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From:   Arnd Bergmann <arnd@arndb.de>
Date:   Tue, 11 Dec 2018 22:53:03 +0100
Message-ID: <CAK8P3a1yn7RAp7Q29dx5Rcb0mCoDpcHPzxSGqKHdgfJd+=iiNw@mail.gmail.com>
Subject: Re: [PATCH] mm/mmu_notifier: fix mmu_notifier_range_init warning
To:     David Rientjes <rientjes@google.com>
Cc:     =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= <jglisse@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Stephen Rothwell <sfr@canb.auug.org.au>,
        Michal Hocko <mhocko@suse.com>,
        Mike Rapoport <rppt@linux.vnet.ibm.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Tue, Dec 11, 2018 at 10:43 PM David Rientjes <rientjes@google.com> wrote:
>
> On Tue, 11 Dec 2018, Jerome Glisse wrote:

>
> Hmm, strange that Arnd's build failure is only reporting about an unused
> variable instead of MMU_NOTIFY_CLEAR being undefined :/
>
> I think this should be done so that anybody using
> mmu_notifier_range_init() doesn't need to worry about the implications of
> *any* unused formal parameter as a result of how the #define is formed:

Your patch below is more or less what I tried at first, and that resulted
in another build failure for

mm/hugetlb.c:   mmu_notifier_range_init(&range, mm, start, end,
MMU_NOTIFY_CLEAR);
mm/hugetlb.c-   adjust_range_if_pmd_sharing_possible(vma,
&range.start, &range.end);

where range.end refers to a nonexisting member of range.

          Arnd