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=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. > 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. Since this is completely based on user's choice/decision, no one will complain about that. >> 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! > Yes, of course. I'd like to fix those commands to accept preferred names. > 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. > 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 > > Same as #3. > 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. > > 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. > 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. > > 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? > 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=="block", ENV{ID_SERIAL}=="scsi-SATA_WDC_WD5000AAKS-_WD-WCASY6088049", SYMLINK+="disk/by-preferred/foo", PROGRAM=”write_preferred_name %p foo” To access a device from by-preferred persistently, I create new symbolic 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. > 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, -- Nao NISHIJIMA Software Platform Research Dept. Linux Technology Center Hitachi, Ltd., YOKOHAMA Research Laboratory Email： nao.nishijima.xt@xxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
