Code review comment for lp:~yuningdodo/usb-creator/usb-creator.lp1273925+lp1289269

I re-checked it, even with usb-creator-kde the free space is also considered as zero after "erase disk". I believe it's a different issue.

By the way, during my experiment I noticed that if we manually zeroed the disk (dd if=/dev/zero of=/dev/sdb bs=1M count=1) then usb-creator will report an error whilte erasing it.