Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755300Ab1F2Lkn (ORCPT ); Wed, 29 Jun 2011 07:40:43 -0400 Received: from mail-pv0-f174.google.com ([74.125.83.174]:54312 "EHLO mail-pv0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751769Ab1F2Lkj (ORCPT ); Wed, 29 Jun 2011 07:40:39 -0400 MIME-Version: 1.0 In-Reply-To: <4E0AF2BA.2040706@gmail.com> References: <1302756608.2854.10.camel@perseus.themaw.net> <4DA4B6A8.7030804@gmail.com> <4DA5DCB8.3040101@gmail.com> <4DA5F569.9020309@gmail.com> <24792.1302808448@redhat.com> <4E0AF2BA.2040706@gmail.com> From: Michal Suchanek Date: Wed, 29 Jun 2011 13:40:19 +0200 X-Google-Sender-Auth: 6FiMDak1uZ_k8Z2Mc0gYjkcvYY4 Message-ID: Subject: Re: Union mount and overlayfs bake off? To: Ric Wheeler Cc: David Howells , Alexander Viro , Ian Kent , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Jeff Moyer , miklos@szeredi.hu, Christoph Hellwig Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1743 Lines: 41 On 29 June 2011 11:39, Ric Wheeler wrote: > > I think that it has been a while since David reposted the refreshed patch > set for union mounts & know that overlayfs has recent updates as well. > > Despite that, I have not seen a lot of feedback from reviewers or testers. > I can only attest that I can build working live CD on top of either overlayfs or unionmount. This is not a good metric for reliability because issues were found with both solutions after the live CDs were working fine already. However, it is an usability metric in that both solutions are from the alpha stage in which crucial features were missing or broken way into the beta stage in which corner case issues are discovered but the solution is generally working. Somebody was running racer on top of overlayfs which uncovered some problems with overlayfs itself and linux vfs in general. Unionmount has supposedly its own testsuite but I have never seen that. There are some issues with neither creating full emulation of a traditional filesystem and the cost of hiding more effects of the union from userspace to make the filesystem look more traditional. With something touching VFS, however, it is important to decide how (and if) these corner case issues should be resolved because they could possibly affect unrelated parts of the system. Reviewing all raised concerns is unfortunately taking quite some time, and then addressing them in code will probably require more. Thanks Michal -- 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/