Re: handling unrecognised mount options

[Andrew Morton <akpm@digeo.com>]

Andries Brouwer <aebr@win.tue.nl> wrote:
>
> On Sun, Mar 16, 2003 at 03:00:03AM -0800, Andrew Morton wrote:
> 
> > None of my machines will successfully boot into 2.4 kernels because I have
> > "commit=30" added to the ext3 mount options in /etc/fstab.
> > 
> > The ext3 driver in those kernels does not to recognise that option and it
> > fails the mount.
> > 
> > This seems to be a fairly gratuitous and pointless forward-incompatibility.
> > 
> > I propose that henceforth filesystems will, when presented with an
> > unrecognised mount option, warn and proceed with the mount anyway.
> > 
> > Can anyone see any problems with that?
> 
> I would prefer the conservative approach, doing the mount only
> when also some "force" flag is present.
> 
> Mounting is a dangerous operation.
> An incorrect mount can crash the kernel and can damage the filesystem.
> 

The only way we could have a problem here is if someone made a
back-incompatible change to a filesystem format which would cause problems
for older kernels.  And then _required_ that newer kernel be given this mount
option.

I just cannot think of any other scenario in which the current behaviour
makes sense.  And it is objectionable.

Certainly it does not make sense for ext2 and ext3 where we have
compatibility flags for these things.  So I'm at least looking for an
argument aganst changing this behaviour for ext2/3.