1 files changed, 23 insertions, 5 deletions

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index f783af900208..306ad0ed19ef 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -2810,10 +2810,28 @@ void css_task_iter_end(struct css_task_iter *it)
  */
 int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from)
 {
+        LIST_HEAD(preloaded_csets);
+        struct cgrp_cset_link *link;
         struct css_task_iter it;
         struct task_struct *task;
-        int ret = 0;
+        int ret;
+
+        mutex_lock(&cgroup_mutex);
+
+        /* all tasks in @from are being moved, all csets are source */
+        down_read(&css_set_rwsem);
+        list_for_each_entry(link, &from->cset_links, cset_link)
+                cgroup_migrate_add_src(link->cset, to, &preloaded_csets);
+        up_read(&css_set_rwsem);
 
+        ret = cgroup_migrate_prepare_dst(to, &preloaded_csets);
+        if (ret)
+                goto out_err;
+
+        /*
+         * Migrate tasks one-by-one until @form is empty.  This fails iff
+         * ->can_attach() fails.
+         */
         do {
                 css_task_iter_start(&from->dummy_css, &it);
                 task = css_task_iter_next(&it);
@@ -2822,13 +2840,13 @@ int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from)
                 css_task_iter_end(&it);
 
                 if (task) {
-                        mutex_lock(&cgroup_mutex);
-                        ret = cgroup_attach_task(to, task, false);
-                        mutex_unlock(&cgroup_mutex);
+                        ret = cgroup_migrate(to, task, false);
                         put_task_struct(task);
                 }
         } while (task && !ret);
-
+out_err:
+        cgroup_migrate_finish(&preloaded_csets);
+        mutex_unlock(&cgroup_mutex);
         return ret;
 }