kern/122961: write operation on msdosfs file system causes panic

[Bruce Evans]

On Tue, 22 Apr 2008, Dominic Fandrey wrote:

> Bruce Evans wrote:
>> On Mon, 21 Apr 2008, Dominic Fandrey wrote:
>> This seems to be a bug in usb (umass) or the particular usb drive...
>> ...
>> 
>> To check that this is the bug, mount msdosfs with -o noclusterr,noclusterw
>> under RELENG_7 or later (the bug also affects RELENG_6, but these mount
>> options are broken in RELENG_6). ...
>
> # mount -t msdosfs -o noatime,noexec,-L=en_GB.UTF-8,noclusterr,noclusterw 
> /dev/da0 /mnt/tmp
> mount_msdosfs: /dev/da0: mount option <noclusterw> is unknown: Invalid 
> argument
>
> It seems they are also broken under RELENG_7 from the day before yesterday.

Oops, it is indeed broken there too.  msdosfs in RELENG_7 is in the state
that I thought RELENG_6 was in (missing critical MFCs only for nocluster*
in the options list and to fix panics related to the dirty flag), while
msdosfs in RELENG_6 is just too old to support clustering.

The broken nocluster* can be worked around by upgrading to a version of
mount_msdsosfs(8) that hasn't been broken by using nmount(2).
mount_msdsosfs(8) from RELENG_5 should work.

Bruce