72 lines
2.5 KiB
C
72 lines
2.5 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef BTRFS_LRU_CACHE_H
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#define BTRFS_LRU_CACHE_H
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#include <linux/types.h>
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#include <linux/maple_tree.h>
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#include <linux/list.h>
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/*
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* A cache entry. This is meant to be embedded in a structure of a user of
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* this module. Similar to how struct list_head and struct rb_node are used.
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*
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* Note: it should be embedded as the first element in a struct (offset 0), and
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* this module assumes it was allocated with kmalloc(), so it calls kfree() when
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* it needs to free an entry.
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*/
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struct btrfs_lru_cache_entry {
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struct list_head lru_list;
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u64 key;
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/*
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* Optional generation associated to a key. Use 0 if not needed/used.
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* Entries with the same key and different generations are stored in a
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* linked list, so use this only for cases where there's a small number
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* of different generations.
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*/
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u64 gen;
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/*
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* The maple tree uses unsigned long type for the keys, which is 32 bits
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* on 32 bits systems, and 64 bits on 64 bits systems. So if we want to
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* use something like inode numbers as keys, which are always a u64, we
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* have to deal with this in a special way - we store the key in the
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* entry itself, as a u64, and the values inserted into the maple tree
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* are linked lists of entries - so in case we are on a 64 bits system,
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* that list always has a single entry, while on 32 bits systems it
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* may have more than one, with each entry having the same value for
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* their lower 32 bits of the u64 key.
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*/
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struct list_head list;
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};
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struct btrfs_lru_cache {
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struct list_head lru_list;
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struct maple_tree entries;
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/* Number of entries stored in the cache. */
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unsigned int size;
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/* Maximum number of entries the cache can have. */
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unsigned int max_size;
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};
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#define btrfs_lru_cache_for_each_entry_safe(cache, entry, tmp) \
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list_for_each_entry_safe_reverse((entry), (tmp), &(cache)->lru_list, lru_list)
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static inline struct btrfs_lru_cache_entry *btrfs_lru_cache_lru_entry(
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struct btrfs_lru_cache *cache)
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{
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return list_first_entry_or_null(&cache->lru_list,
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struct btrfs_lru_cache_entry, lru_list);
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}
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void btrfs_lru_cache_init(struct btrfs_lru_cache *cache, unsigned int max_size);
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struct btrfs_lru_cache_entry *btrfs_lru_cache_lookup(struct btrfs_lru_cache *cache,
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u64 key, u64 gen);
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int btrfs_lru_cache_store(struct btrfs_lru_cache *cache,
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struct btrfs_lru_cache_entry *new_entry,
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gfp_t gfp);
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void btrfs_lru_cache_remove(struct btrfs_lru_cache *cache,
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struct btrfs_lru_cache_entry *entry);
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void btrfs_lru_cache_clear(struct btrfs_lru_cache *cache);
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#endif
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