Re: [PATCH]: jiffies wrap in ll_rw_blk.c

[Olivier Galibert]

On Wed, Nov 20, 2002 at 09:19:33PM +0000, 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

Signed vs. unsigned is actually irrelevant in two-complement systems
as long as you don't compare.  Only the int/long issue has an actual
effect.

  OG.