linux-kernel - Re: [PATCH] lib/div64: off by one in shift

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Message-Id: <20190128094503.19e9f2ae0b286f7b1f743d70@linux-foundation.org>
Date:   Mon, 28 Jan 2019 09:45:03 -0800
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Stanislaw Gruszka <sgruszka@...hat.com>
Cc:     linux-kernel@...r.kernel.org, Oleg Nesterov <oleg@...hat.com>,
        Brian Behlendorf <behlendorf1@...l.gov>,
        Siarhei Volkau <lis8215@...il.com>
Subject: Re: [PATCH] lib/div64: off by one in shift

On Mon, 28 Jan 2019 15:49:04 +0100 Stanislaw Gruszka <sgruszka@...hat.com> wrote:

> fls counts bits starting from 1 to 32 (returns 0 for zero argument).
> If we add 1 we shift right one bit more and loose precision from
> divisor, what cause function incorect results with some numbers.
> 
> Corrected code was tested in user-space, see bugzilla:
> https://bugzilla.kernel.org/show_bug.cgi?id=202391

What are the usersoace-visible runtime effects of this change?

Thanks.