Large msdosfs disk will not mount on RELENG_6

Richard Coleman rcoleman at
Sun Nov 26 22:49:33 PST 2006

Rink Springer wrote:
> On Mon, Nov 27, 2006 at 07:34:09AM +0100, Rink Springer wrote:
>> Looking at /sys/fs/msdosfs/msdosfs_vfsops.c seems to hint the existance
>> of options MSDOSFS_LARGE; this avoids the error message and will let you
>> mount the disk.
> Oh, and before I forget: this option is defined in /sys/conf/NOTES as
> well (a pure #ifdef in source code is not enough, of course :-)
> ---
> # Experimental support for large MS-DOS filesystems.
> #
> # WARNING: This uses at least 32 bytes of kernel memory (which is not
> # reclaimed until the FS is unmounted) for each file on disk to map
> # between the 32-bit inode numbers used by VFS and the 64-bit
> # pseudo-inode
> # numbers used internally by msdosfs. This is only safe to use in
> # certain
> # controlled situations (e.g. read-only FS with less than 1 million
> # files).
> # Since the mappings do not persist across unmounts (or reboots), these
> # filesystems are not suitable for exporting through NFS, or any other
> # application that requires fixed inode numbers.
> options         MSDOSFS_LARGE
> ---
> Regards,

It didn't occur to me to check NOTES, since this is on a very GENERIC box.  I did check the man 
pages for both msdosfs and mount_msdosfs, as well as the "storage" chapter in the handbook.  I 
didn't see this error message or that kernel option mentioned there.

Richard Coleman
rcoleman at

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