| Message ID | 20211025124910.56433-1-songmuchun@bytedance.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | mm: list_lru: fix the return value of list_lru_count_one() | expand |
diff --git a/mm/list_lru.c b/mm/list_lru.c index a6031f1c5bd7..2bba1cd68bb3 100644 --- a/mm/list_lru.c +++ b/mm/list_lru.c @@ -176,13 +176,16 @@ unsigned long list_lru_count_one(struct list_lru *lru, { struct list_lru_node *nlru = &lru->node[nid]; struct list_lru_one *l; - unsigned long count; + long count; rcu_read_lock(); l = list_lru_from_memcg_idx(nlru, memcg_cache_id(memcg)); count = READ_ONCE(l->nr_items); rcu_read_unlock(); + if (unlikely(count < 0)) + count = 0; + return count; } EXPORT_SYMBOL_GPL(list_lru_count_one);
Since commit 2788cf0c401c ("memcg: reparent list_lrus and free kmemcg_id on css offline"), ->nr_items can be negative during memory cgroup reparenting. In this case, list_lru_count_one() will return an unusual and huge value, which can surprise users. At least for now it hasn’t affected any users. But it is better to let list_lru_count_ont() returns zero when ->nr_items is negative. Signed-off-by: Muchun Song <songmuchun@bytedance.com> --- mm/list_lru.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)