Memory controller: task migration

Allow tasks to migrate from one cgroup to the other.  We migrate
mm_struct's mem_cgroup only when the thread group id migrates.

Signed-off-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Cc: Pavel Emelianov <xemul@openvz.org>
Cc: Paul Menage <menage@google.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Kirill Korotaev <dev@sw.ru>
Cc: Herbert Poetzl <herbert@13thfloor.at>
Cc: David Rientjes <rientjes@google.com>
Cc: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index ebca767292dc2ad2aac09d47e1c819e600fa02ce..b25df2a9d024a5673cd573ef4fc8b0adc184f671 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -326,11 +326,46 @@ static int mem_cgroup_populate(struct cgroup_subsys *ss,
                                        ARRAY_SIZE(mem_cgroup_files));
 }
 
+static void mem_cgroup_move_task(struct cgroup_subsys *ss,
+                               struct cgroup *cont,
+                               struct cgroup *old_cont,
+                               struct task_struct *p)
+{
+       struct mm_struct *mm;
+       struct mem_cgroup *mem, *old_mem;
+
+       mm = get_task_mm(p);
+       if (mm == NULL)
+               return;
+
+       mem = mem_cgroup_from_cont(cont);
+       old_mem = mem_cgroup_from_cont(old_cont);
+
+       if (mem == old_mem)
+               goto out;
+
+       /*
+        * Only thread group leaders are allowed to migrate, the mm_struct is
+        * in effect owned by the leader
+        */
+       if (p->tgid != p->pid)
+               goto out;
+
+       css_get(&mem->css);
+       rcu_assign_pointer(mm->mem_cgroup, mem);
+       css_put(&old_mem->css);
+
+out:
+       mmput(mm);
+       return;
+}
+
 struct cgroup_subsys mem_cgroup_subsys = {
        .name = "memory",
        .subsys_id = mem_cgroup_subsys_id,
        .create = mem_cgroup_create,
        .destroy = mem_cgroup_destroy,
        .populate = mem_cgroup_populate,
+       .attach = mem_cgroup_move_task,
        .early_init = 1,
 };