[parted-devel] [PATCH] Detect Ext4 (Parted Alioth #188)

[Debarshi Ray]

I spent some time over the last couple of days trying to make
libparted detect Ext4 filesystems [1]. Here ([2] and below) is a very
preliminary 'git diff' against the current Git master. I have not yet
tested it extensively, but I just wanted to know whether I am on the
right track or not.

diff --git a/libparted/fs/ext2/ext2_fs.h b/libparted/fs/ext2/ext2_fs.h
index 713cc21..08d0c38 100644
--- a/libparted/fs/ext2/ext2_fs.h
+++ b/libparted/fs/ext2/ext2_fs.h
@@ -59,6 +59,8 @@

 #define EXT2_FEATURE_INCOMPAT_FILETYPE		0x0002
 #define EXT3_FEATURE_INCOMPAT_RECOVER		0x0004
+#define EXT4_FEATURE_INCOMPAT_EXTENTS           0x0040
+#define EXT4_FEATURE_INCOMPAT_64BIT             0x0080

 /*
  * Special inodes numbers
diff --git a/libparted/fs/ext2/interface.c b/libparted/fs/ext2/interface.c
index 8935840..48ee61a 100644
--- a/libparted/fs/ext2/interface.c
+++ b/libparted/fs/ext2/interface.c
@@ -32,7 +32,7 @@ static PedFileSystemType _ext3_type;
 struct ext2_dev_handle*
ext2_make_dev_handle_from_parted_geometry(PedGeometry* geom);

 static PedGeometry*
-_ext2_generic_probe (PedGeometry* geom, int expect_ext3)
+_ext2_generic_probe (PedGeometry* geom, int expect_ext_ver)
 {
 	struct ext2_super_block sb;

@@ -46,10 +46,23 @@ _ext2_generic_probe (PedGeometry* geom, int expect_ext3)
 		PedSector group_nr = EXT2_SUPER_BLOCK_GROUP_NR(sb);
 		PedSector first_data_block = EXT2_SUPER_FIRST_DATA_BLOCK(sb);
 		int version = EXT2_SUPER_REV_LEVEL(sb);
-		int is_ext3 = (EXT2_SUPER_FEATURE_COMPAT(sb)
-				& EXT3_FEATURE_COMPAT_HAS_JOURNAL) != 0;
-
-		if (expect_ext3 != is_ext3)
+		int is_ext3 = 0;
+		int is_ext4 = 0;
+
+                is_ext3 = (EXT2_SUPER_FEATURE_COMPAT (sb)
+			   & EXT3_FEATURE_COMPAT_HAS_JOURNAL) != 0;
+                if (is_ext3) {
+                        is_ext4 = is_ext3 && ((EXT2_SUPER_FEATURE_INCOMPAT (sb)
+                                      & EXT4_FEATURE_INCOMPAT_EXTENTS) != 0);
+                        if (is_ext4)
+                                is_ext3 = 0;
+                }
+
+		if (expect_ext_ver == 2 && (is_ext3 || is_ext4))
+			return NULL;
+		if (expect_ext_ver == 3 && !is_ext3)
+			return NULL;
+		else if (expect_ext_ver == 4 && !is_ext4)
 			return NULL;

 		if (version > 0 && group_nr > 0) {
@@ -64,7 +77,8 @@ _ext2_generic_probe (PedGeometry* geom, int expect_ext3)
 				return NULL;
 			ped_geometry_init (&probe_geom, geom->dev,
 					   start, block_count * block_size);
-			return _ext2_generic_probe (&probe_geom, expect_ext3);
+			return _ext2_generic_probe (&probe_geom,
+                                                    expect_ext_ver);
 		} else {
 			return ped_geometry_new (geom->dev, geom->start,
 						 block_count * block_size);
@@ -76,13 +90,19 @@ _ext2_generic_probe (PedGeometry* geom, int expect_ext3)
 static PedGeometry*
 _ext2_probe (PedGeometry* geom)
 {
-	return _ext2_generic_probe (geom, 0);
+	return _ext2_generic_probe (geom, 2);
 }

 static PedGeometry*
 _ext3_probe (PedGeometry* geom)
 {
-	return _ext2_generic_probe (geom, 1);
+	return _ext2_generic_probe (geom, 3);
+}
+
+static PedGeometry*
+_ext4_probe (PedGeometry* geom)
+{
+	return _ext2_generic_probe (geom, 4);
 }

 #ifndef DISCOVER_ONLY
@@ -323,6 +343,20 @@ static PedFileSystemOps _ext3_ops = {
 #endif /* !DISCOVER_ONLY */
 };

+static PedFileSystemOps _ext4_ops = {
+	probe:		_ext4_probe,
+	clobber:	NULL,
+	open:		NULL,
+	create:         NULL,
+	close:		NULL,
+	check:          NULL,
+	resize:		NULL,
+	copy:           NULL,
+	get_create_constraint:	NULL,
+	get_copy_constraint:	NULL,
+	get_resize_constraint:	NULL
+};
+
 #define EXT23_BLOCK_SIZES ((int[6]){512, 1024, 2048, 4096, 8192, 0})

 static PedFileSystemType _ext2_type = {
@@ -339,14 +373,23 @@ static PedFileSystemType _ext3_type = {
        block_sizes:      EXT23_BLOCK_SIZES
 };

+static PedFileSystemType _ext4_type = {
+       next:		 NULL,
+       ops:		 &_ext4_ops,
+       name:		 "ext4",
+       block_sizes:      EXT23_BLOCK_SIZES
+};
+
 void ped_file_system_ext2_init ()
 {
 	ped_file_system_type_register (&_ext2_type);
 	ped_file_system_type_register (&_ext3_type);
+	ped_file_system_type_register (&_ext4_type);
 }

 void ped_file_system_ext2_done ()
 {
 	ped_file_system_type_unregister (&_ext2_type);
 	ped_file_system_type_unregister (&_ext3_type);
+	ped_file_system_type_unregister (&_ext4_type);
 }

Comments?

Happy hacking,
Debarshi

----
[1] http://parted.alioth.debian.org/cgi-bin/trac.cgi/ticket/188
[2] http://rishi.fedorapeople.org/gnu/parted-ext4-probe.patch