/* SPDX-License-Identifier: GPL-2.0 */

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

  #include <linux/nodemask.h>

  #include <linux/shrinker.h>

  struct mem_cgroup;

  /* list_lru_walk_cb has to always return one of those */
  enum lru_status {
  	LRU_REMOVED,		/* item removed from list */

  	LRU_REMOVED_RETRY,	/* item removed, but lock has been
  				   dropped and reacquired */

  	LRU_ROTATE,		/* item referenced, give another pass */
  	LRU_SKIP,		/* item cannot be locked, skip */
  	LRU_RETRY,		/* item not freeable. May drop the lock
  				   internally, but has to return locked. */
  };

  struct list_lru_one {

  	struct list_head	list;

  	/* may become negative during memcg reparenting */

  	long			nr_items;

  };
  
  struct list_lru_memcg {

  	struct rcu_head		rcu;

  	/* array of per cgroup lists, indexed by memcg_cache_id */

  	struct list_lru_one	*lru[];

  };
  
  struct list_lru_node {
  	/* protects all lists on the node, including per cgroup */
  	spinlock_t		lock;
  	/* global list, used for the root cgroup in cgroup aware lrus */
  	struct list_lru_one	lru;

  #ifdef CONFIG_MEMCG_KMEM

  	/* for cgroup aware lrus points to per cgroup lists, otherwise NULL */

  	struct list_lru_memcg	__rcu *memcg_lrus;

  #endif

  	long nr_items;

  } ____cacheline_aligned_in_smp;
  
  struct list_lru {

  	struct list_lru_node	*node;

  #ifdef CONFIG_MEMCG_KMEM

  	struct list_head	list;

  	int			shrinker_id;

  	bool			memcg_aware;

  #endif

  };

  void list_lru_destroy(struct list_lru *lru);

  int __list_lru_init(struct list_lru *lru, bool memcg_aware,

  		    struct lock_class_key *key, struct shrinker *shrinker);

  #define list_lru_init(lru)				\
  	__list_lru_init((lru), false, NULL, NULL)
  #define list_lru_init_key(lru, key)			\
  	__list_lru_init((lru), false, (key), NULL)
  #define list_lru_init_memcg(lru, shrinker)		\
  	__list_lru_init((lru), true, NULL, shrinker)

  
  int memcg_update_all_list_lrus(int num_memcgs);

  void memcg_drain_all_list_lrus(int src_idx, struct mem_cgroup *dst_memcg);

  
  /**
   * list_lru_add: add an element to the lru list's tail
   * @list_lru: the lru pointer
   * @item: the item to be added.
   *
   * If the element is already part of a list, this function returns doing
   * nothing. Therefore the caller does not need to keep state about whether or
   * not the element already belongs in the list and is allowed to lazy update
   * it. Note however that this is valid for *a* list, not *this* list. If
   * the caller organize itself in a way that elements can be in more than
   * one type of list, it is up to the caller to fully remove the item from
   * the previous list (with list_lru_del() for instance) before moving it
   * to @list_lru
   *
   * Return value: true if the list was updated, false otherwise
   */
  bool list_lru_add(struct list_lru *lru, struct list_head *item);
  
  /**
   * list_lru_del: delete an element to the lru list
   * @list_lru: the lru pointer
   * @item: the item to be deleted.
   *
   * This function works analogously as list_lru_add in terms of list
   * manipulation. The comments about an element already pertaining to
   * a list are also valid for list_lru_del.
   *
   * Return value: true if the list was updated, false otherwise
   */
  bool list_lru_del(struct list_lru *lru, struct list_head *item);
  
  /**

   * list_lru_count_one: return the number of objects currently held by @lru

   * @lru: the lru pointer.

   * @nid: the node id to count from.

   * @memcg: the cgroup to count from.

   *
   * Always return a non-negative number, 0 for empty lists. There is no
   * guarantee that the list is not updated while the count is being computed.
   * Callers that want such a guarantee need to provide an outer lock.
   */

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

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

  
  static inline unsigned long list_lru_shrink_count(struct list_lru *lru,
  						  struct shrink_control *sc)
  {

  	return list_lru_count_one(lru, sc->nid, sc->memcg);

  }

  static inline unsigned long list_lru_count(struct list_lru *lru)
  {
  	long count = 0;
  	int nid;

  	for_each_node_state(nid, N_NORMAL_MEMORY)

  		count += list_lru_count_node(lru, nid);
  
  	return count;
  }

  void list_lru_isolate(struct list_lru_one *list, struct list_head *item);
  void list_lru_isolate_move(struct list_lru_one *list, struct list_head *item,
  			   struct list_head *head);
  
  typedef enum lru_status (*list_lru_walk_cb)(struct list_head *item,
  		struct list_lru_one *list, spinlock_t *lock, void *cb_arg);

  /**

   * list_lru_walk_one: walk a list_lru, isolating and disposing freeable items.

   * @lru: the lru pointer.

   * @nid: the node id to scan from.

   * @memcg: the cgroup to scan from.

   * @isolate: callback function that is resposible for deciding what to do with
   *  the item currently being scanned
   * @cb_arg: opaque type that will be passed to @isolate
   * @nr_to_walk: how many items to scan.
   *
   * This function will scan all elements in a particular list_lru, calling the
   * @isolate callback for each of those items, along with the current list
   * spinlock and a caller-provided opaque. The @isolate callback can choose to
   * drop the lock internally, but *must* return with the lock held. The callback
   * will return an enum lru_status telling the list_lru infrastructure what to
   * do with the object being scanned.
   *
   * Please note that nr_to_walk does not mean how many objects will be freed,
   * just how many objects will be scanned.
   *
   * Return value: the number of objects effectively removed from the LRU.
   */

  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);

  /**
   * list_lru_walk_one_irq: walk a list_lru, isolating and disposing freeable items.
   * @lru: the lru pointer.
   * @nid: the node id to scan from.
   * @memcg: the cgroup to scan from.
   * @isolate: callback function that is resposible for deciding what to do with
   *  the item currently being scanned
   * @cb_arg: opaque type that will be passed to @isolate
   * @nr_to_walk: how many items to scan.
   *
   * Same as @list_lru_walk_one except that the spinlock is acquired with
   * spin_lock_irq().
   */
  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);

  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);
  
  static inline unsigned long

  list_lru_shrink_walk(struct list_lru *lru, struct shrink_control *sc,
  		     list_lru_walk_cb isolate, void *cb_arg)
  {

  	return list_lru_walk_one(lru, sc->nid, sc->memcg, isolate, cb_arg,
  				 &sc->nr_to_scan);

  }
  
  static inline unsigned long

  list_lru_shrink_walk_irq(struct list_lru *lru, struct shrink_control *sc,
  			 list_lru_walk_cb isolate, void *cb_arg)
  {
  	return list_lru_walk_one_irq(lru, sc->nid, sc->memcg, isolate, cb_arg,
  				     &sc->nr_to_scan);
  }
  
  static inline unsigned long

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

  	for_each_node_state(nid, N_NORMAL_MEMORY) {

  		isolated += list_lru_walk_node(lru, nid, isolate,
  					       cb_arg, &nr_to_walk);
  		if (nr_to_walk <= 0)
  			break;
  	}
  	return isolated;
  }

  #endif /* _LRU_LIST_H */