cgroup, memcg, cpuset: implement cgroup_taskset_for_each_leader()

[karo-tx-linux.git] / mm / memcontrol.c

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 9f331402e5025fd790b3ca340bdcb946c199d1a5..33c8dad6830f86b36eb8fca89f734e1b16f139a9 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4828,7 +4828,7 @@ static int mem_cgroup_can_attach(struct cgroup_subsys_state *css,
 {
        struct mem_cgroup *memcg = mem_cgroup_from_css(css);
        struct mem_cgroup *from;
-       struct task_struct *p;
+       struct task_struct *leader, *p;
        struct mm_struct *mm;
        unsigned long move_flags;
        int ret = 0;
@@ -4842,7 +4842,20 @@ static int mem_cgroup_can_attach(struct cgroup_subsys_state *css,
        if (!move_flags)
                return 0;
 
-       p = cgroup_taskset_first(tset);
+       /*
+        * Multi-process migrations only happen on the default hierarchy
+        * where charge immigration is not used.  Perform charge
+        * immigration if @tset contains a leader and whine if there are
+        * multiple.
+        */
+       p = NULL;
+       cgroup_taskset_for_each_leader(leader, tset) {
+               WARN_ON_ONCE(p);
+               p = leader;
+       }
+       if (!p)
+               return 0;
+
        from = mem_cgroup_from_task(p);
 
        VM_BUG_ON(from == memcg);