linux-kernel - Re: [PATCH 10/12] selftests/mm: move uffd* routines from vm

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Message-ID: <ZHqU6j4PAzy7ene0@x1n>
Date:   Fri, 2 Jun 2023 21:18:34 -0400
From:   Peter Xu <peterx@...hat.com>
To:     John Hubbard <jhubbard@...dia.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        David Hildenbrand <david@...hat.com>,
        Shuah Khan <shuah@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>, linux-mm@...ck.org,
        linux-kselftest@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 10/12] selftests/mm: move uffd* routines from vm_util.c
 to uffd-common.c

On Fri, Jun 02, 2023 at 05:43:19PM -0700, John Hubbard wrote:
> On 6/2/23 15:52, John Hubbard wrote:
> > On 6/2/23 15:38, Peter Xu wrote:
> > ...
> > > > I think we're in agreement that we want to only include uffd-common.h
> > > > where it's actually required. Likewise with the uffd*() routines. So I
> > > > would like to still move this over, yes, just to have things in their
> > > > best-named location.
> > > 
> > > Sorry I didn't get it - e.g. I'm confused why we need to export
> > > uffd_test_ops into ksm unit test, it doesn't make much sense to me..
> > 
> > Oh, I see what you mean, finally. Yes. ksm should not need that.
> > 
> 
> ...whoops, correction, our very own David Hildenbrand recently made
> changes that contradict the claim that "ksm and uffd selftests are
> independent". In fact, ksm now *intentionally* depends upon uffd, as of
> commit 93fb70aa5904c ("selftests/vm: add KSM unmerge tests"), aha!
> 
> That added commit added a call to test_unmerge_uffd_wp(), to
> ksm_functional_tests.c .
> 
> So this needs to stay approximately as-is, it seems.

So I think it depends on what is "as-is" to me in the above sentence. :)

test_unmerge_uffd_wp() impled its own uffd ioctls, and it still doesn't use
any of uffd-common.h of now (e.g. uffd_test_ops).

IMHO if we want we can let test_unmerge_uffd_wp() reuse either
uffd_get_features(), uffd_open(), uffd_register() etc., but still all of
them are provided by vm_util.h not uffd-common.h for now, and that's
intended (vm_util.h can contain uffd helpers, or whatever helpers as long
as generic mm/ unit tests need).

We can even move wp_range() from uffd-common.[ch] into vm_utils.[ch], then
it can also share that (need to replace err(), that's uffd-common
specific).  Not necessary anything must be done in this series, though.

Thanks,

-- 
Peter Xu