Large msdosfs disk will not mount on RELENG_6

Oliver Fromme olli at
Mon Nov 27 09:05:13 PST 2006

Richard Coleman wrote:
 > Oliver Fromme wrote:
 > > [...]
 > > However, if the size of the file system exceeds 128 MB

That should be 128 GB, of course.

 > [...]
 > Because of the potential panics that were mention, I can understand a 
 > reluctance to change the default.  But I suspect that (attempting to) 
 > mount a large msdosfs disk is a much more common occurrence than using a 
 > smaller msdosfs disk over NFS.

Well, the mentioned problems (running out of kernel memory
and NFS export difficulties) can occur with msdosfs file
systems of any size, including ones that are smaller than
128 GB.  It would be really annoying to not be able to
mount a USB stick with a lot of files on a machine with
small RAM (it could panic the machine without warning).

On the other hand, the default (no MSDOSFS_LARGE) is safe
for any number of files, i.e. you cannot panic the system,
but you're limited to 128 GB file system size.  (Well, you
_can_ cause a panic with certain broken file systems, but
that's a different story.)

It's really chosing the lesser of two evils, but which one
is the lesser?  The answer depends on whom you ask.  :-)

I think the best solution would be to convert the kernel
option into a mount option, so you can select your evil at
mount time without having to recompile and reboot.  Then
you would even be able to mount your USB stick with the
first hack and -- at the same time -- mount your external
big disk with the second hack.

Someone would have to code that, of course.  I'm afraid I'm
not volunteering (lack of time).  It shouldn't be fairly
easy to code, though: just add a flag to the mount (similar
to the existing flag for win95 long file names) that
indicates which hack to use, and select the apropriate hack
at runtime, basically replacing the current #ifdef with an
ordinary if(...).

Best regards

Oliver Fromme,  secnetix GmbH & Co. KG, Marktplatz 29, 85567 Grafing
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