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 #include "lru_cache.h" 10 11 /* 12 * A cache entry. This is meant to be embedded in a structure of a user of 13 * this module. Similar to how struct list_head and struct rb_node are used. 14 * 15 * Note: it should be embedded as the first element in a struct (offset 0), and 16 * this module assumes it was allocated with kmalloc(), so it calls kfree() when 17 * it needs to free an entry. 18 */ 19 struct btrfs_lru_cache_entry { 20 struct list_head lru_list; 21 u64 key; 22 /* 23 * Optional generation associated to a key. Use 0 if not needed/used. 24 * Entries with the same key and different generations are stored in a 25 * linked list, so use this only for cases where there's a small number 26 * of different generations. 27 */ 28 u64 gen; 29 /* 30 * The maple tree uses unsigned long type for the keys, which is 32 bits 31 * on 32 bits systems, and 64 bits on 64 bits systems. So if we want to 32 * use something like inode numbers as keys, which are always a u64, we 33 * have to deal with this in a special way - we store the key in the 34 * entry itself, as a u64, and the values inserted into the maple tree 35 * are linked lists of entries - so in case we are on a 64 bits system, 36 * that list always has a single entry, while on 32 bits systems it 37 * may have more than one, with each entry having the same value for 38 * their lower 32 bits of the u64 key. 39 */ 40 struct list_head list; 41 }; 42 43 struct btrfs_lru_cache { 44 struct list_head lru_list; 45 struct maple_tree entries; 46 /* Number of entries stored in the cache. */ 47 unsigned int size; 48 /* Maximum number of entries the cache can have. */ 49 unsigned int max_size; 50 }; 51 52 #define btrfs_lru_cache_for_each_entry_safe(cache, entry, tmp) \ 53 list_for_each_entry_safe_reverse((entry), (tmp), &(cache)->lru_list, lru_list) 54 55 static inline struct btrfs_lru_cache_entry *btrfs_lru_cache_lru_entry( 56 struct btrfs_lru_cache *cache) 57 { 58 return list_first_entry_or_null(&cache->lru_list, 59 struct btrfs_lru_cache_entry, lru_list); 60 } 61 62 void btrfs_lru_cache_init(struct btrfs_lru_cache *cache, unsigned int max_size); 63 struct btrfs_lru_cache_entry *btrfs_lru_cache_lookup(struct btrfs_lru_cache *cache, 64 u64 key, u64 gen); 65 int btrfs_lru_cache_store(struct btrfs_lru_cache *cache, 66 struct btrfs_lru_cache_entry *new_entry, 67 gfp_t gfp); 68 void btrfs_lru_cache_remove(struct btrfs_lru_cache *cache, 69 struct btrfs_lru_cache_entry *entry); 70 void btrfs_lru_cache_clear(struct btrfs_lru_cache *cache); 71 72 #endif 73