[parted-devel] [PATCH 1/2] libparted: check PMBR before GPT partition table (#805272)

[Brian C. Lane]

On Tue, Mar 20, 2012 at 09:19:40PM -0400, Phillip Susi wrote:
> On 03/20/2012 08:25 PM, Brian C. Lane wrote:
> > From: "Brian C. Lane" <bcl at redhat.com>
> > 
> > The UEFI spec requires that a valid GPT disk label have a PMBR
> > partition. This moves the PMBR check to before the GPT check,
> > exiting gpt_probe with a 0 if the PMBR is not valid.
> > 
> > The previous behavior would cause problems in the following situation:
> >  1. format a disk as GPT
> >  2. re-format it as MSDOS using tools that don't understand GPT
> > 
> > Subsequent operations with parted would then complain about the invlid
> > PMBR, but would not allow the disk to be used as a msdos disk. This
> > change causes parted to tread the disk as a msdos disk.
> 
> I don't think this patch is quite right.  The exception should be fixed rather than removed.  If it is supposed to be a GPT disk, then we should fix the broken PMBR.  If it is not, then we should zap the GPT and then fail to recognize the disk as GPT ( thus allowing it to be recognized as DOS ).
> 

I think we should leave it alone. I don't think we should be offering to
modify the disk when we're probing for the disk partition. The PMBR
isn't broken, it has been removed. I think the chances of a PMBR being
corrupted are much smaller than the chances of someone using old tools
to reformat a GPT disk.

-- 
Brian C. Lane | Anaconda Team | IRC: bcl #anaconda | Port Orchard, WA (PST8PDT)
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