the underlying drive had been hot-unplugged from the system.
This merges the following revisions:
Revision Path
1.94 src/sys/cam/scsi/scsi_cd.c
1.181 src/sys/cam/scsi/scsi_da.c
1.98 src/sys/geom/geom_disk.c
1.5 src/sys/geom/geom_disk.h
1.88 src/sys/geom/geom_subr.c