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#include <linux/xarray.h>
15
16struct mem_cgroup;
17
18/* list_lru_walk_cb has to always return one of those */
19enum lru_status {
20	LRU_REMOVED,		/* item removed from list */
21	LRU_REMOVED_RETRY,	/* item removed, but lock has been
22				   dropped and reacquired */
23	LRU_ROTATE,		/* item referenced, give another pass */
24	LRU_SKIP,		/* item cannot be locked, skip */
25	LRU_RETRY,		/* item not freeable. May drop the lock
26				   internally, but has to return locked. */
27	LRU_STOP,		/* stop lru list walking. May drop the lock
28				   internally, but has to return locked. */
29};
30
31struct list_lru_one {
32	struct list_head	list;
33	/* may become negative during memcg reparenting */
34	long			nr_items;
35};
36
37struct list_lru_memcg {
38	struct rcu_head		rcu;
39	/* array of per cgroup per node lists, indexed by node id */
40	struct list_lru_one	node[];
41};
42
43struct list_lru_node {
44	/* protects all lists on the node, including per cgroup */
45	spinlock_t		lock;
46	/* global list, used for the root cgroup in cgroup aware lrus */
47	struct list_lru_one	lru;
48	long			nr_items;
49} ____cacheline_aligned_in_smp;
50
51struct list_lru {
52	struct list_lru_node	*node;
53#ifdef CONFIG_MEMCG_KMEM
54	struct list_head	list;
55	int			shrinker_id;
56	bool			memcg_aware;
57	struct xarray		xa;
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_memcg(lru, shrinker)		\
68	__list_lru_init((lru), true, NULL, shrinker)
69
70int memcg_list_lru_alloc(struct mem_cgroup *memcg, struct list_lru *lru,
71			 gfp_t gfp);
72void memcg_reparent_list_lrus(struct mem_cgroup *memcg, struct mem_cgroup *parent);
73
74/**
75 * list_lru_add: add an element to the lru list's tail
76 * @lru: the lru pointer
77 * @item: the item to be added.
78 * @nid: the node id of the sublist to add the item to.
79 * @memcg: the cgroup of the sublist to add the item to.
80 *
81 * If the element is already part of a list, this function returns doing
82 * nothing. Therefore the caller does not need to keep state about whether or
83 * not the element already belongs in the list and is allowed to lazy update
84 * it. Note however that this is valid for *a* list, not *this* list. If
85 * the caller organize itself in a way that elements can be in more than
86 * one type of list, it is up to the caller to fully remove the item from
87 * the previous list (with list_lru_del() for instance) before moving it
88 * to @lru.
89 *
90 * Return: true if the list was updated, false otherwise
91 */
92bool list_lru_add(struct list_lru *lru, struct list_head *item, int nid,
93		    struct mem_cgroup *memcg);
94
95/**
96 * list_lru_add_obj: add an element to the lru list's tail
97 * @lru: the lru pointer
98 * @item: the item to be added.
99 *
100 * This function is similar to list_lru_add(), but the NUMA node and the
101 * memcg of the sublist is determined by @item list_head. This assumption is
102 * valid for slab objects LRU such as dentries, inodes, etc.
103 *
104 * Return value: true if the list was updated, false otherwise
105 */
106bool list_lru_add_obj(struct list_lru *lru, struct list_head *item);
107
108/**
109 * list_lru_del: delete an element from the lru list
110 * @lru: the lru pointer
111 * @item: the item to be deleted.
112 * @nid: the node id of the sublist to delete the item from.
113 * @memcg: the cgroup of the sublist to delete the item from.
114 *
115 * This function works analogously as list_lru_add() in terms of list
116 * manipulation. The comments about an element already pertaining to
117 * a list are also valid for list_lru_del().
118 *
119 * Return: true if the list was updated, false otherwise
120 */
121bool list_lru_del(struct list_lru *lru, struct list_head *item, int nid,
122		    struct mem_cgroup *memcg);
123
124/**
125 * list_lru_del_obj: delete an element from the lru list
126 * @lru: the lru pointer
127 * @item: the item to be deleted.
128 *
129 * This function is similar to list_lru_del(), but the NUMA node and the
130 * memcg of the sublist is determined by @item list_head. This assumption is
131 * valid for slab objects LRU such as dentries, inodes, etc.
132 *
133 * Return value: true if the list was updated, false otherwise.
134 */
135bool list_lru_del_obj(struct list_lru *lru, struct list_head *item);
136
137/**
138 * list_lru_count_one: return the number of objects currently held by @lru
139 * @lru: the lru pointer.
140 * @nid: the node id to count from.
141 * @memcg: the cgroup to count from.
142 *
143 * There is no guarantee that the list is not updated while the count is being
144 * computed. Callers that want such a guarantee need to provide an outer lock.
145 *
146 * Return: 0 for empty lists, otherwise the number of objects
147 * currently held by @lru.
148 */
149unsigned long list_lru_count_one(struct list_lru *lru,
150				 int nid, struct mem_cgroup *memcg);
151unsigned long list_lru_count_node(struct list_lru *lru, int nid);
152
153static inline unsigned long list_lru_shrink_count(struct list_lru *lru,
154						  struct shrink_control *sc)
155{
156	return list_lru_count_one(lru, sc->nid, sc->memcg);
157}
158
159static inline unsigned long list_lru_count(struct list_lru *lru)
160{
161	long count = 0;
162	int nid;
163
164	for_each_node_state(nid, N_NORMAL_MEMORY)
165		count += list_lru_count_node(lru, nid);
166
167	return count;
168}
169
170void list_lru_isolate(struct list_lru_one *list, struct list_head *item);
171void list_lru_isolate_move(struct list_lru_one *list, struct list_head *item,
172			   struct list_head *head);
173
174typedef enum lru_status (*list_lru_walk_cb)(struct list_head *item,
175		struct list_lru_one *list, spinlock_t *lock, void *cb_arg);
176
177/**
178 * list_lru_walk_one: walk a @lru, isolating and disposing freeable items.
179 * @lru: the lru pointer.
180 * @nid: the node id to scan from.
181 * @memcg: the cgroup to scan from.
182 * @isolate: callback function that is responsible for deciding what to do with
183 *  the item currently being scanned
184 * @cb_arg: opaque type that will be passed to @isolate
185 * @nr_to_walk: how many items to scan.
186 *
187 * This function will scan all elements in a particular @lru, calling the
188 * @isolate callback for each of those items, along with the current list
189 * spinlock and a caller-provided opaque. The @isolate callback can choose to
190 * drop the lock internally, but *must* return with the lock held. The callback
191 * will return an enum lru_status telling the @lru infrastructure what to
192 * do with the object being scanned.
193 *
194 * Please note that @nr_to_walk does not mean how many objects will be freed,
195 * just how many objects will be scanned.
196 *
197 * Return: the number of objects effectively removed from the LRU.
198 */
199unsigned long list_lru_walk_one(struct list_lru *lru,
200				int nid, struct mem_cgroup *memcg,
201				list_lru_walk_cb isolate, void *cb_arg,
202				unsigned long *nr_to_walk);
203/**
204 * list_lru_walk_one_irq: walk a @lru, isolating and disposing freeable items.
205 * @lru: the lru pointer.
206 * @nid: the node id to scan from.
207 * @memcg: the cgroup to scan from.
208 * @isolate: callback function that is responsible for deciding what to do with
209 *  the item currently being scanned
210 * @cb_arg: opaque type that will be passed to @isolate
211 * @nr_to_walk: how many items to scan.
212 *
213 * Same as list_lru_walk_one() except that the spinlock is acquired with
214 * spin_lock_irq().
215 */
216unsigned long list_lru_walk_one_irq(struct list_lru *lru,
217				    int nid, struct mem_cgroup *memcg,
218				    list_lru_walk_cb isolate, void *cb_arg,
219				    unsigned long *nr_to_walk);
220unsigned long list_lru_walk_node(struct list_lru *lru, int nid,
221				 list_lru_walk_cb isolate, void *cb_arg,
222				 unsigned long *nr_to_walk);
223
224static inline unsigned long
225list_lru_shrink_walk(struct list_lru *lru, struct shrink_control *sc,
226		     list_lru_walk_cb isolate, void *cb_arg)
227{
228	return list_lru_walk_one(lru, sc->nid, sc->memcg, isolate, cb_arg,
229				 &sc->nr_to_scan);
230}
231
232static inline unsigned long
233list_lru_shrink_walk_irq(struct list_lru *lru, struct shrink_control *sc,
234			 list_lru_walk_cb isolate, void *cb_arg)
235{
236	return list_lru_walk_one_irq(lru, sc->nid, sc->memcg, isolate, cb_arg,
237				     &sc->nr_to_scan);
238}
239
240static inline unsigned long
241list_lru_walk(struct list_lru *lru, list_lru_walk_cb isolate,
242	      void *cb_arg, unsigned long nr_to_walk)
243{
244	long isolated = 0;
245	int nid;
246
247	for_each_node_state(nid, N_NORMAL_MEMORY) {
248		isolated += list_lru_walk_node(lru, nid, isolate,
249					       cb_arg, &nr_to_walk);
250		if (nr_to_walk <= 0)
251			break;
252	}
253	return isolated;
254}
255#endif /* _LRU_LIST_H */
256