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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef BTRFS_LRU_CACHE_H
#define BTRFS_LRU_CACHE_H
#include <linux/types.h>
#include <linux/maple_tree.h>
#include <linux/list.h>
/*
* A cache entry. This is meant to be embedded in a structure of a user of
* this module. Similar to how struct list_head and struct rb_node are used.
*
* Note: it should be embedded as the first element in a struct (offset 0), and
* this module assumes it was allocated with kmalloc(), so it calls kfree() when
* it needs to free an entry.
*/
struct btrfs_lru_cache_entry {
struct list_head lru_list;
u64 key;
/*
* Optional generation associated to a key. Use 0 if not needed/used.
* Entries with the same key and different generations are stored in a
* linked list, so use this only for cases where there's a small number
* of different generations.
*/
u64 gen;
/*
* The maple tree uses unsigned long type for the keys, which is 32 bits
* on 32 bits systems, and 64 bits on 64 bits systems. So if we want to
* use something like inode numbers as keys, which are always a u64, we
* have to deal with this in a special way - we store the key in the
* entry itself, as a u64, and the values inserted into the maple tree
* are linked lists of entries - so in case we are on a 64 bits system,
* that list always has a single entry, while on 32 bits systems it
* may have more than one, with each entry having the same value for
* their lower 32 bits of the u64 key.
*/
struct list_head list;
};
struct btrfs_lru_cache {
struct list_head lru_list;
struct maple_tree entries;
/* Number of entries stored in the cache. */
unsigned int size;
/* Maximum number of entries the cache can have. */
unsigned int max_size;
};
#define btrfs_lru_cache_for_each_entry_safe(cache, entry, tmp) \
list_for_each_entry_safe_reverse((entry), (tmp), &(cache)->lru_list, lru_list)
static inline struct btrfs_lru_cache_entry *btrfs_lru_cache_lru_entry(
struct btrfs_lru_cache *cache)
{
return list_first_entry_or_null(&cache->lru_list,
struct btrfs_lru_cache_entry, lru_list);
}
void btrfs_lru_cache_init(struct btrfs_lru_cache *cache, unsigned int max_size);
struct btrfs_lru_cache_entry *btrfs_lru_cache_lookup(struct btrfs_lru_cache *cache,
u64 key, u64 gen);
int btrfs_lru_cache_store(struct btrfs_lru_cache *cache,
struct btrfs_lru_cache_entry *new_entry,
gfp_t gfp);
void btrfs_lru_cache_remove(struct btrfs_lru_cache *cache,
struct btrfs_lru_cache_entry *entry);
void btrfs_lru_cache_clear(struct btrfs_lru_cache *cache);
#endif
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