4.3.4 Modifying the on-disk cache

It is safe to modify the on-disk cache while Polipo is running as long as no file is ever modified in place. More precisely, the only safe operations are to unlink (remove, delete) files in the disk cache, or to atomically add new files to the cache (by performing an exclusive open, or by using one of the ‘link’ or ‘rename’ system calls). It is not safe to truncate a file in place.