Return-Path: Received: from shutemov.name ([188.40.19.243]:54103 "EHLO shutemov.name" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752890Ab0L3KoR (ORCPT ); Thu, 30 Dec 2010 05:44:17 -0500 Date: Thu, 30 Dec 2010 12:44:16 +0200 From: "Kirill A. Shutemov" To: Rob Landley Cc: "Kirill A. Shutemov" , Rob Landley , Trond Myklebust , "J. Bruce Fields" , Neil Brown , Pavel Emelyanov , linux-nfs@vger.kernel.org, "David S. Miller" , netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 00/12] make rpc_pipefs be mountable multiple time Message-ID: <20101230104416.GA31824@shutemov.name> References: <1293628470-28386-1-git-send-email-kas@openvz.org> <20101230085139.GA29697@shutemov.name> <4D1C4C7C.6050606@parallels.com> <20101230094433.GB29697@shutemov.name> <4D1C5953.6020200@parallels.com> Content-Type: text/plain; charset=us-ascii In-Reply-To: <4D1C5953.6020200@parallels.com> Sender: linux-nfs-owner@vger.kernel.org List-ID: MIME-Version: 1.0 On Thu, Dec 30, 2010 at 04:05:07AM -0600, Rob Landley wrote: > On 12/30/2010 03:44 AM, Kirill A. Shutemov wrote: > >>> If no rpcmount mountoption, no rpc_pipefs was found at > >>> '/var/lib/nfs/rpc_pipefs' and we are in init's mount namespace, we use > >>> init_rpc_pipefs. > >> > >> It's the "we are in init's mount namespace" that I was wondering about. > >> > >> So if I naievely chroot, nfs mount stops working the way it did before I > >> chrooted unless I do an extra setup step? > > > > No. It will work as before since you are still in init's mount namespace. > > Creating new mount namespace changes rules. > > Ah, CLONE_NEWNS and then you need /var/lib/nfs/rpc_pipefs. Got it. > > I'm kind of surprised that the kernel cares about a specific path under > /var/lib. (Seems like policy in the kernel somehow.) Yep. It's bad, but there is way to overwrite the default. Other way is to leave 'rpcmount' mountoption without default. get_rpc_pipefs(NULL) in init's mount namespace will always return init_rpc_pipefs, without filesystem lookup. get_rpc_pipefs(NULL) in non-init's mount namespace will always return error. So you will have to specify 'rpcmount' mountoption for every nfs mount in container. Hmm, I guess, it may confuse user. Or we can try to move the default to userspace. /sbin/mount.nfs? > Can't it just > check the current process's mount list to see if an instance of > rpc_pipefs is mounted in the current namespace the way lxc looks for > cgroups? Or are there potential performance/scalability issues with that? What should we do if we have several rpc_pipefs mounts in the namespace? -- Kirill A. Shutemov