lkml.org 
[lkml]   [2021]   [Oct]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH] mm: list_lru: fix the return value of list_lru_count_one()
Date
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(-)

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);
--
2.11.0
\
 
 \ /
  Last update: 2021-10-25 14:50    [W:0.041 / U:0.092 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site