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
14 struct mem_cgroup;
15
16 /* list_lru_walk_cb has to always return one of those */
17 enum 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
27 struct list_lru_one {
28 struct list_head list;
29 /* may become negative during memcg reparenting */
30 long nr_items;
31 };
32
33 struct list_lru_memcg {
34 /* array of per cgroup lists, indexed by memcg_cache_id */
35 struct list_lru_one *lru[0];
36 };
37
38 struct 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 #if defined(CONFIG_MEMCG) && !defined(CONFIG_SLOB)
44 /* for cgroup aware lrus points to per cgroup lists, otherwise NULL */
45 struct list_lru_memcg *memcg_lrus;
46 #endif
47 long nr_items;
48 } ____cacheline_aligned_in_smp;
49
50 struct list_lru {
51 struct list_lru_node *node;
52 #if defined(CONFIG_MEMCG) && !defined(CONFIG_SLOB)
53 struct list_head list;
54 #endif
55 };
56
57 void list_lru_destroy(struct list_lru *lru);
58 int __list_lru_init(struct list_lru *lru, bool memcg_aware,
59 struct lock_class_key *key);
60
61 #define list_lru_init(lru) __list_lru_init((lru), false, NULL)
62 #define list_lru_init_key(lru, key) __list_lru_init((lru), false, (key))
63 #define list_lru_init_memcg(lru) __list_lru_init((lru), true, NULL)
64
65 int memcg_update_all_list_lrus(int num_memcgs);
66 void memcg_drain_all_list_lrus(int src_idx, int dst_idx);
67
68 /**
69 * list_lru_add: add an element to the lru list's tail
70 * @list_lru: the lru pointer
71 * @item: the item to be added.
72 *
73 * If the element is already part of a list, this function returns doing
74 * nothing. Therefore the caller does not need to keep state about whether or
75 * not the element already belongs in the list and is allowed to lazy update
76 * it. Note however that this is valid for *a* list, not *this* list. If
77 * the caller organize itself in a way that elements can be in more than
78 * one type of list, it is up to the caller to fully remove the item from
79 * the previous list (with list_lru_del() for instance) before moving it
80 * to @list_lru
81 *
82 * Return value: true if the list was updated, false otherwise
83 */
84 bool list_lru_add(struct list_lru *lru, struct list_head *item);
85
86 /**
87 * list_lru_del: delete an element to the lru list
88 * @list_lru: the lru pointer
89 * @item: the item to be deleted.
90 *
91 * This function works analogously as list_lru_add in terms of list
92 * manipulation. The comments about an element already pertaining to
93 * a list are also valid for list_lru_del.
94 *
95 * Return value: true if the list was updated, false otherwise
96 */
97 bool list_lru_del(struct list_lru *lru, struct list_head *item);
98
99 /**
100 * list_lru_count_one: return the number of objects currently held by @lru
101 * @lru: the lru pointer.
102 * @nid: the node id to count from.
103 * @memcg: the cgroup to count from.
104 *
105 * Always return a non-negative number, 0 for empty lists. There is no
106 * guarantee that the list is not updated while the count is being computed.
107 * Callers that want such a guarantee need to provide an outer lock.
108 */
109 unsigned long list_lru_count_one(struct list_lru *lru,
110 int nid, struct mem_cgroup *memcg);
111 unsigned long list_lru_count_node(struct list_lru *lru, int nid);
112
113 static inline unsigned long list_lru_shrink_count(struct list_lru *lru,
114 struct shrink_control *sc)
115 {
116 return list_lru_count_one(lru, sc->nid, sc->memcg);
117 }
118
119 static inline unsigned long list_lru_count(struct list_lru *lru)
120 {
121 long count = 0;
122 int nid;
123
124 for_each_node_state(nid, N_NORMAL_MEMORY)
125 count += list_lru_count_node(lru, nid);
126
127 return count;
128 }
129
130 void list_lru_isolate(struct list_lru_one *list, struct list_head *item);
131 void list_lru_isolate_move(struct list_lru_one *list, struct list_head *item,
132 struct list_head *head);
133
134 typedef enum lru_status (*list_lru_walk_cb)(struct list_head *item,
135 struct list_lru_one *list, spinlock_t *lock, void *cb_arg);
136
137 /**
138 * list_lru_walk_one: walk a list_lru, isolating and disposing freeable items.
139 * @lru: the lru pointer.
140 * @nid: the node id to scan from.
141 * @memcg: the cgroup to scan from.
142 * @isolate: callback function that is resposible for deciding what to do with
143 * the item currently being scanned
144 * @cb_arg: opaque type that will be passed to @isolate
145 * @nr_to_walk: how many items to scan.
146 *
147 * This function will scan all elements in a particular list_lru, calling the
148 * @isolate callback for each of those items, along with the current list
149 * spinlock and a caller-provided opaque. The @isolate callback can choose to
150 * drop the lock internally, but *must* return with the lock held. The callback
151 * will return an enum lru_status telling the list_lru infrastructure what to
152 * do with the object being scanned.
153 *
154 * Please note that nr_to_walk does not mean how many objects will be freed,
155 * just how many objects will be scanned.
156 *
157 * Return value: the number of objects effectively removed from the LRU.
158 */
159 unsigned long list_lru_walk_one(struct list_lru *lru,
160 int nid, struct mem_cgroup *memcg,
161 list_lru_walk_cb isolate, void *cb_arg,
162 unsigned long *nr_to_walk);
163 unsigned long list_lru_walk_node(struct list_lru *lru, int nid,
164 list_lru_walk_cb isolate, void *cb_arg,
165 unsigned long *nr_to_walk);
166
167 static inline unsigned long
168 list_lru_shrink_walk(struct list_lru *lru, struct shrink_control *sc,
169 list_lru_walk_cb isolate, void *cb_arg)
170 {
171 return list_lru_walk_one(lru, sc->nid, sc->memcg, isolate, cb_arg,
172 &sc->nr_to_scan);
173 }
174
175 static inline unsigned long
176 list_lru_walk(struct list_lru *lru, list_lru_walk_cb isolate,
177 void *cb_arg, unsigned long nr_to_walk)
178 {
179 long isolated = 0;
180 int nid;
181
182 for_each_node_state(nid, N_NORMAL_MEMORY) {
183 isolated += list_lru_walk_node(lru, nid, isolate,
184 cb_arg, &nr_to_walk);
185 if (nr_to_walk <= 0)
186 break;
187 }
188 return isolated;
189 }
190 #endif /* _LRU_LIST_H */
191
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