From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759841AbZEBUW4 (ORCPT ); Sat, 2 May 2009 16:22:56 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757063AbZEBUWr (ORCPT ); Sat, 2 May 2009 16:22:47 -0400 Received: from mail-fx0-f158.google.com ([209.85.220.158]:43823 "EHLO mail-fx0-f158.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756838AbZEBUWq (ORCPT ); Sat, 2 May 2009 16:22:46 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=googlemail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=dbYiwVCb8Z21k09LIL/kCuDJdws2inRGC+cxhQAg6x0xyyFHDxMHOWtbtJM0nOuUyE UiXiUHgjWuhffespho4T7ARm/G+VkRctceJgRny+Q/o37utBbX3+LonTQt1Cy4VEC0Er xm84HHfpHuXHvu57Vs8gr8/l66dy3SNjzxOrg= MIME-Version: 1.0 In-Reply-To: References: <1241097822.2516.3.camel@poy> <20090502071636.GA9487@infradead.org> Date: Sat, 2 May 2009 21:22:44 +0100 Message-ID: <9b2b86520905021322l31845d2dubad98d78380aa1d5@mail.gmail.com> Subject: Re: [PATCH] driver-core: devtmpfs - driver core maintained /dev tmpfs From: Alan Jenkins To: Kay Sievers Cc: Christoph Hellwig , linux-kernel , Greg KH , Jan Blunck , linux-arch@vger.kernel.org, viro@zeniv.linux.org.uk, torvalds@osdl.org, akpm@osdl.org, adam@yggdrasil.com Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 5/2/09, Kay Sievers wrote: > On Sat, May 2, 2009 at 09:16, Christoph Hellwig wrote: >> >After the rootfs is mounted by the kernel, the >>> populated tmpfs is mounted at /dev. In initramfs, it can be moved >>> to the manually mounted root filesystem before /sbin/init is >>> executed. >> >> That for example is something that is not acceptable. We really don't >> want the kernel to mess with the initial namespace in such a major way. > > There is nothing like "mess around", it's not mounted at all, until > the kernel mounts the root filesystem at /, then devtmpfs is mounted > the first time, and only if it's compiled in because you asked for it. > Also, just try: > egrep 'mknod|create_dev' init/*.c > and see what we currently do. > >> Counter-proposal: Re-introduce a proper mini-devfs. All nodes in there >> are kernel-created and not changeable which sorts out that whole >> mess of both drivers and userspace messing with tree topology we had >> both in original devfs and this new devtmpfs. Single-instance so it can >> be >> populated before it's actually mounted somewhere, that way the kernel >> doesn't have to do any policy devicision on where it's mounted. > > That sounds worse than devtpfs, and does not help for most of the > mentioned problems we are trying to solve here. On a narrow issue: do you really object to moving the "mount dev -t devfs2 /dev" into userspace (and therefore giving it a user-visible name)?? That would address Cristophs particular objection about "messing around" with the initial namespace. It means I can be 100% sure I can boot an old initramfs with this option enabled. And it gives a nice clean way for new initramfs' to test for this feature - when they try to mount it, it fails. It would seem to make for a rather smoother migration path. It shouldn't mean too many more LOC, you're already doing the "single instance" thing. Thanks Alan