From mboxrd@z Thu Jan 1 00:00:00 1970 From: hooanon05@yahoo.co.jp Subject: Re: New filesystem for Linux kernel Date: Wed, 25 Feb 2009 01:26:59 +0900 Message-ID: <15922.1235492819@jrobl> References: <7558.1235374266@jrobl> <7769.1235374482@jrobl> <49A268A7.1010708@slax.org> <49A26ACC.90804@slax.org> <49A3AC14.2050107@slax.org> <11287.1235481490@jrobl> Cc: tomas@slax.org, akpm@linux-foundation.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org To: Miklos Szeredi Return-path: Received: from vsmtp04.dti.ne.jp ([202.216.231.139]:46983 "EHLO vsmtp04.dti.ne.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751645AbZBXQ1T (ORCPT ); Tue, 24 Feb 2009 11:27:19 -0500 In-Reply-To: Sender: linux-fsdevel-owner@vger.kernel.org List-ID: Miklos Szeredi: > It's always easier to review something with less features, even if > that feature set is too little for real world use. Generally I agree with you. > The simplest version is with all branches read-only. That gets rid of > a _huge_ amount of complexity, yet it's still useful in some > situations. It also deals with a lot of the basic infrastucture > needed for stacking. If you really think it is a better way to get merged into mainline, then I'll try implement such version. > And that's when one starts thinking about whether unioning is really > the right solution. Instead this could be implemented with a special > filesystem format that only contains deltas to the data, metatata and > directory tree. It would be much more space efficient, could easily > handle renames, hard links etc, without all the hacks that > unionfs/aufs does. It sounds like an ODF (on disk format) version of unionfs (while it seems to be inactive). At implementing, I don't think it easier to maintain delta of filedata and metadata. Since aufs has a writable branch in it, it is better and easier to maintain data in a branch fs. If you think there should not be any writable branch in aufs, and all "write" goes to a new filesystem format, then it is equivalent to a writable branch, isn't it? If you say "just a part of write" goes to a new fs, then I don't think we can support several essential features, for instance mmap. J. R. Okajima