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