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[198.145.29.99]) by mx.google.com with ESMTPS id w186si7379142pgd.48.2019.07.02.13.54.19 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 02 Jul 2019 13:54:19 -0700 (PDT) Received-SPF: pass (google.com: domain of akpm@linux-foundation.org designates 198.145.29.99 as permitted sender) client-ip=198.145.29.99; Authentication-Results: mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b="NJc3a/ai"; spf=pass (google.com: domain of akpm@linux-foundation.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org Received: from akpm3.svl.corp.google.com (unknown [104.133.8.65]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 3344D20673; Tue, 2 Jul 2019 20:54:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1562100859; bh=rVBWY9NKk3peUyI1EC9GF70mJHGF/edO4QPbzMYTAPs=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=NJc3a/aiBmbIeNeNSP0XS9Oba/camnFTOL9hqC8zm7j1dF2QBonphwxy7DsLeJtYF taFkYBHmMv1mufJj2/5bJblCqD5zSvM01FR3QX6HWCg5fFJ3YTOzltXbwqPlS9VVVr MZDir0n73svKaPTv20CmYRaLCPorogn8uUu9W1GY= Date: Tue, 2 Jul 2019 13:54:18 -0700 From: Andrew Morton To: Guenter Roeck Cc: linux-mm@kvack.org, Stephen Rothwell , Robin Murphy , linux-kernel@vger.kernel.org, "Kirill A. Shutemov" Subject: Re: [PATCH -next] mm: Mark undo_dev_pagemap as __maybe_unused Message-Id: <20190702135418.ce51c988e88ca0d9546a2a11@linux-foundation.org> In-Reply-To: <1562072523-22311-1-git-send-email-linux@roeck-us.net> References: <1562072523-22311-1-git-send-email-linux@roeck-us.net> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, 2 Jul 2019 06:02:03 -0700 Guenter Roeck wrote: > Several mips builds generate the following build warning. > > mm/gup.c:1788:13: warning: 'undo_dev_pagemap' defined but not used > > The function is declared unconditionally but only called from behind > various ifdefs. Mark it __maybe_unused. > > ... > > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -1785,7 +1785,8 @@ static inline pte_t gup_get_pte(pte_t *ptep) > } > #endif /* CONFIG_GUP_GET_PTE_LOW_HIGH */ > > -static void undo_dev_pagemap(int *nr, int nr_start, struct page **pages) > +static void __maybe_unused undo_dev_pagemap(int *nr, int nr_start, > + struct page **pages) > { > while ((*nr) - nr_start) { > struct page *page = pages[--(*nr)]; It's not our preferred way of doing it but yes, it would be a bit of a mess and a bit of a maintenance burden to get the ifdefs correct. And really, __maybe_unused isn't a bad way at all - it ensures that the function always gets build-tested and the compiler will remove it so we don't have to play the chase-the-ifdefs game.