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 ++------ kernel/cpuset.c | 6 +----- kernel/sched/core.c | 9 +++------ kernel/sched/cpuacct.c | 11 ++--------- 4 files changed, 8 insertions(+), 26 deletions(-) (limited to 'kernel') 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); diff --git a/kernel/cpuset.c b/kernel/cpuset.c index 6e9cbdde25bd..259a4af37e69 100644 --- a/kernel/cpuset.c +++ b/kernel/cpuset.c @@ -133,11 +133,7 @@ static inline struct cpuset *task_cs(struct task_struct *task) static inline struct cpuset *parent_cs(struct cpuset *cs) { - struct cgroup *pcgrp = cs->css.cgroup->parent; - - if (pcgrp) - return cgroup_cs(pcgrp); - return NULL; + return css_cs(css_parent(&cs->css)); } #ifdef CONFIG_NUMA diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 5bccb0277129..7a10742b389a 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -7114,13 +7114,10 @@ static struct cgroup_subsys_state *cpu_cgroup_css_alloc(struct cgroup *cgrp) static int cpu_cgroup_css_online(struct cgroup *cgrp) { struct task_group *tg = cgroup_tg(cgrp); - struct task_group *parent; + struct task_group *parent = css_tg(css_parent(&tg->css)); - if (!cgrp->parent) - return 0; - - parent = cgroup_tg(cgrp->parent); - sched_online_group(tg, parent); + if (parent) + sched_online_group(tg, parent); return 0; } diff --git a/kernel/sched/cpuacct.c b/kernel/sched/cpuacct.c index 8ccfa10cc89f..f6926a149a71 100644 --- a/kernel/sched/cpuacct.c +++ b/kernel/sched/cpuacct.c @@ -50,16 +50,9 @@ static inline struct cpuacct *task_ca(struct task_struct *tsk) return css_ca(task_css(tsk, cpuacct_subsys_id)); } -static inline struct cpuacct *__parent_ca(struct cpuacct *ca) -{ - return cgroup_ca(ca->css.cgroup->parent); -} - static inline struct cpuacct *parent_ca(struct cpuacct *ca) { - if (!ca->css.cgroup->parent) - return NULL; - return cgroup_ca(ca->css.cgroup->parent); + return css_ca(css_parent(&ca->css)); } static DEFINE_PER_CPU(u64, root_cpuacct_cpuusage); @@ -284,7 +277,7 @@ void cpuacct_account_field(struct task_struct *p, int index, u64 val) while (ca != &root_cpuacct) { kcpustat = this_cpu_ptr(ca->cpustat); kcpustat->cpustat[index] += val; - ca = __parent_ca(ca); + ca = parent_ca(ca); } rcu_read_unlock(); } -- cgit v1.2.3