[gparted] Use BlockSpecial in LUKS_Info module cache (#767842)

[Curtis Gedak <gedakc src gnome org>]

commit 7cd574cac5f7d076ebd94795f5c6f41b333fdee7
Author: Mike Fleetwood <mike fleetwood googlemail com>
Date:   Mon Jul 4 09:12:51 2016 +0100

    Use BlockSpecial in LUKS_Info module cache (#767842)
    
    The LUKS_Info module cache is loaded from "dmsetup" command and compares
    block special files, therefore switch to using BlockSpecial objects so
    that comparisons are performed by major, minor device number.
    
    Bug 767842 - File system usage missing when tools report alternate block
                 device names

 include/LUKS_Info.h |   11 +++++------
 src/LUKS_Info.cc    |   43 ++++++++++++++-----------------------------
 2 files changed, 19 insertions(+), 35 deletions(-)
---
diff --git a/include/LUKS_Info.h b/include/LUKS_Info.h
index 8b3fe20..a9a7979 100644
--- a/include/LUKS_Info.h
+++ b/include/LUKS_Info.h
@@ -25,6 +25,7 @@
 #ifndef GPARTED_LUKS_INFO_H
 #define GPARTED_LUKS_INFO_H
 
+#include "../include/BlockSpecial.h"
 #include "../include/Utils.h"
 
 #include <glibmm/ustring.h>
@@ -35,12 +36,10 @@ namespace GParted
 
 struct LUKS_Mapping
 {
-       Glib::ustring name;    // Name of the dm-crypt mapping
-       unsigned long major;   // Major device number of the underlying block device
-       unsigned long minor;   // Minor device number of the underlying block device
-       Glib::ustring path;    // Path of the underlying block device
-       Byte_Value    offset;  // Offset to the start of the mapping in the underlying block device
-       Byte_Value    length;  // Length of the mapping in the underlying block device
+       Glib::ustring name;       // Name of the dm-crypt mapping
+       BlockSpecial  container;  // Underlying block device containing the LUKS mapping
+       Byte_Value    offset;     // Offset to the start of the mapping in the underlying block device
+       Byte_Value    length;     // Length of the mapping in the underlying block device
 };
 
 class LUKS_Info
diff --git a/src/LUKS_Info.cc b/src/LUKS_Info.cc
index 8337295..cba7b78 100644
--- a/src/LUKS_Info.cc
+++ b/src/LUKS_Info.cc
@@ -15,6 +15,7 @@
  */
 
 #include "../include/LUKS_Info.h"
+#include "../include/BlockSpecial.h"
 #include "../include/Utils.h"
 
 #include <stdio.h>
@@ -97,18 +98,16 @@ void LUKS_Info::load_cache()
 
                // Extract LUKS underlying device containing the encrypted data.  May be
                // either a device name (/dev/sda1) or major, minor pair (8:1).
-               luks_map.major = 0UL;
-               luks_map.minor = 0UL;
-               luks_map.path.clear();
+               luks_map.container = BlockSpecial();
                Glib::ustring devpath = fields[DMCRYPT_FIELD_devpath];
                unsigned long maj = 0UL;
                unsigned long min = 0UL;
                if ( devpath.length() > 0 && devpath[0] == '/' )
-                       luks_map.path = devpath;
+                       luks_map.container = BlockSpecial( devpath );
                else if ( sscanf( devpath.c_str(), "%lu:%lu", &maj, &min ) == 2 )
                {
-                       luks_map.major = maj;
-                       luks_map.minor = min;
+                       luks_map.container.m_major = maj;
+                       luks_map.container.m_minor = min;
                }
                else
                        continue;
@@ -135,35 +134,21 @@ void LUKS_Info::load_cache()
 // or not found substitute when no entry exists.
 const LUKS_Mapping & LUKS_Info::get_cache_entry_internal( const Glib::ustring & path )
 {
-       // First scan the cache looking for an underlying block device path match.
-       // (Totally in memory)
+       BlockSpecial bs = BlockSpecial( path );
        for ( unsigned int i = 0 ; i < luks_mapping_cache.size() ; i ++ )
        {
-               if ( path == luks_mapping_cache[i].path )
-                       return luks_mapping_cache[i];
-       }
-
-       // Second scan the cache looking for an underlying block device major, minor
-       // match.  (Requires single stat(2) call per search)
-       struct stat sb;
-       if ( stat( path.c_str(), &sb ) == 0 && S_ISBLK( sb.st_mode ) )
-       {
-               unsigned long maj = major( sb.st_rdev );
-               unsigned long min = minor( sb.st_rdev );
-               for ( unsigned int i = 0 ; i < luks_mapping_cache.size() ; i ++ )
+               if ( bs == luks_mapping_cache[i].container )
                {
-                       if ( maj == luks_mapping_cache[i].major && min == luks_mapping_cache[i].minor )
-                       {
-                               // Store path in cache to avoid stat() call on subsequent
-                               // query for the same path.
-                               luks_mapping_cache[i].path = path;
-
-                               return luks_mapping_cache[i];
-                       }
+                       // Store underlying block device path in the BlockSpecial object
+                       // if not already known.  Not required, just for completeness.
+                       if ( ! luks_mapping_cache[i].container.m_name.length() )
+                               luks_mapping_cache[i].container.m_name = path;
+
+                       return luks_mapping_cache[i];
                }
        }
 
-       static LUKS_Mapping not_found = {"", 0UL, 0UL, "", -1LL, -1LL};
+       static LUKS_Mapping not_found = {"", BlockSpecial(), -1LL, -1LL};
        return not_found;
 }