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a38e4082 DC |
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> | |
3b1d58a4 | 11 | #include <linux/nodemask.h> |
a38e4082 DC |
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 | ||
3b1d58a4 | 22 | struct list_lru_node { |
a38e4082 DC |
23 | spinlock_t lock; |
24 | struct list_head list; | |
25 | /* kept as signed so we can catch imbalance bugs */ | |
26 | long nr_items; | |
3b1d58a4 DC |
27 | } ____cacheline_aligned_in_smp; |
28 | ||
29 | struct list_lru { | |
30 | /* | |
31 | * Because we use a fixed-size array, this struct can be very big if | |
32 | * MAX_NUMNODES is big. If this becomes a problem this is fixable by | |
33 | * turning this into a pointer and dynamically allocating this to | |
34 | * nr_node_ids. This quantity is firwmare-provided, and still would | |
35 | * provide room for all nodes at the cost of a pointer lookup and an | |
36 | * extra allocation. Because that allocation will most likely come from | |
37 | * a different slab cache than the main structure holding this | |
38 | * structure, we may very well fail. | |
39 | */ | |
40 | struct list_lru_node node[MAX_NUMNODES]; | |
41 | nodemask_t active_nodes; | |
a38e4082 DC |
42 | }; |
43 | ||
44 | int list_lru_init(struct list_lru *lru); | |
45 | ||
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 | */ | |
62 | bool 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 | */ | |
75 | bool list_lru_del(struct list_lru *lru, struct list_head *item); | |
76 | ||
77 | /** | |
6a4f496f | 78 | * list_lru_count_node: return the number of objects currently held by @lru |
a38e4082 | 79 | * @lru: the lru pointer. |
6a4f496f | 80 | * @nid: the node id to count from. |
a38e4082 DC |
81 | * |
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 | */ | |
6a4f496f GC |
86 | unsigned long list_lru_count_node(struct list_lru *lru, int nid); |
87 | static inline unsigned long list_lru_count(struct list_lru *lru) | |
88 | { | |
89 | long count = 0; | |
90 | int nid; | |
91 | ||
92 | for_each_node_mask(nid, lru->active_nodes) | |
93 | count += list_lru_count_node(lru, nid); | |
94 | ||
95 | return count; | |
96 | } | |
a38e4082 DC |
97 | |
98 | typedef enum lru_status | |
99 | (*list_lru_walk_cb)(struct list_head *item, spinlock_t *lock, void *cb_arg); | |
100 | /** | |
6a4f496f | 101 | * list_lru_walk_node: walk a list_lru, isolating and disposing freeable items. |
a38e4082 | 102 | * @lru: the lru pointer. |
6a4f496f | 103 | * @nid: the node id to scan from. |
a38e4082 DC |
104 | * @isolate: callback function that is resposible for deciding what to do with |
105 | * the item currently being scanned | |
106 | * @cb_arg: opaque type that will be passed to @isolate | |
107 | * @nr_to_walk: how many items to scan. | |
108 | * | |
109 | * This function will scan all elements in a particular list_lru, calling the | |
110 | * @isolate callback for each of those items, along with the current list | |
111 | * spinlock and a caller-provided opaque. The @isolate callback can choose to | |
112 | * drop the lock internally, but *must* return with the lock held. The callback | |
113 | * will return an enum lru_status telling the list_lru infrastructure what to | |
114 | * do with the object being scanned. | |
115 | * | |
116 | * Please note that nr_to_walk does not mean how many objects will be freed, | |
117 | * just how many objects will be scanned. | |
118 | * | |
119 | * Return value: the number of objects effectively removed from the LRU. | |
120 | */ | |
6a4f496f GC |
121 | unsigned long list_lru_walk_node(struct list_lru *lru, int nid, |
122 | list_lru_walk_cb isolate, void *cb_arg, | |
123 | unsigned long *nr_to_walk); | |
124 | ||
125 | static inline unsigned long | |
126 | list_lru_walk(struct list_lru *lru, list_lru_walk_cb isolate, | |
127 | void *cb_arg, unsigned long nr_to_walk) | |
128 | { | |
129 | long isolated = 0; | |
130 | int nid; | |
131 | ||
132 | for_each_node_mask(nid, lru->active_nodes) { | |
133 | isolated += list_lru_walk_node(lru, nid, isolate, | |
134 | cb_arg, &nr_to_walk); | |
135 | if (nr_to_walk <= 0) | |
136 | break; | |
137 | } | |
138 | return isolated; | |
139 | } | |
a38e4082 | 140 | #endif /* _LRU_LIST_H */ |