On Sun, 8 Apr 2018 06:12:13 +0300 "Michael S. Tsirkin" <m...@redhat.com> wrote:
> On Sat, Apr 07, 2018 at 01:08:43PM -0700, Linus Torvalds wrote:
> > On Thu, Apr 5, 2018 at 2:03 PM, Michael S. Tsirkin <m...@redhat.com> wrote:
> > >
> > > nr = get_user_pages_fast(addr, nr, gup->flags & 1, pages
> > > + i);
> > > - i += nr;
> > > + if (nr > 0)
> > > + i += nr;
> >
> > Can we just make this robust while at it, and just make it
> >
> > if (nr <= 0)
> > break;
> >
> > instead? Then it doesn't care about zero vs negative error, and
> > wouldn't get stuck in an endless loop if it got zero.
> >
> > Linus
>
> I don't mind though it alredy breaks out on the next cycle:
>
> if (nr != gup->nr_pages_per_call)
> break;
>
> the only issue is i getting corrupted when nr < 0;
>
It does help readability to have the thing bail out as soon as we see
something go bad. This?
--- a/mm/gup_benchmark.c~mm-gup_benchmark-handle-gup-failures-fix
+++ a/mm/gup_benchmark.c
@@ -41,8 +41,9 @@ static int __gup_benchmark_ioctl(unsigne
}
nr = get_user_pages_fast(addr, nr, gup->flags & 1, pages + i);
- if (nr > 0)
- i += nr;
+ if (nr <= 0)
+ break;
+ i += nr;
}
end_time = ktime_get();
_
