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