[PATCH] mm: swap: use mem_cgroup_is_root() instead of deferencing css->parent

[Yang Shi]

mem_cgroup_is_root() is preferred API to check if memcg is root or not.
Use it instead of deferencing css->parent.

Cc: Huang Ying <ying.huang@xxxxxxxxx>
Cc: Tim Chen <tim.c.chen@xxxxxxxxx>
Signed-off-by: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx>
---
 include/linux/swap.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/swap.h b/include/linux/swap.h
index a8f6d5d..8739063 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -623,7 +623,7 @@ static inline int mem_cgroup_swappiness(struct mem_cgroup *memcg)
 		return vm_swappiness;
 
 	/* root ? */
-	if (mem_cgroup_disabled() || !memcg->css.parent)
+	if (mem_cgroup_disabled() || mem_cgroup_is_root(memcg))
 		return vm_swappiness;
 
 	return memcg->swappiness;
-- 
1.8.3.1