
* we have to use IRQ-safe primitives here to avoid deadlock.
*/
spin_lock_irq(&nlru->lock);
rcu_assign_pointer(nlru->memcg_lrus, new);
spin_unlock_irq(&nlru->lock);
kvfree_rcu(old, rcu);
return 0;
}