From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nao Nishijima Subject: Re: [PATCH 0/3] [RFC] Persistent device name using preferred name Date: Fri, 17 Jun 2011 14:58:10 +0900 Message-ID: <4DFAECF2.9060105@hitachi.com> References: <20110615081610.2237.44767.stgit@ltc233.sdl.hitachi.co.jp> <20110615153711.GB10160@kroah.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from mail9.hitachi.co.jp ([133.145.228.44]:40486 "EHLO mail9.hitachi.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750808Ab1FQF6V (ORCPT ); Fri, 17 Jun 2011 01:58:21 -0400 In-Reply-To: <20110615153711.GB10160@kroah.com> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Greg KH Cc: linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, James.Bottomley@HansenPartnership.com, kay.sievers@vrfy.org, jcm@redhat.com, hare@suse.de, stefanr@s5r6.in-berlin.de, yrl.pp-manager.tt@hitachi.com Hi Greg, (2011/06/16 0:37), Greg KH wrote: > On Wed, Jun 15, 2011 at 05:16:10PM +0900, Nao Nishijima wrote: >> Hi, >> >> This patch series provides preferred name into kernel and procfs >> messages. Preferred name is user's preferred name for a device. >> >> The purpose of this feature is to solve the persistent device >> naming issues which was discussed here: >> >> http://marc.info/?l=3Dlinux-scsi&m=3D130200794615884&w=3D2 >> >> There are four issues. >> 1. kernel messages doesn't show persistent device names >=20 > That is because a persistent device name could be anything, there are > multiple ways of defining a device, and the kernel will not know them > all as multiple ones could be in use for the same device. > Right, thus I'd like to solve it by assigning a unique preferred name to each device. I mean, user of preferred name will decide to use one way of defining a device, then kernel can show the name as a persistent name for him.=E3=80=80Since this is completely based on user's choice/d= ecision, no one will=E3=80=80complain about that. >> 2. procfs messages doesn't show persistent device names >=20 > See above. >=20 >> 3. Some commands didn't support persistent device name in arguments >=20 > Then fix the commands! >=20 Yes, of course. I'd like to fix those commands to accept preferred name= s. > Seriously, this could be done by now, it's been over a year since thi= s > was first discussed. All distros could have the updated packages by = now > and this would not be an issue. >=20 > I still think this is the correct way to solve the problem as it is a > userspace issue, not a kernel one. >=20 Agreed. In #3 and #4, I don't think it can solve in kernel space now. >> 4. Some commands message didn't show persistent device names >=20 > Same as #3. >=20 Yeah. Again, I've changed my mind, I'll try to fix those commands. >> Then I suggested the intermediate device naming which changes >> the naming scheme, but it was rejected. I realized that we should >> use udev to provide persistent device names instead of change the >> naming scheme. >=20 > Yes. >=20 >> In LKML discussion, a new idea was suggested by James Bottomley. >> This idea allows kernel messages show preferred names by adding a >> new attribute to a device, kernel messages show this new attribute. >> This idea's advantage is not to change the current naming scheme. >> >> I tried implementation of preferred name, and then there are two >> discussion points. >> >> (a) Which devices need support? >> Preferred name is stored in struct device. Therefore it is available >> for all devices if we make preferred name support with other device >> types. >> >> This patch series only support scsi block device. Is there the devic= e >> which needs support? (e.g. Ntwork devices, generic SCSI devices, etc= =2E) >> >> (b) What kind of procfs form is good? >> I implemented preferred name something like this, >> >> (preferred name assigned foo to sda) >> #cat /proc/partitions >> major minor #blocks name >> >> 8 0 488386584 foo >> 8 1 194560 foo1 >> ... >> >> Do you needs device name filed? >> Something like this, >> >> (preferred name assigned foo to sda) >> #cat /proc/partitions >> major minor #blocks name preferred >> >> 8 0 488386584 sda foo >> 8 1 194560 sda1 foo1 >> ... >=20 > Sorry, but you can not change the format of procfs files without > breaking a lot of tools, that's no longer allowed. >=20 OK, I would not change the format of procfs files. >> Issue 3 and 4 is command releated issue. Commands have to be >> modified to use preferred name. We need to create library for >> preferred name. >=20 > Again, this is quite simple and could have been finished by now :( >=20 :( >> Our goal is to solve those issues, and users can use and see >> preferred name anywhere. >=20 > I don't see how your proposed solution would solve the issue of > userspace using different persistant names for the same device. How > would it know which one is correct? >=20 My proposal don't use current persistent device names for access. Those are used in a udev rule as information to identify a device. Something like this: (Example: using by-id) SUBSYSTEM=3D=3D"block", ENV{ID_SERIAL}=3D=3D"scsi-SATA_WDC_WD5000AAKS-_WD-WCASY6088049", SYMLINK+=3D"disk/by-preferred/foo", PROGRAM=3D=E2=80=9Dwrite_preferred_= name %p foo=E2=80=9D To access a device from by-preferred persistently, I create new symboli= c link from /dev/disk/by-preferred/foo to /dev/sdX. > Again, this is a userspace thing, not a kernel thing, please solve it= in > userspace. >=20 To solve it in userspace, we need mapping of a device name to a device every boot-up time. But if kernel messages can show preferred name, we can identify a device from only kernel messages. Thanks, --=20 Nao NISHIJIMA Software Platform Research Dept. Linux Technology Center Hitachi, Ltd., YOKOHAMA Research Laboratory Email=EF=BC=9A nao.nishijima.xt@hitachi.com -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html