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Dave Chinnera38e4082013-08-28 10:17:58 +10001/*
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>
Dave Chinner3b1d58a2013-08-28 10:18:00 +100011#include <linux/nodemask.h>
Vladimir Davydov503c3582015-02-12 14:58:47 -080012#include <linux/shrinker.h>
Dave Chinnera38e4082013-08-28 10:17:58 +100013
14/* list_lru_walk_cb has to always return one of those */
15enum lru_status {
16 LRU_REMOVED, /* item removed from list */
Johannes Weiner449dd692014-04-03 14:47:56 -070017 LRU_REMOVED_RETRY, /* item removed, but lock has been
18 dropped and reacquired */
Dave Chinnera38e4082013-08-28 10:17:58 +100019 LRU_ROTATE, /* item referenced, give another pass */
20 LRU_SKIP, /* item cannot be locked, skip */
21 LRU_RETRY, /* item not freeable. May drop the lock
22 internally, but has to return locked. */
23};
24
Dave Chinner3b1d58a2013-08-28 10:18:00 +100025struct list_lru_node {
Dave Chinnera38e4082013-08-28 10:17:58 +100026 spinlock_t lock;
27 struct list_head list;
28 /* kept as signed so we can catch imbalance bugs */
29 long nr_items;
Dave Chinner3b1d58a2013-08-28 10:18:00 +100030} ____cacheline_aligned_in_smp;
31
32struct list_lru {
Glauber Costa5ca302c2013-08-28 10:18:18 +100033 struct list_lru_node *node;
Vladimir Davydovc0a5b562015-02-12 14:59:07 -080034#ifdef CONFIG_MEMCG_KMEM
35 struct list_head list;
36#endif
Dave Chinnera38e4082013-08-28 10:17:58 +100037};
38
Glauber Costa5ca302c2013-08-28 10:18:18 +100039void list_lru_destroy(struct list_lru *lru);
Johannes Weiner449dd692014-04-03 14:47:56 -070040int list_lru_init_key(struct list_lru *lru, struct lock_class_key *key);
41static inline int list_lru_init(struct list_lru *lru)
42{
43 return list_lru_init_key(lru, NULL);
44}
Dave Chinnera38e4082013-08-28 10:17:58 +100045
46/**
47 * list_lru_add: add an element to the lru list's tail
48 * @list_lru: the lru pointer
49 * @item: the item to be added.
50 *
51 * If the element is already part of a list, this function returns doing
52 * nothing. Therefore the caller does not need to keep state about whether or
53 * not the element already belongs in the list and is allowed to lazy update
54 * it. Note however that this is valid for *a* list, not *this* list. If
55 * the caller organize itself in a way that elements can be in more than
56 * one type of list, it is up to the caller to fully remove the item from
57 * the previous list (with list_lru_del() for instance) before moving it
58 * to @list_lru
59 *
60 * Return value: true if the list was updated, false otherwise
61 */
62bool list_lru_add(struct list_lru *lru, struct list_head *item);
63
64/**
65 * list_lru_del: delete an element to the lru list
66 * @list_lru: the lru pointer
67 * @item: the item to be deleted.
68 *
69 * This function works analogously as list_lru_add in terms of list
70 * manipulation. The comments about an element already pertaining to
71 * a list are also valid for list_lru_del.
72 *
73 * Return value: true if the list was updated, false otherwise
74 */
75bool list_lru_del(struct list_lru *lru, struct list_head *item);
76
77/**
Glauber Costa6a4f4962013-08-28 10:18:02 +100078 * list_lru_count_node: return the number of objects currently held by @lru
Dave Chinnera38e4082013-08-28 10:17:58 +100079 * @lru: the lru pointer.
Glauber Costa6a4f4962013-08-28 10:18:02 +100080 * @nid: the node id to count from.
Dave Chinnera38e4082013-08-28 10:17:58 +100081 *
82 * Always return a non-negative number, 0 for empty lists. There is no
83 * guarantee that the list is not updated while the count is being computed.
84 * Callers that want such a guarantee need to provide an outer lock.
85 */
Glauber Costa6a4f4962013-08-28 10:18:02 +100086unsigned long list_lru_count_node(struct list_lru *lru, int nid);
Vladimir Davydov503c3582015-02-12 14:58:47 -080087
88static inline unsigned long list_lru_shrink_count(struct list_lru *lru,
89 struct shrink_control *sc)
90{
91 return list_lru_count_node(lru, sc->nid);
92}
93
Glauber Costa6a4f4962013-08-28 10:18:02 +100094static inline unsigned long list_lru_count(struct list_lru *lru)
95{
96 long count = 0;
97 int nid;
98
Vladimir Davydovff0b67e2015-02-12 14:59:04 -080099 for_each_node_state(nid, N_NORMAL_MEMORY)
Glauber Costa6a4f4962013-08-28 10:18:02 +1000100 count += list_lru_count_node(lru, nid);
101
102 return count;
103}
Dave Chinnera38e4082013-08-28 10:17:58 +1000104
105typedef enum lru_status
106(*list_lru_walk_cb)(struct list_head *item, spinlock_t *lock, void *cb_arg);
107/**
Glauber Costa6a4f4962013-08-28 10:18:02 +1000108 * list_lru_walk_node: walk a list_lru, isolating and disposing freeable items.
Dave Chinnera38e4082013-08-28 10:17:58 +1000109 * @lru: the lru pointer.
Glauber Costa6a4f4962013-08-28 10:18:02 +1000110 * @nid: the node id to scan from.
Dave Chinnera38e4082013-08-28 10:17:58 +1000111 * @isolate: callback function that is resposible for deciding what to do with
112 * the item currently being scanned
113 * @cb_arg: opaque type that will be passed to @isolate
114 * @nr_to_walk: how many items to scan.
115 *
116 * This function will scan all elements in a particular list_lru, calling the
117 * @isolate callback for each of those items, along with the current list
118 * spinlock and a caller-provided opaque. The @isolate callback can choose to
119 * drop the lock internally, but *must* return with the lock held. The callback
120 * will return an enum lru_status telling the list_lru infrastructure what to
121 * do with the object being scanned.
122 *
123 * Please note that nr_to_walk does not mean how many objects will be freed,
124 * just how many objects will be scanned.
125 *
126 * Return value: the number of objects effectively removed from the LRU.
127 */
Glauber Costa6a4f4962013-08-28 10:18:02 +1000128unsigned long list_lru_walk_node(struct list_lru *lru, int nid,
129 list_lru_walk_cb isolate, void *cb_arg,
130 unsigned long *nr_to_walk);
131
132static inline unsigned long
Vladimir Davydov503c3582015-02-12 14:58:47 -0800133list_lru_shrink_walk(struct list_lru *lru, struct shrink_control *sc,
134 list_lru_walk_cb isolate, void *cb_arg)
135{
136 return list_lru_walk_node(lru, sc->nid, isolate, cb_arg,
137 &sc->nr_to_scan);
138}
139
140static inline unsigned long
Glauber Costa6a4f4962013-08-28 10:18:02 +1000141list_lru_walk(struct list_lru *lru, list_lru_walk_cb isolate,
142 void *cb_arg, unsigned long nr_to_walk)
143{
144 long isolated = 0;
145 int nid;
146
Vladimir Davydovff0b67e2015-02-12 14:59:04 -0800147 for_each_node_state(nid, N_NORMAL_MEMORY) {
Glauber Costa6a4f4962013-08-28 10:18:02 +1000148 isolated += list_lru_walk_node(lru, nid, isolate,
149 cb_arg, &nr_to_walk);
150 if (nr_to_walk <= 0)
151 break;
152 }
153 return isolated;
154}
Dave Chinnera38e4082013-08-28 10:17:58 +1000155#endif /* _LRU_LIST_H */