From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hannes Reinecke Subject: Re: [PATCH 1/3] [RFC] genhd: add a new attribute in device structure Date: Fri, 17 Jun 2011 08:27:30 +0200 Message-ID: <4DFAF3D2.5030506@suse.de> References: <20110615081610.2237.44767.stgit@ltc233.sdl.hitachi.co.jp> <20110615081627.2237.9620.stgit@ltc233.sdl.hitachi.co.jp> <20110615153337.GA10160@kroah.com> <4DF9F11F.705@hitachi.com> <20110616154129.GA31498@kroah.com> <1308239454.2436.34.camel@mulgrave> <20110616161442.GA32113@kroah.com> <1308241506.2436.44.camel@mulgrave> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from cantor.suse.de ([195.135.220.2]:50961 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751743Ab1FQG1d (ORCPT ); Fri, 17 Jun 2011 02:27:33 -0400 In-Reply-To: Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Kay Sievers Cc: James Bottomley , Greg KH , Nao Nishijima , linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, jcm@redhat.com, stefanr@s5r6.in-berlin.de, yrl.pp-manager.tt@hitachi.com On 06/16/2011 07:20 PM, Kay Sievers wrote: > On Thu, Jun 16, 2011 at 19:09, Kay Sievers wro= te: >> On Thu, Jun 16, 2011 at 18:25, James Bottomley >> wrote: >>> On Thu, 2011-06-16 at 09:14 -0700, Greg KH wrote: >>>> All userspace naming will be taken care of by the usual udev rules= , so >>>>> for disks, something like /dev/disk/by-preferred/ which wo= uld be >>>>> the usual symbolic link. >>>> >>>> No, udev can not create such a link after the preferred name is se= t, as >>>> it has no way of knowing that the name was set. >>> >>> It can if we trigger a uevent. Note: I'm not advocating this ... I= 'd be >>> equally happy having whatever sets the kernel name create the link = (or >>> tickle udev to create it). We definitely require device links, tho= ugh, >>> to get this to work. > > Guess all that would work now, including mount(8) not canonicalizing. > What would happen if we mount: > /dev/disk/by-pretty/foo > and some tool later thinks the pretty name should better be 'bar', it > writes the name to /sys, we get a uevent, the old link disappears, we > get a new link, mount has no device node anymore for the mounted > device ... > > So we basically get a one-shot additional pretty name? Guess, the > _single_ name changed anytime later just asks for serious problems. W= e > need to set it very early to be really useful, but how, where is it > coming from? > Well, certain storage arrays are able to print out the user-defined=20 name for the LUNs: # sg_vpd -p 0xc8 /dev/sdc Extended device identification (RDAC) VPD Page: Volume Unique Identifier: 60080e50001bf1f0000005004ddb05a4 Creation Number: 1280, Timestamp: Tue May 24 03:11:00 2011 Volume User Label: mas-1 Storage Array Unique Identifier: 60080e50001bf1f0000000004d418973 Storage Array User Label: LSI-SAS-DIF Logical Unit Number: 0000000000000000 where the 'Volume User Label' is the name the administrator has=20 given to the LUN on the storage array. So for these kind of things it would be useful. However, a single pretty name is quite a limitation. And I also fail to see why this can't be handled in userspace. Cheers, Hannes --=20 Dr. Hannes Reinecke zSeries & Storage hare@suse.de +49 911 74053 688 SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 N=C3=BCrnberg GF: J. Hawn, J. Guild, F. Imend=C3=B6rffer, HRB 16746 (AG N=C3=BCrnberg= ) -- 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