From: Theodore Tso Subject: Re: [PATCH] ext4: Remove "extents" mount option Date: Wed, 7 Jan 2009 09:45:02 -0500 Message-ID: <20090107144502.GC17110@mit.edu> References: <1231267777-18831-1-git-send-email-tytso@mit.edu> <20090107053250.GA9617@skywalker> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Ext4 Developers List To: "Aneesh Kumar K.V" Return-path: Received: from THUNK.ORG ([69.25.196.29]:47038 "EHLO thunker.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753906AbZAGOpE (ORCPT ); Wed, 7 Jan 2009 09:45:04 -0500 Content-Disposition: inline In-Reply-To: <20090107053250.GA9617@skywalker> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Wed, Jan 07, 2009 at 11:02:50AM +0530, Aneesh Kumar K.V wrote: > On Tue, Jan 06, 2009 at 01:49:37PM -0500, Theodore Ts'o wrote: > > This mount option is largely superfluous, and in fact the way it was > > implemented was buggy; if a filesystem which did not have the extents > > feature flag was mounted -o extents, the filesystem would attempt to > > create and use extents-based file even though the extents feature flag > > was not eabled. The simplest thing to do is to nuke the mount option > > entirely. It's not all that useful to force the non-creation of new > > extent-based files if the filesystem can support it. > > > > Ext4 -> Ext3 migration story is to mount the filesystem with -o > noextents and copy the file around. If we remove the -o noextents > options how do we force the creation of non extent format files ? 1) How much do we care about ext4->ext3 migration? 2) That only deals with extent-based files; it doesn't deal with any of the other ext4-specific features. What's the scenario you're thinking about here? When would it be useful for users to be able to downgrade extent-based files to indirect block files by copying files around? - Ted