1/* SPDX-License-Identifier: GPL-2.0 */
2/*
3 * Copyright (c) 2013 Red Hat, Inc. and Parallels Inc. All rights reserved.
4 * Authors: David Chinner and Glauber Costa
5 *
6 * Generic LRU infrastructure
7 */
8#ifndef _LRU_LIST_H
9#define _LRU_LIST_H
10
11#include <linux/list.h>
12#include <linux/nodemask.h>
13#include <linux/shrinker.h>
14
15struct mem_cgroup;
16
17/* list_lru_walk_cb has to always return one of those */
18enum lru_status {
19	LRU_REMOVED,		/* item removed from list */
20	LRU_REMOVED_RETRY,	/* item removed, but lock has been
21				   dropped and reacquired */
22	LRU_ROTATE,		/* item referenced, give another pass */
23	LRU_SKIP,		/* item cannot be locked, skip */
24	LRU_RETRY,		/* item not freeable. May drop the lock
25				   internally, but has to return locked. */
26};
27
28struct list_lru_one {
29	struct list_head	list;
30	/* may become negative during memcg reparenting */
31	long			nr_items;
32};
33
34struct list_lru_memcg {
35	struct rcu_head		rcu;
36	/* array of per cgroup lists, indexed by memcg_cache_id */
37	struct list_lru_one	*lru[];
38};
39
40struct list_lru_node {
41	/* protects all lists on the node, including per cgroup */
42	spinlock_t		lock;
43	/* global list, used for the root cgroup in cgroup aware lrus */
44	struct list_lru_one	lru;
45#ifdef CONFIG_MEMCG_KMEM
46	/* for cgroup aware lrus points to per cgroup lists, otherwise NULL */
47	struct list_lru_memcg	__rcu *memcg_lrus;
48#endif
49	long nr_items;
50} ____cacheline_aligned_in_smp;
51
52struct list_lru {
53	struct list_lru_node	*node;
54#ifdef CONFIG_MEMCG_KMEM
55	struct list_head	list;
56	int			shrinker_id;
57	bool			memcg_aware;
58#endif
59};
60
61void list_lru_destroy(struct list_lru *lru);
62int __list_lru_init(struct list_lru *lru, bool memcg_aware,
63		    struct lock_class_key *key, struct shrinker *shrinker);
64
65#define list_lru_init(lru)				\
66	__list_lru_init((lru), false, NULL, NULL)
67#define list_lru_init_key(lru, key)			\
68	__list_lru_init((lru), false, (key), NULL)
69#define list_lru_init_memcg(lru, shrinker)		\
70	__list_lru_init((lru), true, NULL, shrinker)
71
72int memcg_update_all_list_lrus(int num_memcgs);
73void memcg_drain_all_list_lrus(int src_idx, struct mem_cgroup *dst_memcg);
74
75/**
76 * list_lru_add: add an element to the lru list's tail
77 * @list_lru: the lru pointer
78 * @item: the item to be added.
79 *
80 * If the element is already part of a list, this function returns doing
81 * nothing. Therefore the caller does not need to keep state about whether or
82 * not the element already belongs in the list and is allowed to lazy update
83 * it. Note however that this is valid for *a* list, not *this* list. If
84 * the caller organize itself in a way that elements can be in more than
85 * one type of list, it is up to the caller to fully remove the item from
86 * the previous list (with list_lru_del() for instance) before moving it
87 * to @list_lru
88 *
89 * Return value: true if the list was updated, false otherwise
90 */
91bool list_lru_add(struct list_lru *lru, struct list_head *item);
92
93/**
94 * list_lru_del: delete an element to the lru list
95 * @list_lru: the lru pointer
96 * @item: the item to be deleted.
97 *
98 * This function works analogously as list_lru_add in terms of list
99 * manipulation. The comments about an element already pertaining to
100 * a list are also valid for list_lru_del.
101 *
102 * Return value: true if the list was updated, false otherwise
103 */
104bool list_lru_del(struct list_lru *lru, struct list_head *item);
105
106/**
107 * list_lru_count_one: return the number of objects currently held by @lru
108 * @lru: the lru pointer.
109 * @nid: the node id to count from.
110 * @memcg: the cgroup to count from.
111 *
112 * Always return a non-negative number, 0 for empty lists. There is no
113 * guarantee that the list is not updated while the count is being computed.
114 * Callers that want such a guarantee need to provide an outer lock.
115 */
116unsigned long list_lru_count_one(struct list_lru *lru,
117				 int nid, struct mem_cgroup *memcg);
118unsigned long list_lru_count_node(struct list_lru *lru, int nid);
119
120static inline unsigned long list_lru_shrink_count(struct list_lru *lru,
121						  struct shrink_control *sc)
122{
123	return list_lru_count_one(lru, sc->nid, sc->memcg);
124}
125
126static inline unsigned long list_lru_count(struct list_lru *lru)
127{
128	long count = 0;
129	int nid;
130
131	for_each_node_state(nid, N_NORMAL_MEMORY)
132		count += list_lru_count_node(lru, nid);
133
134	return count;
135}
136
137void list_lru_isolate(struct list_lru_one *list, struct list_head *item);
138void list_lru_isolate_move(struct list_lru_one *list, struct list_head *item,
139			   struct list_head *head);
140
141typedef enum lru_status (*list_lru_walk_cb)(struct list_head *item,
142		struct list_lru_one *list, spinlock_t *lock, void *cb_arg);
143
144/**
145 * list_lru_walk_one: walk a list_lru, isolating and disposing freeable items.
146 * @lru: the lru pointer.
147 * @nid: the node id to scan from.
148 * @memcg: the cgroup to scan from.
149 * @isolate: callback function that is resposible for deciding what to do with
150 *  the item currently being scanned
151 * @cb_arg: opaque type that will be passed to @isolate
152 * @nr_to_walk: how many items to scan.
153 *
154 * This function will scan all elements in a particular list_lru, calling the
155 * @isolate callback for each of those items, along with the current list
156 * spinlock and a caller-provided opaque. The @isolate callback can choose to
157 * drop the lock internally, but *must* return with the lock held. The callback
158 * will return an enum lru_status telling the list_lru infrastructure what to
159 * do with the object being scanned.
160 *
161 * Please note that nr_to_walk does not mean how many objects will be freed,
162 * just how many objects will be scanned.
163 *
164 * Return value: the number of objects effectively removed from the LRU.
165 */
166unsigned long list_lru_walk_one(struct list_lru *lru,
167				int nid, struct mem_cgroup *memcg,
168				list_lru_walk_cb isolate, void *cb_arg,
169				unsigned long *nr_to_walk);
170/**
171 * list_lru_walk_one_irq: walk a list_lru, isolating and disposing freeable items.
172 * @lru: the lru pointer.
173 * @nid: the node id to scan from.
174 * @memcg: the cgroup to scan from.
175 * @isolate: callback function that is resposible for deciding what to do with
176 *  the item currently being scanned
177 * @cb_arg: opaque type that will be passed to @isolate
178 * @nr_to_walk: how many items to scan.
179 *
180 * Same as @list_lru_walk_one except that the spinlock is acquired with
181 * spin_lock_irq().
182 */
183unsigned long list_lru_walk_one_irq(struct list_lru *lru,
184				    int nid, struct mem_cgroup *memcg,
185				    list_lru_walk_cb isolate, void *cb_arg,
186				    unsigned long *nr_to_walk);
187unsigned long list_lru_walk_node(struct list_lru *lru, int nid,
188				 list_lru_walk_cb isolate, void *cb_arg,
189				 unsigned long *nr_to_walk);
190
191static inline unsigned long
192list_lru_shrink_walk(struct list_lru *lru, struct shrink_control *sc,
193		     list_lru_walk_cb isolate, void *cb_arg)
194{
195	return list_lru_walk_one(lru, sc->nid, sc->memcg, isolate, cb_arg,
196				 &sc->nr_to_scan);
197}
198
199static inline unsigned long
200list_lru_shrink_walk_irq(struct list_lru *lru, struct shrink_control *sc,
201			 list_lru_walk_cb isolate, void *cb_arg)
202{
203	return list_lru_walk_one_irq(lru, sc->nid, sc->memcg, isolate, cb_arg,
204				     &sc->nr_to_scan);
205}
206
207static inline unsigned long
208list_lru_walk(struct list_lru *lru, list_lru_walk_cb isolate,
209	      void *cb_arg, unsigned long nr_to_walk)
210{
211	long isolated = 0;
212	int nid;
213
214	for_each_node_state(nid, N_NORMAL_MEMORY) {
215		isolated += list_lru_walk_node(lru, nid, isolate,
216					       cb_arg, &nr_to_walk);
217		if (nr_to_walk <= 0)
218			break;
219	}
220	return isolated;
221}
222#endif /* _LRU_LIST_H */
223