kern/40442: Meizu M6 unmount problems: cache synchronization failed

[Thomas Klausner <wiz%NetBSD.org@localhost>]

>Number:         40442
>Category:       kern
>Synopsis:       Meizu M6 unmount problems: cache synchronization failed
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue Jan 20 23:30:00 +0000 2009
>Originator:     Thomas Klausner
>Release:        NetBSD 5.99.5
>Organization:
Curiosity is the very basis of education and if you tell me that 
curiosity killed the cat, I say only that the cat died nobly.
- Arnold Edinborough
>Environment:
        
        
Architecture: x86_64
Machine: amd64
>Description:
When unmounting the fat file system on my portable MP3 player, a
Meizu M6 SP 8GB, I have to wait for a long time, until it fails with
umass0: Phase Error, residue = 0
sd0: cache synchronization failed
>How-To-Repeat:
Plugin in a Meizu M6 SP 8GB, dmesg says:
umass0 at uhub2 port 1 configuration 1 interface 0
umass0: Meizu   Electronics MiniPlayer, rev 2.00/1.00, addr 5
umass0: using SCSI over Bulk-Only
scsibus0 at umass0: 2 targets, 1 lun per target
sd0 at scsibus0 target 0 lun 0: <Meizu, MiniPlayer, 1.00> disk removable
sd0: 7820 MB, 7840 cyl, 16 head, 32 sec, 512 bytes/sect x 16015360 sectors

Mount the file system on it, do something, unmount:
# mount_msdos /dev/sd0a /mnt
# touch /mnt/a
# time umount /mnt

real    12m10.896s
user    0m0.000s
sys     0m0.025s
#

dmesg now contains:
umass0: Phase Error, residue = 0
sd0: cache synchronization failed
>Fix:
Yes, please.

>Unformatted: