138 lines
4.5 KiB
C
138 lines
4.5 KiB
C
/*
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* Copyright (c) 2013 Red Hat, Inc. and Parallels Inc. All rights reserved.
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* Authors: David Chinner and Glauber Costa
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*
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* Generic LRU infrastructure
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*/
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#ifndef _LRU_LIST_H
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#define _LRU_LIST_H
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#include <linux/list.h>
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#include <linux/nodemask.h>
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/* list_lru_walk_cb has to always return one of those */
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enum lru_status {
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LRU_REMOVED, /* item removed from list */
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LRU_REMOVED_RETRY, /* item removed, but lock has been
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dropped and reacquired */
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LRU_ROTATE, /* item referenced, give another pass */
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LRU_SKIP, /* item cannot be locked, skip */
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LRU_RETRY, /* item not freeable. May drop the lock
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internally, but has to return locked. */
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};
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struct list_lru_node {
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spinlock_t lock;
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struct list_head list;
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/* kept as signed so we can catch imbalance bugs */
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long nr_items;
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} ____cacheline_aligned_in_smp;
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struct list_lru {
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struct list_lru_node *node;
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nodemask_t active_nodes;
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};
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void list_lru_destroy(struct list_lru *lru);
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int list_lru_init_key(struct list_lru *lru, struct lock_class_key *key);
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static inline int list_lru_init(struct list_lru *lru)
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{
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return list_lru_init_key(lru, NULL);
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}
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/**
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* list_lru_add: add an element to the lru list's tail
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* @list_lru: the lru pointer
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* @item: the item to be added.
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*
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* If the element is already part of a list, this function returns doing
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* nothing. Therefore the caller does not need to keep state about whether or
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* not the element already belongs in the list and is allowed to lazy update
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* it. Note however that this is valid for *a* list, not *this* list. If
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* the caller organize itself in a way that elements can be in more than
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* one type of list, it is up to the caller to fully remove the item from
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* the previous list (with list_lru_del() for instance) before moving it
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* to @list_lru
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*
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* Return value: true if the list was updated, false otherwise
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*/
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bool list_lru_add(struct list_lru *lru, struct list_head *item);
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/**
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* list_lru_del: delete an element to the lru list
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* @list_lru: the lru pointer
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* @item: the item to be deleted.
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*
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* This function works analogously as list_lru_add in terms of list
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* manipulation. The comments about an element already pertaining to
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* a list are also valid for list_lru_del.
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*
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* Return value: true if the list was updated, false otherwise
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*/
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bool list_lru_del(struct list_lru *lru, struct list_head *item);
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/**
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* list_lru_count_node: return the number of objects currently held by @lru
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* @lru: the lru pointer.
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* @nid: the node id to count from.
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*
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* Always return a non-negative number, 0 for empty lists. There is no
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* guarantee that the list is not updated while the count is being computed.
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* Callers that want such a guarantee need to provide an outer lock.
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*/
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unsigned long list_lru_count_node(struct list_lru *lru, int nid);
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static inline unsigned long list_lru_count(struct list_lru *lru)
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{
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long count = 0;
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int nid;
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for_each_node_mask(nid, lru->active_nodes)
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count += list_lru_count_node(lru, nid);
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return count;
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}
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typedef enum lru_status
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(*list_lru_walk_cb)(struct list_head *item, spinlock_t *lock, void *cb_arg);
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/**
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* list_lru_walk_node: walk a list_lru, isolating and disposing freeable items.
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* @lru: the lru pointer.
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* @nid: the node id to scan from.
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* @isolate: callback function that is resposible for deciding what to do with
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* the item currently being scanned
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* @cb_arg: opaque type that will be passed to @isolate
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* @nr_to_walk: how many items to scan.
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*
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* This function will scan all elements in a particular list_lru, calling the
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* @isolate callback for each of those items, along with the current list
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* spinlock and a caller-provided opaque. The @isolate callback can choose to
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* drop the lock internally, but *must* return with the lock held. The callback
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* will return an enum lru_status telling the list_lru infrastructure what to
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* do with the object being scanned.
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*
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* Please note that nr_to_walk does not mean how many objects will be freed,
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* just how many objects will be scanned.
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*
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* Return value: the number of objects effectively removed from the LRU.
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*/
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unsigned long list_lru_walk_node(struct list_lru *lru, int nid,
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list_lru_walk_cb isolate, void *cb_arg,
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unsigned long *nr_to_walk);
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static inline unsigned long
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list_lru_walk(struct list_lru *lru, list_lru_walk_cb isolate,
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void *cb_arg, unsigned long nr_to_walk)
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{
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long isolated = 0;
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int nid;
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for_each_node_mask(nid, lru->active_nodes) {
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isolated += list_lru_walk_node(lru, nid, isolate,
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cb_arg, &nr_to_walk);
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if (nr_to_walk <= 0)
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break;
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}
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return isolated;
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}
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#endif /* _LRU_LIST_H */
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