Re: [PATCH] cifs: handle termination of cifs oplockd kernel thread

[Christoph Hellwig <hch@infradead.org>]

On Fri, Apr 29, 2005 at 04:09:09PM -0500, Steve French wrote:
> > does and who revied that?  Things like that don't have a business in the
> > kernel, and certainly not as ioctl.
> 
> Other filesystems such as smbfs had an ioctl that returned the uid of 
> the mounter which they used (in the smbfs case in smbumount).  This was 
> required by the unmount helper to determine if the unmount would allow a 
> user to unmount a particular mount that they mounted.   Unlike in the 
> case of mount, for unmount  you can not use the owner uid of the mount 
> target to tell who mounted that mount.   I had not received any better 
> suggestions as to how to address it.   I had proposed various 
> alternatives - exporting in in /proc/mounts e.g.   

exporting the uid using the show_options superblock methods sounds like
a much better option.

> As we try to gradually obsolete smbfs, this came up with various users 
> (there was even a bugzilla bug opened for adding it) who said that they 
> need the ability to unmount their own mounts for network filesystems 
> without using /etc/fstab.    Unfortunately for network filesytsems, 
> unlike local filesystems, it is impractical to put every possible mount 
> target in /etc/fstab since servers get renamed and the universe of 
> possible cifs mount targets for a user is large.

Do you use the same suid wrapper hack for mounts as fuse?  Maybe you
should chime in on that thread so we can find a proper solution.

> 
> There seemed only three alternatives -
> 1) mimic the smbfs ioctl -   as can be seen from smbfs and smbumount 
> source this has portability problems because apparently there is no 
> guarantee that uid_t is the same size in kernel and in userspace - smbfs 
> actually has two ioctls for different sizes of uid field - this seemed 
> like a bad idea
> 2) export the uid in /proc/mounts - same problem as above

No.  /proc/self/mounts is an ASCII format, so there's no problem with
differemt sizes.