[gparted] Update parsing of btrfs filesystem show for file system usage (#733601)

[Curtis Gedak <gedakc src gnome org>]

commit 422829ebff7ebee820b25afe35054ceee69579bd
Author: Mike Fleetwood <mike fleetwood googlemail com>
Date:   Wed Jul 23 00:56:13 2014 +0100

    Update parsing of btrfs filesystem show for file system usage (#733601)
    
    Patch 3/4 - btrfs::read_label()
    
    This patch changes the btrfs file system usage reading code to resolve
    issue 1/2 by ignoring the exit status from the 'btrfs filesystem show'
    command and relying on parsing the required information to determine
    success or failure.
    
    Bug #733601 - Btrfs: Warnings and missing label with btrfs-progs 3.12
                  and 3.14

 src/btrfs.cc |  114 +++++++++++++++++++++++++++++-----------------------------
 1 files changed, 57 insertions(+), 57 deletions(-)
---
diff --git a/src/btrfs.cc b/src/btrfs.cc
index 188a41b..7df2a2a 100644
--- a/src/btrfs.cc
+++ b/src/btrfs.cc
@@ -207,71 +207,71 @@ void btrfs::set_used_sectors( Partition & partition )
        //  4) Extents can be and are relocated to other devices within the file system
        //     when shrinking a device.
        if ( btrfs_found )
-               exit_status = Utils::execute_command( "btrfs filesystem show " + partition .get_path(), 
output, error, true ) ;
+               Utils::execute_command( "btrfs filesystem show " + partition .get_path(), output, error, true 
) ;
        else
-               exit_status = Utils::execute_command( "btrfs-show " + partition .get_path(), output, error, 
true ) ;
-       if ( ! exit_status )
-       {
-               //Extract the per device size figure.  Guesstimate the per device used
-               // figure as discussed above.  Example output:
-               //
-               //      Label: none  uuid: 36eb51a2-2927-4c92-820f-b2f0b5cdae50
-               //              Total devices 2 FS bytes used 156.00KB
-               //              devid    2 size 2.00GB used 512.00MB path /dev/sdb2
-               //              devid    1 size 2.00GB used 240.75MB path /dev/sdb1
-               //
-               // Calculations:
-               //      ptn fs size = devid size
-               //      ptn fs used = total fs used * devid used / sum devid used
-
-               Byte_Value ptn_size = partition .get_byte_length() ;
-               Byte_Value total_fs_used = -1 ;  //total fs used
-               Byte_Value sum_devid_used = 0 ;  //sum devid used
-               Byte_Value devid_used = -1 ;     //devid used
-               Byte_Value devid_size = -1 ;     //devid size
-
-               //Btrfs file system wide used bytes (extents and items)
-               Glib::ustring str ;
-               if ( ! ( str = Utils::regexp_label( output, "FS bytes used ([0-9\\.]+( ?[KMGTPE]?i?B)?)" ) ) 
.empty() )
-                       total_fs_used = Utils::round( btrfs_size_to_gdouble( str ) ) ;
+               Utils::execute_command( "btrfs-show " + partition .get_path(), output, error, true ) ;
+       //In many cases the exit status doesn't reflect valid output or an error condition
+       //  so rely on parsing the output to determine success.
 
-               Glib::ustring::size_type offset = 0 ;
-               Glib::ustring::size_type index ;
-               while ( ( index = output .find( "devid ", offset ) ) != Glib::ustring::npos )
+       //Extract the per device size figure.  Guesstimate the per device used
+       // figure as discussed above.  Example output:
+       //
+       //      Label: none  uuid: 36eb51a2-2927-4c92-820f-b2f0b5cdae50
+       //              Total devices 2 FS bytes used 156.00KB
+       //              devid    2 size 2.00GB used 512.00MB path /dev/sdb2
+       //              devid    1 size 2.00GB used 240.75MB path /dev/sdb1
+       //
+       // Calculations:
+       //      ptn fs size = devid size
+       //      ptn fs used = total fs used * devid used / sum devid used
+
+       Byte_Value ptn_size = partition .get_byte_length() ;
+       Byte_Value total_fs_used = -1 ;  //total fs used
+       Byte_Value sum_devid_used = 0 ;  //sum devid used
+       Byte_Value devid_used = -1 ;     //devid used
+       Byte_Value devid_size = -1 ;     //devid size
+
+       //Btrfs file system wide used bytes (extents and items)
+       Glib::ustring str ;
+       if ( ! ( str = Utils::regexp_label( output, "FS bytes used ([0-9\\.]+( ?[KMGTPE]?i?B)?)" ) ) .empty() 
)
+               total_fs_used = Utils::round( btrfs_size_to_gdouble( str ) ) ;
+
+       Glib::ustring::size_type offset = 0 ;
+       Glib::ustring::size_type index ;
+       while ( ( index = output .find( "devid ", offset ) ) != Glib::ustring::npos )
+       {
+               Glib::ustring devid_path = Utils::regexp_label( output .substr( index ),
+                                                               "devid .* path (/dev/[[:graph:]]+)" ) ;
+               if ( ! devid_path .empty() )
                {
-                       Glib::ustring devid_path = Utils::regexp_label( output .substr( index ),
-                                                                       "devid .* path (/dev/[[:graph:]]+)" ) 
;
-                       if ( ! devid_path .empty() )
+                       //Btrfs per devid used bytes (chunks)
+                       Byte_Value used = -1 ;
+                       if ( ! ( str = Utils::regexp_label( output .substr( index ),
+                                                           "devid .* used ([0-9\\.]+( ?[KMGTPE]?i?B)?) path" 
) ) .empty() )
                        {
-                               //Btrfs per devid used bytes (chunks)
-                               Byte_Value used = -1 ;
-                               if ( ! ( str = Utils::regexp_label( output .substr( index ),
-                                                                   "devid .* used ([0-9\\.]+( 
?[KMGTPE]?i?B)?) path" ) ) .empty() )
-                               {
-                                       used = btrfs_size_to_num( str, ptn_size, false ) ;
-                                       sum_devid_used += used ;
-                                       if ( devid_path == partition .get_path() )
-                                               devid_used = used ;
-                               }
-
+                               used = btrfs_size_to_num( str, ptn_size, false ) ;
+                               sum_devid_used += used ;
                                if ( devid_path == partition .get_path() )
-                               {
-                                       //Btrfs per device size bytes (chunks)
-                                       if ( ! ( str = Utils::regexp_label( output .substr( index ),
-                                                                           "devid .* size ([0-9\\.]+( 
?[KMGTPE]?i?B)?) used " ) ) .empty() )
-                                               devid_size = btrfs_size_to_num( str, ptn_size, true ) ;
-                               }
+                                       devid_used = used ;
                        }
-                       offset = index + 5 ;  //Next find starts immediately after current "devid"
-               }
 
-               if ( total_fs_used > -1 && devid_size > -1 && devid_used > -1 && sum_devid_used > 0 )
-               {
-                       T = Utils::round( devid_size / double(partition .sector_size) ) ;               //ptn 
fs size
-                       double ptn_fs_used = total_fs_used * ( devid_used / double(sum_devid_used) ) ;  //ptn 
fs used
-                       N = T - Utils::round( ptn_fs_used / double(partition .sector_size) ) ;
-                       partition .set_sector_usage( T, N ) ;
+                       if ( devid_path == partition .get_path() )
+                       {
+                               //Btrfs per device size bytes (chunks)
+                               if ( ! ( str = Utils::regexp_label( output .substr( index ),
+                                                                   "devid .* size ([0-9\\.]+( 
?[KMGTPE]?i?B)?) used " ) ) .empty() )
+                                       devid_size = btrfs_size_to_num( str, ptn_size, true ) ;
+                       }
                }
+               offset = index + 5 ;  //Next find starts immediately after current "devid"
+       }
+
+       if ( total_fs_used > -1 && devid_size > -1 && devid_used > -1 && sum_devid_used > 0 )
+       {
+               T = Utils::round( devid_size / double(partition .sector_size) ) ;               //ptn fs size
+               double ptn_fs_used = total_fs_used * ( devid_used / double(sum_devid_used) ) ;  //ptn fs used
+               N = T - Utils::round( ptn_fs_used / double(partition .sector_size) ) ;
+               partition .set_sector_usage( T, N ) ;
        }
        else
        {