/*
   * Copyright (c) 2013 Red Hat, Inc. and Parallels Inc. All rights reserved.
   * Authors: David Chinner and Glauber Costa
   *
   * Generic LRU infrastructure
   */
  #include <linux/kernel.h>
  #include <linux/module.h>

  #include <linux/mm.h>

  #include <linux/list_lru.h>

  #include <linux/slab.h>

  #include <linux/mutex.h>

  #include <linux/memcontrol.h>

  #ifdef CONFIG_MEMCG_KMEM

  static LIST_HEAD(list_lrus);
  static DEFINE_MUTEX(list_lrus_mutex);
  
  static void list_lru_register(struct list_lru *lru)
  {
  	mutex_lock(&list_lrus_mutex);
  	list_add(&lru->list, &list_lrus);
  	mutex_unlock(&list_lrus_mutex);
  }
  
  static void list_lru_unregister(struct list_lru *lru)
  {
  	mutex_lock(&list_lrus_mutex);
  	list_del(&lru->list);
  	mutex_unlock(&list_lrus_mutex);
  }

  static int lru_shrinker_id(struct list_lru *lru)
  {
  	return lru->shrinker_id;
  }

  static inline bool list_lru_memcg_aware(struct list_lru *lru)
  {

  	/*
  	 * This needs node 0 to be always present, even
  	 * in the systems supporting sparse numa ids.
  	 */

  	return !!lru->node[0].memcg_lrus;
  }
  
  static inline struct list_lru_one *
  list_lru_from_memcg_idx(struct list_lru_node *nlru, int idx)
  {

  	struct list_lru_memcg *memcg_lrus;

  	/*

  	 * Either lock or RCU protects the array of per cgroup lists
  	 * from relocation (see memcg_update_list_lru_node).

  	 */

  	memcg_lrus = rcu_dereference_check(nlru->memcg_lrus,
  					   lockdep_is_held(&nlru->lock));
  	if (memcg_lrus && idx >= 0)
  		return memcg_lrus->lru[idx];

  	return &nlru->lru;
  }

  static __always_inline struct mem_cgroup *mem_cgroup_from_kmem(void *ptr)
  {
  	struct page *page;
  
  	if (!memcg_kmem_enabled())
  		return NULL;
  	page = virt_to_head_page(ptr);
  	return page->mem_cgroup;
  }

  static inline struct list_lru_one *

  list_lru_from_kmem(struct list_lru_node *nlru, void *ptr,
  		   struct mem_cgroup **memcg_ptr)

  {

  	struct list_lru_one *l = &nlru->lru;
  	struct mem_cgroup *memcg = NULL;

  
  	if (!nlru->memcg_lrus)

  		goto out;

  
  	memcg = mem_cgroup_from_kmem(ptr);
  	if (!memcg)

  		goto out;

  	l = list_lru_from_memcg_idx(nlru, memcg_cache_id(memcg));
  out:
  	if (memcg_ptr)
  		*memcg_ptr = memcg;
  	return l;

  }
  #else

  static void list_lru_register(struct list_lru *lru)
  {
  }
  
  static void list_lru_unregister(struct list_lru *lru)
  {
  }

  static int lru_shrinker_id(struct list_lru *lru)
  {
  	return -1;
  }

  static inline bool list_lru_memcg_aware(struct list_lru *lru)
  {
  	return false;
  }
  
  static inline struct list_lru_one *
  list_lru_from_memcg_idx(struct list_lru_node *nlru, int idx)
  {
  	return &nlru->lru;
  }
  
  static inline struct list_lru_one *

  list_lru_from_kmem(struct list_lru_node *nlru, void *ptr,
  		   struct mem_cgroup **memcg_ptr)

  {

  	if (memcg_ptr)
  		*memcg_ptr = NULL;

  	return &nlru->lru;
  }

  #endif /* CONFIG_MEMCG_KMEM */

  bool list_lru_add(struct list_lru *lru, struct list_head *item)
  {

  	int nid = page_to_nid(virt_to_page(item));
  	struct list_lru_node *nlru = &lru->node[nid];

  	struct mem_cgroup *memcg;

  	struct list_lru_one *l;

  
  	spin_lock(&nlru->lock);

  	if (list_empty(item)) {

  		l = list_lru_from_kmem(nlru, item, &memcg);

  		list_add_tail(item, &l->list);

  		/* Set shrinker bit if the first element was added */
  		if (!l->nr_items++)
  			memcg_set_shrinker_bit(memcg, nid,
  					       lru_shrinker_id(lru));

  		nlru->nr_items++;

  		spin_unlock(&nlru->lock);

  		return true;
  	}

  	spin_unlock(&nlru->lock);

  	return false;
  }
  EXPORT_SYMBOL_GPL(list_lru_add);
  
  bool list_lru_del(struct list_lru *lru, struct list_head *item)
  {

  	int nid = page_to_nid(virt_to_page(item));
  	struct list_lru_node *nlru = &lru->node[nid];

  	struct list_lru_one *l;

  
  	spin_lock(&nlru->lock);

  	if (!list_empty(item)) {

  		l = list_lru_from_kmem(nlru, item, NULL);

  		list_del_init(item);

  		l->nr_items--;

  		nlru->nr_items--;

  		spin_unlock(&nlru->lock);

  		return true;
  	}

  	spin_unlock(&nlru->lock);

  	return false;
  }
  EXPORT_SYMBOL_GPL(list_lru_del);

  void list_lru_isolate(struct list_lru_one *list, struct list_head *item)
  {
  	list_del_init(item);
  	list->nr_items--;
  }
  EXPORT_SYMBOL_GPL(list_lru_isolate);
  
  void list_lru_isolate_move(struct list_lru_one *list, struct list_head *item,
  			   struct list_head *head)
  {
  	list_move(item, head);
  	list->nr_items--;
  }
  EXPORT_SYMBOL_GPL(list_lru_isolate_move);

  unsigned long list_lru_count_one(struct list_lru *lru,
  				 int nid, struct mem_cgroup *memcg)

  {

  	struct list_lru_node *nlru = &lru->node[nid];

  	struct list_lru_one *l;
  	unsigned long count;

  	rcu_read_lock();

  	l = list_lru_from_memcg_idx(nlru, memcg_cache_id(memcg));

  	count = l->nr_items;

  	rcu_read_unlock();

  
  	return count;
  }

  EXPORT_SYMBOL_GPL(list_lru_count_one);
  
  unsigned long list_lru_count_node(struct list_lru *lru, int nid)
  {

  	struct list_lru_node *nlru;

  	nlru = &lru->node[nid];
  	return nlru->nr_items;

  }

  EXPORT_SYMBOL_GPL(list_lru_count_node);

  static unsigned long

  __list_lru_walk_one(struct list_lru_node *nlru, int memcg_idx,

  		    list_lru_walk_cb isolate, void *cb_arg,
  		    unsigned long *nr_to_walk)

  {

  	struct list_lru_one *l;

  	struct list_head *item, *n;

  	unsigned long isolated = 0;

  	l = list_lru_from_memcg_idx(nlru, memcg_idx);

  restart:

  	list_for_each_safe(item, n, &l->list) {

  		enum lru_status ret;

  
  		/*
  		 * decrement nr_to_walk first so that we don't livelock if we
  		 * get stuck on large numbesr of LRU_RETRY items
  		 */

  		if (!*nr_to_walk)

  			break;

  		--*nr_to_walk;

  		ret = isolate(item, l, &nlru->lock, cb_arg);

  		switch (ret) {

  		case LRU_REMOVED_RETRY:
  			assert_spin_locked(&nlru->lock);

  			/* fall through */

  		case LRU_REMOVED:

  			isolated++;

  			nlru->nr_items--;

  			/*
  			 * If the lru lock has been dropped, our list
  			 * traversal is now invalid and so we have to
  			 * restart from scratch.
  			 */
  			if (ret == LRU_REMOVED_RETRY)
  				goto restart;

  			break;
  		case LRU_ROTATE:

  			list_move_tail(item, &l->list);

  			break;
  		case LRU_SKIP:
  			break;
  		case LRU_RETRY:

  			/*
  			 * The lru lock has been dropped, our list traversal is
  			 * now invalid and so we have to restart from scratch.
  			 */

  			assert_spin_locked(&nlru->lock);

  			goto restart;
  		default:
  			BUG();
  		}

  	}

  	return isolated;
  }

  
  unsigned long
  list_lru_walk_one(struct list_lru *lru, int nid, struct mem_cgroup *memcg,
  		  list_lru_walk_cb isolate, void *cb_arg,
  		  unsigned long *nr_to_walk)
  {

  	struct list_lru_node *nlru = &lru->node[nid];
  	unsigned long ret;
  
  	spin_lock(&nlru->lock);

  	ret = __list_lru_walk_one(nlru, memcg_cache_id(memcg), isolate, cb_arg,
  				  nr_to_walk);

  	spin_unlock(&nlru->lock);
  	return ret;

  }
  EXPORT_SYMBOL_GPL(list_lru_walk_one);

  unsigned long
  list_lru_walk_one_irq(struct list_lru *lru, int nid, struct mem_cgroup *memcg,
  		      list_lru_walk_cb isolate, void *cb_arg,
  		      unsigned long *nr_to_walk)
  {
  	struct list_lru_node *nlru = &lru->node[nid];
  	unsigned long ret;
  
  	spin_lock_irq(&nlru->lock);
  	ret = __list_lru_walk_one(nlru, memcg_cache_id(memcg), isolate, cb_arg,
  				  nr_to_walk);
  	spin_unlock_irq(&nlru->lock);
  	return ret;
  }

  unsigned long list_lru_walk_node(struct list_lru *lru, int nid,
  				 list_lru_walk_cb isolate, void *cb_arg,
  				 unsigned long *nr_to_walk)
  {
  	long isolated = 0;
  	int memcg_idx;

  	isolated += list_lru_walk_one(lru, nid, NULL, isolate, cb_arg,
  				      nr_to_walk);

  	if (*nr_to_walk > 0 && list_lru_memcg_aware(lru)) {
  		for_each_memcg_cache_index(memcg_idx) {

  			struct list_lru_node *nlru = &lru->node[nid];
  
  			spin_lock(&nlru->lock);

  			isolated += __list_lru_walk_one(nlru, memcg_idx,
  							isolate, cb_arg,
  							nr_to_walk);

  			spin_unlock(&nlru->lock);

  			if (*nr_to_walk <= 0)
  				break;
  		}
  	}
  	return isolated;
  }

  EXPORT_SYMBOL_GPL(list_lru_walk_node);

  static void init_one_lru(struct list_lru_one *l)
  {
  	INIT_LIST_HEAD(&l->list);
  	l->nr_items = 0;
  }

  #ifdef CONFIG_MEMCG_KMEM

  static void __memcg_destroy_list_lru_node(struct list_lru_memcg *memcg_lrus,
  					  int begin, int end)
  {
  	int i;
  
  	for (i = begin; i < end; i++)
  		kfree(memcg_lrus->lru[i]);
  }
  
  static int __memcg_init_list_lru_node(struct list_lru_memcg *memcg_lrus,
  				      int begin, int end)
  {
  	int i;
  
  	for (i = begin; i < end; i++) {
  		struct list_lru_one *l;
  
  		l = kmalloc(sizeof(struct list_lru_one), GFP_KERNEL);
  		if (!l)
  			goto fail;
  
  		init_one_lru(l);
  		memcg_lrus->lru[i] = l;
  	}
  	return 0;
  fail:
  	__memcg_destroy_list_lru_node(memcg_lrus, begin, i - 1);
  	return -ENOMEM;
  }
  
  static int memcg_init_list_lru_node(struct list_lru_node *nlru)
  {

  	struct list_lru_memcg *memcg_lrus;

  	int size = memcg_nr_cache_ids;

  	memcg_lrus = kvmalloc(sizeof(*memcg_lrus) +
  			      size * sizeof(void *), GFP_KERNEL);
  	if (!memcg_lrus)

  		return -ENOMEM;

  	if (__memcg_init_list_lru_node(memcg_lrus, 0, size)) {
  		kvfree(memcg_lrus);

  		return -ENOMEM;
  	}

  	RCU_INIT_POINTER(nlru->memcg_lrus, memcg_lrus);

  
  	return 0;
  }
  
  static void memcg_destroy_list_lru_node(struct list_lru_node *nlru)
  {

  	struct list_lru_memcg *memcg_lrus;
  	/*
  	 * This is called when shrinker has already been unregistered,
  	 * and nobody can use it. So, there is no need to use kvfree_rcu().
  	 */
  	memcg_lrus = rcu_dereference_protected(nlru->memcg_lrus, true);
  	__memcg_destroy_list_lru_node(memcg_lrus, 0, memcg_nr_cache_ids);
  	kvfree(memcg_lrus);
  }
  
  static void kvfree_rcu(struct rcu_head *head)
  {
  	struct list_lru_memcg *mlru;
  
  	mlru = container_of(head, struct list_lru_memcg, rcu);
  	kvfree(mlru);

  }
  
  static int memcg_update_list_lru_node(struct list_lru_node *nlru,
  				      int old_size, int new_size)
  {
  	struct list_lru_memcg *old, *new;
  
  	BUG_ON(old_size > new_size);

  	old = rcu_dereference_protected(nlru->memcg_lrus,
  					lockdep_is_held(&list_lrus_mutex));
  	new = kvmalloc(sizeof(*new) + new_size * sizeof(void *), GFP_KERNEL);

  	if (!new)
  		return -ENOMEM;
  
  	if (__memcg_init_list_lru_node(new, old_size, new_size)) {

  		kvfree(new);

  		return -ENOMEM;
  	}

  	memcpy(&new->lru, &old->lru, old_size * sizeof(void *));

  
  	/*

  	 * The locking below allows readers that hold nlru->lock avoid taking
  	 * rcu_read_lock (see list_lru_from_memcg_idx).

  	 *
  	 * Since list_lru_{add,del} may be called under an IRQ-safe lock,
  	 * we have to use IRQ-safe primitives here to avoid deadlock.
  	 */
  	spin_lock_irq(&nlru->lock);

  	rcu_assign_pointer(nlru->memcg_lrus, new);

  	spin_unlock_irq(&nlru->lock);

  	call_rcu(&old->rcu, kvfree_rcu);

  	return 0;
  }
  
  static void memcg_cancel_update_list_lru_node(struct list_lru_node *nlru,
  					      int old_size, int new_size)
  {

  	struct list_lru_memcg *memcg_lrus;
  
  	memcg_lrus = rcu_dereference_protected(nlru->memcg_lrus,
  					       lockdep_is_held(&list_lrus_mutex));

  	/* do not bother shrinking the array back to the old size, because we
  	 * cannot handle allocation failures here */

  	__memcg_destroy_list_lru_node(memcg_lrus, old_size, new_size);

  }
  
  static int memcg_init_list_lru(struct list_lru *lru, bool memcg_aware)
  {
  	int i;

  	if (!memcg_aware)
  		return 0;
  
  	for_each_node(i) {
  		if (memcg_init_list_lru_node(&lru->node[i]))

  			goto fail;
  	}
  	return 0;
  fail:

  	for (i = i - 1; i >= 0; i--) {
  		if (!lru->node[i].memcg_lrus)
  			continue;

  		memcg_destroy_list_lru_node(&lru->node[i]);

  	}

  	return -ENOMEM;
  }
  
  static void memcg_destroy_list_lru(struct list_lru *lru)
  {
  	int i;
  
  	if (!list_lru_memcg_aware(lru))
  		return;

  	for_each_node(i)

  		memcg_destroy_list_lru_node(&lru->node[i]);
  }
  
  static int memcg_update_list_lru(struct list_lru *lru,
  				 int old_size, int new_size)
  {
  	int i;
  
  	if (!list_lru_memcg_aware(lru))
  		return 0;

  	for_each_node(i) {

  		if (memcg_update_list_lru_node(&lru->node[i],
  					       old_size, new_size))
  			goto fail;
  	}
  	return 0;
  fail:

  	for (i = i - 1; i >= 0; i--) {
  		if (!lru->node[i].memcg_lrus)
  			continue;

  		memcg_cancel_update_list_lru_node(&lru->node[i],
  						  old_size, new_size);

  	}

  	return -ENOMEM;
  }
  
  static void memcg_cancel_update_list_lru(struct list_lru *lru,
  					 int old_size, int new_size)
  {
  	int i;
  
  	if (!list_lru_memcg_aware(lru))
  		return;

  	for_each_node(i)

  		memcg_cancel_update_list_lru_node(&lru->node[i],
  						  old_size, new_size);
  }
  
  int memcg_update_all_list_lrus(int new_size)
  {
  	int ret = 0;
  	struct list_lru *lru;
  	int old_size = memcg_nr_cache_ids;
  
  	mutex_lock(&list_lrus_mutex);
  	list_for_each_entry(lru, &list_lrus, list) {
  		ret = memcg_update_list_lru(lru, old_size, new_size);
  		if (ret)
  			goto fail;
  	}
  out:
  	mutex_unlock(&list_lrus_mutex);
  	return ret;
  fail:
  	list_for_each_entry_continue_reverse(lru, &list_lrus, list)
  		memcg_cancel_update_list_lru(lru, old_size, new_size);
  	goto out;
  }

  static void memcg_drain_list_lru_node(struct list_lru *lru, int nid,

  				      int src_idx, struct mem_cgroup *dst_memcg)

  {

  	struct list_lru_node *nlru = &lru->node[nid];

  	int dst_idx = dst_memcg->kmemcg_id;

  	struct list_lru_one *src, *dst;

  	bool set;

  
  	/*
  	 * Since list_lru_{add,del} may be called under an IRQ-safe lock,
  	 * we have to use IRQ-safe primitives here to avoid deadlock.
  	 */
  	spin_lock_irq(&nlru->lock);
  
  	src = list_lru_from_memcg_idx(nlru, src_idx);
  	dst = list_lru_from_memcg_idx(nlru, dst_idx);
  
  	list_splice_init(&src->list, &dst->list);

  	set = (!dst->nr_items && src->nr_items);

  	dst->nr_items += src->nr_items;

  	if (set)
  		memcg_set_shrinker_bit(dst_memcg, nid, lru_shrinker_id(lru));

  	src->nr_items = 0;
  
  	spin_unlock_irq(&nlru->lock);
  }
  
  static void memcg_drain_list_lru(struct list_lru *lru,

  				 int src_idx, struct mem_cgroup *dst_memcg)

  {
  	int i;
  
  	if (!list_lru_memcg_aware(lru))
  		return;

  	for_each_node(i)

  		memcg_drain_list_lru_node(lru, i, src_idx, dst_memcg);

  }

  void memcg_drain_all_list_lrus(int src_idx, struct mem_cgroup *dst_memcg)

  {
  	struct list_lru *lru;
  
  	mutex_lock(&list_lrus_mutex);
  	list_for_each_entry(lru, &list_lrus, list)

  		memcg_drain_list_lru(lru, src_idx, dst_memcg);

  	mutex_unlock(&list_lrus_mutex);
  }

  #else
  static int memcg_init_list_lru(struct list_lru *lru, bool memcg_aware)
  {
  	return 0;
  }
  
  static void memcg_destroy_list_lru(struct list_lru *lru)
  {
  }

  #endif /* CONFIG_MEMCG_KMEM */

  
  int __list_lru_init(struct list_lru *lru, bool memcg_aware,

  		    struct lock_class_key *key, struct shrinker *shrinker)

  {

  	int i;

  	size_t size = sizeof(*lru->node) * nr_node_ids;

  	int err = -ENOMEM;

  #ifdef CONFIG_MEMCG_KMEM
  	if (shrinker)
  		lru->shrinker_id = shrinker->id;
  	else
  		lru->shrinker_id = -1;
  #endif

  	memcg_get_cache_ids();

  
  	lru->node = kzalloc(size, GFP_KERNEL);
  	if (!lru->node)

  		goto out;

  	for_each_node(i) {

  		spin_lock_init(&lru->node[i].lock);

  		if (key)
  			lockdep_set_class(&lru->node[i].lock, key);

  		init_one_lru(&lru->node[i].lru);
  	}
  
  	err = memcg_init_list_lru(lru, memcg_aware);
  	if (err) {
  		kfree(lru->node);

  		/* Do this so a list_lru_destroy() doesn't crash: */
  		lru->node = NULL;

  		goto out;

  	}

  	list_lru_register(lru);

  out:
  	memcg_put_cache_ids();
  	return err;

  }

  EXPORT_SYMBOL_GPL(__list_lru_init);

  
  void list_lru_destroy(struct list_lru *lru)
  {

  	/* Already destroyed or not yet initialized? */
  	if (!lru->node)
  		return;

  
  	memcg_get_cache_ids();

  	list_lru_unregister(lru);

  
  	memcg_destroy_list_lru(lru);

  	kfree(lru->node);

  	lru->node = NULL;

  #ifdef CONFIG_MEMCG_KMEM
  	lru->shrinker_id = -1;
  #endif

  	memcg_put_cache_ids();

  }
  EXPORT_SYMBOL_GPL(list_lru_destroy);