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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 | for_each_node_mask(nid, lru->active_nodes) { |
124 | isolated += list_lru_walk_node(lru, nid, isolate, |
125 | cb_arg, &nr_to_walk); |
126 | if (nr_to_walk <= 0) |
127 | break; |
128 | } |
129 | return isolated; |
130 | } |
131 | #endif /* _LRU_LIST_H */ |
132 |
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