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    Subject[PATCH 3/8] cgroup: add function to get task's cgroup
    Date
    From: Aditya Kali <adityakali@google.com>

    get_task_cgroup() returns the (reference counted) cgroup of the
    given task.

    Signed-off-by: Aditya Kali <adityakali@google.com>
    Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
    ---
    include/linux/cgroup.h | 1 +
    kernel/cgroup.c | 25 +++++++++++++++++++++++++
    2 files changed, 26 insertions(+)

    diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
    index 22e3754..29f0b02 100644
    --- a/include/linux/cgroup.h
    +++ b/include/linux/cgroup.h
    @@ -326,6 +326,7 @@ static inline bool css_tryget_online(struct cgroup_subsys_state *css)
    return percpu_ref_tryget_live(&css->refcnt);
    return true;
    }
    +struct cgroup *get_task_cgroup(struct task_struct *task);

    /**
    * css_put - put a css reference
    diff --git a/kernel/cgroup.c b/kernel/cgroup.c
    index f1603c1..e29c346 100644
    --- a/kernel/cgroup.c
    +++ b/kernel/cgroup.c
    @@ -2210,6 +2210,31 @@ char *task_cgroup_path(struct task_struct *task, char *buf, size_t buflen)
    }
    EXPORT_SYMBOL_GPL(task_cgroup_path);

    +/*
    + * get_task_cgroup - returns the cgroup of the task in the default cgroup
    + * hierarchy.
    + *
    + * @task: target task
    + * This function returns the @task's cgroup on the default cgroup hierarchy. The
    + * returned cgroup has its reference incremented (by calling cgroup_get()). So
    + * the caller must cgroup_put() the obtained reference once it is done with it.
    + */
    +struct cgroup *get_task_cgroup(struct task_struct *task)
    +{
    + struct cgroup *cgrp;
    +
    + mutex_lock(&cgroup_mutex);
    + spin_lock_bh(&css_set_lock);
    +
    + cgrp = task_cgroup_from_root(task, &cgrp_dfl_root);
    + cgroup_get(cgrp);
    +
    + spin_unlock_bh(&css_set_lock);
    + mutex_unlock(&cgroup_mutex);
    + return cgrp;
    +}
    +EXPORT_SYMBOL_GPL(get_task_cgroup);
    +
    /* used to track tasks and other necessary states during migration */
    struct cgroup_taskset {
    /* the src and dst cset list running through cset->mg_node */
    --
    1.7.9.5


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