Re: [PATCH] staging: exfat: add exfat filesystem code to staging

Gao Xiang
2019-08-30T12:04:41Z

Hi Dan,

On Fri, Aug 30, 2019 at 02:26:12PM +0300, Dan Carpenter wrote:
> On Fri, Aug 30, 2019 at 04:43:33PM +0800, Gao Xiang wrote:
> > Hi Dan,
> >
> > On Fri, Aug 30, 2019 at 11:34:45AM +0300, Dan Carpenter wrote:
> > > On Fri, Aug 30, 2019 at 12:04:41AM +0800, Gao Xiang wrote:
> > > > Anyway, I'm fine to delete them all if you like, but I think majority of these
> > > > are meaningful.
> > > >
> > > > data.c- /* page is already locked */
> > > > data.c- DBG_BUGON(PageUptodate(page));
> > > > data.c-
> > > > data.c: if (unlikely(err))
> > > > data.c- SetPageError(page);
> > > > data.c- else
> > > > data.c- SetPageUptodate(page);
> > >
> > > If we cared about speed here then we would delete the DBG_BUGON() check
> > > because that's going to be expensive. The likely/unlikely annotations
> > > should be used in places a reasonable person thinks it will make a
> > > difference to benchmarks.
> >
> > DBG_BUGON will be a no-op ((void)x) in non-debugging mode,
>
> It expands to:
>
> ((void)PageUptodate(page));
>
> Calling PageUptodate() doesn't do anything, but it isn't free. The
> time it takes to do that function call completely negates any speed up
> from using likely/unlikely.
>
> I'm really not trying to be a jerk...

You are right, I recalled that PageUptodate is not as simple as it implys.
Yes, those are all removed now... I am ok with that,
thanks for your suggestion :)

Thanks,
Gao Xiang

>
> regards,
> dan carpenter
>