Re: [PATCH] Refuse to install on XFS destroying its superblock

[Robert Millan]

On Fri, Oct 16, 2009 at 11:08:31PM +0200, Vladimir 'phcoder' Serbinenko wrote:
> Robert Millan wrote:
> > On Fri, Oct 16, 2009 at 10:09:41PM +0200, Vladimir 'phcoder' Serbinenko 
> > wrote:
> >   
> >> Robert Millan wrote:
> >>     
> >>> On Fri, Oct 16, 2009 at 06:01:56PM +0200, Jordi Mallach wrote:
> >>>   
> >>>       
> >>>> On Fri, Oct 16, 2009 at 04:03:01PM +0200, Vladimir 'phcoder' Serbinenko 
> >>>> wrote:
> >>>>     
> >>>>         
> >>>>> +  if (memcmp (tmp_img, "XFSB", 4) == 0)
> >>>>> +    grub_util_error ("Can't install on XFS.");
> >>>>>       
> >>>>>           
> >>>> Can this error message give some more detail on what the problem is?
> >>>>     
> >>>>         
> >>> I suggest something like:
> >>>
> >>>   grub_util_warn ("Refusing to overwrite XFS meta-data.");
> >>>
> >>> This is more informative, and with grub_util_warn() user has an 
> >>> opportunity to
> >>> override it if she knows what she's doing.
> >>>
> >>>   
> >>>       
> >> Installing with blocklists/to partition is considered
> >> backward-compatibility feature. We never supported a config with XFS why
> >> we would want bw-compat for it?
> >>     
> >
> > Because we can't reliably tell if it's a config with XFS, only the user can.
> > This is an issue for both MBR or PBR installs.
> >
> > Maybe "XFSB" is only a remnant from one of this disk / partition former
> > lifes.  Maybe it's a valid XFS but user no longer cares about it.  Or
> > maybe a DOS-style label was created on top of it, without overwriting the 
> > first
> > 440 bytes.  Or maybe another filesystem had overwritten most XFS metadata
> > but preserved the first block (this is conceivable since other filesystems
> > tend to avoid using the first block).
> >
> > If user has to workaround GRUB heuristics by dd'ing zeros into a partition
> > before running grub-install, this is a sign GRUB isn't doing the right 
> > thing.
> >
> >   
> Well, ok. But then I would ask to use a separate --force e.g.
> --force-destroy-xfs since users and distributions tend to use --force
> too much

Ok.

-- 
Robert Millan

  The DRM opt-in fallacy: "Your data belongs to us. We will decide when (and
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