[gparted] Erase file system signatures before creating a partition table (#743181)

[Curtis Gedak <gedakc src gnome org>]

commit e7ed209020331aa26cb4b2f60bfa984a78d7fdf0
Author: Mike Fleetwood <mike fleetwood googlemail com>
Date:   Sat Feb 14 20:49:45 2015 +0000

    Erase file system signatures before creating a partition table (#743181)
    
    When writing "loop" partition table over the top of some whole disk
    device file system types GParted continued to show those whole disk
    device file systems rather than the virtual unknown partition from the
    "loop" partition table.
    
    This affected btrfs, jfs, reiser4 and reiserfs.  It occurred because of
    several factors:
    1) Libparted only zeroed the first and last 9.5 KiB (assuming 512 byte
       sectors) of the device before writing a new partition table.  See
       ped_disk_clobber().
    2) These file systems have their super blocks and therefore signatures
       after the first 9.5 KiB.
    3) Whole disk device file system detection is performed using blkid
       before checking for a libparted "loop" partition table.  See
       GParted_Core::set_devices_thread().
    
    Ref:
    libparted 3.2: disk.c:ped_disk_clobber()
    http://git.savannah.gnu.org/cgit/parted.git/tree/libparted/disk.c?id=v3.2#n302
    
    Fix by always erasing any possible file system signatures on the device
    before creating a new "loop" partition table.
    
    NOTE:
    This is typically taking up to 0.5 seconds in my testing on a 5400 RPM
    hard drive, during which time the GParted UI is hung and the create
    partition table dialog shows the apply button pressed but no other
    progress indication.
    
    Bug 743181 - Add unpartitioned drive read-write support

 include/GParted_Core.h |    5 +++--
 src/GParted_Core.cc    |   27 +++++++++++++++++++++++++--
 src/Win_GParted.cc     |    2 +-
 3 files changed, 29 insertions(+), 5 deletions(-)
---
diff --git a/include/GParted_Core.h b/include/GParted_Core.h
index 55434c0..1c85ca1 100644
--- a/include/GParted_Core.h
+++ b/include/GParted_Core.h
@@ -46,8 +46,9 @@ public:
        bool snap_to_mebibyte( const Device & device, Partition & partition, Glib::ustring & error ) ;
        bool snap_to_alignment( const Device & device, Partition & partition, Glib::ustring & error ) ;
        bool apply_operation_to_disk( Operation * operation );
-       
-       bool set_disklabel( const Glib::ustring & device_path, const Glib::ustring & disklabel ) ;
+
+       bool set_disklabel( const Device & device, const Glib::ustring & disklabel );
+       bool new_disklabel( const Glib::ustring & device_path, const Glib::ustring & disklabel );
 
        bool toggle_flag( const Partition & partition, const Glib::ustring & flag, bool state ) ;
        
diff --git a/src/GParted_Core.cc b/src/GParted_Core.cc
index e4f5584..8d43526 100644
--- a/src/GParted_Core.cc
+++ b/src/GParted_Core.cc
@@ -802,10 +802,33 @@ bool GParted_Core::apply_operation_to_disk( Operation * operation )
        return succes ;
 }
 
-bool GParted_Core::set_disklabel( const Glib::ustring & device_path, const Glib::ustring & disklabel ) 
+bool GParted_Core::set_disklabel( const Device & device, const Glib::ustring & disklabel )
+{
+       Glib::ustring device_path = device.get_path();
+
+       if ( disklabel == "loop" )
+       {
+               // Ensure that any previous whole disk device file system can't be
+               // recognised in preference to the "loop" partition table signature about
+               // to be written.
+               OperationDetail dummy_od;
+               Partition temp_partition;
+               temp_partition.Set_Unallocated( device_path,
+                                               true,
+                                               0LL,
+                                               device.length - 1LL,
+                                               device.sector_size,
+                                               false );
+               erase_filesystem_signatures( temp_partition, dummy_od );
+       }
+
+       return new_disklabel( device_path, disklabel );
+}
+
+bool GParted_Core::new_disklabel( const Glib::ustring & device_path, const Glib::ustring & disklabel )
 {
        bool return_value = false ;
-       
+
        PedDevice* lp_device = NULL ;
        PedDisk* lp_disk = NULL ;
        if ( get_device( device_path, lp_device ) )
diff --git a/src/Win_GParted.cc b/src/Win_GParted.cc
index fac415a..609bfcf 100644
--- a/src/Win_GParted.cc
+++ b/src/Win_GParted.cc
@@ -2396,7 +2396,7 @@ void Win_GParted::activate_disklabel()
 
        if ( dialog .run() == Gtk::RESPONSE_APPLY )
        {
-               if ( ! gparted_core .set_disklabel( devices[ current_device ] .get_path(), dialog 
.Get_Disklabel() ) )
+               if ( ! gparted_core.set_disklabel( devices[current_device], dialog.Get_Disklabel() ) )
                {
                        Gtk::MessageDialog dialog( *this,
                                                   _("Error while creating partition table"),