Pre-populate BlockSpecial cache while reading /proc/partitions (#767842)

GParted is already reading /proc/partitions to get whole disk device
names.  The file also contains the major, minor device number of every
partition.  Use this information to pre-populate the cache in the
BlockSpecial class.

    # cat /proc/partitions
    major minor  #blocks  name

       8        0   20971520 sda
       8        1     512000 sda1
       8        2   20458496 sda2
    ...
       9        3    1047552 md3
     259        2     262144 md3p1
     259        3     262144 md3p2
    ...
     253        0   18317312 dm-0
     253        1    2097152 dm-1
     253        2    8383872 dm-2
     253        3    1048576 dm-3

Note that for Device-Mapper names (dm-*) the kernel is not using the
canonical user space names (mapper/*).  There is no harm in
pre-populating the cache with these names and will help if tools report
them too.  It is just that for DMRaid, LVM and LUKS, GParted uses the
canonical /dev/mapper/* names so will still have to call stat() once for
each such name.

For plain disks (sd*) and Linux Software RAID arrays (md*) the kernel
name is the common user space name too, therefore matches what GParted
uses and pre-populating does avoid calling stat() at all for these
names.

Bug 767842 - File system usage missing when tools report alternate block
             device names

include/BlockSpecial.h

@@ -43,6 +43,8 @@ public:
 	unsigned long m_minor;  // {"", 0, 0}.
 
 	static void clear_cache();
+	static void register_block_special( const Glib::ustring & name,
+	                                    unsigned long major, unsigned long minor );
 };
 
 // Operator overloading > The Decision between Member and Non-member

src/BlockSpecial.cc

@@ -79,6 +79,16 @@ void BlockSpecial::clear_cache()
 	mm_number_cache.clear();
 }
 
+void BlockSpecial::register_block_special( const Glib::ustring & name,
+                                           unsigned long major, unsigned long minor )
+{
+	MM_Number pair;
+	pair.m_major = major;
+	pair.m_minor = minor;
+	// Add new, or update existing, cache entry for name to major, minor pair
+	mm_number_cache[name] = pair;
+}
+
 bool operator==( const BlockSpecial & lhs, const BlockSpecial & rhs )
 {
 	if ( lhs.m_major > 0UL && lhs.m_minor > 0UL )

src/GParted_Core.cc

@@ -169,7 +169,8 @@ void GParted_Core::set_devices_thread( std::vector<Device> * pdevices )
 	BlockSpecial::clear_cache();            // MUST BE FIRST.  Cache of name to major, minor
 	                                        // numbers incrementally loaded when BlockSpecial
 	                                        // objects are created in the following caches.
-	Proc_Partitions_Info pp_info( true ) ;  //Refresh cache of proc partition information
+	Proc_Partitions_Info pp_info( true ) ;  // SHOULD BE SECOND.  Caches /proc/partitions and
+	                                        // pre-populates BlockSpecial cache.
 	FS_Info fs_info( true ) ;  //Refresh cache of file system information
 	DMRaid dmraid( true ) ;    //Refresh cache of dmraid device information
 	LVM2_PV_Info::clear_cache();            // Cache automatically loaded if and when needed

src/Proc_Partitions_Info.cc

@@ -15,11 +15,13 @@
  */
 
 #include "../include/Proc_Partitions_Info.h"
+#include "../include/BlockSpecial.h"
 #include "../include/Utils.h"
 
 #include <glibmm/ustring.h>
 #include <vector>
 #include <fstream>
+#include <stdio.h>
 
 namespace GParted
 {
@@ -73,10 +75,23 @@ void Proc_Partitions_Info::load_proc_partitions_info_cache()
 		std::string line ;
 		Glib::ustring device;
 
-		// Read whole disk device names, excluding partitions, from
-		// /proc/partitions and save in this cache.
 		while ( getline( proc_partitions, line ) )
 		{
+			// Pre-populate BlockSpecial cache with major, minor numbers of
+			// all names found from /proc/partitions.
+			Glib::ustring name = Utils::regexp_label( line,
+			        "^[[:blank:]]*[[:digit:]]+[[:blank:]]+[[:digit:]]+[[:blank:]]+[[:digit:]]+[[:blank:]]+([[:graph:]]+)$" );
+			if ( name == "" )
+				continue;
+			unsigned long maj;
+			unsigned long min;
+			if ( sscanf( line.c_str(), "%lu %lu", &maj, &min ) != 2 )
+				continue;
+			BlockSpecial::register_block_special( "/dev/" + name, maj, min );
+
+			// Recognise only whole disk device names, excluding partitions,
+			// from /proc/partitions and save in this cache.
+
 			//Whole disk devices are the ones we want.
 			//Device names without a trailing digit refer to the whole disk.
 			device = Utils::regexp_label(line, "^[\t ]+[0-9]+[\t ]+[0-9]+[\t ]+[0-9]+[\t ]+([^0-9]+)$") ;