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 --- kernel/cgroup_freezer.c | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-) (limited to 'kernel/cgroup_freezer.c') diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c index 1db686e47a22..657a73cd44c4 100644 --- a/kernel/cgroup_freezer.c +++ b/kernel/cgroup_freezer.c @@ -62,11 +62,7 @@ static inline struct freezer *task_freezer(struct task_struct *task) static struct freezer *parent_freezer(struct freezer *freezer) { - struct cgroup *pcg = freezer->css.cgroup->parent; - - if (pcg) - return cgroup_freezer(pcg); - return NULL; + return css_freezer(css_parent(&freezer->css)); } bool cgroup_freezing(struct task_struct *task) @@ -234,7 +230,7 @@ static void freezer_fork(struct task_struct *task) * The root cgroup is non-freezable, so we can skip the * following check. */ - if (!freezer->css.cgroup->parent) + if (!parent_freezer(freezer)) goto out; spin_lock_irq(&freezer->lock); -- cgit v1.2.3