rem: previous->notification_hook(previous->id);
add: previous->notification_hook(previous->id, previous->notification_data);
context: write_cached_block(block_cache *cache, cached_block *block, bool deleteTransaction = true){	cache_transaction *previous = block->previous_transaction;	int32 blockSize = cache->block_size;	if (write_pos(cache->fd, block->block_number * blockSize, block->data, blockSize) < blockSize) {		dprintf("could not write back block %Ld\n", block->block_number);		return B_IO_ERROR;	}	if (previous != NULL) {		previous->blocks.Remove(block);		block->previous_transaction = NULL;		if (--previous->num_blocks == 0) {			if (previous->notification_hook != NULL)				previous->notification_hook(previous->id);			if (deleteTransaction)				delete_transaction(cache, previous);		}	}	return B_OK;}