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authorMuchun Song <songmuchun@bytedance.com>2021-11-05 13:37:50 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2021-11-06 13:30:35 -0700
commit41d17431df4aa7c57761e04f81c94fb3c3beedf4 (patch)
tree5847dee7f7d5e734fbd7fb7c625c1100700707f6 /mm/list_lru.c
parent60ec6a48eec24986a6414740a2481d22efc1b2f9 (diff)
mm: list_lru: fix the return value of 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. Link: https://lkml.kernel.org/r/20211025124910.56433-1-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>
Diffstat (limited to 'mm/list_lru.c')
-rw-r--r--mm/list_lru.c5
1 files changed, 4 insertions, 1 deletions
diff --git a/mm/list_lru.c b/mm/list_lru.c
index 9a1f7df1afc9..7572f8e70b86 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);