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