From: Andreas Dilger Subject: Re: [RFC] add FIEMAP ioctl to efficiently map file allocation Date: Tue, 1 May 2007 15:32:36 -0700 Message-ID: <20070501223236.GM5722@schatzie.adilger.int> References: <20070412110550.GM5967@schatzie.adilger.int> <20070416112252.GJ48531920@melbourne.sgi.com> <20070419002139.GK5967@schatzie.adilger.int> <20070419015426.GM48531920@melbourne.sgi.com> <20070430224401.GX5967@schatzie.adilger.int> <20070501042254.GD77450368@melbourne.sgi.com> <1177994346.3362.5.camel@entropy> <20070501142049.GG77450368@melbourne.sgi.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Nicholas Miell , linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, xfs@oss.sgi.com, hch@infradead.org To: David Chinner Return-path: Received: from mail.clusterfs.com ([206.168.112.78]:60176 "EHLO mail.clusterfs.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754523AbXEAWcm (ORCPT ); Tue, 1 May 2007 18:32:42 -0400 Content-Disposition: inline In-Reply-To: <20070501142049.GG77450368@melbourne.sgi.com> Sender: linux-ext4-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org On May 02, 2007 00:20 +1000, David Chinner wrote: > My point was that there is a difference between specification and > implementation - if the specification says something is compulsory, > then they must be implemented in the filesystem. This is easy > enough to ensure by code review - we don't need additional interface > complexity for this.... What you seem to be missing about my proposal is that the FLAG_INCOMPAT is for future use by that part of the specification we haven't thought of yet... Having COMPAT/INCOMPAT flags has been very useful for ext2/3/4, and is much better than having version numbers for the interface. Cheers, Andreas -- Andreas Dilger Principal Software Engineer Cluster File Systems, Inc.