+ guarantee_online_mems(task_cs(tsk),&tsk->mems_allowed);
+}
+
+/*
+ * cpuset_change_task_nodemask - change task's mems_allowed and mempolicy
+ * @tsk: the task to change
+ * @newmems: new nodes that the task will be set
+ *
+ * In order to avoid seeing no nodes if the old and new nodes are disjoint,
+ * we structure updates as setting all new allowed nodes, then clearing newly
+ * disallowed ones.
+ */
+static void cpuset_change_task_nodemask(struct task_struct *tsk,
+ nodemask_t *newmems)
+{
+repeat:
+ /*
+ * Allow tasks that have access to memory reserves because they have
+ * been OOM killed to get memory anywhere.
+ */
+ if (unlikely(test_thread_flag(TIF_MEMDIE)))
+ return;
+ if (current->flags & PF_EXITING) /* Let dying task have memory */
+ return;
+
+ task_lock(tsk);
+ nodes_or(tsk->mems_allowed, tsk->mems_allowed, *newmems);
+ mpol_rebind_task(tsk, newmems, MPOL_REBIND_STEP1);
+
+
+ /*
+ * ensure checking ->mems_allowed_change_disable after setting all new
+ * allowed nodes.
+ *
+ * the read-side task can see an nodemask with new allowed nodes and
+ * old allowed nodes. and if it allocates page when cpuset clears newly
+ * disallowed ones continuous, it can see the new allowed bits.
+ *
+ * And if setting all new allowed nodes is after the checking, setting
+ * all new allowed nodes and clearing newly disallowed ones will be done
+ * continuous, and the read-side task may find no node to alloc page.
+ */
+ smp_mb();
+
+ /*
+ * Allocation of memory is very fast, we needn't sleep when waiting
+ * for the read-side.
+ */
+ while (ACCESS_ONCE(tsk->mems_allowed_change_disable)) {
+ task_unlock(tsk);
+ if (!task_curr(tsk))
+ yield();
+ goto repeat;
+ }
+
+ /*
+ * ensure checking ->mems_allowed_change_disable before clearing all new
+ * disallowed nodes.
+ *
+ * if clearing newly disallowed bits before the checking, the read-side
+ * task may find no node to alloc page.
+ */
+ smp_mb();
+
+ mpol_rebind_task(tsk, newmems, MPOL_REBIND_STEP2);
+ tsk->mems_allowed = *newmems;
+ task_unlock(tsk);
+}
+
+/*
+ * Update task's mems_allowed and rebind its mempolicy and vmas' mempolicy
+ * of it to cpuset's new mems_allowed, and migrate pages to new nodes if
+ * memory_migrate flag is set. Called with cgroup_mutex held.
+ */
+static void cpuset_change_nodemask(struct task_struct *p,
+ struct cgroup_scanner *scan)
+{
+ struct mm_struct *mm;
+ struct cpuset *cs;
+ int migrate;
+ const nodemask_t *oldmem = scan->data;
+ NODEMASK_ALLOC(nodemask_t, newmems, GFP_KERNEL);
+
+ if (!newmems)
+ return;
+
+ cs = cgroup_cs(scan->cg);
+ guarantee_online_mems(cs, newmems);
+
+ cpuset_change_task_nodemask(p, newmems);
+
+ NODEMASK_FREE(newmems);
+
+ mm = get_task_mm(p);
+ if (!mm)
+ return;
+
+ migrate = is_memory_migrate(cs);
+
+ mpol_rebind_mm(mm, &cs->mems_allowed);
+ if (migrate)
+ cpuset_migrate_mm(mm, oldmem, &cs->mems_allowed);
+ mmput(mm);
+}
+
+static void *cpuset_being_rebound;
+
+/**
+ * update_tasks_nodemask - Update the nodemasks of tasks in the cpuset.
+ * @cs: the cpuset in which each task's mems_allowed mask needs to be changed
+ * @oldmem: old mems_allowed of cpuset cs
+ * @heap: if NULL, defer allocating heap memory to cgroup_scan_tasks()
+ *
+ * Called with cgroup_mutex held
+ * No return value. It's guaranteed that cgroup_scan_tasks() always returns 0
+ * if @heap != NULL.
+ */
+static void update_tasks_nodemask(struct cpuset *cs, const nodemask_t *oldmem,
+ struct ptr_heap *heap)
+{
+ struct cgroup_scanner scan;
+
+ cpuset_being_rebound = cs; /* causes mpol_dup() rebind */
+
+ scan.cg = cs->css.cgroup;
+ scan.test_task = NULL;
+ scan.process_task = cpuset_change_nodemask;
+ scan.heap = heap;
+ scan.data = (nodemask_t *)oldmem;
+
+ /*
+ * The mpol_rebind_mm() call takes mmap_sem, which we couldn't
+ * take while holding tasklist_lock. Forks can happen - the
+ * mpol_dup() cpuset_being_rebound check will catch such forks,
+ * and rebind their vma mempolicies too. Because we still hold
+ * the global cgroup_mutex, we know that no other rebind effort
+ * will be contending for the global variable cpuset_being_rebound.
+ * It's ok if we rebind the same mm twice; mpol_rebind_mm()
+ * is idempotent. Also migrate pages in each mm to new nodes.
+ */
+ cgroup_scan_tasks(&scan);
+
+ /* We're done rebinding vmas to this cpuset's new mems_allowed. */
+ cpuset_being_rebound = NULL;