ext3: make default data ordering mode configurable

This makes the defautl ext3 data ordering mode (when no explicit
ordering is set) configurable, so as to allow people to default to
'data=writeback' and get the resulting latency improvements.

This is a non-issue if a filesystem has been explicitly set to some
ordering (with 'tune2fs').

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/ext3/Kconfig

@@ -28,6 +28,25 @@ config EXT3_FS
 	  To compile this file system support as a module, choose M here: the
 	  module will be called ext3.
 
+config EXT3_DEFAULTS_TO_ORDERED
+	bool "Default to 'data=ordered' in ext3 (legacy option)"
+	depends on EXT3_FS
+	help
+	  If a filesystem does not explicitly specify a data ordering
+	  mode, and the journal capability allowed it, ext3 used to
+	  historically default to 'data=ordered'.
+
+	  That was a rather unfortunate choice, because it leads to all
+	  kinds of latency problems, and the 'data=writeback' mode is more
+	  appropriate these days.
+
+	  You should probably always answer 'n' here, and if you really
+	  want to use 'data=ordered' mode, set it in the filesystem itself
+	  with 'tune2fs -o journal_data_ordered'.
+
+	  But if you really want to enable the legacy default, you can do
+	  so by answering 'y' to this question.
+
 config EXT3_FS_XATTR
 	bool "Ext3 extended attributes"
 	depends on EXT3_FS