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 */ 132