memcontrol.c

		if (signal_pending(current))
			return -EINTR;

		progress = try_to_free_mem_cgroup_pages(memcg, GFP_KERNEL,
						false);
		if (!progress) {
			nr_retries--;
			/* maybe some writeback is necessary */
			congestion_wait(BLK_RW_ASYNC, HZ/10);
		}

	}
	lru_add_drain();
	mem_cgroup_reparent_charges(memcg);

	return 0;
}

static int mem_cgroup_force_empty_write(struct cgroup_subsys_state *css,
					unsigned int event)
{
	struct mem_cgroup *memcg = mem_cgroup_from_css(css);

	if (mem_cgroup_is_root(memcg))
		return -EINVAL;
	return mem_cgroup_force_empty(memcg);
}

static u64 mem_cgroup_hierarchy_read(struct cgroup_subsys_state *css,
				     struct cftype *cft)
{
	return mem_cgroup_from_css(css)->use_hierarchy;
}

static int mem_cgroup_hierarchy_write(struct cgroup_subsys_state *css,
				      struct cftype *cft, u64 val)
{
	int retval = 0;
	struct mem_cgroup *memcg = mem_cgroup_from_css(css);
	struct mem_cgroup *parent_memcg = mem_cgroup_from_css(css_parent(&memcg->css));

	mutex_lock(&memcg_create_mutex);

	if (memcg->use_hierarchy == val)
		goto out;

	/*
	 * If parent's use_hierarchy is set, we can't make any modifications
	 * in the child subtrees. If it is unset, then the change can
	 * occur, provided the current cgroup has no children.
	 *
	 * For the root cgroup, parent_mem is NULL, we allow value to be
	 * set if there are no children.
	 */
	if ((!parent_memcg || !parent_memcg->use_hierarchy) &&
				(val == 1 || val == 0)) {
		if (list_empty(&memcg->css.cgroup->children))
			memcg->use_hierarchy = val;
		else
			retval = -EBUSY;
	} else
		retval = -EINVAL;

out:
	mutex_unlock(&memcg_create_mutex);

	return retval;
}


static unsigned long mem_cgroup_recursive_stat(struct mem_cgroup *memcg,
					       enum mem_cgroup_stat_index idx)
{
	struct mem_cgroup *iter;
	long val = 0;

	/* Per-cpu values can be negative, use a signed accumulator */
	for_each_mem_cgroup_tree(iter, memcg)
		val += mem_cgroup_read_stat(iter, idx);

	if (val < 0) /* race ? */
		val = 0;
	return val;
}

static inline u64 mem_cgroup_usage(struct mem_cgroup *memcg, bool swap)
{
	u64 val;

	if (!mem_cgroup_is_root(memcg)) {
		if (!swap)
			return res_counter_read_u64(&memcg->res, RES_USAGE);
		else
			return res_counter_read_u64(&memcg->memsw, RES_USAGE);
	}

	/*
	 * Transparent hugepages are still accounted for in MEM_CGROUP_STAT_RSS
	 * as well as in MEM_CGROUP_STAT_RSS_HUGE.
	 */
	val = mem_cgroup_recursive_stat(memcg, MEM_CGROUP_STAT_CACHE);
	val += mem_cgroup_recursive_stat(memcg, MEM_CGROUP_STAT_RSS);

	if (swap)
		val += mem_cgroup_recursive_stat(memcg, MEM_CGROUP_STAT_SWAP);

	return val << PAGE_SHIFT;
}

static u64 mem_cgroup_read_u64(struct cgroup_subsys_state *css,
				   struct cftype *cft)
{
	struct mem_cgroup *memcg = mem_cgroup_from_css(css);
	u64 val;
	int name;
	enum res_type type;

	type = MEMFILE_TYPE(cft->private);
	name = MEMFILE_ATTR(cft->private);

	switch (type) {
	case _MEM:
		if (name == RES_USAGE)
			val = mem_cgroup_usage(memcg, false);
		else
			val = res_counter_read_u64(&memcg->res, name);
		break;
	case _MEMSWAP:
		if (name == RES_USAGE)
			val = mem_cgroup_usage(memcg, true);
		else
			val = res_counter_read_u64(&memcg->memsw, name);
		break;
	case _KMEM:
		val = res_counter_read_u64(&memcg->kmem, name);
		break;
	default:
		BUG();
	}

	return val;
}

#ifdef CONFIG_MEMCG_KMEM
/* should be called with activate_kmem_mutex held */
static int __memcg_activate_kmem(struct mem_cgroup *memcg,
				 unsigned long long limit)
{
	int err = 0;
	int memcg_id;

	if (memcg_kmem_is_active(memcg))
		return 0;

	/*
	 * We are going to allocate memory for data shared by all memory
	 * cgroups so let's stop accounting here.
	 */
	memcg_stop_kmem_account();

	/*
	 * For simplicity, we won't allow this to be disabled.  It also can't
	 * be changed if the cgroup has children already, or if tasks had
	 * already joined.
	 *
	 * If tasks join before we set the limit, a person looking at
	 * kmem.usage_in_bytes will have no way to determine when it took
	 * place, which makes the value quite meaningless.
	 *
	 * After it first became limited, changes in the value of the limit are
	 * of course permitted.
	 */
	mutex_lock(&memcg_create_mutex);
	if (cgroup_task_count(memcg->css.cgroup) || memcg_has_children(memcg))
		err = -EBUSY;
	mutex_unlock(&memcg_create_mutex);
	if (err)
		goto out;

	memcg_id = ida_simple_get(&kmem_limited_groups,
				  0, MEMCG_CACHES_MAX_SIZE, GFP_KERNEL);
	if (memcg_id < 0) {
		err = memcg_id;
		goto out;
	}

	/*
	 * Make sure we have enough space for this cgroup in each root cache's
	 * memcg_params.
	 */
	err = memcg_update_all_caches(memcg_id + 1);
	if (err)
		goto out_rmid;

	memcg->kmemcg_id = memcg_id;
	INIT_LIST_HEAD(&memcg->memcg_slab_caches);
	mutex_init(&memcg->slab_caches_mutex);

	/*
	 * We couldn't have accounted to this cgroup, because it hasn't got the
	 * active bit set yet, so this should succeed.
	 */
	err = res_counter_set_limit(&memcg->kmem, limit);
	VM_BUG_ON(err);

	static_key_slow_inc(&memcg_kmem_enabled_key);
	/*
	 * Setting the active bit after enabling static branching will
	 * guarantee no one starts accounting before all call sites are
	 * patched.
	 */
	memcg_kmem_set_active(memcg);
out:
	memcg_resume_kmem_account();
	return err;

out_rmid:
	ida_simple_remove(&kmem_limited_groups, memcg_id);
	goto out;
}

static int memcg_activate_kmem(struct mem_cgroup *memcg,
			       unsigned long long limit)
{
	int ret;

	mutex_lock(&activate_kmem_mutex);
	ret = __memcg_activate_kmem(memcg, limit);
	mutex_unlock(&activate_kmem_mutex);
	return ret;
}

static int memcg_update_kmem_limit(struct mem_cgroup *memcg,
				   unsigned long long val)
{
	int ret;

	if (!memcg_kmem_is_active(memcg))
		ret = memcg_activate_kmem(memcg, val);
	else
		ret = res_counter_set_limit(&memcg->kmem, val);
	return ret;
}

static int memcg_propagate_kmem(struct mem_cgroup *memcg)
{
	int ret = 0;
	struct mem_cgroup *parent = parent_mem_cgroup(memcg);

	if (!parent)
		return 0;

	mutex_lock(&activate_kmem_mutex);
	/*
	 * If the parent cgroup is not kmem-active now, it cannot be activated
	 * after this point, because it has at least one child already.
	 */
	if (memcg_kmem_is_active(parent))
		ret = __memcg_activate_kmem(memcg, RES_COUNTER_MAX);
	mutex_unlock(&activate_kmem_mutex);
	return ret;
}
#else
static int memcg_update_kmem_limit(struct mem_cgroup *memcg,
				   unsigned long long val)
{
	return -EINVAL;
}
#endif /* CONFIG_MEMCG_KMEM */

/*
 * The user of this function is...
 * RES_LIMIT.
 */
static int mem_cgroup_write(struct cgroup_subsys_state *css, struct cftype *cft,
			    const char *buffer)
{
	struct mem_cgroup *memcg = mem_cgroup_from_css(css);
	enum res_type type;
	int name;
	unsigned long long val;
	int ret;

	type = MEMFILE_TYPE(cft->private);
	name = MEMFILE_ATTR(cft->private);

	switch (name) {
	case RES_LIMIT:
		if (mem_cgroup_is_root(memcg)) { /* Can't set limit on root */
			ret = -EINVAL;
			break;
		}
		/* This function does all necessary parse...reuse it */
		ret = res_counter_memparse_write_strategy(buffer, &val);
		if (ret)
			break;
		if (type == _MEM)
			ret = mem_cgroup_resize_limit(memcg, val);
		else if (type == _MEMSWAP)
			ret = mem_cgroup_resize_memsw_limit(memcg, val);
		else if (type == _KMEM)
			ret = memcg_update_kmem_limit(memcg, val);
		else
			return -EINVAL;
		break;
	case RES_SOFT_LIMIT:
		ret = res_counter_memparse_write_strategy(buffer, &val);
		if (ret)
			break;
		/*
		 * For memsw, soft limits are hard to implement in terms
		 * of semantics, for now, we support soft limits for
		 * control without swap
		 */
		if (type == _MEM)
			ret = res_counter_set_soft_limit(&memcg->res, val);
		else
			ret = -EINVAL;
		break;
	default:
		ret = -EINVAL; /* should be BUG() ? */
		break;
	}
	return ret;
}

static void memcg_get_hierarchical_limit(struct mem_cgroup *memcg,
		unsigned long long *mem_limit, unsigned long long *memsw_limit)
{
	unsigned long long min_limit, min_memsw_limit, tmp;

	min_limit = res_counter_read_u64(&memcg->res, RES_LIMIT);
	min_memsw_limit = res_counter_read_u64(&memcg->memsw, RES_LIMIT);
	if (!memcg->use_hierarchy)
		goto out;

	while (css_parent(&memcg->css)) {
		memcg = mem_cgroup_from_css(css_parent(&memcg->css));
		if (!memcg->use_hierarchy)
			break;
		tmp = res_counter_read_u64(&memcg->res, RES_LIMIT);
		min_limit = min(min_limit, tmp);
		tmp = res_counter_read_u64(&memcg->memsw, RES_LIMIT);
		min_memsw_limit = min(min_memsw_limit, tmp);
	}
out:
	*mem_limit = min_limit;
	*memsw_limit = min_memsw_limit;
}

static int mem_cgroup_reset(struct cgroup_subsys_state *css, unsigned int event)
{
	struct mem_cgroup *memcg = mem_cgroup_from_css(css);
	int name;
	enum res_type type;

	type = MEMFILE_TYPE(event);
	name = MEMFILE_ATTR(event);

	switch (name) {
	case RES_MAX_USAGE:
		if (type == _MEM)
			res_counter_reset_max(&memcg->res);
		else if (type == _MEMSWAP)
			res_counter_reset_max(&memcg->memsw);
		else if (type == _KMEM)
			res_counter_reset_max(&memcg->kmem);
		else
			return -EINVAL;
		break;
	case RES_FAILCNT:
		if (type == _MEM)
			res_counter_reset_failcnt(&memcg->res);
		else if (type == _MEMSWAP)
			res_counter_reset_failcnt(&memcg->memsw);
		else if (type == _KMEM)
			res_counter_reset_failcnt(&memcg->kmem);
		else
			return -EINVAL;
		break;
	}

	return 0;
}

static u64 mem_cgroup_move_charge_read(struct cgroup_subsys_state *css,
					struct cftype *cft)
{
	return mem_cgroup_from_css(css)->move_charge_at_immigrate;
}

#ifdef CONFIG_MMU
static int mem_cgroup_move_charge_write(struct cgroup_subsys_state *css,
					struct cftype *cft, u64 val)
{
	struct mem_cgroup *memcg = mem_cgroup_from_css(css);

	if (val >= (1 << NR_MOVE_TYPE))
		return -EINVAL;

	/*
	 * No kind of locking is needed in here, because ->can_attach() will
	 * check this value once in the beginning of the process, and then carry
	 * on with stale data. This means that changes to this value will only
	 * affect task migrations starting after the change.
	 */
	memcg->move_charge_at_immigrate = val;
	return 0;
}
#else
static int mem_cgroup_move_charge_write(struct cgroup_subsys_state *css,
					struct cftype *cft, u64 val)
{
	return -ENOSYS;
}
#endif

#ifdef CONFIG_NUMA
static int memcg_numa_stat_show(struct seq_file *m, void *v)
{
	struct numa_stat {
		const char *name;
		unsigned int lru_mask;
	};

	static const struct numa_stat stats[] = {
		{ "total", LRU_ALL },
		{ "file", LRU_ALL_FILE },
		{ "anon", LRU_ALL_ANON },
		{ "unevictable", BIT(LRU_UNEVICTABLE) },
	};
	const struct numa_stat *stat;
	int nid;
	unsigned long nr;
	struct mem_cgroup *memcg = mem_cgroup_from_css(seq_css(m));

	for (stat = stats; stat < stats + ARRAY_SIZE(stats); stat++) {
		nr = mem_cgroup_nr_lru_pages(memcg, stat->lru_mask);
		seq_printf(m, "%s=%lu", stat->name, nr);
		for_each_node_state(nid, N_MEMORY) {
			nr = mem_cgroup_node_nr_lru_pages(memcg, nid,
							  stat->lru_mask);
			seq_printf(m, " N%d=%lu", nid, nr);
		}
		seq_putc(m, '\n');
	}

	for (stat = stats; stat < stats + ARRAY_SIZE(stats); stat++) {
		struct mem_cgroup *iter;

		nr = 0;
		for_each_mem_cgroup_tree(iter, memcg)
			nr += mem_cgroup_nr_lru_pages(iter, stat->lru_mask);
		seq_printf(m, "hierarchical_%s=%lu", stat->name, nr);
		for_each_node_state(nid, N_MEMORY) {
			nr = 0;
			for_each_mem_cgroup_tree(iter, memcg)
				nr += mem_cgroup_node_nr_lru_pages(
					iter, nid, stat->lru_mask);
			seq_printf(m, " N%d=%lu", nid, nr);
		}
		seq_putc(m, '\n');
	}

	return 0;
}
#endif /* CONFIG_NUMA */

static inline void mem_cgroup_lru_names_not_uptodate(void)
{
	BUILD_BUG_ON(ARRAY_SIZE(mem_cgroup_lru_names) != NR_LRU_LISTS);
}

static int memcg_stat_show(struct seq_file *m, void *v)
{
	struct mem_cgroup *memcg = mem_cgroup_from_css(seq_css(m));
	struct mem_cgroup *mi;
	unsigned int i;

	for (i = 0; i < MEM_CGROUP_STAT_NSTATS; i++) {
		if (i == MEM_CGROUP_STAT_SWAP && !do_swap_account)
			continue;
		seq_printf(m, "%s %ld\n", mem_cgroup_stat_names[i],
			   mem_cgroup_read_stat(memcg, i) * PAGE_SIZE);
	}

	for (i = 0; i < MEM_CGROUP_EVENTS_NSTATS; i++)
		seq_printf(m, "%s %lu\n", mem_cgroup_events_names[i],
			   mem_cgroup_read_events(memcg, i));

	for (i = 0; i < NR_LRU_LISTS; i++)
		seq_printf(m, "%s %lu\n", mem_cgroup_lru_names[i],
			   mem_cgroup_nr_lru_pages(memcg, BIT(i)) * PAGE_SIZE);

	/* Hierarchical information */
	{
		unsigned long long limit, memsw_limit;
		memcg_get_hierarchical_limit(memcg, &limit, &memsw_limit);
		seq_printf(m, "hierarchical_memory_limit %llu\n", limit);
		if (do_swap_account)
			seq_printf(m, "hierarchical_memsw_limit %llu\n",
				   memsw_limit);
	}

	for (i = 0; i < MEM_CGROUP_STAT_NSTATS; i++) {
		long long val = 0;

		if (i == MEM_CGROUP_STAT_SWAP && !do_swap_account)
			continue;
		for_each_mem_cgroup_tree(mi, memcg)
			val += mem_cgroup_read_stat(mi, i) * PAGE_SIZE;
		seq_printf(m, "total_%s %lld\n", mem_cgroup_stat_names[i], val);
	}

	for (i = 0; i < MEM_CGROUP_EVENTS_NSTATS; i++) {
		unsigned long long val = 0;

		for_each_mem_cgroup_tree(mi, memcg)
			val += mem_cgroup_read_events(mi, i);
		seq_printf(m, "total_%s %llu\n",
			   mem_cgroup_events_names[i], val);
	}

	for (i = 0; i < NR_LRU_LISTS; i++) {
		unsigned long long val = 0;

		for_each_mem_cgroup_tree(mi, memcg)
			val += mem_cgroup_nr_lru_pages(mi, BIT(i)) * PAGE_SIZE;
		seq_printf(m, "total_%s %llu\n", mem_cgroup_lru_names[i], val);
	}

#ifdef CONFIG_DEBUG_VM
	{
		int nid, zid;
		struct mem_cgroup_per_zone *mz;
		struct zone_reclaim_stat *rstat;
		unsigned long recent_rotated[2] = {0, 0};
		unsigned long recent_scanned[2] = {0, 0};

		for_each_online_node(nid)
			for (zid = 0; zid < MAX_NR_ZONES; zid++) {
				mz = mem_cgroup_zoneinfo(memcg, nid, zid);
				rstat = &mz->lruvec.reclaim_stat;

				recent_rotated[0] += rstat->recent_rotated[0];
				recent_rotated[1] += rstat->recent_rotated[1];
				recent_scanned[0] += rstat->recent_scanned[0];
				recent_scanned[1] += rstat->recent_scanned[1];
			}
		seq_printf(m, "recent_rotated_anon %lu\n", recent_rotated[0]);
		seq_printf(m, "recent_rotated_file %lu\n", recent_rotated[1]);
		seq_printf(m, "recent_scanned_anon %lu\n", recent_scanned[0]);
		seq_printf(m, "recent_scanned_file %lu\n", recent_scanned[1]);
	}
#endif

	return 0;
}

static u64 mem_cgroup_swappiness_read(struct cgroup_subsys_state *css,
				      struct cftype *cft)
{
	struct mem_cgroup *memcg = mem_cgroup_from_css(css);

	return mem_cgroup_swappiness(memcg);
}

static int mem_cgroup_swappiness_write(struct cgroup_subsys_state *css,
				       struct cftype *cft, u64 val)
{
	struct mem_cgroup *memcg = mem_cgroup_from_css(css);
	struct mem_cgroup *parent = mem_cgroup_from_css(css_parent(&memcg->css));

	if (val > 100 || !parent)
		return -EINVAL;

	mutex_lock(&memcg_create_mutex);

	/* If under hierarchy, only empty-root can set this value */
	if ((parent->use_hierarchy) || memcg_has_children(memcg)) {
		mutex_unlock(&memcg_create_mutex);
		return -EINVAL;
	}

	memcg->swappiness = val;

	mutex_unlock(&memcg_create_mutex);

	return 0;
}

static void __mem_cgroup_threshold(struct mem_cgroup *memcg, bool swap)
{
	struct mem_cgroup_threshold_ary *t;
	u64 usage;
	int i;

	rcu_read_lock();
	if (!swap)
		t = rcu_dereference(memcg->thresholds.primary);
	else
		t = rcu_dereference(memcg->memsw_thresholds.primary);

	if (!t)
		goto unlock;

	usage = mem_cgroup_usage(memcg, swap);

	/*
	 * current_threshold points to threshold just below or equal to usage.
	 * If it's not true, a threshold was crossed after last
	 * call of __mem_cgroup_threshold().
	 */
	i = t->current_threshold;

	/*
	 * Iterate backward over array of thresholds starting from
	 * current_threshold and check if a threshold is crossed.
	 * If none of thresholds below usage is crossed, we read
	 * only one element of the array here.
	 */
	for (; i >= 0 && unlikely(t->entries[i].threshold > usage); i--)
		eventfd_signal(t->entries[i].eventfd, 1);

	/* i = current_threshold + 1 */
	i++;

	/*
	 * Iterate forward over array of thresholds starting from
	 * current_threshold+1 and check if a threshold is crossed.
	 * If none of thresholds above usage is crossed, we read
	 * only one element of the array here.
	 */
	for (; i < t->size && unlikely(t->entries[i].threshold <= usage); i++)
		eventfd_signal(t->entries[i].eventfd, 1);

	/* Update current_threshold */
	t->current_threshold = i - 1;
unlock:
	rcu_read_unlock();
}

static void mem_cgroup_threshold(struct mem_cgroup *memcg)
{
	while (memcg) {
		__mem_cgroup_threshold(memcg, false);
		if (do_swap_account)
			__mem_cgroup_threshold(memcg, true);

		memcg = parent_mem_cgroup(memcg);
	}
}

static int compare_thresholds(const void *a, const void *b)
{
	const struct mem_cgroup_threshold *_a = a;
	const struct mem_cgroup_threshold *_b = b;

	if (_a->threshold > _b->threshold)
		return 1;

	if (_a->threshold < _b->threshold)
		return -1;

	return 0;
}

static int mem_cgroup_oom_notify_cb(struct mem_cgroup *memcg)
{
	struct mem_cgroup_eventfd_list *ev;

	list_for_each_entry(ev, &memcg->oom_notify, list)
		eventfd_signal(ev->eventfd, 1);
	return 0;
}

static void mem_cgroup_oom_notify(struct mem_cgroup *memcg)
{
	struct mem_cgroup *iter;

	for_each_mem_cgroup_tree(iter, memcg)
		mem_cgroup_oom_notify_cb(iter);
}

static int __mem_cgroup_usage_register_event(struct mem_cgroup *memcg,
	struct eventfd_ctx *eventfd, const char *args, enum res_type type)
{
	struct mem_cgroup_thresholds *thresholds;
	struct mem_cgroup_threshold_ary *new;
	u64 threshold, usage;
	int i, size, ret;

	ret = res_counter_memparse_write_strategy(args, &threshold);
	if (ret)
		return ret;

	mutex_lock(&memcg->thresholds_lock);

	if (type == _MEM)
		thresholds = &memcg->thresholds;
	else if (type == _MEMSWAP)
		thresholds = &memcg->memsw_thresholds;
	else
		BUG();

	usage = mem_cgroup_usage(memcg, type == _MEMSWAP);

	/* Check if a threshold crossed before adding a new one */
	if (thresholds->primary)
		__mem_cgroup_threshold(memcg, type == _MEMSWAP);

	size = thresholds->primary ? thresholds->primary->size + 1 : 1;

	/* Allocate memory for new array of thresholds */
	new = kmalloc(sizeof(*new) + size * sizeof(struct mem_cgroup_threshold),
			GFP_KERNEL);
	if (!new) {
		ret = -ENOMEM;
		goto unlock;
	}
	new->size = size;

	/* Copy thresholds (if any) to new array */
	if (thresholds->primary) {
		memcpy(new->entries, thresholds->primary->entries, (size - 1) *
				sizeof(struct mem_cgroup_threshold));
	}

	/* Add new threshold */
	new->entries[size - 1].eventfd = eventfd;
	new->entries[size - 1].threshold = threshold;

	/* Sort thresholds. Registering of new threshold isn't time-critical */
	sort(new->entries, size, sizeof(struct mem_cgroup_threshold),
			compare_thresholds, NULL);

	/* Find current threshold */
	new->current_threshold = -1;
	for (i = 0; i < size; i++) {
		if (new->entries[i].threshold <= usage) {
			/*
			 * new->current_threshold will not be used until
			 * rcu_assign_pointer(), so it's safe to increment
			 * it here.
			 */
			++new->current_threshold;
		} else
			break;
	}

	/* Free old spare buffer and save old primary buffer as spare */
	kfree(thresholds->spare);
	thresholds->spare = thresholds->primary;

	rcu_assign_pointer(thresholds->primary, new);

	/* To be sure that nobody uses thresholds */
	synchronize_rcu();

unlock:
	mutex_unlock(&memcg->thresholds_lock);

	return ret;
}

static int mem_cgroup_usage_register_event(struct mem_cgroup *memcg,
	struct eventfd_ctx *eventfd, const char *args)
{
	return __mem_cgroup_usage_register_event(memcg, eventfd, args, _MEM);
}

static int memsw_cgroup_usage_register_event(struct mem_cgroup *memcg,
	struct eventfd_ctx *eventfd, const char *args)
{
	return __mem_cgroup_usage_register_event(memcg, eventfd, args, _MEMSWAP);
}

static void __mem_cgroup_usage_unregister_event(struct mem_cgroup *memcg,
	struct eventfd_ctx *eventfd, enum res_type type)
{
	struct mem_cgroup_thresholds *thresholds;
	struct mem_cgroup_threshold_ary *new;
	u64 usage;
	int i, j, size;

	mutex_lock(&memcg->thresholds_lock);
	if (type == _MEM)
		thresholds = &memcg->thresholds;
	else if (type == _MEMSWAP)
		thresholds = &memcg->memsw_thresholds;
	else
		BUG();

	if (!thresholds->primary)
		goto unlock;

	usage = mem_cgroup_usage(memcg, type == _MEMSWAP);

	/* Check if a threshold crossed before removing */
	__mem_cgroup_threshold(memcg, type == _MEMSWAP);

	/* Calculate new number of threshold */
	size = 0;
	for (i = 0; i < thresholds->primary->size; i++) {
		if (thresholds->primary->entries[i].eventfd != eventfd)
			size++;
	}

	new = thresholds->spare;

	/* Set thresholds array to NULL if we don't have thresholds */
	if (!size) {
		kfree(new);
		new = NULL;
		goto swap_buffers;
	}

	new->size = size;

	/* Copy thresholds and find current threshold */
	new->current_threshold = -1;
	for (i = 0, j = 0; i < thresholds->primary->size; i++) {
		if (thresholds->primary->entries[i].eventfd == eventfd)
			continue;

		new->entries[j] = thresholds->primary->entries[i];
		if (new->entries[j].threshold <= usage) {
			/*
			 * new->current_threshold will not be used
			 * until rcu_assign_pointer(), so it's safe to increment
			 * it here.
			 */
			++new->current_threshold;
		}
		j++;
	}

swap_buffers:
	/* Swap primary and spare array */
	thresholds->spare = thresholds->primary;
	/* If all events are unregistered, free the spare array */
	if (!new) {
		kfree(thresholds->spare);
		thresholds->spare = NULL;
	}

	rcu_assign_pointer(thresholds->primary, new);

	/* To be sure that nobody uses thresholds */
	synchronize_rcu();
unlock:
	mutex_unlock(&memcg->thresholds_lock);
}

static void mem_cgroup_usage_unregister_event(struct mem_cgroup *memcg,
	struct eventfd_ctx *eventfd)
{
	return __mem_cgroup_usage_unregister_event(memcg, eventfd, _MEM);
}

static void memsw_cgroup_usage_unregister_event(struct mem_cgroup *memcg,
	struct eventfd_ctx *eventfd)
{
	return __mem_cgroup_usage_unregister_event(memcg, eventfd, _MEMSWAP);
}

static int mem_cgroup_oom_register_event(struct mem_cgroup *memcg,
	struct eventfd_ctx *eventfd, const char *args)
{
	struct mem_cgroup_eventfd_list *event;

	event = kmalloc(sizeof(*event),	GFP_KERNEL);
	if (!event)
		return -ENOMEM;

	spin_lock(&memcg_oom_lock);

	event->eventfd = eventfd;
	list_add(&event->list, &memcg->oom_notify);

	/* already in OOM ? */
	if (atomic_read(&memcg->under_oom))
		eventfd_signal(eventfd, 1);
	spin_unlock(&memcg_oom_lock);

	return 0;
}

static void mem_cgroup_oom_unregister_event(struct mem_cgroup *memcg,
	struct eventfd_ctx *eventfd)
{
	struct mem_cgroup_eventfd_list *ev, *tmp;

	spin_lock(&memcg_oom_lock);

	list_for_each_entry_safe(ev, tmp, &memcg->oom_notify, list) {
		if (ev->eventfd == eventfd) {
			list_del(&ev->list);
			kfree(ev);
		}
	}

	spin_unlock(&memcg_oom_lock);
}

static int mem_cgroup_oom_control_read(struct seq_file *sf, void *v)
{
	struct mem_cgroup *memcg = mem_cgroup_from_css(seq_css(sf));

	seq_printf(sf, "oom_kill_disable %d\n", memcg->oom_kill_disable);
	seq_printf(sf, "under_oom %d\n", (bool)atomic_read(&memcg->under_oom));
	return 0;
}

static int mem_cgroup_oom_control_write(struct cgroup_subsys_state *css,
	struct cftype *cft, u64 val)
{
	struct mem_cgroup *memcg = mem_cgroup_from_css(css);
	struct mem_cgroup *parent = mem_cgroup_from_css(css_parent(&memcg->css));

	/* cannot set to root cgroup and only 0 and 1 are allowed */
	if (!parent || !((val == 0) || (val == 1)))
		return -EINVAL;

	mutex_lock(&memcg_create_mutex);
	/* oom-kill-disable is a flag for subhierarchy. */
	if ((parent->use_hierarchy) || memcg_has_children(memcg)) {
		mutex_unlock(&memcg_create_mutex);
		return -EINVAL;
	}
	memcg->oom_kill_disable = val;
	if (!val)
		memcg_oom_recover(memcg);
	mutex_unlock(&memcg_create_mutex);
	return 0;
}

#ifdef CONFIG_MEMCG_KMEM
static int memcg_init_kmem(struct mem_cgroup *memcg, struct cgroup_subsys *ss)
{
	int ret;

	memcg->kmemcg_id = -1;
	ret = memcg_propagate_kmem(memcg);
	if (ret)
		return ret;

	return mem_cgroup_sockets_init(memcg, ss);
}

static void memcg_destroy_kmem(struct mem_cgroup *memcg)
{
	mem_cgroup_sockets_destroy(memcg);
}

static void kmem_cgroup_css_offline(struct mem_cgroup *memcg)
{
	if (!memcg_kmem_is_active(memcg))
		return;

	/*
	 * kmem charges can outlive the cgroup. In the case of slab
	 * pages, for instance, a page contain objects from various
	 * processes. As we prevent from taking a reference for every
	 * such allocation we have to be careful when doing uncharge
	 * (see memcg_uncharge_kmem) and here during offlining.
	 *
	 * The idea is that that only the _last_ uncharge which sees
	 * the dead memcg will drop the last reference. An additional
	 * reference is taken here before the group is marked dead
	 * which is then paired with css_put during uncharge resp. here.
	 *
	 * Although this might sound strange as this path is called from
	 * css_offline() when the referencemight have dropped down to 0
	 * and shouldn't be incremented anymore (css_tryget would fail)
	 * we do not have other options because of the kmem allocations
	 * lifetime.
	 */
	css_get(&memcg->css);

	memcg_kmem_mark_dead(memcg);

	if (res_counter_read_u64(&memcg->kmem, RES_USAGE) != 0)
		return;

	if (memcg_kmem_test_and_clear_dead(memcg))
		css_put(&memcg->css);
}
#else
static int memcg_init_kmem(struct mem_cgroup *memcg, struct cgroup_subsys *ss)
{
	return 0;
}

static void memcg_destroy_kmem(struct mem_cgroup *memcg)
{
}

static void kmem_cgroup_css_offline(struct mem_cgroup *memcg)