linux-kernel - Re: [RFC PATCH 2/8] mm/madvise: remove unnecessary check on madvise_dontneed

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Date:   Mon, 27 Sep 2021 05:52:12 -0700
From:   Nadav Amit <nadav.amit@...il.com>
To:     "Kirill A. Shutemov" <kirill@...temov.name>
Cc:     Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Peter Xu <peterx@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Minchan Kim <minchan@...nel.org>,
        Colin Cross <ccross@...gle.com>,
        Suren Baghdasarya <surenb@...gle.com>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>
Subject: Re: [RFC PATCH 2/8] mm/madvise: remove unnecessary check on
 madvise_dontneed_free()



> On Sep 27, 2021, at 5:19 AM, Kirill A. Shutemov <kirill@...temov.name> wrote:
> 
> On Mon, Sep 27, 2021 at 04:05:47AM -0700, Nadav Amit wrote:
>> Having said that, if you want, I can turn this condition into
>> WARN_ON_ONCE() or VM_BUG_ON(), although I really see no reason to
>> do so.
> 
> BUILD_BUG() should be fine here.

It does not work. At least my gcc is not smart enough to figure it
out in build time.

I can put instead:

	BUILD_BUG_ON(__builtin_constant_p(behavior));

for potentially smarter compilers (clang?), but I doubt it would work.