From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-fsdevel-owner@vger.kernel.org>
Received: from zeniv.linux.org.uk ([195.92.253.2]:46112 "EHLO
        ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1757399AbcKXUjE (ORCPT
        <rfc822;linux-fsdevel@vger.kernel.org>);
        Thu, 24 Nov 2016 15:39:04 -0500
Date: Thu, 24 Nov 2016 20:39:00 +0000
From: Al Viro <viro@ZenIV.linux.org.uk>
To: Fabian Frederick <fabf@skynet.be>
Cc: tytso@mit.edu, Jan Kara <jack@suse.com>,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/1 linux-next] ext4: add compatibility flag check
Message-ID: <20161124203900.GS1555@ZenIV.linux.org.uk>
References: <1480016861-24432-1-git-send-email-fabf@skynet.be>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <1480016861-24432-1-git-send-email-fabf@skynet.be>
Sender: linux-fsdevel-owner@vger.kernel.org
List-ID: <linux-fsdevel.vger.kernel.org>

On Thu, Nov 24, 2016 at 08:47:41PM +0100, Fabian Frederick wrote:
> data=journal mount option should disable O_DIRECT access
> (See Documentation/filesystems/ext4.txt) but open operations
> using O_CREAT|O_RDWR|O_DIRECT|O_SYNC have no warning in return and file is being
> created. This patch adds vfs super_operations compatibility flag function
> returning -EPERM in such a case.

Why not simply check it in ->open()?  Occam's Razor and all such...