[PATCH v2 7/8] mm: memcontrol: move obj_cgroup_uncharge_pages() out of css_set_lock

[Muchun Song]

The css_set_lock is used to guard the list of inherited objcgs. So there
is no need to uncharge kernel memory under css_set_lock. Just move it
out of the lock.

Signed-off-by: Muchun Song <songmuc...@bytedance.com>
Reviewed-by: Shakeel Butt <shake...@google.com>
Acked-by: Roman Gushchin <g...@fb.com>
Acked-by: Johannes Weiner <han...@cmpxchg.org>
---
 mm/memcontrol.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index c4eebe2a2914..e0c398fe7443 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -289,9 +289,10 @@ static void obj_cgroup_release(struct percpu_ref *ref)
        WARN_ON_ONCE(nr_bytes & (PAGE_SIZE - 1));
        nr_pages = nr_bytes >> PAGE_SHIFT;
 
-       spin_lock_irqsave(&css_set_lock, flags);
        if (nr_pages)
                obj_cgroup_uncharge_pages(objcg, nr_pages);
+
+       spin_lock_irqsave(&css_set_lock, flags);
        list_del(&objcg->list);
        spin_unlock_irqrestore(&css_set_lock, flags);
 
-- 
2.11.0