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Date:   Tue, 11 Dec 2018 14:25:02 -0800 (PST)
From:   David Rientjes <rientjes@google.com>
To:     Arnd Bergmann <arnd@arndb.de>
cc:     =?UTF-8?Q?J=C3=A9r=C3=B4me_Glisse?= <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>
Subject: Re: [PATCH] mm/mmu_notifier: fix mmu_notifier_range_init warning
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On Tue, 11 Dec 2018, Arnd Bergmann 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.
> 

Isn't that separate?  It seems like there is a strict dependency that 
CONFIG_HUGETLBFS has on CONFIG_MMU_NOTIFIER.