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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>
Dave Chinnera38e4082013-08-28 10:17:58 +100012
13/* list_lru_walk_cb has to always return one of those */
14enum lru_status {
15 LRU_REMOVED, /* item removed from list */
Johannes Weiner449dd692014-04-03 14:47:56 -070016 LRU_REMOVED_RETRY, /* item removed, but lock has been
17 dropped and reacquired */
Dave Chinnera38e4082013-08-28 10:17:58 +100018 LRU_ROTATE, /* item referenced, give another pass */
19 LRU_SKIP, /* item cannot be locked, skip */
20 LRU_RETRY, /* item not freeable. May drop the lock
21 internally, but has to return locked. */
22};
23
Dave Chinner3b1d58a2013-08-28 10:18:00 +100024struct list_lru_node {
Dave Chinnera38e4082013-08-28 10:17:58 +100025 spinlock_t lock;
26 struct list_head list;
27 /* kept as signed so we can catch imbalance bugs */
28 long nr_items;
Dave Chinner3b1d58a2013-08-28 10:18:00 +100029} ____cacheline_aligned_in_smp;
30
31struct list_lru {
Glauber Costa5ca302c2013-08-28 10:18:18 +100032 struct list_lru_node *node;
Dave Chinner3b1d58a2013-08-28 10:18:00 +100033 nodemask_t active_nodes;
Dave Chinnera38e4082013-08-28 10:17:58 +100034};
35
Glauber Costa5ca302c2013-08-28 10:18:18 +100036void list_lru_destroy(struct list_lru *lru);
Johannes Weiner449dd692014-04-03 14:47:56 -070037int list_lru_init_key(struct list_lru *lru, struct lock_class_key *key);
38static inline int list_lru_init(struct list_lru *lru)
39{
40 return list_lru_init_key(lru, NULL);
41}
Dave Chinnera38e4082013-08-28 10:17:58 +100042
43/**
44 * list_lru_add: add an element to the lru list's tail
45 * @list_lru: the lru pointer
46 * @item: the item to be added.
47 *
48 * If the element is already part of a list, this function returns doing
49 * nothing. Therefore the caller does not need to keep state about whether or
50 * not the element already belongs in the list and is allowed to lazy update
51 * it. Note however that this is valid for *a* list, not *this* list. If
52 * the caller organize itself in a way that elements can be in more than
53 * one type of list, it is up to the caller to fully remove the item from
54 * the previous list (with list_lru_del() for instance) before moving it
55 * to @list_lru
56 *
57 * Return value: true if the list was updated, false otherwise
58 */
59bool list_lru_add(struct list_lru *lru, struct list_head *item);
60
61/**
62 * list_lru_del: delete an element to the lru list
63 * @list_lru: the lru pointer
64 * @item: the item to be deleted.
65 *
66 * This function works analogously as list_lru_add in terms of list
67 * manipulation. The comments about an element already pertaining to
68 * a list are also valid for list_lru_del.
69 *
70 * Return value: true if the list was updated, false otherwise
71 */
72bool list_lru_del(struct list_lru *lru, struct list_head *item);
73
74/**
Glauber Costa6a4f4962013-08-28 10:18:02 +100075 * list_lru_count_node: return the number of objects currently held by @lru
Dave Chinnera38e4082013-08-28 10:17:58 +100076 * @lru: the lru pointer.
Glauber Costa6a4f4962013-08-28 10:18:02 +100077 * @nid: the node id to count from.
Dave Chinnera38e4082013-08-28 10:17:58 +100078 *
79 * Always return a non-negative number, 0 for empty lists. There is no
80 * guarantee that the list is not updated while the count is being computed.
81 * Callers that want such a guarantee need to provide an outer lock.
82 */
Glauber Costa6a4f4962013-08-28 10:18:02 +100083unsigned long list_lru_count_node(struct list_lru *lru, int nid);
84static inline unsigned long list_lru_count(struct list_lru *lru)
85{
86 long count = 0;
87 int nid;
88
89 for_each_node_mask(nid, lru->active_nodes)
90 count += list_lru_count_node(lru, nid);
91
92 return count;
93}
Dave Chinnera38e4082013-08-28 10:17:58 +100094
95typedef enum lru_status
96(*list_lru_walk_cb)(struct list_head *item, spinlock_t *lock, void *cb_arg);
97/**
Glauber Costa6a4f4962013-08-28 10:18:02 +100098 * list_lru_walk_node: walk a list_lru, isolating and disposing freeable items.
Dave Chinnera38e4082013-08-28 10:17:58 +100099 * @lru: the lru pointer.
Glauber Costa6a4f4962013-08-28 10:18:02 +1000100 * @nid: the node id to scan from.
Dave Chinnera38e4082013-08-28 10:17:58 +1000101 * @isolate: callback function that is resposible for deciding what to do with
102 * the item currently being scanned
103 * @cb_arg: opaque type that will be passed to @isolate
104 * @nr_to_walk: how many items to scan.
105 *
106 * This function will scan all elements in a particular list_lru, calling the
107 * @isolate callback for each of those items, along with the current list
108 * spinlock and a caller-provided opaque. The @isolate callback can choose to
109 * drop the lock internally, but *must* return with the lock held. The callback
110 * will return an enum lru_status telling the list_lru infrastructure what to
111 * do with the object being scanned.
112 *
113 * Please note that nr_to_walk does not mean how many objects will be freed,
114 * just how many objects will be scanned.
115 *
116 * Return value: the number of objects effectively removed from the LRU.
117 */
Glauber Costa6a4f4962013-08-28 10:18:02 +1000118unsigned long list_lru_walk_node(struct list_lru *lru, int nid,
119 list_lru_walk_cb isolate, void *cb_arg,
120 unsigned long *nr_to_walk);
121
122static inline unsigned long
123list_lru_walk(struct list_lru *lru, list_lru_walk_cb isolate,
124 void *cb_arg, unsigned long nr_to_walk)
125{
126 long isolated = 0;
127 int nid;
128
129 for_each_node_mask(nid, lru->active_nodes) {
130 isolated += list_lru_walk_node(lru, nid, isolate,
131 cb_arg, &nr_to_walk);
132 if (nr_to_walk <= 0)
133 break;
134 }
135 return isolated;
136}
Dave Chinnera38e4082013-08-28 10:17:58 +1000137#endif /* _LRU_LIST_H */