Commit 63876986 authored by Tejun Heo's avatar Tejun Heo

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: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarLi Zefan <lizefan@huawei.com>
parent a7c6d554
......@@ -209,9 +209,7 @@ static inline struct blkcg *bio_blkcg(struct bio *bio)
*/
static inline struct blkcg *blkcg_parent(struct blkcg *blkcg)
{
struct cgroup *pcg = blkcg->css.cgroup->parent;
return pcg ? cgroup_to_blkcg(pcg) : NULL;
return css_to_blkcg(css_parent(&blkcg->css));
}
/**
......
......@@ -646,6 +646,21 @@ struct cgroup_subsys {
#undef IS_SUBSYS_ENABLED
#undef SUBSYS
/**
* css_parent - find the parent css
* @css: the target cgroup_subsys_state
*
* Return the parent css of @css. This function is guaranteed to return
* non-NULL parent as long as @css isn't the root.
*/
static inline
struct cgroup_subsys_state *css_parent(struct cgroup_subsys_state *css)
{
struct cgroup *parent_cgrp = css->cgroup->parent;
return parent_cgrp ? parent_cgrp->subsys[css->ss->subsys_id] : NULL;
}
/**
* cgroup_css - obtain a cgroup's css for the specified subsystem
* @cgrp: the cgroup of interest
......
......@@ -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);
......
......@@ -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
......
......@@ -7114,12 +7114,9 @@ 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);
if (parent)
sched_online_group(tg, parent);
return 0;
}
......
......@@ -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();
}
......
......@@ -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)
......
......@@ -1524,10 +1524,8 @@ static unsigned long mem_cgroup_margin(struct mem_cgroup *memcg)
int mem_cgroup_swappiness(struct mem_cgroup *memcg)
{
struct cgroup *cgrp = memcg->css.cgroup;
/* root ? */
if (cgrp->parent == NULL)
if (!css_parent(&memcg->css))
return vm_swappiness;
return memcg->swappiness;
......@@ -5026,11 +5024,7 @@ static int mem_cgroup_hierarchy_write(struct cgroup *cont, struct cftype *cft,
{
int retval = 0;
struct mem_cgroup *memcg = mem_cgroup_from_cont(cont);
struct cgroup *parent = cont->parent;
struct mem_cgroup *parent_memcg = NULL;
if (parent)
parent_memcg = mem_cgroup_from_cont(parent);
struct mem_cgroup *parent_memcg = mem_cgroup_from_css(css_parent(&memcg->css));
mutex_lock(&memcg_create_mutex);
......@@ -5282,18 +5276,15 @@ static int mem_cgroup_write(struct cgroup *cont, struct cftype *cft,
static void memcg_get_hierarchical_limit(struct mem_cgroup *memcg,
unsigned long long *mem_limit, unsigned long long *memsw_limit)
{
struct cgroup *cgroup;
unsigned long long min_limit, min_memsw_limit, tmp;
min_limit = res_counter_read_u64(&memcg->res, RES_LIMIT);
min_memsw_limit = res_counter_read_u64(&memcg->memsw, RES_LIMIT);
cgroup = memcg->css.cgroup;
if (!memcg->use_hierarchy)
goto out;
while (cgroup->parent) {
cgroup = cgroup->parent;
memcg = mem_cgroup_from_cont(cgroup);
while (css_parent(&memcg->css)) {
memcg = mem_cgroup_from_css(css_parent(&memcg->css));
if (!memcg->use_hierarchy)
break;
tmp = res_counter_read_u64(&memcg->res, RES_LIMIT);
......@@ -5523,16 +5514,11 @@ static int mem_cgroup_swappiness_write(struct cgroup *cgrp, struct cftype *cft,
u64 val)
{
struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
struct mem_cgroup *parent;
if (val > 100)
return -EINVAL;
struct mem_cgroup *parent = mem_cgroup_from_css(css_parent(&memcg->css));
if (cgrp->parent == NULL)
if (val > 100 || !parent)
return -EINVAL;
parent = mem_cgroup_from_cont(cgrp->parent);
mutex_lock(&memcg_create_mutex);
/* If under hierarchy, only empty-root can set this value */
......@@ -5861,14 +5847,12 @@ static int mem_cgroup_oom_control_write(struct cgroup *cgrp,
struct cftype *cft, u64 val)
{
struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
struct mem_cgroup *parent;
struct mem_cgroup *parent = mem_cgroup_from_css(css_parent(&memcg->css));
/* cannot set to root cgroup and only 0 and 1 are allowed */
if (!cgrp->parent || !((val == 0) || (val == 1)))
if (!parent || !((val == 0) || (val == 1)))
return -EINVAL;
parent = mem_cgroup_from_cont(cgrp->parent);
mutex_lock(&memcg_create_mutex);
/* oom-kill-disable is a flag for subhierarchy. */
if ((parent->use_hierarchy) || memcg_has_children(memcg)) {
......@@ -6266,15 +6250,14 @@ free_out:
static int
mem_cgroup_css_online(struct cgroup *cont)
{
struct mem_cgroup *memcg, *parent;
struct mem_cgroup *memcg = mem_cgroup_from_cont(cont);
struct mem_cgroup *parent = mem_cgroup_from_css(css_parent(&memcg->css));
int error = 0;
if (!cont->parent)
if (!parent)
return 0;
mutex_lock(&memcg_create_mutex);
memcg = mem_cgroup_from_cont(cont);
parent = mem_cgroup_from_cont(cont->parent);
memcg->use_hierarchy = parent->use_hierarchy;
memcg->oom_kill_disable = parent->oom_kill_disable;
......
......@@ -50,9 +50,11 @@ static struct cgroup_subsys_state *cgrp_css_alloc(struct cgroup *cgrp)
static int cgrp_css_online(struct cgroup *cgrp)
{
if (cgrp->parent)
cgrp_cls_state(cgrp)->classid =
cgrp_cls_state(cgrp->parent)->classid;
struct cgroup_cls_state *cs = cgrp_cls_state(cgrp);
struct cgroup_cls_state *parent = css_cls_state(css_parent(&cs->css));
if (parent)
cs->classid = parent->classid;
return 0;
}
......
......@@ -198,13 +198,11 @@ static inline bool is_devcg_online(const struct dev_cgroup *devcg)
*/
static int devcgroup_online(struct cgroup *cgroup)
{
struct dev_cgroup *dev_cgroup, *parent_dev_cgroup = NULL;
struct dev_cgroup *dev_cgroup = cgroup_to_devcgroup(cgroup);
struct dev_cgroup *parent_dev_cgroup = css_to_devcgroup(css_parent(&dev_cgroup->css));
int ret = 0;
mutex_lock(&devcgroup_mutex);
dev_cgroup = cgroup_to_devcgroup(cgroup);
if (cgroup->parent)
parent_dev_cgroup = cgroup_to_devcgroup(cgroup->parent);
if (parent_dev_cgroup == NULL)
dev_cgroup->behavior = DEVCG_DEFAULT_ALLOW;
......@@ -394,12 +392,10 @@ static bool may_access(struct dev_cgroup *dev_cgroup,
static int parent_has_perm(struct dev_cgroup *childcg,
struct dev_exception_item *ex)
{
struct cgroup *pcg = childcg->css.cgroup->parent;
struct dev_cgroup *parent;
struct dev_cgroup *parent = css_to_devcgroup(css_parent(&childcg->css));
if (!pcg)
if (!parent)
return 1;
parent = cgroup_to_devcgroup(pcg);
return may_access(parent, ex, childcg->behavior);
}
......@@ -524,15 +520,11 @@ static int devcgroup_update_access(struct dev_cgroup *devcgroup,
char temp[12]; /* 11 + 1 characters needed for a u32 */
int count, rc = 0;
struct dev_exception_item ex;
struct cgroup *p = devcgroup->css.cgroup;
struct dev_cgroup *parent = NULL;
struct dev_cgroup *parent = css_to_devcgroup(css_parent(&devcgroup->css));
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
if (p->parent)
parent = cgroup_to_devcgroup(p->parent);
memset(&ex, 0, sizeof(ex));
b = buffer;
......
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