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Date: Wed, 20 Nov 2002 16:00:44 -0500
From: Luben Tuikov <luben@splentec.com>
Organization: Splentec Ltd.
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To: Alan Cox <alan@lxorguk.ukuu.org.uk>
CC: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, axboe@suse.de
Subject: Re: [PATCH]: jiffies wrap in ll_rw_blk.c
References: <3DDBF413.C06DAF2E@splentec.com> <1037827173.3267.78.camel@irongate.swansea.linux.org.uk>
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Alan Cox wrote:
> 
> On Wed, 2002-11-20 at 20:44, Luben Tuikov wrote:
> > --- ll_rw_blk.c.old     Wed Nov 20 15:32:50 2002
> > +++ ll_rw_blk.c Wed Nov 20 15:33:06 2002
> > @@ -2092,7 +2092,7 @@
> >                 complete(req->waiting);
> >
> >         if (disk) {
> > -               unsigned long duration = jiffies - req->start_time;
> > +               unsigned long duration = (signed) jiffies - (signed) req->start_time;
> >                 switch (rq_data_dir(req)) {
> 
> It was right before. Your patch breaks it. Think about it in unsigned
> maths
> 
>               0x00000002 - 0xFFFFFFFF = 0x00000003

0x2 - (-0x1) = 0x2 + 0x1 = 0x3

Right! I thought (signed) does the job. I actually tried
it both ways and works all right. I guess either way works fine.

-- 
Luben
-
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