ext4: make online defrag error reporting consistent

Make the error reporting behavior resulting from the unsupported use
of online defrag on files with data journaling enabled consistent with
that implemented for bigalloc file systems. Difference found with
ext4/308.
Signed-off-by: NEric Whitney <enwlinux@gmail.com>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>
Reviewed-by: NDarrick J. Wong <darrick.wong@oracle.com>

fs/ext4/move_extent.c

@@ -571,12 +571,16 @@ ext4_move_extents(struct file *o_filp, struct file *d_filp, __u64 orig_blk,
 			orig_inode->i_ino, donor_inode->i_ino);
 		return -EINVAL;
 	}
-	/* TODO: This is non obvious task to swap blocks for inodes with full
-	   jornaling enabled */
+
+	/* TODO: it's not obvious how to swap blocks for inodes with full
+	   journaling enabled */
 	if (ext4_should_journal_data(orig_inode) ||
 	    ext4_should_journal_data(donor_inode)) {
-		return -EINVAL;
+		ext4_msg(orig_inode->i_sb, KERN_ERR,
+			 "Online defrag not supported with data journaling");
+		return -EOPNOTSUPP;
 	}
+
 	/* Protect orig and donor inodes against a truncate */
 	lock_two_nondirectories(orig_inode, donor_inode);