From 6387698699afd72d6304566fb6ccf84bffe07c56 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Thu, 8 Aug 2013 20:11:23 -0400 Subject: cgroup: add css_parent() Currently, controllers have to explicitly follow the cgroup hierarchy to find the parent of a given css. cgroup is moving towards using cgroup_subsys_state as the main controller interface construct, so let's provide a way to climb the hierarchy using just csses. This patch implements css_parent() which, given a css, returns its parent. The function is guarnateed to valid non-NULL parent css as long as the target css is not at the top of the hierarchy. freezer, cpuset, cpu, cpuacct, hugetlb, memory, net_cls and devices are converted to use css_parent() instead of accessing cgroup->parent directly. * __parent_ca() is dropped from cpuacct and its usage is replaced with parent_ca(). The only difference between the two was NULL test on cgroup->parent which is now embedded in css_parent() making the distinction moot. Note that eventually a css->parent field will be added to css and the NULL check in css_parent() will go away. This patch shouldn't cause any behavior differences. Signed-off-by: Tejun Heo Acked-by: Li Zefan --- mm/hugetlb_cgroup.c | 6 +----- 1 file changed, 1 insertion(+), 5 deletions(-) (limited to 'mm/hugetlb_cgroup.c') diff --git a/mm/hugetlb_cgroup.c b/mm/hugetlb_cgroup.c index 95585a0b9c8..57ecb5d2513 100644 --- a/mm/hugetlb_cgroup.c +++ b/mm/hugetlb_cgroup.c @@ -59,11 +59,7 @@ static inline bool hugetlb_cgroup_is_root(struct hugetlb_cgroup *h_cg) static inline struct hugetlb_cgroup * parent_hugetlb_cgroup(struct hugetlb_cgroup *h_cg) { - struct cgroup *parent = h_cg->css.cgroup->parent; - - if (!parent) - return NULL; - return hugetlb_cgroup_from_cgroup(parent); + return hugetlb_cgroup_from_css(css_parent(&h_cg->css)); } static inline bool hugetlb_cgroup_have_usage(struct hugetlb_cgroup *h_cg) -- cgit v1.2.3-18-g5258