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