16  * Ext2 and ext4 use this cache for deduplication of extended attribute blocks.
21  * identifies a cache entry.
33 	/* Maximum entries in cache to avoid degrading hash too much */
38 	/* Number of entries in cache */
41 	/* Work for shrinking when the cache has too many entries */
47 static unsigned long mb_cache_shrink(struct mb_cache *cache,
50 static inline struct hlist_bl_head *mb_cache_entry_head(struct mb_cache *cache,  in mb_cache_entry_head()  argument
53 	return &cache->c_hash[hash_32(key, cache->c_bucket_bits)];  in mb_cache_entry_head()
58  * in cache
63  * mb_cache_entry_create - create entry in cache
64  * @cache - cache where the entry should be created
70  * Creates entry in @cache with key @key and value @value. The function returns
71  * -EBUSY if entry with the same key and value already exists in cache.
74 int mb_cache_entry_create(struct mb_cache *cache, gfp_t mask, u32 key,  in mb_cache_entry_create()  argument
82 	if (cache->c_entry_count >= cache->c_max_entries)  in mb_cache_entry_create()
83 		schedule_work(&cache->c_shrink_work);  in mb_cache_entry_create()
85 	if (cache->c_entry_count >= 2*cache->c_max_entries)  in mb_cache_entry_create()
86 		mb_cache_shrink(cache, SYNC_SHRINK_BATCH);  in mb_cache_entry_create()
97 	 * avoids nesting of cache->c_list_lock into hash table bit locks which  in mb_cache_entry_create()
106 	head = mb_cache_entry_head(cache, key);  in mb_cache_entry_create()
117 	spin_lock(&cache->c_list_lock);  in mb_cache_entry_create()
118 	list_add_tail(&entry->e_list, &cache->c_list);  in mb_cache_entry_create()
119 	cache->c_entry_count++;  in mb_cache_entry_create()
120 	spin_unlock(&cache->c_list_lock);  in mb_cache_entry_create()
121 	mb_cache_entry_put(cache, entry);  in mb_cache_entry_create()
127 void __mb_cache_entry_free(struct mb_cache *cache, struct mb_cache_entry *entry)  in __mb_cache_entry_free()  argument
131 	head = mb_cache_entry_head(cache, entry->e_key);  in __mb_cache_entry_free()
152 static struct mb_cache_entry *__entry_find(struct mb_cache *cache,  in __entry_find()  argument
160 	head = mb_cache_entry_head(cache, key);  in __entry_find()
179 		mb_cache_entry_put(cache, old_entry);  in __entry_find()
186  * @cache: cache where we should search
189  * Search in @cache for a reusable entry with key @key. Grabs reference to the
192 struct mb_cache_entry *mb_cache_entry_find_first(struct mb_cache *cache,  in mb_cache_entry_find_first()  argument
195 	return __entry_find(cache, NULL, key);  in mb_cache_entry_find_first()
201  * @cache: cache where we should search
209 struct mb_cache_entry *mb_cache_entry_find_next(struct mb_cache *cache,  in mb_cache_entry_find_next()  argument
212 	return __entry_find(cache, entry, entry->e_key);  in mb_cache_entry_find_next()
217  * mb_cache_entry_get - get a cache entry by value (and key)
218  * @cache - cache we work with
222 struct mb_cache_entry *mb_cache_entry_get(struct mb_cache *cache, u32 key,  in mb_cache_entry_get()  argument
229 	head = mb_cache_entry_head(cache, key);  in mb_cache_entry_get()
243 /* mb_cache_entry_delete - try to remove a cache entry
244  * @cache - cache we work with
248  * Remove entry from cache @cache with key @key and value @value.
250 void mb_cache_entry_delete(struct mb_cache *cache, u32 key, u64 value)  in mb_cache_entry_delete()  argument
256 	head = mb_cache_entry_head(cache, key);  in mb_cache_entry_delete()
263 			spin_lock(&cache->c_list_lock);  in mb_cache_entry_delete()
266 				if (!WARN_ONCE(cache->c_entry_count == 0,  in mb_cache_entry_delete()
268 					cache->c_entry_count--;  in mb_cache_entry_delete()
271 			spin_unlock(&cache->c_list_lock);  in mb_cache_entry_delete()
272 			mb_cache_entry_put(cache, entry);  in mb_cache_entry_delete()
280 /* mb_cache_entry_delete_or_get - remove a cache entry if it has no users
281  * @cache - cache we work with
285  * Remove entry from cache @cache with key @key and value @value. The removal
287  * entry was successfully removed or there's no entry in cache. Otherwise the
291 struct mb_cache_entry *mb_cache_entry_delete_or_get(struct mb_cache *cache,  in mb_cache_entry_delete_or_get()  argument
296 	entry = mb_cache_entry_get(cache, key, value);  in mb_cache_entry_delete_or_get()
307 	spin_lock(&cache->c_list_lock);  in mb_cache_entry_delete_or_get()
310 	cache->c_entry_count--;  in mb_cache_entry_delete_or_get()
311 	spin_unlock(&cache->c_list_lock);  in mb_cache_entry_delete_or_get()
312 	__mb_cache_entry_free(cache, entry);  in mb_cache_entry_delete_or_get()
317 /* mb_cache_entry_touch - cache entry got used
318  * @cache - cache the entry belongs to
321  * Marks entry as used to give hit higher chances of surviving in cache.
323 void mb_cache_entry_touch(struct mb_cache *cache,  in mb_cache_entry_touch()  argument
333 	struct mb_cache *cache = container_of(shrink, struct mb_cache,  in mb_cache_count()  local
336 	return cache->c_entry_count;  in mb_cache_count()
339 /* Shrink number of entries in cache */
340 static unsigned long mb_cache_shrink(struct mb_cache *cache,  in mb_cache_shrink()  argument
346 	spin_lock(&cache->c_list_lock);  in mb_cache_shrink()
347 	while (nr_to_scan-- && !list_empty(&cache->c_list)) {  in mb_cache_shrink()
348 		entry = list_first_entry(&cache->c_list,  in mb_cache_shrink()
354 			list_move_tail(&entry->e_list, &cache->c_list);  in mb_cache_shrink()
358 		cache->c_entry_count--;  in mb_cache_shrink()
359 		spin_unlock(&cache->c_list_lock);  in mb_cache_shrink()
360 		__mb_cache_entry_free(cache, entry);  in mb_cache_shrink()
363 		spin_lock(&cache->c_list_lock);  in mb_cache_shrink()
365 	spin_unlock(&cache->c_list_lock);  in mb_cache_shrink()
373 	struct mb_cache *cache = container_of(shrink, struct mb_cache,  in mb_cache_scan()  local
375 	return mb_cache_shrink(cache, sc->nr_to_scan);  in mb_cache_scan()
378 /* We shrink 1/X of the cache when we have too many entries in it */
383 	struct mb_cache *cache = container_of(work, struct mb_cache,  in mb_cache_shrink_worker()  local
385 	mb_cache_shrink(cache, cache->c_max_entries / SHRINK_DIVISOR);  in mb_cache_shrink_worker()
389  * mb_cache_create - create cache
392  * Create cache for keys with 2^bucket_bits hash entries.
396 	struct mb_cache *cache;  in mb_cache_create()  local
400 	cache = kzalloc(sizeof(struct mb_cache), GFP_KERNEL);  in mb_cache_create()
401 	if (!cache)  in mb_cache_create()
403 	cache->c_bucket_bits = bucket_bits;  in mb_cache_create()
404 	cache->c_max_entries = bucket_count << 4;  in mb_cache_create()
405 	INIT_LIST_HEAD(&cache->c_list);  in mb_cache_create()
406 	spin_lock_init(&cache->c_list_lock);  in mb_cache_create()
407 	cache->c_hash = kmalloc_array(bucket_count,  in mb_cache_create()
410 	if (!cache->c_hash) {  in mb_cache_create()
411 		kfree(cache);  in mb_cache_create()
415 		INIT_HLIST_BL_HEAD(&cache->c_hash[i]);  in mb_cache_create()
417 	cache->c_shrink.count_objects = mb_cache_count;  in mb_cache_create()
418 	cache->c_shrink.scan_objects = mb_cache_scan;  in mb_cache_create()
419 	cache->c_shrink.seeks = DEFAULT_SEEKS;  in mb_cache_create()
420 	if (register_shrinker(&cache->c_shrink)) {  in mb_cache_create()
421 		kfree(cache->c_hash);  in mb_cache_create()
422 		kfree(cache);  in mb_cache_create()
426 	INIT_WORK(&cache->c_shrink_work, mb_cache_shrink_worker);  in mb_cache_create()
428 	return cache;  in mb_cache_create()
436  * mb_cache_destroy - destroy cache
437  * @cache: the cache to destroy
439  * Free all entries in cache and cache itself. Caller must make sure nobody
440  * (except shrinker) can reach @cache when calling this.
442 void mb_cache_destroy(struct mb_cache *cache)  in mb_cache_destroy()  argument
446 	unregister_shrinker(&cache->c_shrink);  in mb_cache_destroy()
449 	 * We don't bother with any locking. Cache must not be used at this  in mb_cache_destroy()
452 	list_for_each_entry_safe(entry, next, &cache->c_list, e_list) {  in mb_cache_destroy()
455 		mb_cache_entry_put(cache, entry);  in mb_cache_destroy()
457 	kfree(cache->c_hash);  in mb_cache_destroy()
458 	kfree(cache);  in mb_cache_destroy()
481 MODULE_DESCRIPTION("Meta block cache (for extended attributes)");