ext4: Do not override ext2 or ext3 if built they are built as modules

The CONFIG_EXT4_USE_FOR_EXT23 option must not try to take over the
ext2 or ext3 file systems if the those file system drivers are
configured to be built as mdoules.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

fs/ext4/Kconfig

@@ -28,7 +28,7 @@ config EXT4_FS
 
 config EXT4_USE_FOR_EXT23
 	bool "Use ext4 for ext2/ext3 file systems"
-	depends on !EXT3_FS || !EXT2_FS
+	depends on EXT3_FS=n || EXT2_FS=n
 	default y
 	help
 	  Allow the ext4 file system driver code to be used for ext2 or

fs/ext4/super.c

@@ -3964,7 +3964,7 @@ 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)
+#if !defined(CONTIG_EXT2_FS) && !defined(CONFIG_EXT2_FS_MODULE) && defined(CONFIG_EXT4_USE_FOR_EXT23)
 static struct file_system_type ext2_fs_type = {
 	.owner		= THIS_MODULE,
 	.name		= "ext2",
@@ -3990,7 +3990,7 @@ 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)
+#if !defined(CONTIG_EXT3_FS) && !defined(CONFIG_EXT3_FS_MODULE) && defined(CONFIG_EXT4_USE_FOR_EXT23)
 static struct file_system_type ext3_fs_type = {
 	.owner		= THIS_MODULE,
 	.name		= "ext3",