9.0-STABLE: Can't umount umass device

[George Mitchell]

uname -a:
FreeBSD wonderland.m5p.com 9.0-STABLE FreeBSD 9.0-STABLE #9: Sun Jun  3 
10:01:09 EDT 2012 
george at wonderland.m5p.com:/usr/obj/usr/src/sys/WONDERLAND  amd64

dmesg | grep umass:
umass0: <Bulk-In, Bulk-Out, Interface> on usbus2
umass0:  SCSI over Bulk-Only; quirks = 0x4000
umass0:3:0:-1: Attached to scbus3
(probe0:umass-sim0:0:0:0): TEST UNIT READY. CDB: 0 0 0 0 0 0
(probe0:umass-sim0:0:0:0): CAM status: SCSI Status Error
(probe0:umass-sim0:0:0:0): SCSI status: Check Condition
(probe0:umass-sim0:0:0:0): SCSI sense: UNIT ATTENTION asc:28,0 (Not 
ready to ready change, medium may have changed)
da0 at umass-sim0 bus 0 scbus3 target 0 lun 0

# mount -t msdosfs /dev/da0s1 /flash
# umount /flash
umount: unmount of /flash failed: Device busy

-- George Mitchell