2 files changed, 68 insertions, 0 deletions

diff --git a/fs/ext4/Kconfig b/fs/ext4/Kconfig
index 9f2d45d75b1a..a6b4e93833d6 100644
--- a/fs/ext4/Kconfig
+++ b/fs/ext4/Kconfig
@@ -26,6 +26,16 @@ config EXT4_FS
 
 	  If unsure, say N.
 
+config EXT4_USE_FOR_EXT23
+	bool "Use ext4 for ext2/ext3 file systems"
+	depends on !EXT3_FS || !EXT2_FS
+	default y
+	help
+	  Allow the ext4 file system driver code to be used for ext2 or
+	  ext3 file system mounts.  This allows users to reduce their
+	  compiled kernel size by using one file system driver for
+	  ext2, ext3, and ext4 file systems.
+
 config EXT4_FS_XATTR
 	bool "Ext4 extended attributes"
 	depends on EXT4_FS
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 5a2db612950b..30476daf966e 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -3960,6 +3960,58 @@ static int ext4_get_sb(struct file_system_type *fs_type, int flags,
 	return get_sb_bdev(fs_type, flags, dev_name, data, ext4_fill_super,mnt);
 }
 
+#if !defined(CONTIG_EXT2_FS) && defined(CONFIG_EXT4_USE_FOR_EXT23)
+static struct file_system_type ext2_fs_type = {
+	.owner		= THIS_MODULE,
+	.name		= "ext2",
+	.get_sb		= ext4_get_sb,
+	.kill_sb	= kill_block_super,
+	.fs_flags	= FS_REQUIRES_DEV,
+};
+
+static inline void register_as_ext2(void)
+{
+	int err = register_filesystem(&ext2_fs_type);
+	if (err)
+		printk(KERN_WARNING
+		       "EXT4-fs: Unable to register as ext2 (%d)\n", err);
+}
+
+static inline void unregister_as_ext2(void)
+{
+	unregister_filesystem(&ext2_fs_type);
+}
+#else
+static inline void register_as_ext2(void) { }
+static inline void unregister_as_ext2(void) { }
+#endif
+
+#if !defined(CONTIG_EXT3_FS) && defined(CONFIG_EXT4_USE_FOR_EXT23)
+static struct file_system_type ext3_fs_type = {
+	.owner		= THIS_MODULE,
+	.name		= "ext3",
+	.get_sb		= ext4_get_sb,
+	.kill_sb	= kill_block_super,
+	.fs_flags	= FS_REQUIRES_DEV,
+};
+
+static inline void register_as_ext3(void)
+{
+	int err = register_filesystem(&ext3_fs_type);
+	if (err)
+		printk(KERN_WARNING
+		       "EXT4-fs: Unable to register as ext3 (%d)\n", err);
+}
+
+static inline void unregister_as_ext3(void)
+{
+	unregister_filesystem(&ext3_fs_type);
+}
+#else
+static inline void register_as_ext3(void) { }
+static inline void unregister_as_ext3(void) { }
+#endif
+
 static struct file_system_type ext4_fs_type = {
 	.owner		= THIS_MODULE,
 	.name		= "ext4",
@@ -3989,11 +4041,15 @@ static int __init init_ext4_fs(void)
 	err = init_inodecache();
 	if (err)
 		goto out1;
+	register_as_ext2();
+	register_as_ext3();
 	err = register_filesystem(&ext4_fs_type);
 	if (err)
 		goto out;
 	return 0;
 out:
+	unregister_as_ext2();
+	unregister_as_ext3();
 	destroy_inodecache();
 out1:
 	exit_ext4_xattr();
@@ -4009,6 +4065,8 @@ out4:
 
 static void __exit exit_ext4_fs(void)
 {
+	unregister_as_ext2();
+	unregister_as_ext3();
 	unregister_filesystem(&ext4_fs_type);
 	destroy_inodecache();
 	exit_ext4_xattr();