[gparted] Update parsing of btrfs filesystem show for the UUID (#733601)

[Curtis Gedak <gedakc src gnome org>]

commit 82c6265fa5599bd5acfe33abecaa99de150d71e9
Author: Mike Fleetwood <mike fleetwood googlemail com>
Date:   Tue Jul 22 17:57:33 2014 +0100

    Update parsing of btrfs filesystem show for the UUID (#733601)
    
    Issue 1/2 - GParted shows warnings for mounted btrfs file systems
    
    'btrfs filesystem show /dev/PTN' command is used to query details of a
    btrfs file system.  When the file system is mounted the command reports
    failed exit status 1, but only when using btrfs-progs v3.14 and v3.14.1.
    This causes GParted to: (1) report warnings from the failed commands for
    a mounted btrfs file system, (2) fail to determine file system usage
    figures and (3) fail to display the mount point and busy indicator for
    non-mounting devices in multi-device btrfs file systems.  The label is
    also read using the secondary blkid method via the FS_Info cache.
    
    Failed exit status 1 when the btrfs file system is mounted:
    
        # fgrep sdb1 /proc/mounts
        /dev/sdb1 /mnt/1 btrfs rw,seclabel,relatime,space_cache 0 0
        # btrfs filesystem show /dev/sdb1
        Label: 'test1-btrfs'  uuid: 033e6b07-ee6a-4620-a585-8580a2b83275
                Total devices 1 FS bytes used 192.00KiB
                devid    1 size 2.00GiB used 240.75MiB path /dev/sdb1
    
        Btrfs v3.14.1
        # echo $?
        1
    
    Successful exit status 0 when the btrfs file system is unmounted:
    
        # umount /dev/sdb1
        # btrfs filesystem show /dev/sdb1
        Label: 'test1-btrfs'  uuid: 033e6b07-ee6a-4620-a585-8580a2b83275
                Total devices 1 FS bytes used 192.00KiB
                devid    1 size 2.00GiB used 240.75MiB path /dev/sdb1
    
        Btrfs v3.14.1
        # echo $?
        0
    
    Fix by ignoring the exit status of the 'btrfs filesystem show' command
    and rely on parsing the required information to determine success or
    failure.  The output from the older 'btrfs-show' command is almost
    identical so the same code will parse it in all cases.
    
    Patch 1/4 - btrfs::read_uuid()
    
    This patch changes the secondary method used to read the btrfs UUID to
    resolve issue 1/2 as described above.
    
    Bug #733601 - Btrfs: Warnings and missing label with btrfs-progs 3.12
                  and 3.14

 src/btrfs.cc |   24 +++++++++---------------
 1 files changed, 9 insertions(+), 15 deletions(-)
---
diff --git a/src/btrfs.cc b/src/btrfs.cc
index c88ac2b..7a6a841 100644
--- a/src/btrfs.cc
+++ b/src/btrfs.cc
@@ -406,22 +406,16 @@ void btrfs::read_label( Partition & partition )
 void btrfs::read_uuid( Partition & partition )
 {
        if ( btrfs_found )
-       {
-               exit_status = Utils::execute_command( "btrfs filesystem show " + partition .get_path(), 
output, error, true ) ;
-               if ( ! exit_status )
-               {
-                       partition .uuid = Utils::regexp_label( output, "uuid:[[:blank:]]*(" 
RFC4122_NONE_NIL_UUID_REGEXP ")" ) ;
-               }
-       }
+               Utils::execute_command( "btrfs filesystem show " + partition .get_path(), output, error, true 
) ;
+       else
+               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 uuid_str = Utils::regexp_label( output, "uuid:[[:blank:]]*(" 
RFC4122_NONE_NIL_UUID_REGEXP ")" ) ;
+       if ( ! uuid_str .empty() )
+               partition .uuid = uuid_str ;
        else
-       {
-               exit_status = Utils::execute_command( "btrfs-show " + partition .get_path(), output, error, 
true ) ;
-               if ( ! exit_status )
-               {
-                       partition .uuid = Utils::regexp_label( output, "uuid:[[:blank:]]*(" 
RFC4122_NONE_NIL_UUID_REGEXP ")" ) ;
-               }
-       }
-       if ( exit_status )
        {
                if ( ! output .empty() )
                        partition .messages .push_back( output ) ;