cgroups: Add an API to attach a task to current task's cgroup

Add a new kernel API to attach a task to current task's cgroup
in all the active hierarchies.

Signed-off-by: Sridhar Samudrala <sri@us.ibm.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Paul Menage <menage@google.com>
Acked-by: Li Zefan <lizf@cn.fujitsu.com>

1 files changed, 23 insertions, 0 deletions

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 422cb19f156e..37642ad9cca8 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1788,6 +1788,29 @@ out:
         return retval;
 }
 
+/**
+ * cgroup_attach_task_current_cg - attach task 'tsk' to current task's cgroup
+ * @tsk: the task to be attached
+ */
+int cgroup_attach_task_current_cg(struct task_struct *tsk)
+{
+        struct cgroupfs_root *root;
+        struct cgroup *cur_cg;
+        int retval = 0;
+
+        cgroup_lock();
+        for_each_active_root(root) {
+                cur_cg = task_cgroup_from_root(current, root);
+                retval = cgroup_attach_task(cur_cg, tsk);
+                if (retval)
+                        break;
+        }
+        cgroup_unlock();
+
+        return retval;
+}
+EXPORT_SYMBOL_GPL(cgroup_attach_task_current_cg);
+
 /*
  * Attach task with pid 'pid' to cgroup 'cgrp'. Call with cgroup_mutex
  * held. May take task_lock of task