2 * Copyright (c) 2013 Red Hat, Inc. and Parallels Inc. All rights reserved.
3 * Authors: David Chinner and Glauber Costa
5 * Generic LRU infrastructure
10 #include <linux/list.h>
11 #include <linux/nodemask.h>
12 #include <linux/shrinker.h>
14 /* list_lru_walk_cb has to always return one of those */
16 LRU_REMOVED, /* item removed from list */
17 LRU_REMOVED_RETRY, /* item removed, but lock has been
18 dropped and reacquired */
19 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. */
25 struct list_lru_node {
27 struct list_head list;
28 /* kept as signed so we can catch imbalance bugs */
30 } ____cacheline_aligned_in_smp;
33 struct list_lru_node *node;
34 nodemask_t active_nodes;
37 void list_lru_destroy(struct list_lru *lru);
38 int list_lru_init_key(struct list_lru *lru, struct lock_class_key *key);
39 static inline int list_lru_init(struct list_lru *lru)
41 return list_lru_init_key(lru, NULL);
45 * list_lru_add: add an element to the lru list's tail
46 * @list_lru: the lru pointer
47 * @item: the item to be added.
49 * If the element is already part of a list, this function returns doing
50 * nothing. Therefore the caller does not need to keep state about whether or
51 * not the element already belongs in the list and is allowed to lazy update
52 * it. Note however that this is valid for *a* list, not *this* list. If
53 * the caller organize itself in a way that elements can be in more than
54 * one type of list, it is up to the caller to fully remove the item from
55 * the previous list (with list_lru_del() for instance) before moving it
58 * Return value: true if the list was updated, false otherwise
60 bool list_lru_add(struct list_lru *lru, struct list_head *item);
63 * list_lru_del: delete an element to the lru list
64 * @list_lru: the lru pointer
65 * @item: the item to be deleted.
67 * This function works analogously as list_lru_add in terms of list
68 * manipulation. The comments about an element already pertaining to
69 * a list are also valid for list_lru_del.
71 * Return value: true if the list was updated, false otherwise
73 bool list_lru_del(struct list_lru *lru, struct list_head *item);
76 * list_lru_count_node: return the number of objects currently held by @lru
77 * @lru: the lru pointer.
78 * @nid: the node id to count from.
80 * Always return a non-negative number, 0 for empty lists. There is no
81 * guarantee that the list is not updated while the count is being computed.
82 * Callers that want such a guarantee need to provide an outer lock.
84 unsigned long list_lru_count_node(struct list_lru *lru, int nid);
86 static inline unsigned long list_lru_shrink_count(struct list_lru *lru,
87 struct shrink_control *sc)
89 return list_lru_count_node(lru, sc->nid);
92 static inline unsigned long list_lru_count(struct list_lru *lru)
97 for_each_node_mask(nid, lru->active_nodes)
98 count += list_lru_count_node(lru, nid);
103 typedef enum lru_status
104 (*list_lru_walk_cb)(struct list_head *item, spinlock_t *lock, void *cb_arg);
106 * list_lru_walk_node: walk a list_lru, isolating and disposing freeable items.
107 * @lru: the lru pointer.
108 * @nid: the node id to scan from.
109 * @isolate: callback function that is resposible for deciding what to do with
110 * the item currently being scanned
111 * @cb_arg: opaque type that will be passed to @isolate
112 * @nr_to_walk: how many items to scan.
114 * This function will scan all elements in a particular list_lru, calling the
115 * @isolate callback for each of those items, along with the current list
116 * spinlock and a caller-provided opaque. The @isolate callback can choose to
117 * drop the lock internally, but *must* return with the lock held. The callback
118 * will return an enum lru_status telling the list_lru infrastructure what to
119 * do with the object being scanned.
121 * Please note that nr_to_walk does not mean how many objects will be freed,
122 * just how many objects will be scanned.
124 * Return value: the number of objects effectively removed from the LRU.
126 unsigned long list_lru_walk_node(struct list_lru *lru, int nid,
127 list_lru_walk_cb isolate, void *cb_arg,
128 unsigned long *nr_to_walk);
130 static inline unsigned long
131 list_lru_shrink_walk(struct list_lru *lru, struct shrink_control *sc,
132 list_lru_walk_cb isolate, void *cb_arg)
134 return list_lru_walk_node(lru, sc->nid, isolate, cb_arg,
138 static inline unsigned long
139 list_lru_walk(struct list_lru *lru, list_lru_walk_cb isolate,
140 void *cb_arg, unsigned long nr_to_walk)
145 for_each_node_mask(nid, lru->active_nodes) {
146 isolated += list_lru_walk_node(lru, nid, isolate,
147 cb_arg, &nr_to_walk);
153 #endif /* _LRU_LIST_H */