Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756727Ab1FIDwA (ORCPT ); Wed, 8 Jun 2011 23:52:00 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:53551 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756365Ab1FIDv6 (ORCPT ); Wed, 8 Jun 2011 23:51:58 -0400 Date: Wed, 8 Jun 2011 20:52:33 -0700 From: Andrew Morton To: NeilBrown Cc: Miklos Szeredi , viro@ZenIV.linux.org.uk, torvalds@linux-foundation.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, apw@canonical.com, nbd@openwrt.org, hramrach@centrum.cz, jordipujolp@gmail.com, ezk@fsl.cs.sunysb.edu, mszeredi@suse.cz Subject: Re: [PATCH 0/7] overlay filesystem: request for inclusion Message-Id: <20110608205233.ebfedc4d.akpm@linux-foundation.org> In-Reply-To: <20110609115934.3c53f78f@notabene.brown> References: <1306932380-10280-1-git-send-email-miklos@szeredi.hu> <20110608153208.dc705cda.akpm@linux-foundation.org> <20110609115934.3c53f78f@notabene.brown> X-Mailer: Sylpheed 2.7.1 (GTK+ 2.18.9; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1920 Lines: 52 On Thu, 9 Jun 2011 11:59:34 +1000 NeilBrown wrote: > On Wed, 8 Jun 2011 15:32:08 -0700 Andrew Morton > wrote: > > > On Wed, 1 Jun 2011 14:46:13 +0200 > > Miklos Szeredi wrote: > > > > > I'd like to ask for overlayfs to be merged into 3.1. > > > > Dumb questions: > > > > I've never really understood the need for fs overlaying. Who wants it? > > What are the use-cases? > > https://lwn.net/Articles/324291/ > > I think the strongest use case is that LIVE-DVD's want it to have a write-able > root filesystem which is stored on the DVD. Well, these things have been around for over 20 years. What motivated the developers of other OS's to develop these things and how are their users using them? > > > > This sort of thing could be implemented in userspace and wired up via > > fuse, I assume. Has that been attempted and why is it inadequate? > > I think that would be a valid question if the proposal was large and > complex. But overlayfs is really quite small and self-contained. Not merging it would be even smaller and simpler. If there is a userspace alternative then that option should be evaluated and compared in a rational manner. Another issue: there have been numerous attempts at Linux overlay filesystems from numerous parties. Does (or will) this implementation satisfy all their requirements? Because if not, we're in a situation where the in-kernel code is unfixably inadequate so we end up merging another similar-looking thing, or the presence of this driver makes it harder for them to get other drivers merged and the other parties' requirements remain unsatisfied. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/