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cgroup: separate out cset_group_from_root() from task_cgroup_from_root()

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This will be used by the planned migration path update.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
This commit is contained in:
Tejun Heo 2014-02-25 10:04:02 -05:00
parent b3dc094e93
commit ceb6a081f6
1 changed files with 17 additions and 12 deletions
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29
kernel/cgroup.c
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@ -758,25 +758,15 @@ static void cgroup_destroy_root(struct cgroupfs_root *root)
cgroup_free_root(root);
}
/*
* Return the cgroup for "task" from the given hierarchy. Must be
* called with cgroup_mutex and css_set_rwsem held.
*/
static struct cgroup *task_cgroup_from_root(struct task_struct *task,
/* look up cgroup associated with given css_set on the specified hierarchy */
static struct cgroup *cset_cgroup_from_root(struct css_set *cset,
struct cgroupfs_root *root)
{
struct css_set *cset;
struct cgroup *res = NULL;
lockdep_assert_held(&cgroup_mutex);
lockdep_assert_held(&css_set_rwsem);
/*
* No need to lock the task - since we hold cgroup_mutex the
* task can't change groups, so the only thing that can happen
* is that it exits and its css is set back to init_css_set.
*/
cset = task_css_set(task);
if (cset == &init_css_set) {
res = &root->top_cgroup;
} else {
@ -796,6 +786,21 @@ static struct cgroup *task_cgroup_from_root(struct task_struct *task,
return res;
}
/*
* Return the cgroup for "task" from the given hierarchy. Must be
* called with cgroup_mutex and css_set_rwsem held.
*/
static struct cgroup *task_cgroup_from_root(struct task_struct *task,
struct cgroupfs_root *root)
{
/*
* No need to lock the task - since we hold cgroup_mutex the
* task can't change groups, so the only thing that can happen
* is that it exits and its css is set back to init_css_set.
*/
return cset_cgroup_from_root(task_css_set(task), root);
}
/*
* There is one global cgroup mutex. We also require taking
* task_lock() when dereferencing a task's cgroup subsys pointers.