From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Fri, 21 Sep 2001 00:42:15 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Fri, 21 Sep 2001 00:42:04 -0400 Received: from rj.sgi.com ([204.94.215.100]:58801 "EHLO rj.sgi.com") by vger.kernel.org with ESMTP id ; Fri, 21 Sep 2001 00:41:54 -0400 Date: Fri, 21 Sep 2001 15:42:00 +1100 From: Nathan Scott To: Steve Lord Cc: hch@ns.caldera.de, Alan Cox , "Gonyou, Austin" , narancs@narancs.tii.matav.hu, linux-xfs@oss.sgi.com, linux-kernel@vger.kernel.org Subject: Re: XFS to main kernel source Message-ID: <20010921154159.H416300@wobbly.melbourne.sgi.com> In-Reply-To: <200109210325.f8L3PKi20270@jen.americas.sgi.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5i In-Reply-To: <200109210325.f8L3PKi20270@jen.americas.sgi.com>; from lord@sgi.com on Thu, Sep 20, 2001 at 10:25:20PM -0500 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org hi, On Thu, Sep 20, 2001 at 10:25:20PM -0500, Steve Lord wrote: > > On Sep 20, 2001 16:31 -0500, Steve Lord wrote: > > > XFS quotas are transactional, when space is added to a file the quota is > > > adjusted in the same transaction. It is fairly hard to do this without your > > > own quota code. > > > > Actually not. The quotas in ext3 are transactional as well. It's just > > that the "ext3" journal layer allows nested transactions, so it is possible > > to start a write transaction, call into the journal code which calls back > > into the ext3 write code to start a nested transaction on the journal file > > (i.e. it is in the same transaction as the initial write), and then the > > initial write completes. > > OK, good point, but doing a major rewrite of XFS to use a different > transaction mechanism is not really on the cards, plus we have on disk > compatibility with the Irix version to consider. > XFS also uses quite a different _model_ of quota, and it is tightly integrated into XFS (by its very nature). There are a number of issues that it attempts to address, and in particular it works around the inherent problems of the traditional quotacheck/mount/quotaon/quotaoff model (ie. the BSD quota model which the Linux VFS also uses, and which was used in IRIX for the EFS filesystem). Its simply different, there are advantages and disadvantages of each way, but XFS is particularly aimed at scalability, and the desire to never have to run quotacheck(8) on large filesystems was one of the issues which the original design aimed to address. So XFS quota should be a non-issue. I have had discussions with Jan Kara and Alan in the past about how to most cleanly integrate it with their (new) VFS quota, and they seem happy with the design we collectively came up with (its slightly different to the one in both the XFS patch and Alan's patch at the moment). cheers. -- Nathan