From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753097Ab1GHPrm (ORCPT ); Fri, 8 Jul 2011 11:47:42 -0400 Received: from out5.smtp.messagingengine.com ([66.111.4.29]:50385 "EHLO out5.smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750900Ab1GHPrk (ORCPT ); Fri, 8 Jul 2011 11:47:40 -0400 X-Sasl-enc: vMo3x/Cq40j0BzxgjtTz9+8nzf2/bK3U2WM8+JiKbpmV 1310140060 Date: Fri, 8 Jul 2011 08:47:36 -0700 From: Greg KH To: Kay Sievers Cc: Nao Nishijima , linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org, James.Bottomley@hansenpartnership.com, jcm@redhat.com, dle-develop@lists.sourceforge.net, Masami Hiramatsu , yrl.pp-manager.tt@hitachi.com, dgilbert@interlog.com, stefanr@s5r6.in-berlin.de, hare@suse.de Subject: Re: [RFC PATCH 0/4] Persistent device name using alias name Message-ID: <20110708154736.GA7320@kroah.com> References: <20110708084547.2091.55262.stgit@ltc197.sdl.hitachi.co.jp> <20110708145408.GA2283@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jul 08, 2011 at 05:41:36PM +0200, Kay Sievers wrote: > On Fri, Jul 8, 2011 at 16:54, Greg KH wrote: > > On Fri, Jul 08, 2011 at 05:45:47PM +0900, Nao Nishijima wrote: > >> This patch series provides an "alias name" of the disk into kernel and procfs > >> messages. The user can assign a preferred name to an alias name of the device. > >> > >> Based on previous discussion (*), I changed patches as follows > >> - This is "alias name" > >> - An "alias name" is stored in gendisk struct > >> - Add document to Documentation/ABI/testing/sysfs-block > >> - When the user changes an "alias name", kernel notifies udev > >> > >> (*) http://marc.info/?l=linux-scsi&m=130812625531219&w=2 > > > > I don't like it and I don't think it will really solve the root problem > > you are trying to address, but as the patches don't touch any code I > > maintain, there's not much I can do to object to it. > > I can only repeat what I already wrote in detail earlier: > > This approach seems to papers over the problem which emitting and > parsing free-text printk() messages with much-too-dumb tools cause. It > seems to fix the symptoms not the cause. > > You can already write a udev rule today that logs _all_ symlinks of a > device at discovery time, and any later kernel message can safely be > associated with all possible names of the blockdev. No kernel changes > needed, all possible names are covered. That also works good enough > with our current stone-age tools for anybody who is able to scroll > back to the last log udev message in that same log file. > > There can be by-definition no default udev rules assigning a proper > single name to a block device. There is never a valid single name for > a disks, so udev can not ship anything like that in the default setup, > so this stays as a custom hack. > > We absolutely need _structured_ data for logging and error reporting, > not only to solve this problem. Along with the current free-text > printk(), we would be able to attach classifications, device > error/sense data, firmware register dumps and anything > interesting-for-debug to the messages. > > We can't solve that problem in the kernel alone. Structured data from > the kernel will need to feed a smarter userspace logger that can index > and classify messages, merge current userspace data into it, and > provides hooks for the system management to act on critical failures > and raise notifications. > > Structured logging seems like the solution for this and also to many > other problems in this area. Single custom names pushed into the > kernel might cover some rather exotic use cases, but I think, is not > what we are looking for. I totally agree, but hey, no one listens to us :) greg k-h