Re: [PATCH v2 5/8] selftests/mm: introduce helper to read every page in range

SeongJae Park
2026-01-13T00:55:38Z

On Mon, 12 Jan 2026 10:37:26 +0100 Kevin Brodsky <kevin.brodsky@arm.com> wrote:

> On 09/01/2026 02:30, SeongJae Park wrote:
> > On Wed, 7 Jan 2026 16:48:39 +0000 Kevin Brodsky <kevin.brodsky@arm.com> wrote:
> >
> >> FORCE_READ(*addr) ensures that the compiler will emit a load from
> >> addr. Several tests need to trigger such a load for every page in
> >> the range [addr, addr + len), ensuring that every page is faulted
> >> in, if it wasn't already.
> >>
> >> Introduce a new helper force_read_pages_in_range() that does exactly
> >> that and replace existing loops with a call to it.
> > Seems like a good cleanup to me.
>
> Thanks for having a look at this series!

My pleasure!

>
> >> Some of those
> >> loops have a different step size, but reading from every page is
> >> appropriate in all cases.
> > So the test program's behavior is slightly be changed. I believe that
> > shouldn't be problem, but I'm not that familiar with the test code, so not very
> > sure. I'd like to listen voices from people more familiar with those.
> >
> > Meanwhile, I'm curious what do you think about making the helper function
> > receives the step size together, and let the callers just pass their current
> > step size.
>
> That's what I initially considered, but considering this discussion on
> v1 [1] this doesn't seem to be justified. In hugetlb-madvise, reading
> every page instead of every hugepage is unnecessary but still correct
> and the overhead should be negligible. In split_huge_page_test, I don't
> think there's any justification for reading every byte - the intention
> is to fault in pages, like all the other cases this patch touches.
>
> - Kevin
>
> [1]
> https://lore.kernel.org/all/a3ca6293-8f85-4489-a48e-eb8d0d3792c5@kernel.org/

Makes sense, thank you for the link!

Please feel free to add

Reviewed-by: SeongJae Park <sj@kernel.org>

Thanks,
SJ …