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// SPDX-License-Identifier: GPL-2.0
#include <linux/mm.h>
#include "lru_cache.h"
#include "messages.h"
/*
* Initialize a cache object.
*
* @cache: The cache.
* @max_size: Maximum size (number of entries) for the cache.
* Use 0 for unlimited size, it's the user's responsibility to
* trim the cache in that case.
*/
void btrfs_lru_cache_init(struct btrfs_lru_cache *cache, unsigned int max_size)
{
INIT_LIST_HEAD(&cache->lru_list);
mt_init(&cache->entries);
cache->size = 0;
cache->max_size = max_size;
}
static struct btrfs_lru_cache_entry *match_entry(struct list_head *head, u64 key,
u64 gen)
{
struct btrfs_lru_cache_entry *entry;
list_for_each_entry(entry, head, list) {
if (entry->key == key && entry->gen == gen)
return entry;
}
return NULL;
}
/*
* Lookup for an entry in the cache.
*
* @cache: The cache.
* @key: The key of the entry we are looking for.
* @gen: Generation associated to the key.
*
* Returns the entry associated with the key or NULL if none found.
*/
struct btrfs_lru_cache_entry *btrfs_lru_cache_lookup(struct btrfs_lru_cache *cache,
u64 key, u64 gen)
{
struct list_head *head;
struct btrfs_lru_cache_entry *entry;
head = mtree_load(&cache->entries, key);
if (!head)
return NULL;
entry = match_entry(head, key, gen);
if (entry)
list_move_tail(&entry->lru_list, &cache->lru_list);
return entry;
}
/*
* Remove an entry from the cache.
*
* @cache: The cache to remove from.
* @entry: The entry to remove from the cache.
*
* Note: this also frees the memory used by the entry.
*/
void btrfs_lru_cache_remove(struct btrfs_lru_cache *cache,
struct btrfs_lru_cache_entry *entry)
{
struct list_head *prev = entry->list.prev;
ASSERT(cache->size > 0);
ASSERT(!mtree_empty(&cache->entries));
list_del(&entry->list);
list_del(&entry->lru_list);
if (list_empty(prev)) {
struct list_head *head;
/*
* If previous element in the list entry->list is now empty, it
* means it's a head entry not pointing to any cached entries,
* so remove it from the maple tree and free it.
*/
head = mtree_erase(&cache->entries, entry->key);
ASSERT(head == prev);
kfree(head);
}
kfree(entry);
cache->size--;
}
/*
* Store an entry in the cache.
*
* @cache: The cache.
* @entry: The entry to store.
*
* Returns 0 on success and < 0 on error.
*/
int btrfs_lru_cache_store(struct btrfs_lru_cache *cache,
struct btrfs_lru_cache_entry *new_entry,
gfp_t gfp)
{
const u64 key = new_entry->key;
struct list_head *head;
int ret;
head = kmalloc(sizeof(*head), gfp);
if (!head)
return -ENOMEM;
ret = mtree_insert(&cache->entries, key, head, gfp);
if (ret == 0) {
INIT_LIST_HEAD(head);
list_add_tail(&new_entry->list, head);
} else if (ret == -EEXIST) {
kfree(head);
head = mtree_load(&cache->entries, key);
ASSERT(head != NULL);
if (match_entry(head, key, new_entry->gen) != NULL)
return -EEXIST;
list_add_tail(&new_entry->list, head);
} else if (ret < 0) {
kfree(head);
return ret;
}
if (cache->max_size > 0 && cache->size == cache->max_size) {
struct btrfs_lru_cache_entry *lru_entry;
lru_entry = list_first_entry(&cache->lru_list,
struct btrfs_lru_cache_entry,
lru_list);
btrfs_lru_cache_remove(cache, lru_entry);
}
list_add_tail(&new_entry->lru_list, &cache->lru_list);
cache->size++;
return 0;
}
/*
* Empty a cache.
*
* @cache: The cache to empty.
*
* Removes all entries from the cache.
*/
void btrfs_lru_cache_clear(struct btrfs_lru_cache *cache)
{
struct btrfs_lru_cache_entry *entry;
struct btrfs_lru_cache_entry *tmp;
list_for_each_entry_safe(entry, tmp, &cache->lru_list, lru_list)
btrfs_lru_cache_remove(cache, entry);
ASSERT(cache->size == 0);
ASSERT(mtree_empty(&cache->entries));
}
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