From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751683AbWFJTL3 (ORCPT ); Sat, 10 Jun 2006 15:11:29 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751688AbWFJTL2 (ORCPT ); Sat, 10 Jun 2006 15:11:28 -0400 Received: from smtpout.mac.com ([17.250.248.172]:50908 "EHLO smtpout.mac.com") by vger.kernel.org with ESMTP id S1751683AbWFJTL0 (ORCPT ); Sat, 10 Jun 2006 15:11:26 -0400 In-Reply-To: <448992EB.5070405@garzik.org> References: <1149816055.4066.60.camel@dyn9047017069.beaverton.ibm.com> <4488E1A4.20305@garzik.org> <20060609083523.GQ5964@schatzie.adilger.int> <44898EE3.6080903@garzik.org> <448992EB.5070405@garzik.org> Mime-Version: 1.0 (Apple Message framework v746.3) Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed Message-Id: <2DFFC56C-2516-449F-990E-71DDE2601531@mac.com> Cc: linux-kernel@vger.kernel.org, ext2-devel , linux-fsdevel@vger.kernel.org, Andreas Dilger , cmm@us.ibm.com, Andrew Morton , Linus Torvalds Content-Transfer-Encoding: 7bit From: Kyle Moffett Subject: Re: [RFC 0/13] extents and 48bit ext3 Date: Sat, 10 Jun 2006 15:10:30 -0400 To: Jeff Garzik X-Mailer: Apple Mail (2.746.3) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Jun 9, 2006, at 11:25:31, Jeff Garzik wrote: > Overall, I'm surprised that ext3 developers don't see any of the > problems related to progressive, stealth filesystem upgrades. > > Users are never given a clear indication of when their metadata is > being upgraded, there is no clear "line of demarcation" they cross, > when they start using extents. > > Since there is no user-visible fs upgrade event, users do not have > a clear picture of what features are being used -- which means they > are kept in the dark about which kernels are OK to use on their data. > > Do you guys honestly expect users to keep track of which kernels > added specific ext3 features? > > This is why other enterprise filesystems have clear "fs version 1", > "fs version 2" points across which a user migrates. ext3's feature- > flags approach just means that there are a million combinations of > potential old-and-new features, in-tree and third party, all of > which must be supported. One possible solution to the version-confusion that would avoid duplicating features would be to merge the fs/ext{2,3} to fs/ext, then make fs/ext register itself as a filesystem under "ext2", "ext3", and "ext4". Then have each name imply a specific set of features and compatibility. That would allow the same performance optimizations to affect all 3 even as you make metadata changes in the latest version. I've heard quite some griping about the amount of duplicated code between ext2 and ext3; why cause those problems again with an "ext4"? There would probably be some fs/ext/ext{2,3,4} _foo.c files that could be compiled in or out depending on configured FS support, but I would guess that would make it easier on users and developers alike. Cheers, Kyle Moffett