diff options
Diffstat (limited to 'fs/btrfs/lru_cache.c')
| -rw-r--r-- | fs/btrfs/lru_cache.c | 166 |
1 files changed, 166 insertions, 0 deletions
diff --git a/fs/btrfs/lru_cache.c b/fs/btrfs/lru_cache.c new file mode 100644 index 000000000000..0fe0ae54ac67 --- /dev/null +++ b/fs/btrfs/lru_cache.c @@ -0,0 +1,166 @@ +// 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 responsability 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)); +} |