add: TRACE(("cache_transaction_start(): id %ld started\n", transaction->id));
context: cache_transaction_start(void *_cache, transaction_notification_hook hook){	block_cache *cache = (block_cache *)_cache;	cache_transaction *transaction = new cache_transaction;	if (transaction == NULL)		return B_NO_MEMORY;	transaction->id = atomic_add(&cache->next_transaction_id, 1);	transaction->num_blocks = 0;	transaction->first_block = NULL;	transaction->notification_hook = hook;	transaction->open = true;	BenaphoreLocker locker(cache);	hash_insert(cache->transaction_hash, transaction);	return transaction->id;}