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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 : :
13 : : /* list_lru_walk_cb has to always return one of those */
14 : : enum lru_status {
15 : : LRU_REMOVED, /* item removed from list */
16 : : LRU_ROTATE, /* item referenced, give another pass */
17 : : LRU_SKIP, /* item cannot be locked, skip */
18 : : LRU_RETRY, /* item not freeable. May drop the lock
19 : : internally, but has to return locked. */
20 : : };
21 : :
22 : : struct list_lru_node {
23 : : spinlock_t lock;
24 : : struct list_head list;
25 : : /* kept as signed so we can catch imbalance bugs */
26 : : long nr_items;
27 : : } ____cacheline_aligned_in_smp;
28 : :
29 : : struct list_lru {
30 : : struct list_lru_node *node;
31 : : nodemask_t active_nodes;
32 : : };
33 : :
34 : : void list_lru_destroy(struct list_lru *lru);
35 : : int list_lru_init(struct list_lru *lru);
36 : :
37 : : /**
38 : : * list_lru_add: add an element to the lru list's tail
39 : : * @list_lru: the lru pointer
40 : : * @item: the item to be added.
41 : : *
42 : : * If the element is already part of a list, this function returns doing
43 : : * nothing. Therefore the caller does not need to keep state about whether or
44 : : * not the element already belongs in the list and is allowed to lazy update
45 : : * it. Note however that this is valid for *a* list, not *this* list. If
46 : : * the caller organize itself in a way that elements can be in more than
47 : : * one type of list, it is up to the caller to fully remove the item from
48 : : * the previous list (with list_lru_del() for instance) before moving it
49 : : * to @list_lru
50 : : *
51 : : * Return value: true if the list was updated, false otherwise
52 : : */
53 : : bool list_lru_add(struct list_lru *lru, struct list_head *item);
54 : :
55 : : /**
56 : : * list_lru_del: delete an element to the lru list
57 : : * @list_lru: the lru pointer
58 : : * @item: the item to be deleted.
59 : : *
60 : : * This function works analogously as list_lru_add in terms of list
61 : : * manipulation. The comments about an element already pertaining to
62 : : * a list are also valid for list_lru_del.
63 : : *
64 : : * Return value: true if the list was updated, false otherwise
65 : : */
66 : : bool list_lru_del(struct list_lru *lru, struct list_head *item);
67 : :
68 : : /**
69 : : * list_lru_count_node: return the number of objects currently held by @lru
70 : : * @lru: the lru pointer.
71 : : * @nid: the node id to count from.
72 : : *
73 : : * Always return a non-negative number, 0 for empty lists. There is no
74 : : * guarantee that the list is not updated while the count is being computed.
75 : : * Callers that want such a guarantee need to provide an outer lock.
76 : : */
77 : : unsigned long list_lru_count_node(struct list_lru *lru, int nid);
78 : : static inline unsigned long list_lru_count(struct list_lru *lru)
79 : : {
80 : : long count = 0;
81 : : int nid;
82 : :
83 : : for_each_node_mask(nid, lru->active_nodes)
84 : : count += list_lru_count_node(lru, nid);
85 : :
86 : : return count;
87 : : }
88 : :
89 : : typedef enum lru_status
90 : : (*list_lru_walk_cb)(struct list_head *item, spinlock_t *lock, void *cb_arg);
91 : : /**
92 : : * list_lru_walk_node: walk a list_lru, isolating and disposing freeable items.
93 : : * @lru: the lru pointer.
94 : : * @nid: the node id to scan from.
95 : : * @isolate: callback function that is resposible for deciding what to do with
96 : : * the item currently being scanned
97 : : * @cb_arg: opaque type that will be passed to @isolate
98 : : * @nr_to_walk: how many items to scan.
99 : : *
100 : : * This function will scan all elements in a particular list_lru, calling the
101 : : * @isolate callback for each of those items, along with the current list
102 : : * spinlock and a caller-provided opaque. The @isolate callback can choose to
103 : : * drop the lock internally, but *must* return with the lock held. The callback
104 : : * will return an enum lru_status telling the list_lru infrastructure what to
105 : : * do with the object being scanned.
106 : : *
107 : : * Please note that nr_to_walk does not mean how many objects will be freed,
108 : : * just how many objects will be scanned.
109 : : *
110 : : * Return value: the number of objects effectively removed from the LRU.
111 : : */
112 : : unsigned long list_lru_walk_node(struct list_lru *lru, int nid,
113 : : list_lru_walk_cb isolate, void *cb_arg,
114 : : unsigned long *nr_to_walk);
115 : :
116 : : static inline unsigned long
117 : : list_lru_walk(struct list_lru *lru, list_lru_walk_cb isolate,
118 : : void *cb_arg, unsigned long nr_to_walk)
119 : : {
120 : : long isolated = 0;
121 : : int nid;
122 : :
123 [ + + ][ + + ]: 20 : for_each_node_mask(nid, lru->active_nodes) {
124 : 6 : isolated += list_lru_walk_node(lru, nid, isolate,
125 : : cb_arg, &nr_to_walk);
126 [ + - ]: 6 : if (nr_to_walk <= 0)
127 : : break;
128 : : }
129 : : return isolated;
130 : : }
131 : : #endif /* _LRU_LIST_H */
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