Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752223AbcKGIIU (ORCPT ); Mon, 7 Nov 2016 03:08:20 -0500 Received: from mail-it0-f68.google.com ([209.85.214.68]:36789 "EHLO mail-it0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751134AbcKGIHz (ORCPT ); Mon, 7 Nov 2016 03:07:55 -0500 MIME-Version: 1.0 X-Originating-IP: [217.173.44.24] In-Reply-To: References: <1477380887-21333-1-git-send-email-mszeredi@redhat.com> <1477380887-21333-4-git-send-email-mszeredi@redhat.com> <20161025115748.ydhkkp5cfcdnjzwn@home.ouaza.com> From: Miklos Szeredi Date: Mon, 7 Nov 2016 09:07:53 +0100 Message-ID: Subject: Re: [PATCH 3/3] ovl: redirect on rename-dir To: Konstantin Khlebnikov Cc: Raphael Hertzog , Miklos Szeredi , "linux-unionfs@vger.kernel.org" , Guillem Jover , linux-fsdevel , Linux Kernel Mailing List Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2310 Lines: 48 On Sun, Nov 6, 2016 at 8:14 PM, Konstantin Khlebnikov wrote: > On Wed, Oct 26, 2016 at 2:12 PM, Miklos Szeredi wrote: >> On Tue, Oct 25, 2016 at 1:57 PM, Raphael Hertzog wrote: >> >>> Do you plan to make it the default in the future when it has been >>> available for a while? >>> >>> Barring any regression introduced by your patch, it seems that the feature >>> is best available by default since it allows legitimate operations to >>> succeed that are otherwise refused. I understand that it makes it >>> impossible to mount the overlay filesystem with an older kernel but is >>> that problem more widespread than the one we're fixing here? On my side, >>> overlayfs is only used in scenarios where the kernel is always the same >>> (or newer compared to what created the initial filesystem). >> >> I think it would be safe to make it the default if upperdir is empty. >> Nonempty implies that it was created with old kernel (or it was >> crafted by hand). But there should be a way to explicitly turn it >> off; either because of the need for backward compatibility or because >> the old format is simply easier to work with for humans. >> >> How about: >> >> - If upper is nonempty, then leave redirect feature alone except when >> mount option "-oredirect=on" is used to force enabling it. >> - If upper is empty, then enable redirect feature except when mount >> option "-oredirect=off" is used to force disabling it. > > I don't like this empty-nonempty upper logic. > > I think this feature should be off by default and be enabled > explicitly in mount option. > Available features could be listed in sysfs /sys/fs/overlay/..., like ext4 does. > > Overlayfs mounting anyway is complicated operation. > User must know a lot about it and provide persistent state for each mount: > list layers in correct order, work and uppder directory on the same disk, etc. > Enabled features is a part of this state. > > Probably this could be solved in userspace tool "mount.overlay" - it could load > features and layers from config file or xattr and set required mount > options automatically. It seems there are some conflicting opinions here. I have mine too, but I'll let this simmer and concentrate on actual features for now. Thanks, Miklos