Sure, you are still dependent on constraints to durability and atomicity of the filesystem write of the new data. But this is handled properly in most modern fi

Sure, you are still dependent on constraints to durability and atomicity of the filesystem write of the new data. But this is handled properly in most modern filesystems (ext3,ext4,zfs) by default (as data=ordered ensures data writes precede metadata writes). The point of rename() is to prevent a version to ever exist that mixes the old and the new version, which it always does, regardless of the filesystem.