include/linux/list_lru.h

   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>
  11 #include <linux/nodemask.h>
  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_REMOVED_RETRY,      /* item removed, but lock has been
  17                                    dropped and reacquired */
  18         LRU_ROTATE,             /* item referenced, give another pass */
  19         LRU_SKIP,               /* item cannot be locked, skip */
  20         LRU_RETRY,              /* item not freeable. May drop the lock
  21                                    internally, but has to return locked. */
  22 };
  23
  24 struct list_lru_node {
  25         spinlock_t              lock;
  26         struct list_head        list;
  27         /* kept as signed so we can catch imbalance bugs */
  28         long                    nr_items;
  29 } ____cacheline_aligned_in_smp;
  30
  31 struct list_lru {
  32         struct list_lru_node    *node;
  33         nodemask_t              active_nodes;
  34 };
  35
  36 void list_lru_destroy(struct list_lru *lru);
  37 int list_lru_init_key(struct list_lru *lru, struct lock_class_key *key);
  38 static inline int list_lru_init(struct list_lru *lru)
  39 {
  40         return list_lru_init_key(lru, NULL);
  41 }
  42
  43 /**
  44  * list_lru_add: add an element to the lru list's tail
  45  * @list_lru: the lru pointer
  46  * @item: the item to be added.
  47  *
  48  * If the element is already part of a list, this function returns doing
  49  * nothing. Therefore the caller does not need to keep state about whether or
  50  * not the element already belongs in the list and is allowed to lazy update
  51  * it. Note however that this is valid for *a* list, not *this* list. If
  52  * the caller organize itself in a way that elements can be in more than
  53  * one type of list, it is up to the caller to fully remove the item from
  54  * the previous list (with list_lru_del() for instance) before moving it
  55  * to @list_lru
  56  *
  57  * Return value: true if the list was updated, false otherwise
  58  */
  59 bool list_lru_add(struct list_lru *lru, struct list_head *item);
  60
  61 /**
  62  * list_lru_del: delete an element to the lru list
  63  * @list_lru: the lru pointer
  64  * @item: the item to be deleted.
  65  *
  66  * This function works analogously as list_lru_add in terms of list
  67  * manipulation. The comments about an element already pertaining to
  68  * a list are also valid for list_lru_del.
  69  *
  70  * Return value: true if the list was updated, false otherwise
  71  */
  72 bool list_lru_del(struct list_lru *lru, struct list_head *item);
  73
  74 /**
  75  * list_lru_count_node: return the number of objects currently held by @lru
  76  * @lru: the lru pointer.
  77  * @nid: the node id to count from.
  78  *
  79  * Always return a non-negative number, 0 for empty lists. There is no
  80  * guarantee that the list is not updated while the count is being computed.
  81  * Callers that want such a guarantee need to provide an outer lock.
  82  */
  83 unsigned long list_lru_count_node(struct list_lru *lru, int nid);
  84 static inline unsigned long list_lru_count(struct list_lru *lru)
  85 {
  86         long count = 0;
  87         int nid;
  88
  89         for_each_node_mask(nid, lru->active_nodes)
  90                 count += list_lru_count_node(lru, nid);
  91
  92         return count;
  93 }
  94
  95 typedef enum lru_status
  96 (*list_lru_walk_cb)(struct list_head *item, spinlock_t *lock, void *cb_arg);
  97 /**
  98  * list_lru_walk_node: walk a list_lru, isolating and disposing freeable items.
  99  * @lru: the lru pointer.
 100  * @nid: the node id to scan from.
 101  * @isolate: callback function that is resposible for deciding what to do with
 102  *  the item currently being scanned
 103  * @cb_arg: opaque type that will be passed to @isolate
 104  * @nr_to_walk: how many items to scan.
 105  *
 106  * This function will scan all elements in a particular list_lru, calling the
 107  * @isolate callback for each of those items, along with the current list
 108  * spinlock and a caller-provided opaque. The @isolate callback can choose to
 109  * drop the lock internally, but *must* return with the lock held. The callback
 110  * will return an enum lru_status telling the list_lru infrastructure what to
 111  * do with the object being scanned.
 112  *
 113  * Please note that nr_to_walk does not mean how many objects will be freed,
 114  * just how many objects will be scanned.
 115  *
 116  * Return value: the number of objects effectively removed from the LRU.
 117  */
 118 unsigned long list_lru_walk_node(struct list_lru *lru, int nid,
 119                                  list_lru_walk_cb isolate, void *cb_arg,
 120                                  unsigned long *nr_to_walk);
 121
 122 static inline unsigned long
 123 list_lru_walk(struct list_lru *lru, list_lru_walk_cb isolate,
 124               void *cb_arg, unsigned long nr_to_walk)
 125 {
 126         long isolated = 0;
 127         int nid;
 128
 129         for_each_node_mask(nid, lru->active_nodes) {
 130                 isolated += list_lru_walk_node(lru, nid, isolate,
 131                                                cb_arg, &nr_to_walk);
 132                 if (nr_to_walk <= 0)
 133                         break;
 134         }
 135         return isolated;
 136 }
 137 #endif /* _LRU_LIST_H */