From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754131AbYICWgu (ORCPT ); Wed, 3 Sep 2008 18:36:50 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751828AbYICWgm (ORCPT ); Wed, 3 Sep 2008 18:36:42 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:37291 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751086AbYICWgm (ORCPT ); Wed, 3 Sep 2008 18:36:42 -0400 Date: Wed, 3 Sep 2008 15:36:37 -0700 From: Andrew Morton To: Nye Liu Cc: nyet@nyet.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] INITRAMFS: Add option to preserve mtime from INITRAMFS cpio images Message-Id: <20080903153637.0e9dc471.akpm@linux-foundation.org> In-Reply-To: <20080903223114.GA9456@mrv.com> References: <20080805195232.GA5183@curtisfong.org> <20080903202938.GA9065@curtisfong.org> <20080903152231.6b82d9bf.akpm@linux-foundation.org> <20080903223114.GA9456@mrv.com> X-Mailer: Sylpheed version 2.2.4 (GTK+ 2.8.20; i486-pc-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 On Wed, 3 Sep 2008 15:31:14 -0700 Nye Liu wrote: > On Wed, Sep 03, 2008 at 03:22:31PM -0700, Andrew Morton wrote: > > > From: Nye Liu > > > > > > When unpacking the cpio into the initramfs, mtimes are not preserved by > > > default. This patch adds an INITRAMFS_PRESERVE_MTIME option that allows mtimes > > > stored in the cpio image to be used when constructing the initramfs. For > > > embedded applications that run exclusively out of the initramfs, this is > > > invaluable. > > > > Why is it "invlauable". Please explain this value in full detail - > > it's the whole reason for merging the patch! > > When building embedded application initramfs images, its nice to know > when the files were actually created during the build process - that > makes it easier to see what files were modified when so we can compare > the files that are being used on the image with the files used during > the build process. This might help (for example) to determine if the > target system has all the updated files you expect to see w/o having to > check MD5s etc. > > In our environment, the whole system runs off the initramfs partition, > and seeing the modified times of the shared libraries (for example) > helps us find bugs that may have been introduced by the build system > incorrectly propogating outdated shared libraries into the image. > > Similarly, many of the initializion/configuration files in /etc > might be dynamically built by the build system, and knowing when > they were modified helps us sanity check whether the target system > has the "latest" files etc. > > Finally, we might use last modified times to determine whether a > hot fix should be applied or not to the running ramfs. > Thanks, I updated the changelog. > > gargh. Why does this work? It's normally a big fail to pass a kernel > > address into a system call. I guess we're running under KERNEL_DS here > > and getname() and strncpy_from_user() did the right thing. > > > > On what CPU architecture was this tested? > > > > Wouldn't it be simpler to put a timespec into struct dir_entry then go > > direct to do_utimes() here? > > Did you see this stuff?