From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail104.syd.optusnet.com.au ([211.29.132.246]:54663 "EHLO mail104.syd.optusnet.com.au" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726130AbfGVAFg (ORCPT ); Sun, 21 Jul 2019 20:05:36 -0400 Date: Mon, 22 Jul 2019 10:04:24 +1000 From: Dave Chinner Subject: Re: [PATCH RFC] fs: New zonefs file system Message-ID: <20190722000424.GP7689@dread.disaster.area> References: <20190712030017.14321-1-damien.lemoal@wdc.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-xfs-owner@vger.kernel.org List-ID: List-Id: xfs To: Damien Le Moal Cc: Jeff Moyer , "linux-fsdevel@vger.kernel.org" , "linux-xfs@vger.kernel.org" , Christoph Hellwig , Johannes Thumshirn , Hannes Reinecke , Ting Yao On Sat, Jul 20, 2019 at 07:15:26AM +0000, Damien Le Moal wrote: > Jeff, > > On 2019/07/19 23:25, Jeff Moyer wrote: > > OK, I can see how a file system eases adoption across multiple > > languages, and may, in some cases, be easier to adopt by applications. > > However, I'm not a fan of the file system interface for this usage. > > Once you present a file system, there are certain expectations from > > users, and this fs breaks most of them. > > Your comments got me thinking more about zonefs specifications/features and I am > now wondering if I am not pushing this too far in terms of simplicity. So here > is a new RFC/Question to chew on... While keeping as a target the concept of > "file == zone" or as close to it as possible, what do you think zonefs minimal > feature set should be ? > > One idea I have since a while back now is this: > 1) If a zone is unused, do not show a file for it. This means adding a dynamic > "zone allocation" code and supporting O_CREAT on open, unlink, etc. So have more > normal file system calls behave as with a normal FS. > 2) Allow file names to be decided by the user instead of using a fixed names. > Again, have O_CREAT behave as expected So now you have to implement a persistent directory structure, atomic/transactional updates, etc. You've just added at least 2 orders of magnitude complexity to zonefs and a very substantial amount of additional, ongoing QA to ensure it works correctly. I think keeping it simple by exposing all zones to userspace and leaving it to the application to track/index what zones it is using is the simplest way forward for everyone. Cheers, Dave. -- Dave Chinner david@fromorbit.com