1 /* SPDX-License-Identifier: GPL-2.0 */ 2 3 #ifndef BTRFS_LRU_CACHE_H 4 #define BTRFS_LRU_CACHE_H 5 6 #include <linux/types.h> 7 #include <linux/maple_tree.h> 8 #include <linux/list.h> 9 10 /* 11 * A cache entry. This is meant to be embedded in a structure of a user of 12 * this module. Similar to how struct list_head and struct rb_node are used. 13 * 14 * Note: it should be embedded as the first element in a struct (offset 0), and 15 * this module assumes it was allocated with kmalloc(), so it calls kfree() when 16 * it needs to free an entry. 17 */ 18 struct btrfs_lru_cache_entry { 19 struct list_head lru_list; 20 u64 key; 21 /* 22 * Optional generation associated to a key. Use 0 if not needed/used. 23 * Entries with the same key and different generations are stored in a 24 * linked list, so use this only for cases where there's a small number 25 * of different generations. 26 */ 27 u64 gen; 28 /* 29 * The maple tree uses unsigned long type for the keys, which is 32 bits 30 * on 32 bits systems, and 64 bits on 64 bits systems. So if we want to 31 * use something like inode numbers as keys, which are always a u64, we 32 * have to deal with this in a special way - we store the key in the 33 * entry itself, as a u64, and the values inserted into the maple tree 34 * are linked lists of entries - so in case we are on a 64 bits system, 35 * that list always has a single entry, while on 32 bits systems it 36 * may have more than one, with each entry having the same value for 37 * their lower 32 bits of the u64 key. 38 */ 39 struct list_head list; 40 }; 41 42 struct btrfs_lru_cache { 43 struct list_head lru_list; 44 struct maple_tree entries; 45 /* Number of entries stored in the cache. */ 46 unsigned int size; 47 /* Maximum number of entries the cache can have. */ 48 unsigned int max_size; 49 }; 50 51 #define btrfs_lru_cache_for_each_entry_safe(cache, entry, tmp) \ 52 list_for_each_entry_safe_reverse((entry), (tmp), &(cache)->lru_list, lru_list) 53 54 static inline struct btrfs_lru_cache_entry *btrfs_lru_cache_lru_entry( 55 struct btrfs_lru_cache *cache) 56 { 57 return list_first_entry_or_null(&cache->lru_list, 58 struct btrfs_lru_cache_entry, lru_list); 59 } 60 61 void btrfs_lru_cache_init(struct btrfs_lru_cache *cache, unsigned int max_size); 62 struct btrfs_lru_cache_entry *btrfs_lru_cache_lookup(struct btrfs_lru_cache *cache, 63 u64 key, u64 gen); 64 int btrfs_lru_cache_store(struct btrfs_lru_cache *cache, 65 struct btrfs_lru_cache_entry *new_entry, 66 gfp_t gfp); 67 void btrfs_lru_cache_remove(struct btrfs_lru_cache *cache, 68 struct btrfs_lru_cache_entry *entry); 69 void btrfs_lru_cache_clear(struct btrfs_lru_cache *cache); 70 71 #endif 72