Handle unusual case of missing mdadm but SWRaid arrays active (#756829)

If the installation is unusual / broken such that the mdadm command is
not found but there are active SWRaid arrays, provide a fallback with
some of the information.  In this case populate the cache with details
only available from /proc/mdstat.  Information will be limited to active
arrays only and their members.  No UUIDs or labels.  There will be no
information about inactive arrays and GParted will use it's normal
libparted and blkid identification for those devices and partitions.

As mdadm has gained the capability to manage Fake/BIOS RAID arrays they
also appear in /proc/mdstat when mdadm is used to start them.  Enhance
the parser of /proc/mdstat to only extract information for SWRaid arrays
with recognised metadata versions.

Bug 756829 - SWRaid member detection enhancements

src/SWRaid_Info.cc

@@ -121,13 +121,10 @@ void SWRaid_Info::load_swraid_info_cache()
 
 	swraid_info_cache.clear();
 
-	if ( ! mdadm_found )
-		return;
-
 	// Load SWRaid members into the cache.  Load member device, array UUID and array
 	// label (array name in mdadm terminology).
 	Glib::ustring cmd = "mdadm --examine --scan --verbose";
-	if ( ! Utils::execute_command( cmd, output, error, true ) )
+	if ( mdadm_found && ! Utils::execute_command( cmd, output, error, true ) )
 	{
 		// Extract information from Linux Software RAID arrays only, excluding
 		// IMSM and DDF arrays.  Example output:
@@ -141,13 +138,13 @@ void SWRaid_Info::load_swraid_info_cache()
 		//        devices=/dev/sda6,/dev/sdb6
 		std::vector<Glib::ustring> lines;
 		Utils::split( output, lines, "\n" );
-		enum LINE_TYPE
+		enum MDADM_LINE_TYPE
 		{
-			LINE_TYPE_OTHER   = 0,
+			MDADM_LT_OTHER   = 0,
-			LINE_TYPE_ARRAY   = 1,
+			MDADM_LT_ARRAY   = 1,
-			LINE_TYPE_DEVICES = 2
+			MDADM_LT_DEVICES = 2
 		};
-		LINE_TYPE line_type = LINE_TYPE_OTHER;
+		MDADM_LINE_TYPE mdadm_line_type = MDADM_LT_OTHER;
 		Glib::ustring uuid;
 		Glib::ustring label;
 		for ( unsigned int i = 0 ; i < lines.size() ; i ++ )
@@ -155,7 +152,7 @@ void SWRaid_Info::load_swraid_info_cache()
 			Glib::ustring metadata_type;
 			if ( lines[i].substr( 0, 6 ) == "ARRAY " )
 			{
-				line_type = LINE_TYPE_ARRAY;
+				mdadm_line_type = MDADM_LT_ARRAY;
 				Glib::ustring metadata_type = Utils::regexp_label( lines[i],
 				                                                   "metadata=([[:graph:]]+)" );
 				// Mdadm with these flags doesn't seem to print the
@@ -166,7 +163,7 @@ void SWRaid_Info::load_swraid_info_cache()
 				     metadata_type != "1.2"                               )
 				{
 					// Skip mdadm reported non-Linux Software RAID arrays
-					line_type = LINE_TYPE_OTHER;
+					mdadm_line_type = MDADM_LT_OTHER;
 					continue;
 				}
 
@@ -174,10 +171,10 @@ void SWRaid_Info::load_swraid_info_cache()
 						Utils::regexp_label( lines[i], "UUID=([[:graph:]]+)" ) );
 				label = Utils::regexp_label( lines[i], "name=(.*)$" );
 			}
-			else if ( line_type == LINE_TYPE_ARRAY                       &&
+			else if ( mdadm_line_type == MDADM_LT_ARRAY                  &&
 			          lines[i].find( "devices=" ) != Glib::ustring::npos    )
 			{
-				line_type = LINE_TYPE_DEVICES;
+				mdadm_line_type = MDADM_LT_DEVICES;
 				Glib::ustring devices_str = Utils::regexp_label( lines[i],
 				                                                 "devices=([[:graph:]]+)" );
 				std::vector<Glib::ustring> devices;
@@ -197,7 +194,7 @@ void SWRaid_Info::load_swraid_info_cache()
 			}
 			else
 			{
-				line_type = LINE_TYPE_OTHER;
+				mdadm_line_type = MDADM_LT_OTHER;
 			}
 		}
 	}
@@ -207,37 +204,103 @@ void SWRaid_Info::load_swraid_info_cache()
 	std::ifstream input( "/proc/mdstat" );
 	if ( input )
 	{
-		// Read /proc/mdstat extracting members for active arrays, marking them
+		// Read /proc/mdstat extracting information for Linux Software RAID arrays
-		// active in the cache.  Example fragment of /proc/mdstat:
+		// only, excluding external IMSM and DDF arrays.  Example /proc/mdstat:
-		//     md1 : active raid1 sdb1[0] sdb2[1]
+		//     Personalities : [raid1]
-		//           1047552 blocks super 1.2 [2/2] [UU]
+		//     md127 : inactive sdd[1](S) sdc[0](S)
+		//           6306 blocks super external:imsm
+		//
+		//     md126 : active raid1 sdc[1] sdd[0]
+		//           8383831 blocks super external:/md127/0 [2/2] [UU]
+		//
+		//     md1 : active raid1 sdb1[3] sda1[2]
+		//           524224 blocks super 1.0 [2/2] [UU]
+		//
+		//     md5 : active raid1 sda6[0] sdb6[1]
+		//           524224 blocks [2/2] [UU]
+		//
+		//     unused devices: <none>
+		enum MDSTAT_LINE_TYPE
+		{
+			MDSTAT_LT_OTHER  = 0,
+			MDSTAT_LT_ACTIVE = 1,
+			MDSTAT_LT_BLOCKS = 2
+		};
+		MDSTAT_LINE_TYPE mdstat_line_type = MDSTAT_LT_OTHER;
+		Glib::ustring array;
+		std::vector<Glib::ustring> members;
 		while ( getline( input, line ) )
 		{
 			if ( line.find( " : active " ) != std::string::npos )
 			{
+				mdstat_line_type = MDSTAT_LT_ACTIVE;
 				// Found a line for an active array.  Split into space
 				// separated fields.
 				std::vector<Glib::ustring> fields;
 				Utils::tokenize( line, fields, " " );
+				array = "/dev/" + fields[0];
+				members.clear();
 				for ( unsigned int i = 0 ; i < fields.size() ; i ++ )
 				{
 					Glib::ustring::size_type index = fields[i].find( "[" );
 					if ( index != Glib::ustring::npos )
 					{
 						// Field contains an "[" so got a short
-						// kernel device name of a member.  Set
+						// kernel device name of a member.
-						// array and active flag.
+						members.push_back( "/dev/" + fields[i].substr( 0, index ) );
-						Glib::ustring mpath = "/dev/" +
-						                      fields[i].substr( 0, index );
-						SWRaid_Member & memb = get_cache_entry_by_member( mpath );
-						if ( memb.member == mpath )
-						{
-							memb.array = "/dev/" + fields[0];
-							memb.active = true;
-						}
 					}
 				}
 			}
+			else if ( mdstat_line_type == MDSTAT_LT_ACTIVE         &&
+			          line.find( " blocks " ) != std::string::npos    )
+			{
+				mdstat_line_type = MDSTAT_LT_BLOCKS;
+				// Found a blocks line for an array.
+				Glib::ustring super_type = Utils::regexp_label( line, "super ([[:graph:]]+)" );
+
+				// Kernel doesn't seem to print the super block type for
+				// 0.90 version arrays.  Accept no tag (or empty version)
+				// as well as "0.90".
+				if ( super_type != ""    && super_type != "0.90" &&
+				     super_type != "1.0" && super_type != "1.1"  &&
+				     super_type != "1.2"                            )
+				{
+					// Skip /proc/mdstat reported non-Linux Software RAID arrays
+					mdstat_line_type = MDSTAT_LT_OTHER;
+					continue;
+				}
+
+				for ( unsigned int i = 0 ; i < members.size() ; i ++ )
+				{
+					SWRaid_Member & memb = get_cache_entry_by_member( members[i] );
+					if ( memb.member == members[i] )
+					{
+						// Update existing cache entry, setting
+						// array and active flag.
+						memb.array = array;
+						memb.active = true;
+					}
+					else
+					{
+						// Member not already found in the cache.
+						// (Mdadm command possibly missing).
+						// Insert cache entry.
+						SWRaid_Member new_memb;
+						new_memb.member = members[i];
+						new_memb.array = array;
+						new_memb.uuid = "";
+						new_memb.label = "";
+						new_memb.active = true;
+						swraid_info_cache.push_back( new_memb );
+					}
+				}
+				array.clear();
+				members.clear();
+			}
+			else
+			{
+				mdstat_line_type = MDSTAT_LT_OTHER;
+			}
 		}
 		input.close();
 	}