ext4: collapse handling of data=ordered and data=writeback codepaths

The only difference between how we handle data=ordered and
data=writeback is a single call to ext4_jbd2_file_inode().  Eliminate
code duplication by factoring out redundant the code paths.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: Lukas Czerner <lczerner@redhat.com>
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 3b83cd6..f91e11b 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1374,6 +1374,7 @@
 	EXT4_STATE_DIOREAD_LOCK,	/* Disable support for dio read
 					   nolocking */
 	EXT4_STATE_MAY_INLINE_DATA,	/* may have in-inode data */
+	EXT4_STATE_ORDERED_MODE,	/* data=ordered mode */
 };
 
 #define EXT4_INODE_BIT_FNS(name, field, offset)				\