On Sat, Aug 10, 2019 at 06:46:57AM -0700, Roopa Prabhu wrote:

On Fri, Aug 9, 2019 at 8:46 AM Michal Kubecek [off-list ref] wrote:

quoted

On Fri, Aug 09, 2019 at 08:40:25AM -0700, Roopa Prabhu wrote:

quoted

to that point, I am also not sure why we have a new API For multiple
names. I mean why support more than two names  (existing old name and
a new name to remove the length limitation) ?

One use case is to allow "predictable names" from udev/systemd to work
the way do for e.g. block devices, see

  http://lkml.kernel.org/r/20190628162716.GF29149@unicorn.suse.cz

thanks for the link. don't know the details about alternate block
device names. Does user-space generate multiple and assign them to a
kernel object as proposed in this series ?. is there a limit to number
of names ?. my understanding of 'predictable names' was still a single
name but predictable structure to the name.

It is a single name but IMHO mostly because we can only have one name.
For block devices, udev uses symlinks to create multiple aliases based
on different naming schemes, e.g.

mike@lion:~> find -L /dev/disk/ -samefile /dev/sda2 -exec ls -l {} +
lrwxrwxrwx 1 root root 10 srp  5 21:47 /dev/disk/by-id/ata-WDC_WD30EFRX-68AX9N0_WD-WMC1T3114933-part2 -> ../../sda2
lrwxrwxrwx 1 root root 10 srp  5 21:47 /dev/disk/by-id/scsi-SATA_WDC_WD30EFRX-68A_WD-WMC1T3114933-part2 -> ../../sda2
lrwxrwxrwx 1 root root 10 srp  5 21:47 /dev/disk/by-id/scsi-SATA_WDC_WD30EFRX-68_WD-WMC1T3114933-part2 -> ../../sda2
lrwxrwxrwx 1 root root 10 srp  5 21:47 /dev/disk/by-id/scsi-0ATA_WDC_WD30EFRX-68A_WD-WMC1T3114933-part2 -> ../../sda2
lrwxrwxrwx 1 root root 10 srp  5 21:47 /dev/disk/by-id/scsi-1ATA_WDC_WD30EFRX-68AX9N0_WD-WMC1T3114933-part2 -> ../../sda2
lrwxrwxrwx 1 root root 10 srp  5 21:47 /dev/disk/by-id/scsi-350014ee6589cfea0-part2 -> ../../sda2
lrwxrwxrwx 1 root root 10 srp  5 21:47 /dev/disk/by-id/wwn-0x50014ee6589cfea0-part2 -> ../../sda2
lrwxrwxrwx 1 root root 10 srp  5 21:47 /dev/disk/by-partlabel/root2 -> ../../sda2
lrwxrwxrwx 1 root root 10 srp  5 21:47 /dev/disk/by-partuuid/71affb47-a93b-40fd-8986-d2e227e1b39d -> ../../sda2
lrwxrwxrwx 1 root root 10 srp  5 21:47 /dev/disk/by-path/pci-0000:00:11.0-ata-1-part2 -> ../../sda2
lrwxrwxrwx 1 root root 10 srp  5 21:47 /dev/disk/by-path/pci-0000:00:11.0-scsi-0:0:0:0-part2 -> ../../sda2

Few years ago, udev even dropped support for renaming block and
character devices (NAME="...") so that it now keeps kernel name and only
creates symlinks to it. Recent versions only allow NAME="..." for
network devices.

Michal