bin/43454: gpt(8) and disklabel(8) conflict with each other

[gregoire.sutre%gmail.com@localhost]

>Number:         43454
>Category:       bin
>Synopsis:       gpt(8) and disklabel(8) conflict with each other
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    bin-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Fri Jun 11 08:05:00 +0000 2010
>Originator:     Grégoire Sutre <gregoire.sutre%gmail.com@localhost>
>Release:        NetBSD 5.1_RC2
>Organization:
>Environment:
System: NetBSD niagara 5.1_RC2 NetBSD 5.1_RC2 (NIAGARA) #0: Thu Jun 10 00:19:14 
CEST 2010 instsoft@niagara:/usr/build/usr/src/sys/arch/i386/compile/NIAGARA i386
Architecture: i386
Machine: i386
>Description:

On a gpt-partitioned disk, running disklabel -e -I silently destroys the GPT
header.

Conversely, on a BSD-labeled disk (with a BSD label for the whole disk, i.e.
no DOS partition table in the MBR), running gpt create silently create destroys
the BSD disklabel.

>How-To-Repeat:

$ dd if=/dev/zero of=./testimage.bin bs=10m count=1
$ vnconfig vnd0 testimage.bin

// Create a new BSD disklabel
$ disklabel -e -I vnd0

// Check that the disklabel has been written to the disk
$ disklabel -r vnd0
[ shows the disklabel ]

// Create a new GUID partition table
$ gpt create vnd0

// Observe that the on-disk disklabel was destroyed
$ disklabel -r vnd0
disklabel: could not read existing label


Conversely:

$ dd if=/dev/zero of=./testimage.bin bs=10m count=1
$ vnconfig vnd0 testimage.bin

// Create a new GUID partition table
$ gpt create vnd0

// Add a new GPT partition
$ gpt add -s 10000 vnd0

// Read the GPT to check that the new partition is there
$ gpt show vnd0

// Create a new BSD disklabel
$ disklabel -e -I vnd0

// Observe that the GPT header was destroyed
$ gpt show vnd0
  start   size  index  contents
      0      1         PMBR
      1  20446
  20447     32         Sec GPT table
  20479      1         Sec GPT header


>Fix: