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    SubjectRe: CTL_UNNUMBERED (Re: [PATCH] 9p: Don't use binary sysctl numbers.)
    On Sat, Jul 21, 2007 at 04:36:03PM -0600, Eric W. Biederman wrote:
    > Alexey Dobriyan <adobriyan@gmail.com> writes:
    > > That's separate patch but CTL_UNNUMBERED must die, because it's totally
    > > unneeded. If you don't want sysctl(2) interface just SKIP ->ctl_name
    > > initialization and save one line for something useful.

    [9p and .ctl_name]

    > Now to the issue of using CTL_UNNUMBERED versus knowing that the magic
    > value is zero and we can just leave it uninitialized. I don't much
    > care but given how often people who are not actively watching this
    > mess up I tend to prefer the explicit value.

    mmm, from my own experience the quickest way to add sysctl to kernel is
    to _copy_ from other place and tweak variable name and string itself.
    I'm sure that's what evebody is doing.

    And once you're copy-pasting, existence of CTL_UNNUMBERED or absence of
    it doesn't matter. Propagating of CTL_UNNUMBERED or empty .ctl_name
    depends entirely on the place from where you're copy-pasting.

    And since it doesn't matter, we'd better save one line :)

    > It is a practical
    > question of how do we get the word out that we should not expand the
    > binary interface anymore.

    Article on LWN, scary comment near struct ctl_table::ctl_name, tree-wide
    removal .ctl_name initializers, periodic grepping of -mm and -rc diffs.
    I promise to grep next -mm patch and submit CTL_UNNUMBERED removal :)

    > The only really practical way I can see us doing better then we are
    > today is to have a separate tree that maps binary numbers into ascii
    > strings and so we remove the ctl_name field entirely from ctl_table.

    Not sure how to do this cleanly and without flag-day. And it's
    additional code.

    > That way people attempting to assign binary numbers using old
    > conventions will have code that doesn't even compile, and the
    > developers themselves are more likely to spot the problem.

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