Hi Hannes, Thank you for looking at it. (2011/06/17 15:27), Hannes Reinecke wrote: > On 06/16/2011 07:20 PM, Kay Sievers wrote: >> On Thu, Jun 16, 2011 at 19:09, Kay Sievers<kay.sievers@xxxxxxxx> wrote: >>> On Thu, Jun 16, 2011 at 18:25, James Bottomley >>> <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> 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/<fred> which >>>>>> would be >>>>>> the usual symbolic link. >>>>> >>>>> No, udev can not create such a link after the preferred name is >>>>> set, 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, though, >>>> 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. We >> 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 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 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. > I know that there are several names for one device. Preferred name does not eliminate those names, but just add another pretty name. Usually those machine-generated names are too long and not familiar with users. preferred name will provide a human-readable name and reduce the operation cost. 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
