Hallo, Stefan,

Du meintest am 19.03.12:

When a filesystem is mounted with the degraded option, it is
possible that some of the devices are not there.
btrfs_ioctl_dev_info() crashs in this case because the device
name is a NULL pointer. This ioctl was only used for scrub.

Just for curiosity: can that happen when I first delete a partition/disk  
and then run "btrfs scrub start"?

Viele Gruesse!
Helmut