svn commit: r320803 - head/sbin/mount

[Ian Lepore]

On Sat, 2017-07-08 at 09:50 -0700, Rodney W. Grimes wrote:
> [ Charset UTF-8 unsupported, converting... ]
> > 
> > Author: trasz
> > Date: Sat Jul  8 11:06:27 2017
> > New Revision: 320803
> > URL: https://svnweb.freebsd.org/changeset/base/320803
> > 
> > Log:
> >   Fix "mount -uw /" when the filesystem type doesn't match.
> >   
> >   This basically makes "mount -uw /" work when the filesystem
> >   mounted on / is NFS, but the one configured in fstab(5) is UFS,
> >   which can happen when you forget to modify fstab.
> Please do not silence user errors because they are inconvinient,
> this is a configuration error and the system should fail to 
> mount the incorrectly configured root.
> 
> If we start changing things to silently ignore user configuration
> errors we are going down a very slippery road.
> 

IMO, this change fixes the right problem, but maybe does so the wrong
way.  Mount -u is by definition an update to an existing mount.  There
should be no need to consult /etc/fstab for an existing mount since the
info is available from the kernel.

Note that I say the foregoing with my user hat on.  I haven't looked at
the code to see if there's some reason why my common-sensical way of
thinking about it is actually impossible to implement for some reason.

-- Ian