1 files changed, 49 insertions, 22 deletions

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 3e945fcd8179..41989ab4db57 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -287,6 +287,8 @@ static struct cpuset top_cpuset = {
 static DEFINE_MUTEX(cpuset_mutex);
 static DEFINE_SPINLOCK(callback_lock);
 
+static struct workqueue_struct *cpuset_migrate_mm_wq;
+
 /*
  * CPU / memory hotplug is handled asynchronously.
  */
@@ -972,31 +974,51 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
 }
 
 /*
- * cpuset_migrate_mm
- *
- *    Migrate memory region from one set of nodes to another.
- *
- *    Temporarilly set tasks mems_allowed to target nodes of migration,
- *    so that the migration code can allocate pages on these nodes.
- *
- *    While the mm_struct we are migrating is typically from some
- *    other task, the task_struct mems_allowed that we are hacking
- *    is for our current task, which must allocate new pages for that
- *    migrating memory region.
+ * Migrate memory region from one set of nodes to another.  This is
+ * performed asynchronously as it can be called from process migration path
+ * holding locks involved in process management.  All mm migrations are
+ * performed in the queued order and can be waited for by flushing
+ * cpuset_migrate_mm_wq.
  */
 
+struct cpuset_migrate_mm_work {
+        struct work_struct      work;
+        struct mm_struct        *mm;
+        nodemask_t              from;
+        nodemask_t              to;
+};
+
+static void cpuset_migrate_mm_workfn(struct work_struct *work)
+{
+        struct cpuset_migrate_mm_work *mwork =
+                container_of(work, struct cpuset_migrate_mm_work, work);
+
+        /* on a wq worker, no need to worry about %current's mems_allowed */
+        do_migrate_pages(mwork->mm, &mwork->from, &mwork->to, MPOL_MF_MOVE_ALL);
+        mmput(mwork->mm);
+        kfree(mwork);
+}
+
 static void cpuset_migrate_mm(struct mm_struct *mm, const nodemask_t *from,
                                                         const nodemask_t *to)
 {
-        struct task_struct *tsk = current;
-
-        tsk->mems_allowed = *to;
+        struct cpuset_migrate_mm_work *mwork;
 
-        do_migrate_pages(mm, from, to, MPOL_MF_MOVE_ALL);
+        mwork = kzalloc(sizeof(*mwork), GFP_KERNEL);
+        if (mwork) {
+                mwork->mm = mm;
+                mwork->from = *from;
+                mwork->to = *to;
+                INIT_WORK(&mwork->work, cpuset_migrate_mm_workfn);
+                queue_work(cpuset_migrate_mm_wq, &mwork->work);
+        } else {
+                mmput(mm);
+        }
+}
 
-        rcu_read_lock();
-        guarantee_online_mems(task_cs(tsk), &tsk->mems_allowed);
-        rcu_read_unlock();
+void cpuset_post_attach_flush(void)
+{
+        flush_workqueue(cpuset_migrate_mm_wq);
 }
 
 /*
@@ -1097,7 +1119,8 @@ static void update_tasks_nodemask(struct cpuset *cs)
                 mpol_rebind_mm(mm, &cs->mems_allowed);
                 if (migrate)
                         cpuset_migrate_mm(mm, &cs->old_mems_allowed, &newmems);
-                mmput(mm);
+                else
+                        mmput(mm);
         }
         css_task_iter_end(&it);
 
@@ -1545,11 +1568,11 @@ static void cpuset_attach(struct cgroup_taskset *tset)
                          * @old_mems_allowed is the right nodesets that we
                          * migrate mm from.
                          */
-                        if (is_memory_migrate(cs)) {
+                        if (is_memory_migrate(cs))
                                 cpuset_migrate_mm(mm, &oldcs->old_mems_allowed,
                                                   &cpuset_attach_nodemask_to);
-                        }
-                        mmput(mm);
+                        else
+                                mmput(mm);
                 }
         }
 
@@ -1714,6 +1737,7 @@ out_unlock:
         mutex_unlock(&cpuset_mutex);
         kernfs_unbreak_active_protection(of->kn);
         css_put(&cs->css);
+        flush_workqueue(cpuset_migrate_mm_wq);
         return retval ?: nbytes;
 }
 
@@ -2359,6 +2383,9 @@ void __init cpuset_init_smp(void)
         top_cpuset.effective_mems = node_states[N_MEMORY];
 
         register_hotmemory_notifier(&cpuset_track_online_nodes_nb);
+
+        cpuset_migrate_mm_wq = alloc_ordered_workqueue("cpuset_migrate_mm", 0);
+        BUG_ON(!cpuset_migrate_mm_wq);
 }
 
 /**