makechrootpkg and long union unmount time

[Evangelos Foutras <foutrelis@xxxxxxxxx>]

Hello,

When I'm building a package using makechrootpkg and the build fails or I 
happen to interrupt it, sometimes it gets stuck at the "cleaning up 
unioned mounts" stage for a very long time (from several seconds up to a 
few minutes). During this time, the disk shows intense activity.

Does this happen to others too? Any idea why this is occurring and how 
to prevent it?