It turns out the problem is caused by hdparm's RAID_WORKAROUND option in
/etc/default/hdparm. I'm still not sure whether it's a kernel bug or a
bug in hdparm, but at least disabling this option fixes the problem....

Ing. A.C.J. van Amersfoort (Arno)
Electronics & ICT Engineer
Leiden Institute of Physics (LION), Electronics Department (ELD)
Huygens Laboratory (Room 1007), Leiden University
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