15  * Ext2 and ext4 use this cache for deduplication of extended attribute blocks.
20  * identifies a cache entry.
32 	/* Maximum entries in cache to avoid degrading hash too much */
37 	/* Number of entries in cache */
40 	/* Work for shrinking when the cache has too many entries */
46 static unsigned long mb_cache_shrink(struct mb_cache *cache,
49 static inline struct hlist_bl_head *mb_cache_entry_head(struct mb_cache *cache,  in mb_cache_entry_head()  argument
52 	return &cache->c_hash[hash_32(key, cache->c_bucket_bits)];  in mb_cache_entry_head()
57  * in cache
62  * mb_cache_entry_create - create entry in cache
63  * @cache - cache where the entry should be created
69  * Creates entry in @cache with key @key and value @value. The function returns
70  * -EBUSY if entry with the same key and value already exists in cache.
73 int mb_cache_entry_create(struct mb_cache *cache, gfp_t mask, u32 key,  in mb_cache_entry_create()  argument
81 	if (cache->c_entry_count >= cache->c_max_entries)  in mb_cache_entry_create()
82 		schedule_work(&cache->c_shrink_work);  in mb_cache_entry_create()
84 	if (cache->c_entry_count >= 2*cache->c_max_entries)  in mb_cache_entry_create()
85 		mb_cache_shrink(cache, SYNC_SHRINK_BATCH);  in mb_cache_entry_create()
98 	head = mb_cache_entry_head(cache, key);  in mb_cache_entry_create()
110 	spin_lock(&cache->c_list_lock);  in mb_cache_entry_create()
111 	list_add_tail(&entry->e_list, &cache->c_list);  in mb_cache_entry_create()
114 	cache->c_entry_count++;  in mb_cache_entry_create()
115 	spin_unlock(&cache->c_list_lock);  in mb_cache_entry_create()
127 static struct mb_cache_entry *__entry_find(struct mb_cache *cache,  in __entry_find()  argument
135 	head = mb_cache_entry_head(cache, key);  in __entry_find()
154 		mb_cache_entry_put(cache, old_entry);  in __entry_find()
161  * @cache: cache where we should search
164  * Search in @cache for a reusable entry with key @key. Grabs reference to the
167 struct mb_cache_entry *mb_cache_entry_find_first(struct mb_cache *cache,  in mb_cache_entry_find_first()  argument
170 	return __entry_find(cache, NULL, key);  in mb_cache_entry_find_first()
176  * @cache: cache where we should search
184 struct mb_cache_entry *mb_cache_entry_find_next(struct mb_cache *cache,  in mb_cache_entry_find_next()  argument
187 	return __entry_find(cache, entry, entry->e_key);  in mb_cache_entry_find_next()
192  * mb_cache_entry_get - get a cache entry by value (and key)
193  * @cache - cache we work with
197 struct mb_cache_entry *mb_cache_entry_get(struct mb_cache *cache, u32 key,  in mb_cache_entry_get()  argument
204 	head = mb_cache_entry_head(cache, key);  in mb_cache_entry_get()
219 /* mb_cache_entry_delete - remove a cache entry
220  * @cache - cache we work with
224  * Remove entry from cache @cache with key @key and value @value.
226 void mb_cache_entry_delete(struct mb_cache *cache, u32 key, u64 value)  in mb_cache_entry_delete()  argument
232 	head = mb_cache_entry_head(cache, key);  in mb_cache_entry_delete()
239 			spin_lock(&cache->c_list_lock);  in mb_cache_entry_delete()
242 				if (!WARN_ONCE(cache->c_entry_count == 0,  in mb_cache_entry_delete()
244 					cache->c_entry_count--;  in mb_cache_entry_delete()
247 			spin_unlock(&cache->c_list_lock);  in mb_cache_entry_delete()
248 			mb_cache_entry_put(cache, entry);  in mb_cache_entry_delete()
256 /* mb_cache_entry_touch - cache entry got used
257  * @cache - cache the entry belongs to
260  * Marks entry as used to give hit higher chances of surviving in cache.
262 void mb_cache_entry_touch(struct mb_cache *cache,  in mb_cache_entry_touch()  argument
272 	struct mb_cache *cache = container_of(shrink, struct mb_cache,  in mb_cache_count()  local
275 	return cache->c_entry_count;  in mb_cache_count()
278 /* Shrink number of entries in cache */
279 static unsigned long mb_cache_shrink(struct mb_cache *cache,  in mb_cache_shrink()  argument
286 	spin_lock(&cache->c_list_lock);  in mb_cache_shrink()
287 	while (nr_to_scan-- && !list_empty(&cache->c_list)) {  in mb_cache_shrink()
288 		entry = list_first_entry(&cache->c_list,  in mb_cache_shrink()
292 			list_move_tail(&entry->e_list, &cache->c_list);  in mb_cache_shrink()
296 		cache->c_entry_count--;  in mb_cache_shrink()
301 		spin_unlock(&cache->c_list_lock);  in mb_cache_shrink()
302 		head = mb_cache_entry_head(cache, entry->e_key);  in mb_cache_shrink()
309 		if (mb_cache_entry_put(cache, entry))  in mb_cache_shrink()
312 		spin_lock(&cache->c_list_lock);  in mb_cache_shrink()
314 	spin_unlock(&cache->c_list_lock);  in mb_cache_shrink()
322 	struct mb_cache *cache = container_of(shrink, struct mb_cache,  in mb_cache_scan()  local
324 	return mb_cache_shrink(cache, sc->nr_to_scan);  in mb_cache_scan()
327 /* We shrink 1/X of the cache when we have too many entries in it */
332 	struct mb_cache *cache = container_of(work, struct mb_cache,  in mb_cache_shrink_worker()  local
334 	mb_cache_shrink(cache, cache->c_max_entries / SHRINK_DIVISOR);  in mb_cache_shrink_worker()
338  * mb_cache_create - create cache
341  * Create cache for keys with 2^bucket_bits hash entries.
345 	struct mb_cache *cache;  in mb_cache_create()  local
349 	cache = kzalloc(sizeof(struct mb_cache), GFP_KERNEL);  in mb_cache_create()
350 	if (!cache)  in mb_cache_create()
352 	cache->c_bucket_bits = bucket_bits;  in mb_cache_create()
353 	cache->c_max_entries = bucket_count << 4;  in mb_cache_create()
354 	INIT_LIST_HEAD(&cache->c_list);  in mb_cache_create()
355 	spin_lock_init(&cache->c_list_lock);  in mb_cache_create()
356 	cache->c_hash = kmalloc_array(bucket_count,  in mb_cache_create()
359 	if (!cache->c_hash) {  in mb_cache_create()
360 		kfree(cache);  in mb_cache_create()
364 		INIT_HLIST_BL_HEAD(&cache->c_hash[i]);  in mb_cache_create()
366 	cache->c_shrink.count_objects = mb_cache_count;  in mb_cache_create()
367 	cache->c_shrink.scan_objects = mb_cache_scan;  in mb_cache_create()
368 	cache->c_shrink.seeks = DEFAULT_SEEKS;  in mb_cache_create()
369 	if (register_shrinker(&cache->c_shrink)) {  in mb_cache_create()
370 		kfree(cache->c_hash);  in mb_cache_create()
371 		kfree(cache);  in mb_cache_create()
375 	INIT_WORK(&cache->c_shrink_work, mb_cache_shrink_worker);  in mb_cache_create()
377 	return cache;  in mb_cache_create()
385  * mb_cache_destroy - destroy cache
386  * @cache: the cache to destroy
388  * Free all entries in cache and cache itself. Caller must make sure nobody
389  * (except shrinker) can reach @cache when calling this.
391 void mb_cache_destroy(struct mb_cache *cache)  in mb_cache_destroy()  argument
395 	unregister_shrinker(&cache->c_shrink);  in mb_cache_destroy()
398 	 * We don't bother with any locking. Cache must not be used at this  in mb_cache_destroy()
401 	list_for_each_entry_safe(entry, next, &cache->c_list, e_list) {  in mb_cache_destroy()
409 		mb_cache_entry_put(cache, entry);  in mb_cache_destroy()
411 	kfree(cache->c_hash);  in mb_cache_destroy()
412 	kfree(cache);  in mb_cache_destroy()
435 MODULE_DESCRIPTION("Meta block cache (for extended attributes)");