[gparted] Create BlockSpecial class and use in LVM2_PV_Info (#767842)



commit ab2d4f5ee6a1e139df3f4340e4247954e0f2a6f2
Author: Mike Fleetwood <mike fleetwood googlemail com>
Date:   Wed Jun 22 17:32:01 2016 +0100

    Create BlockSpecial class and use in LVM2_PV_Info (#767842)
    
    In some cases creating an LVM2 Physical Volume on top of a DMRaid array
    reports no usage information and this partition warning:
        Unable to read the contents of this file system!
        Because of this some operations may be unavailable.
        The cause might be a missing software package.
        The following list of software packages is required for lvm2
        pv file system support: lvm2.
    
    For example on Ubuntu 14.04 LTS (with GParted built with
    --enable-libparted-dmraid) create an LVM2 PV in a DMRaid array
    partition.  GParted uses this command:
        # lvm pvcreate -M 2 /dev/mapper/isw_bacdehijbd_MyArray0p2
    
    But LVM reports the PV having a different name:
        # lvm pvs
          PV                                                VG   Fmt  Attr PSize PFree
          /dev/disk/by-id/dm-name-isw_bacdehijbd_MyArray0p2      lvm2 a--  1.00g 1.00g
    
    This alternate name is loaded into the LVM2_PV_Info module cache.  Hence
    when GParted queries partition /dev/mapper/isw_bacdehijbd_MyArray0p2 it
    has no PV information against that name and reports unknown usage.
    
    However they are actually the same block special device; major 252,
    minor 2:
        # ls -l /dev/mapper/isw_bacdehijbd_MyArray0p2
        brw-rw---- 1 root disk 252, 2 Jul  2 11:09 /dev/mapper/isw_bacdehijbd_MyArray0p2
    
        # ls -l /dev/disk/by-id/dm-name-isw_bacdehijbd_MyArray0p2
        lrwxrwxrwx 1 root root 10 Jul  2 11:09 /dev/disk/by-id/dm-name-isw_bacdehijbd_MyArray0p2 -> ../../dm-2
        # ls -l /dev/dm-2
        brw-rw---- 1 root disk 252, 2 Jul  2 11:09 /dev/dm-2
    
    To determine if two names refer to the same block special device their
    major, minor numbers need to be compared, instead of string comparing
    their names.
    
    Implement class BlockSpecial which encapsulates the name and major,
    minor numbers for a block special device.  Also performs comparison as
    needed.  See bug 767842 comments 4 and 5 for further investigation and
    decision for choosing to implement a class.
    
    Replace name strings in the LVM2_PV_Info module with BlockSpecial
    objects performing correct block special device comparison.
    
    Bug 767842 - File system usage missing when tools report alternate block
                 device names

 include/BlockSpecial.h |   54 +++++++++++++++++++++++++++++++++++++++++++++++
 include/LVM2_PV_Info.h |    6 ++++-
 include/Makefile.am    |    1 +
 po/POTFILES.in         |    1 +
 src/BlockSpecial.cc    |   55 ++++++++++++++++++++++++++++++++++++++++++++++++
 src/LVM2_PV_Info.cc    |   28 +++++++++++++-----------
 src/Makefile.am        |    1 +
 7 files changed, 132 insertions(+), 14 deletions(-)
---
diff --git a/include/BlockSpecial.h b/include/BlockSpecial.h
new file mode 100644
index 0000000..376e3b0
--- /dev/null
+++ b/include/BlockSpecial.h
@@ -0,0 +1,54 @@
+/* Copyright (C) 2016 Mike Fleetwood
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+
+/* BlockSpecial
+ *
+ * Representation of a POSIX block special file, e.g. /dev/sda1.  Also
+ * tracks the major, minor device numbers so that different names for
+ * the same block device can be compared equal.
+ * Refs: mknod(1) and mknod(2).
+ */
+
+#ifndef GPARTED_BLOCKSPECIAL_H
+#define GPARTED_BLOCKSPECIAL_H
+
+#include <glibmm/ustring.h>
+
+namespace GParted
+{
+
+class BlockSpecial
+{
+public:
+       BlockSpecial();
+       BlockSpecial( const Glib::ustring & name );
+       ~BlockSpecial();
+
+       Glib::ustring m_name;   // E.g. Block special file {"/dev/sda1", 8, 1},
+       unsigned long m_major;  // plain file {"FILENAME", 0, 0} and empty object
+       unsigned long m_minor;  // {"", 0, 0}.
+};
+
+// Operator overloading > The Decision between Member and Non-member
+// http://stackoverflow.com/questions/4421706/operator-overloading/4421729#4421729
+//     "2. If a binary operator treats both operands equally (it leaves them unchanged),
+//     implement this operator as a non-member function."
+bool operator==( const BlockSpecial & lhs, const BlockSpecial & rhs );
+
+}//GParted
+
+#endif /* GPARTED_BLOCKSPECIAL_H */
diff --git a/include/LVM2_PV_Info.h b/include/LVM2_PV_Info.h
index 25f0e1d..3700947 100644
--- a/include/LVM2_PV_Info.h
+++ b/include/LVM2_PV_Info.h
@@ -25,14 +25,18 @@
 #ifndef GPARTED_LVM2_PV_INFO_H
 #define GPARTED_LVM2_PV_INFO_H
 
+#include "../include/BlockSpecial.h"
 #include "../include/Utils.h"
 
+#include <glibmm/ustring.h>
+#include <vector>
+
 namespace GParted
 {
 
 struct LVM2_PV
 {
-       Glib::ustring pv_name;
+       BlockSpecial  pv_name;
        Byte_Value    pv_size;
        Byte_Value    pv_free;
        Glib::ustring vg_name;
diff --git a/include/Makefile.am b/include/Makefile.am
index 61f722e..32fc41c 100644
--- a/include/Makefile.am
+++ b/include/Makefile.am
@@ -1,6 +1,7 @@
 gparted_includedir = $(pkgincludedir)
 
 EXTRA_DIST = \
+       BlockSpecial.h                  \
        Copy_Blocks.h                   \
        DMRaid.h                        \
        Device.h                        \
diff --git a/po/POTFILES.in b/po/POTFILES.in
index 3ef9bc2..63865aa 100644
--- a/po/POTFILES.in
+++ b/po/POTFILES.in
@@ -3,6 +3,7 @@
 gparted.appdata.xml.in
 gparted.desktop.in.in
 include/Utils.h
+src/BlockSpecial.cc
 src/Copy_Blocks.cc
 src/Dialog_Base_Partition.cc
 src/Dialog_Disklabel.cc
diff --git a/src/BlockSpecial.cc b/src/BlockSpecial.cc
new file mode 100644
index 0000000..1941b3f
--- /dev/null
+++ b/src/BlockSpecial.cc
@@ -0,0 +1,55 @@
+/* Copyright (C) 2016 Mike Fleetwood
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "../include/BlockSpecial.h"
+
+#include <glibmm/ustring.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+namespace GParted
+{
+
+BlockSpecial::BlockSpecial() : m_name( "" ), m_major( 0UL ), m_minor( 0UL )
+{
+}
+
+BlockSpecial::BlockSpecial( const Glib::ustring & name ) : m_name( name ), m_major( 0UL ), m_minor( 0UL )
+{
+       struct stat sb;
+       if ( stat( name.c_str(), &sb ) == 0 && S_ISBLK( sb.st_mode ) )
+       {
+               m_major = major( sb.st_rdev );
+               m_minor = minor( sb.st_rdev );
+       }
+}
+
+BlockSpecial::~BlockSpecial()
+{
+}
+
+bool operator==( const BlockSpecial & lhs, const BlockSpecial & rhs )
+{
+       if ( lhs.m_major > 0UL && lhs.m_minor > 0UL )
+               // Match block special files by major, minor device numbers.
+               return lhs.m_major == rhs.m_major && lhs.m_minor == rhs.m_minor;
+       else
+               // For non-block special files fall back to name string compare.
+               return lhs.m_name == rhs.m_name;
+}
+
+} //GParted
diff --git a/src/LVM2_PV_Info.cc b/src/LVM2_PV_Info.cc
index 07c676c..98a98b7 100644
--- a/src/LVM2_PV_Info.cc
+++ b/src/LVM2_PV_Info.cc
@@ -15,6 +15,7 @@
  */
 
 #include "../include/LVM2_PV_Info.h"
+#include "../include/BlockSpecial.h"
 
 namespace GParted
 {
@@ -37,13 +38,13 @@ enum LV_BIT
 //  lvm_found           - Is the "lvm" command available?
 //  lvm2_pv_cache       - Vector of PV fields: pv_name, pv_size, pv_free, vg_name.
 //                        E.g.
-//                        //pv_name     , pv_size   , pv_free   , vg_name
-//                        [{"/dev/sda10", 1073741824, 1073741824, ""        },
-//                         {"/dev/sda11", 1069547520, 1069547520, "Test-VG1"},
-//                         {"/dev/sda12", 1069547520,  335544320, "Test_VG2"},
-//                         {"/dev/sda13", 1069547520,          0, "Test_VG3"},
-//                         {"/dev/sda14", 1069547520,  566231040, "Test_VG3"},
-//                         {"/dev/sda15", 1069547520,  545259520, "Test-VG4"}
+//                        //pv_name                   , pv_size   , pv_free   , vg_name
+//                        [{BlockSpecial("/dev/sda10"), 1073741824, 1073741824, ""        },
+//                         {BlockSpecial("/dev/sda11"), 1069547520, 1069547520, "Test-VG1"},
+//                         {BlockSpecial("/dev/sda12"), 1069547520,  335544320, "Test_VG2"},
+//                         {BlockSpecial("/dev/sda13"), 1069547520,          0, "Test_VG3"},
+//                         {BlockSpecial("/dev/sda14"), 1069547520,  566231040, "Test_VG3"},
+//                         {BlockSpecial("/dev/sda15"), 1069547520,  545259520, "Test-VG4"}
 //                        ]
 //  lvm2_vg_cache       - Vector storing VG fields: vg_name, vg_attr, lv_name, lv_attr.
 //                        See vgs(8) and lvs(8) for details of vg_attr and lv_attr respectively.
@@ -145,7 +146,7 @@ std::vector<Glib::ustring> LVM2_PV_Info::get_vg_members( const Glib::ustring & v
        {
                if ( vgname == lvm2_pv_cache[i].vg_name )
                {
-                       members.push_back( lvm2_pv_cache[i].pv_name );
+                       members.push_back( lvm2_pv_cache[i].pv_name.m_name );
                }
        }
 
@@ -252,10 +253,10 @@ void LVM2_PV_Info::load_lvm2_pv_info_cache()
                                        Utils::split( Utils::trim( lines[i] ), fields, "," );
                                        if ( fields.size() < PVFIELD_COUNT )
                                                continue;  // Not enough fields
-                                       LVM2_PV pv;
-                                       pv.pv_name = fields[PVFIELD_PV_NAME];
-                                       if ( pv.pv_name.size() == 0 )
+                                       if ( fields[PVFIELD_PV_NAME] == "" )
                                                continue;  // Empty PV name
+                                       LVM2_PV pv;
+                                       pv.pv_name = BlockSpecial( fields[PVFIELD_PV_NAME] );
                                        pv.pv_size = lvm2_pv_size_to_num( fields[PVFIELD_PV_SIZE] );
                                        pv.pv_free = lvm2_pv_size_to_num( fields[PVFIELD_PV_FREE] );
                                        pv.vg_name = fields[PVFIELD_VG_NAME];
@@ -331,12 +332,13 @@ void LVM2_PV_Info::load_lvm2_pv_info_cache()
 // Returns found cache entry or not found substitute.
 const LVM2_PV & LVM2_PV_Info::get_pv_cache_entry_by_name( const Glib::ustring & pvname )
 {
+       BlockSpecial bs_pvname( pvname );
        for ( unsigned int i = 0 ; i < lvm2_pv_cache.size() ; i ++ )
        {
-               if ( pvname == lvm2_pv_cache[i].pv_name )
+               if ( bs_pvname == lvm2_pv_cache[i].pv_name )
                        return lvm2_pv_cache[i];
        }
-       static LVM2_PV pv = {"", -1, -1, ""};
+       static LVM2_PV pv = {BlockSpecial(), -1, -1, ""};
        return pv;
 }
 
diff --git a/src/Makefile.am b/src/Makefile.am
index 819c910..39d6be3 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -12,6 +12,7 @@ AM_CXXFLAGS = -Wall
 sbin_PROGRAMS = gpartedbin
 
 gpartedbin_SOURCES = \
+       BlockSpecial.cc                 \
        Copy_Blocks.cc                  \
        DMRaid.cc                       \
        Device.cc                       \


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