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