Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752823AbcLHRvQ convert rfc822-to-8bit (ORCPT ); Thu, 8 Dec 2016 12:51:16 -0500 Received: from blatinox.fr ([51.254.120.209]:55007 "EHLO vps202351.ovh.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752013AbcLHRvP (ORCPT ); Thu, 8 Dec 2016 12:51:15 -0500 Date: Thu, 8 Dec 2016 12:51:10 -0500 From: =?UTF-8?B?SsOpcsOpbXk=?= Lefaure To: Borislav Petkov Cc: x86@kernel.org, "Kirill A. Shutemov" , linux-kernel@vger.kernel.org Subject: Re: [PATCH] x86/vm86: fix compilation warning on a unused variable Message-ID: <20161208125110.7c17ab83@blatinox-arch> In-Reply-To: <20161208083305.lczvpdi56xwac2gw@pd.tnic> References: <20161208043833.15088-1-jeremy.lefaure@lse.epita.fr> <20161208083305.lczvpdi56xwac2gw@pd.tnic> X-Mailer: Claws Mail 3.14.0-64-g1117a0 (GTK+ 2.24.31; x86_64-unknown-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1790 Lines: 46 On Thu, 8 Dec 2016 09:33:05 +0100 Borislav Petkov wrote: > On Wed, Dec 07, 2016 at 11:38:33PM -0500, Jérémy Lefaure wrote: > > When CONFIG_TRANSPARENT_HUGEPAGE is disabled, split_huge_pmd is a no-op > > stub. In such case, vma is unused and a compiler raises a warning: > > > > arch/x86/kernel/vm86_32.c: In function ‘mark_screen_rdonly’: > > arch/x86/kernel/vm86_32.c:180:26: warning: unused variable ‘vma’ > > [-Wunused-variable] > > struct vm_area_struct *vma = find_vma(mm, 0xA0000); > > ^~~ > > Adding __maybe_unused in the vma declaration fixes this warning. > > > > In addition, checking if CONFIG_TRANSPARENT_HUGEPAGE is enabled avoids > > calling find_vma function for nothing. > > > > Signed-off-by: Jérémy Lefaure > > --- > > arch/x86/kernel/vm86_32.c | 5 +++-- > > 1 file changed, 3 insertions(+), 2 deletions(-) > > > > diff --git a/arch/x86/kernel/vm86_32.c b/arch/x86/kernel/vm86_32.c > > index 01f30e5..0813b76 100644 > > --- a/arch/x86/kernel/vm86_32.c > > +++ b/arch/x86/kernel/vm86_32.c > > @@ -176,8 +176,9 @@ static void mark_screen_rdonly(struct mm_struct *mm) > > goto out; > > pmd = pmd_offset(pud, 0xA0000); > > > > - if (pmd_trans_huge(*pmd)) { > > - struct vm_area_struct *vma = find_vma(mm, 0xA0000); > > + if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && pmd_trans_huge(*pmd)) { > > + struct vm_area_struct __maybe_unused *vma = find_vma(mm, > > + 0xA0000); > > So wouldn't the __maybe_unused alone without changing the if-condition > fix the warning too? > Yes it will. I did not see that pmd_trans_huge returns 0 if CONFIG_TRANSPARENT_HUGEPAGE is disabled. So you're right, the IS_ENABLED(...) in the condition is useless. Thanks, Jérémy