From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932243Ab2DIQLU (ORCPT ); Mon, 9 Apr 2012 12:11:20 -0400 Received: from fieldses.org ([174.143.236.118]:54002 "EHLO fieldses.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932069Ab2DIQLR (ORCPT ); Mon, 9 Apr 2012 12:11:17 -0400 Date: Mon, 9 Apr 2012 12:11:14 -0400 From: "bfields@fieldses.org" To: Stanislav Kinsbursky Cc: Jeff Layton , "Trond.Myklebust@netapp.com" , "linux-nfs@vger.kernel.org" , "linux-kernel@vger.kernel.org" Subject: Re: Grace period Message-ID: <20120409161114.GB6482@fieldses.org> References: <4F7F230A.6080506@parallels.com> <20120406234039.GA20940@fieldses.org> <4F82C6E3.3030009@parallels.com> <20120409094743.56932677@tlielax.poochiereds.net> <4F82F16C.7030303@parallels.com> <20120409112739.6a823d6f@corrin.poochiereds.net> <4F830999.5000504@parallels.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <4F830999.5000504@parallels.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Apr 09, 2012 at 08:08:57PM +0400, Stanislav Kinsbursky wrote: > 09.04.2012 19:27, Jeff Layton пишет: > > > >If you allow one container to hand out conflicting locks while another > >container is allowing reclaims, then you can end up with some very > >difficult to debug silent data corruption. That's the worst possible > >outcome, IMO. We really need to actively keep people from shooting > >themselves in the foot here. > > > >One possibility might be to only allow filesystems to be exported from > >a single container at a time (and allow that to be overridable somehow > >once we have a working active/active serving solution). With that, you > >may be able limp along with a per-container grace period handling > >scheme like you're proposing. > > > > Ok then. Keeping people from shooting themselves here sounds reasonable. > And I like the idea of exporting a filesystem only from once per > network namespace. Unfortunately that's not going to get us very far, especially not in the v4 case where we've got the common read-only pseudoroot that everyone has to share. --b. > Looks like there should be a list of pairs > "exported superblock - network namespace". And if superblock is > exported already in other namespace, then export in new namespace > have to be skipped (replaced?) with appropriate warning (error?) > message shown in log. > Or maybe we even should deny starting of NFS server if one of it's > exports is shared already by other NFS server "instance"? > But any of these ideas would be easy to implement in RAM, and thus > it suits only for containers... > > -- > Best regards, > Stanislav Kinsbursky