1 /* SPDX-License-Identifier: GPL-2.0 */
2 /*
3  * Copyright (c) 2013 Red Hat, Inc. and Parallels Inc. All rights reserved.
4  * Authors: David Chinner and Glauber Costa
5  *
6  * Generic LRU infrastructure
7  */
8 #ifndef _LRU_LIST_H
9 #define _LRU_LIST_H
10 
11 #include <linux/list.h>
12 #include <linux/nodemask.h>
13 #include <linux/shrinker.h>
14 
15 struct mem_cgroup;
16 
17 /* list_lru_walk_cb has to always return one of those */
18 enum lru_status {
19 	LRU_REMOVED,		/* item removed from list */
20 	LRU_REMOVED_RETRY,	/* item removed, but lock has been
21 				   dropped and reacquired */
22 	LRU_ROTATE,		/* item referenced, give another pass */
23 	LRU_SKIP,		/* item cannot be locked, skip */
24 	LRU_RETRY,		/* item not freeable. May drop the lock
25 				   internally, but has to return locked. */
26 };
27 
28 struct list_lru_one {
29 	struct list_head	list;
30 	/* may become negative during memcg reparenting */
31 	long			nr_items;
32 };
33 
34 struct list_lru_memcg {
35 	struct rcu_head		rcu;
36 	/* array of per cgroup lists, indexed by memcg_cache_id */
37 	struct list_lru_one	*lru[0];
38 };
39 
40 struct list_lru_node {
41 	/* protects all lists on the node, including per cgroup */
42 	spinlock_t		lock;
43 	/* global list, used for the root cgroup in cgroup aware lrus */
44 	struct list_lru_one	lru;
45 #ifdef CONFIG_MEMCG_KMEM
46 	/* for cgroup aware lrus points to per cgroup lists, otherwise NULL */
47 	struct list_lru_memcg	__rcu *memcg_lrus;
48 #endif
49 	long nr_items;
50 } ____cacheline_aligned_in_smp;
51 
52 struct list_lru {
53 	struct list_lru_node	*node;
54 #ifdef CONFIG_MEMCG_KMEM
55 	struct list_head	list;
56 	int			shrinker_id;
57 	bool			memcg_aware;
58 #endif
59 };
60 
61 void list_lru_destroy(struct list_lru *lru);
62 int __list_lru_init(struct list_lru *lru, bool memcg_aware,
63 		    struct lock_class_key *key, struct shrinker *shrinker);
64 
65 #define list_lru_init(lru)				\
66 	__list_lru_init((lru), false, NULL, NULL)
67 #define list_lru_init_key(lru, key)			\
68 	__list_lru_init((lru), false, (key), NULL)
69 #define list_lru_init_memcg(lru, shrinker)		\
70 	__list_lru_init((lru), true, NULL, shrinker)
71 
72 int memcg_update_all_list_lrus(int num_memcgs);
73 void memcg_drain_all_list_lrus(int src_idx, struct mem_cgroup *dst_memcg);
74 
75 /**
76  * list_lru_add: add an element to the lru list's tail
77  * @list_lru: the lru pointer
78  * @item: the item to be added.
79  *
80  * If the element is already part of a list, this function returns doing
81  * nothing. Therefore the caller does not need to keep state about whether or
82  * not the element already belongs in the list and is allowed to lazy update
83  * it. Note however that this is valid for *a* list, not *this* list. If
84  * the caller organize itself in a way that elements can be in more than
85  * one type of list, it is up to the caller to fully remove the item from
86  * the previous list (with list_lru_del() for instance) before moving it
87  * to @list_lru
88  *
89  * Return value: true if the list was updated, false otherwise
90  */
91 bool list_lru_add(struct list_lru *lru, struct list_head *item);
92 
93 /**
94  * list_lru_del: delete an element to the lru list
95  * @list_lru: the lru pointer
96  * @item: the item to be deleted.
97  *
98  * This function works analogously as list_lru_add in terms of list
99  * manipulation. The comments about an element already pertaining to
100  * a list are also valid for list_lru_del.
101  *
102  * Return value: true if the list was updated, false otherwise
103  */
104 bool list_lru_del(struct list_lru *lru, struct list_head *item);
105 
106 /**
107  * list_lru_count_one: return the number of objects currently held by @lru
108  * @lru: the lru pointer.
109  * @nid: the node id to count from.
110  * @memcg: the cgroup to count from.
111  *
112  * Always return a non-negative number, 0 for empty lists. There is no
113  * guarantee that the list is not updated while the count is being computed.
114  * Callers that want such a guarantee need to provide an outer lock.
115  */
116 unsigned long list_lru_count_one(struct list_lru *lru,
117 				 int nid, struct mem_cgroup *memcg);
118 unsigned long list_lru_count_node(struct list_lru *lru, int nid);
119 
list_lru_shrink_count(struct list_lru * lru,struct shrink_control * sc)120 static inline unsigned long list_lru_shrink_count(struct list_lru *lru,
121 						  struct shrink_control *sc)
122 {
123 	return list_lru_count_one(lru, sc->nid, sc->memcg);
124 }
125 
list_lru_count(struct list_lru * lru)126 static inline unsigned long list_lru_count(struct list_lru *lru)
127 {
128 	long count = 0;
129 	int nid;
130 
131 	for_each_node_state(nid, N_NORMAL_MEMORY)
132 		count += list_lru_count_node(lru, nid);
133 
134 	return count;
135 }
136 
137 void list_lru_isolate(struct list_lru_one *list, struct list_head *item);
138 void list_lru_isolate_move(struct list_lru_one *list, struct list_head *item,
139 			   struct list_head *head);
140 
141 typedef enum lru_status (*list_lru_walk_cb)(struct list_head *item,
142 		struct list_lru_one *list, spinlock_t *lock, void *cb_arg);
143 
144 /**
145  * list_lru_walk_one: walk a list_lru, isolating and disposing freeable items.
146  * @lru: the lru pointer.
147  * @nid: the node id to scan from.
148  * @memcg: the cgroup to scan from.
149  * @isolate: callback function that is resposible for deciding what to do with
150  *  the item currently being scanned
151  * @cb_arg: opaque type that will be passed to @isolate
152  * @nr_to_walk: how many items to scan.
153  *
154  * This function will scan all elements in a particular list_lru, calling the
155  * @isolate callback for each of those items, along with the current list
156  * spinlock and a caller-provided opaque. The @isolate callback can choose to
157  * drop the lock internally, but *must* return with the lock held. The callback
158  * will return an enum lru_status telling the list_lru infrastructure what to
159  * do with the object being scanned.
160  *
161  * Please note that nr_to_walk does not mean how many objects will be freed,
162  * just how many objects will be scanned.
163  *
164  * Return value: the number of objects effectively removed from the LRU.
165  */
166 unsigned long list_lru_walk_one(struct list_lru *lru,
167 				int nid, struct mem_cgroup *memcg,
168 				list_lru_walk_cb isolate, void *cb_arg,
169 				unsigned long *nr_to_walk);
170 /**
171  * list_lru_walk_one_irq: walk a list_lru, isolating and disposing freeable items.
172  * @lru: the lru pointer.
173  * @nid: the node id to scan from.
174  * @memcg: the cgroup to scan from.
175  * @isolate: callback function that is resposible for deciding what to do with
176  *  the item currently being scanned
177  * @cb_arg: opaque type that will be passed to @isolate
178  * @nr_to_walk: how many items to scan.
179  *
180  * Same as @list_lru_walk_one except that the spinlock is acquired with
181  * spin_lock_irq().
182  */
183 unsigned long list_lru_walk_one_irq(struct list_lru *lru,
184 				    int nid, struct mem_cgroup *memcg,
185 				    list_lru_walk_cb isolate, void *cb_arg,
186 				    unsigned long *nr_to_walk);
187 unsigned long list_lru_walk_node(struct list_lru *lru, int nid,
188 				 list_lru_walk_cb isolate, void *cb_arg,
189 				 unsigned long *nr_to_walk);
190 
191 static inline unsigned long
list_lru_shrink_walk(struct list_lru * lru,struct shrink_control * sc,list_lru_walk_cb isolate,void * cb_arg)192 list_lru_shrink_walk(struct list_lru *lru, struct shrink_control *sc,
193 		     list_lru_walk_cb isolate, void *cb_arg)
194 {
195 	return list_lru_walk_one(lru, sc->nid, sc->memcg, isolate, cb_arg,
196 				 &sc->nr_to_scan);
197 }
198 
199 static inline unsigned long
list_lru_shrink_walk_irq(struct list_lru * lru,struct shrink_control * sc,list_lru_walk_cb isolate,void * cb_arg)200 list_lru_shrink_walk_irq(struct list_lru *lru, struct shrink_control *sc,
201 			 list_lru_walk_cb isolate, void *cb_arg)
202 {
203 	return list_lru_walk_one_irq(lru, sc->nid, sc->memcg, isolate, cb_arg,
204 				     &sc->nr_to_scan);
205 }
206 
207 static inline unsigned long
list_lru_walk(struct list_lru * lru,list_lru_walk_cb isolate,void * cb_arg,unsigned long nr_to_walk)208 list_lru_walk(struct list_lru *lru, list_lru_walk_cb isolate,
209 	      void *cb_arg, unsigned long nr_to_walk)
210 {
211 	long isolated = 0;
212 	int nid;
213 
214 	for_each_node_state(nid, N_NORMAL_MEMORY) {
215 		isolated += list_lru_walk_node(lru, nid, isolate,
216 					       cb_arg, &nr_to_walk);
217 		if (nr_to_walk <= 0)
218 			break;
219 	}
220 	return isolated;
221 }
222 #endif /* _LRU_LIST_H */
223