From 8308ee6051b329284cd16ae66ad37699c4b7130b Mon Sep 17 00:00:00 2001
From: Mike Fleetwood <mike.fleetwood@googlemail.com>
Date: Fri, 19 Jun 2015 13:02:32 +0100
Subject: [PATCH] Support changing the UUID of a btrfs file system (#751337)

Btrfs-progs 4.1, released June 2015, includes support for changing the
UUID of a btrfs file system using the btrfstune command.  Check for
availability by looking for the -u option in the btrfstune help output.
Use btrfstune like this:

    # umount /dev/sdb1
    # btrfstune -f -u /dev/sdb1
    Current fsid: e7ad5dba-d721-4f99-990b-1ba2901c8ad2
    New fsid: 231563d9-e173-410d-b1da-d34c4319a423
    Set superblock flag CHANGING_FSID
    Change fsid in extents
    Change fsid on devices
    Clear superblock flag CHANGING_FSID
    Fsid change finished
    # echo $?
    0

Bug 751337 - btrfstune in btrfs-progs 4.1 supports changing the file
             system UUID
---
 include/btrfs.h |  1 +
 src/btrfs.cc    | 12 ++++++++++++
 2 files changed, 13 insertions(+)

diff --git a/include/btrfs.h b/include/btrfs.h
index ce769368..5a69d666 100644
--- a/include/btrfs.h
+++ b/include/btrfs.h
@@ -39,6 +39,7 @@ public:
 	void read_label( Partition & partition ) ;
 	bool write_label( const Partition & partition, OperationDetail & operationdetail ) ;
 	void read_uuid( Partition & partition ) ;
+	bool write_uuid( const Partition & partition, OperationDetail & operationdetail );
 	bool create( const Partition & new_partition, OperationDetail & operationdetail ) ;
 	bool resize( const Partition & partition_new, OperationDetail & operationdetail, bool fill_partition = false ) ;
 	bool check_repair( const Partition & partition, OperationDetail & operationdetail ) ;
diff --git a/src/btrfs.cc b/src/btrfs.cc
index b3f141fd..a1fee532 100644
--- a/src/btrfs.cc
+++ b/src/btrfs.cc
@@ -107,6 +107,13 @@ FS btrfs::get_filesystem_support()
 		}
 	}
 
+	if ( ! Glib::find_program_in_path( "btrfstune" ).empty() )
+	{
+		Utils::execute_command( "btrfstune --help", output, error, true );
+		if ( Utils::regexp_label( error, "^[[:blank:]]*(-u)[[:blank:]]" ) == "-u" )
+			fs.write_uuid = FS::EXTERNAL;
+	}
+
 	if ( fs .check )
 	{
 		fs .copy = GParted::FS::GPARTED ;
@@ -422,6 +429,11 @@ void btrfs::read_uuid( Partition & partition )
 	}
 }
 
+bool btrfs::write_uuid( const Partition & partition, OperationDetail & operationdetail )
+{
+	return ! execute_command( "btrfstune -f -u " + partition.get_path(), operationdetail );
+}
+
 void btrfs::clear_cache()
 {
 	btrfs_device_cache .clear() ;