From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752683AbeCDKzW convert rfc822-to-8bit (ORCPT ); Sun, 4 Mar 2018 05:55:22 -0500 Received: from ozlabs.org ([103.22.144.67]:55727 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932292AbeCDKzV (ORCPT ); Sun, 4 Mar 2018 05:55:21 -0500 Authentication-Results: ozlabs.org; dmarc=none (p=none dis=none) header.from=ellerman.id.au From: Michael Ellerman To: Mathieu Malaterre Cc: Benjamin Herrenschmidt , Paul Mackerras , Jiri Slaby , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, Mathieu Malaterre Subject: Re: [PATCH 05/21] powerpc: Avoid comparison of unsigned long >= 0 in pfn_valid In-Reply-To: <20180225172236.29650-6-malat@debian.org> References: <20180225172236.29650-1-malat@debian.org> <20180225172236.29650-6-malat@debian.org> Date: Sun, 04 Mar 2018 21:55:17 +1100 Message-ID: <87lgf8gley.fsf@concordia.ellerman.id.au> 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 Mathieu Malaterre writes: > Rewrite comparison since all values compared are of type `unsigned long`. > > Fix a warning (treated as error in W=1): > > CC arch/powerpc/kernel/irq.o > In file included from ./include/linux/bug.h:5:0, > from ./include/linux/cpumask.h:13, > from ./include/linux/smp.h:13, > from ./include/linux/kernel_stat.h:5, > from arch/powerpc/kernel/irq.c:35: > ./include/linux/dma-mapping.h: In function ‘dma_map_resource’: > ./arch/powerpc/include/asm/page.h:129:32: error: comparison of unsigned expression >= 0 is always true [-Werror=type-limits] > #define pfn_valid(pfn) ((pfn) >= ARCH_PFN_OFFSET && (pfn) < max_mapnr) > ^ > Suggested-by: Segher Boessenkool > Signed-off-by: Mathieu Malaterre > --- > arch/powerpc/include/asm/page.h | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/arch/powerpc/include/asm/page.h b/arch/powerpc/include/asm/page.h > index 8da5d4c1cab2..19dea64e7ed2 100644 > --- a/arch/powerpc/include/asm/page.h > +++ b/arch/powerpc/include/asm/page.h > @@ -126,7 +126,8 @@ extern long long virt_phys_offset; > > #ifdef CONFIG_FLATMEM > #define ARCH_PFN_OFFSET ((unsigned long)(MEMORY_START >> PAGE_SHIFT)) > -#define pfn_valid(pfn) ((pfn) >= ARCH_PFN_OFFSET && (pfn) < max_mapnr) > +#define pfn_valid(pfn) \ > + (((pfn) - ARCH_PFN_OFFSET) < (max_mapnr - ARCH_PFN_OFFSET)) I'm not a big fan of this one, because the original code is *far* more obvious as to what it's doing. I'm not sure if we can make this one a static inline, or whether that would help, but it would be worth investigating. cheers