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    SubjectRe: [patch] as-iosched divide by zero fix


    Robert Love wrote:

    >On Wed, 2003-06-11 at 17:24, Andrew Morton wrote:
    >
    >
    >>Do you know what the actual oops is?
    >>
    >
    >I got it all figured out now.
    >
    >It is a divide by zero in update_write_batch() called from
    >as_completed_request().
    >
    >
    >>Odd that starting the X server triggers it. Be interesting if your patch
    >>fixes things for Brian.
    >>
    >
    >I reproduced it without X.
    >
    >The divide by zero is on line 959 with the divide by 'write_time'. It
    >can obviously be zero (see line 950). The divide by 'batch' on line 953
    >seems safe.
    >
    >The correct patch is below.
    >

    Probably put in the other check to be on the safe side.
    And can the check be if (!write_time || (batch / write_time > 2)

    >
    >
    >Most important question: why are only some of us seeing this?
    >

    It would occur if a write batch didn't take any jiffies, which
    isn't very likely. The HZ=100 change probbly brought it out.
    Thanks guys.


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