|From:||Greg KH <greg-AT-kroah.com>|
|To:||Nao Nishijima <nao.nishijima.xt-AT-hitachi.com>|
|Subject:||Re: [PATCH 0/3] [RFC] Persistent device name using preferred name|
|Date:||Wed, 15 Jun 2011 08:37:11 -0700|
|Cc:||linux-scsi-AT-vger.kernel.org, linux-kernel-AT-vger.kernel.org, James.Bottomley-AT-HansenPartnership.com, kay.sievers-AT-vrfy.org, jcm-AT-redhat.com, hare-AT-suse.de, stefanr-AT-s5r6.in-berlin.de, yrl.pp-manager.tt-AT-hitachi.com|
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=linux-scsi&m=130200794615884&w=2 > > There are four issues. > 1. kernel messages doesn't show persistent device names 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. > 2. procfs messages doesn't show persistent device names See above. > 3. Some commands didn't support persistent device name in arguments Then fix the commands! Seriously, this could be done by now, it's been over a year since this was first discussed. All distros could have the updated packages by now and this would not be an issue. I still think this is the correct way to solve the problem as it is a userspace issue, not a kernel one. > 4. Some commands message didn't show persistent device names Same as #3. > 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. Yes. > 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 device > which needs support? (e.g. Ntwork devices, generic SCSI devices, etc.) > > (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 > ... Sorry, but you can not change the format of procfs files without breaking a lot of tools, that's no longer allowed. > 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. Again, this is quite simple and could have been finished by now :( > Our goal is to solve those issues, and users can use and see > preferred name anywhere. 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? Again, this is a userspace thing, not a kernel thing, please solve it in userspace. greg k-h
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