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    SubjectRe: [PATCH 1/3] [RFC] genhd: add a new attribute in device structure
    (2011/06/19 4:55), Kay Sievers wrote:
    > On Sat, Jun 18, 2011 at 21:40, James Bottomley
    > <James.Bottomley@hansenpartnership.com> wrote:
    >> On Fri, 2011-06-17 at 09:22 -0700, Greg KH wrote:
    >>> On Fri, Jun 17, 2011 at 06:12:14PM +0200, Kay Sievers wrote:
    >>>> On Fri, Jun 17, 2011 at 17:39, Kay Sievers <kay.sievers@vrfy.org> wrote:
    >>>>> On Fri, Jun 17, 2011 at 16:49, James Bottomley
    >>>>
    >>>>>> So this is subsystem specific. For the case of a SCSI enclosure, I can
    >>>>>> answer that it's actually burned into the enclosure firmware. When you
    >>>>>> build an enclosure with labels, the label names are stored in a
    >>>>>> diagnostic page. We can actually interrogate the enclosure directly or
    >>>>>> use the ses driver to get these names mapped to current devices.
    >>>>>
    >>>>> To me this sounds like a nice name on top of the current bunch of
    >>>>> names, not like a 'preferred' name.
    >>>>>
    >>>>> I still don't like to introduce any new facility to the kernel that
    >>>>> can handle only one single name. Reality the last years has taught us
    >>>>> a very different story, and we've walked a long way to get where we
    >>>>> are. I really don't believe single names will ever work, it's just a
    >>>>> nice theory.
    >>>>
    >>>> I might need to clarify this a bit.
    >>>>
    >>>> I have no problem in general to add a 'alias' to every disk, and use
    >>>> that when stuff is logged. Just the same way the netifs have an alias.
    >>>> Sure, it might be useful for some use cases. And if that helps to
    >>>> solve any real problem, we should just do it.
    >>>>
    >>>> I just want to make clear, that I don't think that it is anywhere near
    >>>> to a solution for the problems which are described here. And that
    >>>> nobody should see this as an excuse not to get their stuff together
    >>>> and work on the problem, which is that we don't have machine-readable
    >>>> error and debug from the kernel and a smart syslog.
    >>>>
    >>>> If we had that, I'm very sure nobody would even ask for a 'pretty
    >>>> name' in the kernel, and I think that is a good indication that we are
    >>>> not on the right track here.
    >>>
    >>> And I totally agree here, which is why I don't want to accept this
    >>> change to the driver core to add this, as it's not the correct solution.
    >>
    >> OK, fine ... we'll do it as gendisk only then. I suppose that is the
    >> 95% use case anyway.
    >
    > Sounds fine. It's probably easier to have it domain-specific anyway.
    > Just like the netif alias already is.
    >

    Agreed. Our purpose is to output disk's alias name in kernel messages.

    > I would suggest not to call it 'preferred' though, but something
    > similar to 'alias'. Having /dev/disk/by-preferred/ doesn't sound too
    > convincing to me.
    >

    OK, I will change 'preferred name' to 'alias name'.

    > An 'change' uevent when the alias is set sounds fine. I don't think a
    > set-once policy is needed.
    >

    I will intent to implement as follows
    - Change the name from preferred to alias
    - Add alias_name in gendisk
    - Notify 'change' uevent when the alias is set

    Thanks,

    --
    Nao NISHIJIMA
    Software Platform Research Dept. Linux Technology Center
    Hitachi, Ltd., YOKOHAMA Research Laboratory
    Email: nao.nishijima.xt@hitachi.com
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