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    SubjectRe: Network namespaces a path to mergable code.
    On Wed, Jun 28, 2006 at 09:22:40PM +0400, Andrey Savochkin wrote:
    > Hi Eric,
    > On Wed, Jun 28, 2006 at 10:51:26AM -0600, Eric W. Biederman wrote:
    > > Andrey Savochkin <> writes:
    > >
    > > > One possible option to resolve this question is to show 2
    > > > relatively short patches just introducing namespaces for sockets
    > > > in 2 ways: with explicit function parameters and using implicit
    > > > current context. Then people can compare them and vote. Do you
    > > > think it's worth the effort?
    > >
    > > Given that we have two strong opinions in different directions I
    > > think it is worth the effort to resolve this.
    > Do you have time to extract necessary parts of your old patch? Or you
    > aren't afraid of letting me draft an alternative version of socket
    > namespaces basing on your code? :)
    > > In a slightly different vein your second patch introduced a lot of
    > > #ifdef CONFIG_NET_NS in C files. That is something we need to look
    > > closely at.
    > >
    > > So I think the abstraction that we use to access per network
    > > namespace variables needs some work if we are going to allow the
    > > ability to compile out all of the namespace code. The explicit
    > > versus implicit lookup is just one dimension of that problem.
    > This is a good comment.
    > Those ifdef's mostly correspond to places where we walk over lists and
    > need to filter-out entities not belonging to a specific namespace.
    > Those places about the same in your and my implementation. We can
    > think what we can do with them. One trick that I used on several
    > occasions is net_ns_same macro which doesn't evalute its arguments if
    > CONFIG_NET_NS not defined, and thus can be used without ifdef's.

    yes, I think almost all of those cases can be avoided
    while making the code even more readable by using
    proper preprocessor (or even inline) mechanisms

    > Returning to implicit vs explicit function arguments, I belive that
    > implicit arguments are more promising in having zero impact on the
    > code when CONFIG_NET_NS is disabled. Functions like inet_addr_type
    > will translate into exactly the same code as they did without net
    > namespace patches.

    maybe a preprocessor wrapper can help here too ...

    > > >> I'm still curious why many of those chunks can't use existing helper
    > > >> functions, to be cleaned up.
    > > >
    > > > What helper functions are you referring to?
    > >
    > > Basically most of the device list walker functions live in.
    > > net/core/dev.c
    > >
    > > I don't know if the cases you fixed could have used any of those
    > > helper functions but it certainly has me asking that question.
    > >
    > > A general pattern that happens in cleanups is the discovery
    > > that code using an old interface in a problematic way really
    > > could be done much better another way. I didn't dig enough
    > > to see if that was the case in any of the code that you changed.
    > Well, there is obvious improvement of this kind: many protocols walk
    > over device list to find devices with non-NULL protocol specific
    > pointers. For example, IPv6, decnet and others do it on module
    > unloading to clean up. Those places just ask for some simpler standard
    > way of doing it, but I wasn't bold enough for such radical change.

    > Do you think I should try?

    IMHO it could not hurt to have some kind of protocol
    helper library functions or macros ...


    > Best regards
    > Andrey
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