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    SubjectRe: [PATCH] writeback: prevent bandwidth calculation overflow
    On Fri, Nov 19, 2010 at 12:06:52AM +0800, Wu Fengguang wrote:
    > On Fri, Nov 19, 2010 at 12:02:01AM +0800, Peter Zijlstra wrote:
    > > On Thu, 2010-11-18 at 23:44 +0800, Wu Fengguang wrote:
    > > > + pause = HZ * pages_dirtied / (bw + 1);
    > >
    > > Shouldn't that be using something like div64_u64 ?
    >
    > OK, but a dumb question: gcc cannot handle this implicitly?

    Hmm, I'm tempting to do

    pause = HZ * pages_dirtied / ((unsigned long)bw + 1);

    because here "bw" is guaranteed to be smaller than ULONG_MAX.

    Thanks,
    Fengguang



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