ext4: ignore journalled data options on remount if fs has no journal

This avoids a confusing failure in the init scripts when the
/etc/fstab has data=writeback or data=journal but the file system does
not have a journal.  So check for this case explicitly, and warn the
user that we are ignoring the (pointless, since they have no journal)
data=* mount option.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

fs/ext4/super.c

@@ -1683,7 +1683,9 @@ static int parse_options(char *options, struct super_block *sb,
 			data_opt = EXT4_MOUNT_WRITEBACK_DATA;
 		datacheck:
 			if (is_remount) {
-				if (test_opt(sb, DATA_FLAGS) != data_opt) {
+				if (!sbi->s_journal)
+					ext4_msg(sb, KERN_WARNING, "Remounting file system with no journal so ignoring journalled data option");
+				else if (test_opt(sb, DATA_FLAGS) != data_opt) {
 					ext4_msg(sb, KERN_ERR,
 						"Cannot change data mode on remount");
 					return 0;