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    SubjectRe: [PATCH] Traffic control cgroups subsystem
    On Wed, Jul 23, 2008 at 3:34 PM, Patrick McHardy <kaber@trash.net> wrote:
    > Andrew Morton wrote:
    >>
    >> On Tue, 22 Jul 2008 10:44:18 -0700 (PDT)
    >> Ranjit Manomohan <ranjitm@google.com> wrote:
    >>
    >>> @@ -359,7 +370,12 @@ static int flow_classify(struct sk_buff *skb, struct
    >>> tcf_proto *tp,
    >>> classid %= f->divisor;
    >>>
    >>> res->class = 0;
    >>> - res->classid = TC_H_MAKE(f->baseclass, f->baseclass +
    >>> classid);
    >>> +
    >>> + if (key == FLOW_KEY_CGROUP_CLASSID)
    >>> + res->classid = TC_H_MAKE(f->baseclass, classid);
    >>> + else
    >>> + res->classid = TC_H_MAKE(f->baseclass,
    >>> + f->baseclass + classid);
    >>
    >> This causes a warning:
    >>
    >> net/sched/cls_flow.c: In function 'flow_classify':
    >> net/sched/cls_flow.c:344: warning: 'key' may be used uninitialized in this
    >> function
    >>
    >> that warning is a non-issue if we happen to know that f->nkeys can
    >> never be zero. I don't know if that is guaranteed at this code site?
    >
    > It is by the flow_change() function, but special casing the
    > CGROUP_CLASSID is not acceptable anyway. There should be no
    > need for that, a simple linear mapping to classids is done
    > by default in mapping mode, the sk_cgroup_classid simply
    > shouldn't include qdisc IDs.

    I did not want to special case it but I want an identity mapping not a
    linear one. For some reason a baseclass of X:0 is not allowed, and
    there does not seem to be a clean way to get a 1-1 mapping (tc.classid
    -> X:tc.classid). I would have to workaround it by using a baseclass
    of the form X:Y and then subtracting Y from the value written to
    tc.classid which seemed very non intuitive.

    Any particular reason for this restriction? Am I missing any other
    technique of getting a 1-1 mapping using the flow classifier?

    -Thanks,
    Ranjit

    >


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