[gparted] Lazy initialize the cache from querying LVM2 PVs (#160787)

[Curtis Gedak <gedakc src gnome org>]

commit ff8ad0412057dd6644cd290a8affc71786b5d89f
Author: Mike Fleetwood <mike fleetwood googlemail com>
Date:   Sun Dec 11 23:17:52 2011 +0000

    Lazy initialize the cache from querying LVM2 PVs (#160787)
    
    Previously when GParted was started LVM2_PV_Info cache was loaded twice,
    executing LVM2 PV querying commands twice.  Firstly when
    lvm2_pv::get_filesystem_support() was checking if LVM2 PV support was
    available, and secondly when forced by a refresh in
    GParted_Core::set_devices().
    
    Implement lazy initialization.  Only load the cache when forced by the
    above mentioned refresh or having to return a value when the cache is
    not yet loaded.  Do not initialize the cache when just checking if LVM2
    PV support is available.
    
    Bug #160787 - lvm support

 include/LVM2_PV_Info.h |    1 +
 src/LVM2_PV_Info.cc    |   33 ++++++++++++++++++---------------
 2 files changed, 19 insertions(+), 15 deletions(-)
---
diff --git a/include/LVM2_PV_Info.h b/include/LVM2_PV_Info.h
index 9a03ddf..7ddb1a6 100644
--- a/include/LVM2_PV_Info.h
+++ b/include/LVM2_PV_Info.h
@@ -42,6 +42,7 @@ public:
 	Byte_Value get_free_bytes( const Glib::ustring & path ) ;
 	bool has_active_lvs( const Glib::ustring & path ) ;
 private:
+	void initialize_if_required() ;
 	void set_commands_found() ;
 	void load_lvm2_pv_info_cache() ;
 	Glib::ustring get_pv_attr( const Glib::ustring & path, unsigned int entry ) ;
diff --git a/src/LVM2_PV_Info.cc b/src/LVM2_PV_Info.cc
index 28ef858..dc245f2 100644
--- a/src/LVM2_PV_Info.cc
+++ b/src/LVM2_PV_Info.cc
@@ -51,28 +51,16 @@ Glib::ustring LVM2_PV_Info::dmsetup_info_cache = "" ;
 
 LVM2_PV_Info::LVM2_PV_Info()
 {
-	//Ensure that cache has been loaded at least once
-	if ( ! lvm2_pv_info_cache_initialized )
-	{
-		lvm2_pv_info_cache_initialized = true ;
-		set_commands_found() ;
-		load_lvm2_pv_info_cache() ;
-	}
 }
 
 LVM2_PV_Info::LVM2_PV_Info( bool do_refresh )
 {
-	//Ensure that cache has been loaded at least once
-	if ( ! lvm2_pv_info_cache_initialized )
+	if ( do_refresh )
 	{
-		lvm2_pv_info_cache_initialized = true ;
 		set_commands_found() ;
-		if ( do_refresh == false )
-			load_lvm2_pv_info_cache() ;
-	}
-
-	if ( do_refresh )
 		load_lvm2_pv_info_cache() ;
+		lvm2_pv_info_cache_initialized = true ;
+	}
 }
 
 LVM2_PV_Info::~LVM2_PV_Info()
@@ -81,17 +69,21 @@ LVM2_PV_Info::~LVM2_PV_Info()
 
 bool LVM2_PV_Info::is_lvm2_pv_supported()
 {
+	if ( ! lvm2_pv_info_cache_initialized )
+		set_commands_found() ;
 	return ( lvm_found && dmsetup_found ) ;
 }
 
 Glib::ustring LVM2_PV_Info::get_vg_name( const Glib::ustring & path )
 {
+	initialize_if_required() ;
 	return get_pv_attr( path, PVATTR_VG_NAME ) ;
 }
 
 //Return number of free bytes in the PV, or -1 for error.
 Byte_Value LVM2_PV_Info::get_free_bytes( const Glib::ustring & path )
 {
+	initialize_if_required() ;
 	Byte_Value free_bytes = -1 ;
 	Glib::ustring fb_str = get_pv_attr( path, PVATTR_PV_FREE ) ;
 	if ( fb_str != "" )
@@ -108,6 +100,7 @@ Byte_Value LVM2_PV_Info::get_free_bytes( const Glib::ustring & path )
 //Report if any LVs are active in the VG stored in the PV.
 bool LVM2_PV_Info::has_active_lvs( const Glib::ustring & path )
 {
+	initialize_if_required() ;
 	Glib::ustring vgname = get_pv_attr( path, PVATTR_VG_NAME ) ;
 	if ( vgname == "" )
 		//PV not yet included in any VG
@@ -120,6 +113,16 @@ bool LVM2_PV_Info::has_active_lvs( const Glib::ustring & path )
 
 //Private methods
 
+void LVM2_PV_Info::initialize_if_required()
+{
+	if ( ! lvm2_pv_info_cache_initialized )
+	{
+		set_commands_found() ;
+		load_lvm2_pv_info_cache() ;
+		lvm2_pv_info_cache_initialized = true ;
+	}
+}
+
 void LVM2_PV_Info::set_commands_found()
 {
 	//Set status of commands found