1 files changed, 296 insertions, 110 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 9be3cf8a5da4..9a99cfaf0a19 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -89,7 +89,10 @@ enum mem_cgroup_stat_index {
 	MEM_CGROUP_STAT_PGPGIN_COUNT,	/* # of pages paged in */
 	MEM_CGROUP_STAT_PGPGOUT_COUNT,	/* # of pages paged out */
 	MEM_CGROUP_STAT_SWAPOUT, /* # of pages, swapped out */
-	MEM_CGROUP_EVENTS,	/* incremented at every  pagein/pageout */
+	MEM_CGROUP_STAT_DATA, /* end of data requires synchronization */
+	/* incremented at every  pagein/pageout */
+	MEM_CGROUP_EVENTS = MEM_CGROUP_STAT_DATA,
+	MEM_CGROUP_ON_MOVE,	/* someone is moving account between groups */
 
 	MEM_CGROUP_STAT_NSTATS,
 };
@@ -254,6 +257,12 @@ struct mem_cgroup {
 	 * percpu counter.
 	 */
 	struct mem_cgroup_stat_cpu *stat;
+	/*
+	 * used when a cpu is offlined or other synchronizations
+	 * See mem_cgroup_read_stat().
+	 */
+	struct mem_cgroup_stat_cpu nocpu_base;
+	spinlock_t pcp_counter_lock;
 };
 
 /* Stuffs for move charges at task migration. */
@@ -530,14 +539,40 @@ mem_cgroup_largest_soft_limit_node(struct mem_cgroup_tree_per_zone *mctz)
 	return mz;
 }
 
+/*
+ * Implementation Note: reading percpu statistics for memcg.
+ *
+ * Both of vmstat[] and percpu_counter has threshold and do periodic
+ * synchronization to implement "quick" read. There are trade-off between
+ * reading cost and precision of value. Then, we may have a chance to implement
+ * a periodic synchronizion of counter in memcg's counter.
+ *
+ * But this _read() function is used for user interface now. The user accounts
+ * memory usage by memory cgroup and he _always_ requires exact value because
+ * he accounts memory. Even if we provide quick-and-fuzzy read, we always
+ * have to visit all online cpus and make sum. So, for now, unnecessary
+ * synchronization is not implemented. (just implemented for cpu hotplug)
+ *
+ * If there are kernel internal actions which can make use of some not-exact
+ * value, and reading all cpu value can be performance bottleneck in some
+ * common workload, threashold and synchonization as vmstat[] should be
+ * implemented.
+ */
 static s64 mem_cgroup_read_stat(struct mem_cgroup *mem,
 		enum mem_cgroup_stat_index idx)
 {
 	int cpu;
 	s64 val = 0;
 
-	for_each_possible_cpu(cpu)
+	get_online_cpus();
+	for_each_online_cpu(cpu)
 		val += per_cpu(mem->stat->count[idx], cpu);
+#ifdef CONFIG_HOTPLUG_CPU
+	spin_lock(&mem->pcp_counter_lock);
+	val += mem->nocpu_base.count[idx];
+	spin_unlock(&mem->pcp_counter_lock);
+#endif
+	put_online_cpus();
 	return val;
 }
 
@@ -659,40 +694,83 @@ static struct mem_cgroup *try_get_mem_cgroup_from_mm(struct mm_struct *mm)
 	return mem;
 }
 
-/*
- * Call callback function against all cgroup under hierarchy tree.
- */
-static int mem_cgroup_walk_tree(struct mem_cgroup *root, void *data,
-			  int (*func)(struct mem_cgroup *, void *))
+/* The caller has to guarantee "mem" exists before calling this */
+static struct mem_cgroup *mem_cgroup_start_loop(struct mem_cgroup *mem)
 {
-	int found, ret, nextid;
 	struct cgroup_subsys_state *css;
-	struct mem_cgroup *mem;
-
-	if (!root->use_hierarchy)
-		return (*func)(root, data);
+	int found;
 
-	nextid = 1;
-	do {
-		ret = 0;
+	if (!mem) /* ROOT cgroup has the smallest ID */
+		return root_mem_cgroup; /*css_put/get against root is ignored*/
+	if (!mem->use_hierarchy) {
+		if (css_tryget(&mem->css))
+			return mem;
+		return NULL;
+	}
+	rcu_read_lock();
+	/*
+	 * searching a memory cgroup which has the smallest ID under given
+	 * ROOT cgroup. (ID >= 1)
+	 */
+	css = css_get_next(&mem_cgroup_subsys, 1, &mem->css, &found);
+	if (css && css_tryget(css))
+		mem = container_of(css, struct mem_cgroup, css);
+	else
 		mem = NULL;
+	rcu_read_unlock();
+	return mem;
+}
+
+static struct mem_cgroup *mem_cgroup_get_next(struct mem_cgroup *iter,
+					struct mem_cgroup *root,
+					bool cond)
+{
+	int nextid = css_id(&iter->css) + 1;
+	int found;
+	int hierarchy_used;
+	struct cgroup_subsys_state *css;
+
+	hierarchy_used = iter->use_hierarchy;
 
+	css_put(&iter->css);
+	/* If no ROOT, walk all, ignore hierarchy */
+	if (!cond || (root && !hierarchy_used))
+		return NULL;
+
+	if (!root)
+		root = root_mem_cgroup;
+
+	do {
+		iter = NULL;
 		rcu_read_lock();
-		css = css_get_next(&mem_cgroup_subsys, nextid, &root->css,
-				   &found);
+
+		css = css_get_next(&mem_cgroup_subsys, nextid,
+				&root->css, &found);
 		if (css && css_tryget(css))
-			mem = container_of(css, struct mem_cgroup, css);
+			iter = container_of(css, struct mem_cgroup, css);
 		rcu_read_unlock();
-
-		if (mem) {
-			ret = (*func)(mem, data);
-			css_put(&mem->css);
-		}
+		/* If css is NULL, no more cgroups will be found */
 		nextid = found + 1;
-	} while (!ret && css);
+	} while (css && !iter);
 
-	return ret;
+	return iter;
 }
+/*
+ * for_eacn_mem_cgroup_tree() for visiting all cgroup under tree. Please
+ * be careful that "break" loop is not allowed. We have reference count.
+ * Instead of that modify "cond" to be false and "continue" to exit the loop.
+ */
+#define for_each_mem_cgroup_tree_cond(iter, root, cond)	\
+	for (iter = mem_cgroup_start_loop(root);\
+	     iter != NULL;\
+	     iter = mem_cgroup_get_next(iter, root, cond))
+
+#define for_each_mem_cgroup_tree(iter, root) \
+	for_each_mem_cgroup_tree_cond(iter, root, true)
+
+#define for_each_mem_cgroup_all(iter) \
+	for_each_mem_cgroup_tree_cond(iter, NULL, true)
+
 
 static inline bool mem_cgroup_is_root(struct mem_cgroup *mem)
 {
@@ -1051,7 +1129,52 @@ static unsigned int get_swappiness(struct mem_cgroup *memcg)
 	return swappiness;
 }
 
-/* A routine for testing mem is not under move_account */
+static void mem_cgroup_start_move(struct mem_cgroup *mem)
+{
+	int cpu;
+
+	get_online_cpus();
+	spin_lock(&mem->pcp_counter_lock);
+	for_each_online_cpu(cpu)
+		per_cpu(mem->stat->count[MEM_CGROUP_ON_MOVE], cpu) += 1;
+	mem->nocpu_base.count[MEM_CGROUP_ON_MOVE] += 1;
+	spin_unlock(&mem->pcp_counter_lock);
+	put_online_cpus();
+
+	synchronize_rcu();
+}
+
+static void mem_cgroup_end_move(struct mem_cgroup *mem)
+{
+	int cpu;
+
+	if (!mem)
+		return;
+	get_online_cpus();
+	spin_lock(&mem->pcp_counter_lock);
+	for_each_online_cpu(cpu)
+		per_cpu(mem->stat->count[MEM_CGROUP_ON_MOVE], cpu) -= 1;
+	mem->nocpu_base.count[MEM_CGROUP_ON_MOVE] -= 1;
+	spin_unlock(&mem->pcp_counter_lock);
+	put_online_cpus();
+}
+/*
+ * 2 routines for checking "mem" is under move_account() or not.
+ *
+ * mem_cgroup_stealed() - checking a cgroup is mc.from or not. This is used
+ *			  for avoiding race in accounting. If true,
+ *			  pc->mem_cgroup may be overwritten.
+ *
+ * mem_cgroup_under_move() - checking a cgroup is mc.from or mc.to or
+ *			  under hierarchy of moving cgroups. This is for
+ *			  waiting at hith-memory prressure caused by "move".
+ */
+
+static bool mem_cgroup_stealed(struct mem_cgroup *mem)
+{
+	VM_BUG_ON(!rcu_read_lock_held());
+	return this_cpu_read(mem->stat->count[MEM_CGROUP_ON_MOVE]) > 0;
+}
 
 static bool mem_cgroup_under_move(struct mem_cgroup *mem)
 {
@@ -1092,13 +1215,6 @@ static bool mem_cgroup_wait_acct_move(struct mem_cgroup *mem)
 	return false;
 }
 
-static int mem_cgroup_count_children_cb(struct mem_cgroup *mem, void *data)
-{
-	int *val = data;
-	(*val)++;
-	return 0;
-}
-
 /**
  * mem_cgroup_print_oom_info: Called from OOM with tasklist_lock held in read mode.
  * @memcg: The memory cgroup that went over limit
@@ -1173,7 +1289,10 @@ done:
 static int mem_cgroup_count_children(struct mem_cgroup *mem)
 {
 	int num = 0;
- 	mem_cgroup_walk_tree(mem, &num, mem_cgroup_count_children_cb);
+	struct mem_cgroup *iter;
+
+	for_each_mem_cgroup_tree(iter, mem)
+		num++;
 	return num;
 }
 
@@ -1322,49 +1441,39 @@ static int mem_cgroup_hierarchical_reclaim(struct mem_cgroup *root_mem,
 	return total;
 }
 
-static int mem_cgroup_oom_lock_cb(struct mem_cgroup *mem, void *data)
-{
-	int *val = (int *)data;
-	int x;
-	/*
-	 * Logically, we can stop scanning immediately when we find
-	 * a memcg is already locked. But condidering unlock ops and
-	 * creation/removal of memcg, scan-all is simple operation.
-	 */
-	x = atomic_inc_return(&mem->oom_lock);
-	*val = max(x, *val);
-	return 0;
-}
 /*
  * Check OOM-Killer is already running under our hierarchy.
  * If someone is running, return false.
  */
 static bool mem_cgroup_oom_lock(struct mem_cgroup *mem)
 {
-	int lock_count = 0;
+	int x, lock_count = 0;
+	struct mem_cgroup *iter;
 
-	mem_cgroup_walk_tree(mem, &lock_count, mem_cgroup_oom_lock_cb);
+	for_each_mem_cgroup_tree(iter, mem) {
+		x = atomic_inc_return(&iter->oom_lock);
+		lock_count = max(x, lock_count);
+	}
 
 	if (lock_count == 1)
 		return true;
 	return false;
 }
 
-static int mem_cgroup_oom_unlock_cb(struct mem_cgroup *mem, void *data)
+static int mem_cgroup_oom_unlock(struct mem_cgroup *mem)
 {
+	struct mem_cgroup *iter;
+
 	/*
 	 * When a new child is created while the hierarchy is under oom,
 	 * mem_cgroup_oom_lock() may not be called. We have to use
 	 * atomic_add_unless() here.
 	 */
-	atomic_add_unless(&mem->oom_lock, -1, 0);
+	for_each_mem_cgroup_tree(iter, mem)
+		atomic_add_unless(&iter->oom_lock, -1, 0);
 	return 0;
 }
 
-static void mem_cgroup_oom_unlock(struct mem_cgroup *mem)
-{
-	mem_cgroup_walk_tree(mem, NULL,	mem_cgroup_oom_unlock_cb);
-}
 
 static DEFINE_MUTEX(memcg_oom_mutex);
 static DECLARE_WAIT_QUEUE_HEAD(memcg_oom_waitq);
@@ -1462,34 +1571,73 @@ bool mem_cgroup_handle_oom(struct mem_cgroup *mem, gfp_t mask)
 /*
  * Currently used to update mapped file statistics, but the routine can be
  * generalized to update other statistics as well.
+ *
+ * Notes: Race condition
+ *
+ * We usually use page_cgroup_lock() for accessing page_cgroup member but
+ * it tends to be costly. But considering some conditions, we doesn't need
+ * to do so _always_.
+ *
+ * Considering "charge", lock_page_cgroup() is not required because all
+ * file-stat operations happen after a page is attached to radix-tree. There
+ * are no race with "charge".
+ *
+ * Considering "uncharge", we know that memcg doesn't clear pc->mem_cgroup
+ * at "uncharge" intentionally. So, we always see valid pc->mem_cgroup even
+ * if there are race with "uncharge". Statistics itself is properly handled
+ * by flags.
+ *
+ * Considering "move", this is an only case we see a race. To make the race
+ * small, we check MEM_CGROUP_ON_MOVE percpu value and detect there are
+ * possibility of race condition. If there is, we take a lock.
  */
-void mem_cgroup_update_file_mapped(struct page *page, int val)
+
+static void mem_cgroup_update_file_stat(struct page *page, int idx, int val)
 {
 	struct mem_cgroup *mem;
-	struct page_cgroup *pc;
+	struct page_cgroup *pc = lookup_page_cgroup(page);
+	bool need_unlock = false;
 
-	pc = lookup_page_cgroup(page);
 	if (unlikely(!pc))
 		return;
 
-	lock_page_cgroup(pc);
+	rcu_read_lock();
 	mem = pc->mem_cgroup;
-	if (!mem || !PageCgroupUsed(pc))
-		goto done;
+	if (unlikely(!mem || !PageCgroupUsed(pc)))
+		goto out;
+	/* pc->mem_cgroup is unstable ? */
+	if (unlikely(mem_cgroup_stealed(mem))) {
+		/* take a lock against to access pc->mem_cgroup */
+		lock_page_cgroup(pc);
+		need_unlock = true;
+		mem = pc->mem_cgroup;
+		if (!mem || !PageCgroupUsed(pc))
+			goto out;
+	}
 
-	/*
-	 * Preemption is already disabled. We can use __this_cpu_xxx
-	 */
-	if (val > 0) {
-		__this_cpu_inc(mem->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
-		SetPageCgroupFileMapped(pc);
-	} else {
-		__this_cpu_dec(mem->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
-		ClearPageCgroupFileMapped(pc);
+	this_cpu_add(mem->stat->count[idx], val);
+
+	switch (idx) {
+	case MEM_CGROUP_STAT_FILE_MAPPED:
+		if (val > 0)
+			SetPageCgroupFileMapped(pc);
+		else if (!page_mapped(page))
+			ClearPageCgroupFileMapped(pc);
+		break;
+	default:
+		BUG();
 	}
 
-done:
-	unlock_page_cgroup(pc);
+out:
+	if (unlikely(need_unlock))
+		unlock_page_cgroup(pc);
+	rcu_read_unlock();
+	return;
+}
+
+void mem_cgroup_update_file_mapped(struct page *page, int val)
+{
+	mem_cgroup_update_file_stat(page, MEM_CGROUP_STAT_FILE_MAPPED, val);
 }
 
 /*
@@ -1605,15 +1753,55 @@ static void drain_all_stock_sync(void)
 	atomic_dec(&memcg_drain_count);
 }
 
-static int __cpuinit memcg_stock_cpu_callback(struct notifier_block *nb,
+/*
+ * This function drains percpu counter value from DEAD cpu and
+ * move it to local cpu. Note that this function can be preempted.
+ */
+static void mem_cgroup_drain_pcp_counter(struct mem_cgroup *mem, int cpu)
+{
+	int i;
+
+	spin_lock(&mem->pcp_counter_lock);
+	for (i = 0; i < MEM_CGROUP_STAT_DATA; i++) {
+		s64 x = per_cpu(mem->stat->count[i], cpu);
+
+		per_cpu(mem->stat->count[i], cpu) = 0;
+		mem->nocpu_base.count[i] += x;
+	}
+	/* need to clear ON_MOVE value, works as a kind of lock. */
+	per_cpu(mem->stat->count[MEM_CGROUP_ON_MOVE], cpu) = 0;
+	spin_unlock(&mem->pcp_counter_lock);
+}
+
+static void synchronize_mem_cgroup_on_move(struct mem_cgroup *mem, int cpu)
+{
+	int idx = MEM_CGROUP_ON_MOVE;
+
+	spin_lock(&mem->pcp_counter_lock);
+	per_cpu(mem->stat->count[idx], cpu) = mem->nocpu_base.count[idx];
+	spin_unlock(&mem->pcp_counter_lock);
+}
+
+static int __cpuinit memcg_cpu_hotplug_callback(struct notifier_block *nb,
 					unsigned long action,
 					void *hcpu)
 {
 	int cpu = (unsigned long)hcpu;
 	struct memcg_stock_pcp *stock;
+	struct mem_cgroup *iter;
+
+	if ((action == CPU_ONLINE)) {
+		for_each_mem_cgroup_all(iter)
+			synchronize_mem_cgroup_on_move(iter, cpu);
+		return NOTIFY_OK;
+	}
 
-	if (action != CPU_DEAD)
+	if ((action != CPU_DEAD) || action != CPU_DEAD_FROZEN)
 		return NOTIFY_OK;
+
+	for_each_mem_cgroup_all(iter)
+		mem_cgroup_drain_pcp_counter(iter, cpu);
+
 	stock = &per_cpu(memcg_stock, cpu);
 	drain_stock(stock);
 	return NOTIFY_OK;
@@ -3038,6 +3226,7 @@ move_account:
 		lru_add_drain_all();
 		drain_all_stock_sync();
 		ret = 0;
+		mem_cgroup_start_move(mem);
 		for_each_node_state(node, N_HIGH_MEMORY) {
 			for (zid = 0; !ret && zid < MAX_NR_ZONES; zid++) {
 				enum lru_list l;
@@ -3051,6 +3240,7 @@ move_account:
 			if (ret)
 				break;
 		}
+		mem_cgroup_end_move(mem);
 		memcg_oom_recover(mem);
 		/* it seems parent cgroup doesn't have enough mem */
 		if (ret == -ENOMEM)
@@ -3137,33 +3327,25 @@ static int mem_cgroup_hierarchy_write(struct cgroup *cont, struct cftype *cft,
 	return retval;
 }
 
-struct mem_cgroup_idx_data {
-	s64 val;
-	enum mem_cgroup_stat_index idx;
-};
 
-static int
-mem_cgroup_get_idx_stat(struct mem_cgroup *mem, void *data)
+static u64 mem_cgroup_get_recursive_idx_stat(struct mem_cgroup *mem,
+				enum mem_cgroup_stat_index idx)
 {
-	struct mem_cgroup_idx_data *d = data;
-	d->val += mem_cgroup_read_stat(mem, d->idx);
-	return 0;
-}
+	struct mem_cgroup *iter;
+	s64 val = 0;
 
-static void
-mem_cgroup_get_recursive_idx_stat(struct mem_cgroup *mem,
-				enum mem_cgroup_stat_index idx, s64 *val)
-{
-	struct mem_cgroup_idx_data d;
-	d.idx = idx;
-	d.val = 0;
-	mem_cgroup_walk_tree(mem, &d, mem_cgroup_get_idx_stat);
-	*val = d.val;
+	/* each per cpu's value can be minus.Then, use s64 */
+	for_each_mem_cgroup_tree(iter, mem)
+		val += mem_cgroup_read_stat(iter, idx);
+
+	if (val < 0) /* race ? */
+		val = 0;
+	return val;
 }
 
 static inline u64 mem_cgroup_usage(struct mem_cgroup *mem, bool swap)
 {
-	u64 idx_val, val;
+	u64 val;
 
 	if (!mem_cgroup_is_root(mem)) {
 		if (!swap)
@@ -3172,16 +3354,12 @@ static inline u64 mem_cgroup_usage(struct mem_cgroup *mem, bool swap)
 			return res_counter_read_u64(&mem->memsw, RES_USAGE);
 	}
 
-	mem_cgroup_get_recursive_idx_stat(mem, MEM_CGROUP_STAT_CACHE, &idx_val);
-	val = idx_val;
-	mem_cgroup_get_recursive_idx_stat(mem, MEM_CGROUP_STAT_RSS, &idx_val);
-	val += idx_val;
+	val = mem_cgroup_get_recursive_idx_stat(mem, MEM_CGROUP_STAT_CACHE);
+	val += mem_cgroup_get_recursive_idx_stat(mem, MEM_CGROUP_STAT_RSS);
 
-	if (swap) {
-		mem_cgroup_get_recursive_idx_stat(mem,
-				MEM_CGROUP_STAT_SWAPOUT, &idx_val);
-		val += idx_val;
-	}
+	if (swap)
+		val += mem_cgroup_get_recursive_idx_stat(mem,
+				MEM_CGROUP_STAT_SWAPOUT);
 
 	return val << PAGE_SHIFT;
 }
@@ -3389,9 +3567,9 @@ struct {
 };
 
 
-static int mem_cgroup_get_local_stat(struct mem_cgroup *mem, void *data)
+static void
+mem_cgroup_get_local_stat(struct mem_cgroup *mem, struct mcs_total_stat *s)
 {
-	struct mcs_total_stat *s = data;
 	s64 val;
 
 	/* per cpu stat */
@@ -3421,13 +3599,15 @@ static int mem_cgroup_get_local_stat(struct mem_cgroup *mem, void *data)
 	s->stat[MCS_ACTIVE_FILE] += val * PAGE_SIZE;
 	val = mem_cgroup_get_local_zonestat(mem, LRU_UNEVICTABLE);
 	s->stat[MCS_UNEVICTABLE] += val * PAGE_SIZE;
-	return 0;
 }
 
 static void
 mem_cgroup_get_total_stat(struct mem_cgroup *mem, struct mcs_total_stat *s)
 {
-	mem_cgroup_walk_tree(mem, s, mem_cgroup_get_local_stat);
+	struct mem_cgroup *iter;
+
+	for_each_mem_cgroup_tree(iter, mem)
+		mem_cgroup_get_local_stat(iter, s);
 }
 
 static int mem_control_stat_show(struct cgroup *cont, struct cftype *cft,
@@ -3604,7 +3784,7 @@ static int compare_thresholds(const void *a, const void *b)
 	return _a->threshold - _b->threshold;
 }
 
-static int mem_cgroup_oom_notify_cb(struct mem_cgroup *mem, void *data)
+static int mem_cgroup_oom_notify_cb(struct mem_cgroup *mem)
 {
 	struct mem_cgroup_eventfd_list *ev;
 
@@ -3615,7 +3795,10 @@ static int mem_cgroup_oom_notify_cb(struct mem_cgroup *mem, void *data)
 
 static void mem_cgroup_oom_notify(struct mem_cgroup *mem)
 {
-	mem_cgroup_walk_tree(mem, NULL, mem_cgroup_oom_notify_cb);
+	struct mem_cgroup *iter;
+
+	for_each_mem_cgroup_tree(iter, mem)
+		mem_cgroup_oom_notify_cb(iter);
 }
 
 static int mem_cgroup_usage_register_event(struct cgroup *cgrp,
@@ -4032,6 +4215,7 @@ static struct mem_cgroup *mem_cgroup_alloc(void)
 			vfree(mem);
 		mem = NULL;
 	}
+	spin_lock_init(&mem->pcp_counter_lock);
 	return mem;
 }
 
@@ -4158,7 +4342,7 @@ mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
 						&per_cpu(memcg_stock, cpu);
 			INIT_WORK(&stock->work, drain_local_stock);
 		}
-		hotcpu_notifier(memcg_stock_cpu_callback, 0);
+		hotcpu_notifier(memcg_cpu_hotplug_callback, 0);
 	} else {
 		parent = mem_cgroup_from_cont(cont->parent);
 		mem->use_hierarchy = parent->use_hierarchy;
@@ -4513,6 +4697,7 @@ static void mem_cgroup_clear_mc(void)
 	mc.to = NULL;
 	mc.moving_task = NULL;
 	spin_unlock(&mc.lock);
+	mem_cgroup_end_move(from);
 	memcg_oom_recover(from);
 	memcg_oom_recover(to);
 	wake_up_all(&mc.waitq);
@@ -4543,6 +4728,7 @@ static int mem_cgroup_can_attach(struct cgroup_subsys *ss,
 			VM_BUG_ON(mc.moved_charge);
 			VM_BUG_ON(mc.moved_swap);
 			VM_BUG_ON(mc.moving_task);
+			mem_cgroup_start_move(from);
 			spin_lock(&mc.lock);
 			mc.from = from;
 			mc.to = mem;