linux-kernel - Re: [PATCH] xfs: Fix 64-bit division on 32-bit in xlog_state_switch

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Message-ID: <CAMuHMdWp3E3QDnbGDcTZsCiQNP3pLV2nXVmtOD7OEQO8P-9egQ@mail.gmail.com>
Date:   Fri, 11 Jun 2021 08:55:24 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Dave Chinner <david@...morbit.com>
Cc:     Dave Chinner <dchinner@...hat.com>,
        Chandan Babu R <chandanrlinux@...il.com>,
        "Darrick J . Wong" <djwong@...nel.org>,
        Allison Henderson <allison.henderson@...cle.com>,
        Christoph Hellwig <hch@....de>, linux-xfs@...r.kernel.org,
        Linux-Next <linux-next@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        noreply@...erman.id.au
Subject: Re: [PATCH] xfs: Fix 64-bit division on 32-bit in xlog_state_switch_iclogs()

Hi Dave,

On Fri, Jun 11, 2021 at 12:02 AM Dave Chinner <david@...morbit.com> wrote:
> On Thu, Jun 10, 2021 at 01:00:01PM +0200, Geert Uytterhoeven wrote:
> > On 32-bit (e.g. m68k):
> >
> >     ERROR: modpost: "__udivdi3" [fs/xfs/xfs.ko] undefined!
> >
> > Fix this by using a uint32_t intermediate, like before.
> >
> > Reported-by: noreply@...erman.id.au
> > Fixes: 7660a5b48fbef958 ("xfs: log stripe roundoff is a property of the log")
> > Signed-off-by: Geert Uytterhoeven <geert@...ux-m68k.org>
> > ---
> > Compile-tested only.
> > ---
> >  fs/xfs/xfs_log.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
>
> <sigh>
>
> 64 bit division on 32 bit platforms is still a problem in this day
> and age?

They're not a problem.  But you should use the right operations from
<linux/math64.h>, iff you really need these expensive operations.

> Reviewed-by: Dave Chinner <dchinner@...hat.com>

Thanks!

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds