include/linux/list_lru.h

   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         /* array of per cgroup lists, indexed by memcg_cache_id */
  36         struct list_lru_one     *lru[0];
  37 };
  38
  39 struct list_lru_node {
  40         /* protects all lists on the node, including per cgroup */
  41         spinlock_t              lock;
  42         /* global list, used for the root cgroup in cgroup aware lrus */
  43         struct list_lru_one     lru;
  44 #if defined(CONFIG_MEMCG) && !defined(CONFIG_SLOB)
  45         /* for cgroup aware lrus points to per cgroup lists, otherwise NULL */
  46         struct list_lru_memcg   *memcg_lrus;
  47 #endif
  48         long nr_items;
  49 } ____cacheline_aligned_in_smp;
  50
  51 struct list_lru {
  52         struct list_lru_node    *node;
  53 #if defined(CONFIG_MEMCG) && !defined(CONFIG_SLOB)
  54         struct list_head        list;
  55 #endif
  56 };
  57
  58 void list_lru_destroy(struct list_lru *lru);
  59 int __list_lru_init(struct list_lru *lru, bool memcg_aware,
  60                     struct lock_class_key *key);
  61
  62 #define list_lru_init(lru)              __list_lru_init((lru), false, NULL)
  63 #define list_lru_init_key(lru, key)     __list_lru_init((lru), false, (key))
  64 #define list_lru_init_memcg(lru)        __list_lru_init((lru), true, NULL)
  65
  66 int memcg_update_all_list_lrus(int num_memcgs);
  67 void memcg_drain_all_list_lrus(int src_idx, int dst_idx);
  68
  69 /**
  70  * list_lru_add: add an element to the lru list's tail
  71  * @list_lru: the lru pointer
  72  * @item: the item to be added.
  73  *
  74  * If the element is already part of a list, this function returns doing
  75  * nothing. Therefore the caller does not need to keep state about whether or
  76  * not the element already belongs in the list and is allowed to lazy update
  77  * it. Note however that this is valid for *a* list, not *this* list. If
  78  * the caller organize itself in a way that elements can be in more than
  79  * one type of list, it is up to the caller to fully remove the item from
  80  * the previous list (with list_lru_del() for instance) before moving it
  81  * to @list_lru
  82  *
  83  * Return value: true if the list was updated, false otherwise
  84  */
  85 bool list_lru_add(struct list_lru *lru, struct list_head *item);
  86
  87 /**
  88  * list_lru_del: delete an element to the lru list
  89  * @list_lru: the lru pointer
  90  * @item: the item to be deleted.
  91  *
  92  * This function works analogously as list_lru_add in terms of list
  93  * manipulation. The comments about an element already pertaining to
  94  * a list are also valid for list_lru_del.
  95  *
  96  * Return value: true if the list was updated, false otherwise
  97  */
  98 bool list_lru_del(struct list_lru *lru, struct list_head *item);
  99
 100 /**
 101  * list_lru_count_one: return the number of objects currently held by @lru
 102  * @lru: the lru pointer.
 103  * @nid: the node id to count from.
 104  * @memcg: the cgroup to count from.
 105  *
 106  * Always return a non-negative number, 0 for empty lists. There is no
 107  * guarantee that the list is not updated while the count is being computed.
 108  * Callers that want such a guarantee need to provide an outer lock.
 109  */
 110 unsigned long list_lru_count_one(struct list_lru *lru,
 111                                  int nid, struct mem_cgroup *memcg);
 112 unsigned long list_lru_count_node(struct list_lru *lru, int nid);
 113
 114 static inline unsigned long list_lru_shrink_count(struct list_lru *lru,
 115                                                   struct shrink_control *sc)
 116 {
 117         return list_lru_count_one(lru, sc->nid, sc->memcg);
 118 }
 119
 120 static inline unsigned long list_lru_count(struct list_lru *lru)
 121 {
 122         long count = 0;
 123         int nid;
 124
 125         for_each_node_state(nid, N_NORMAL_MEMORY)
 126                 count += list_lru_count_node(lru, nid);
 127
 128         return count;
 129 }
 130
 131 void list_lru_isolate(struct list_lru_one *list, struct list_head *item);
 132 void list_lru_isolate_move(struct list_lru_one *list, struct list_head *item,
 133                            struct list_head *head);
 134
 135 typedef enum lru_status (*list_lru_walk_cb)(struct list_head *item,
 136                 struct list_lru_one *list, spinlock_t *lock, void *cb_arg);
 137
 138 /**
 139  * list_lru_walk_one: walk a list_lru, isolating and disposing freeable items.
 140  * @lru: the lru pointer.
 141  * @nid: the node id to scan from.
 142  * @memcg: the cgroup to scan from.
 143  * @isolate: callback function that is resposible for deciding what to do with
 144  *  the item currently being scanned
 145  * @cb_arg: opaque type that will be passed to @isolate
 146  * @nr_to_walk: how many items to scan.
 147  *
 148  * This function will scan all elements in a particular list_lru, calling the
 149  * @isolate callback for each of those items, along with the current list
 150  * spinlock and a caller-provided opaque. The @isolate callback can choose to
 151  * drop the lock internally, but *must* return with the lock held. The callback
 152  * will return an enum lru_status telling the list_lru infrastructure what to
 153  * do with the object being scanned.
 154  *
 155  * Please note that nr_to_walk does not mean how many objects will be freed,
 156  * just how many objects will be scanned.
 157  *
 158  * Return value: the number of objects effectively removed from the LRU.
 159  */
 160 unsigned long list_lru_walk_one(struct list_lru *lru,
 161                                 int nid, struct mem_cgroup *memcg,
 162                                 list_lru_walk_cb isolate, void *cb_arg,
 163                                 unsigned long *nr_to_walk);
 164 unsigned long list_lru_walk_node(struct list_lru *lru, int nid,
 165                                  list_lru_walk_cb isolate, void *cb_arg,
 166                                  unsigned long *nr_to_walk);
 167
 168 static inline unsigned long
 169 list_lru_shrink_walk(struct list_lru *lru, struct shrink_control *sc,
 170                      list_lru_walk_cb isolate, void *cb_arg)
 171 {
 172         return list_lru_walk_one(lru, sc->nid, sc->memcg, isolate, cb_arg,
 173                                  &sc->nr_to_scan);
 174 }
 175
 176 static inline unsigned long
 177 list_lru_walk(struct list_lru *lru, list_lru_walk_cb isolate,
 178               void *cb_arg, unsigned long nr_to_walk)
 179 {
 180         long isolated = 0;
 181         int nid;
 182
 183         for_each_node_state(nid, N_NORMAL_MEMORY) {
 184                 isolated += list_lru_walk_node(lru, nid, isolate,
 185                                                cb_arg, &nr_to_walk);
 186                 if (nr_to_walk <= 0)
 187                         break;
 188         }
 189         return isolated;
 190 }
 191 #endif /* _LRU_LIST_H */