From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932268AbeCDTqs (ORCPT ); Sun, 4 Mar 2018 14:46:48 -0500 Received: from pegase1.c-s.fr ([93.17.236.30]:2096 "EHLO pegase1.c-s.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932090AbeCDTqq (ORCPT ); Sun, 4 Mar 2018 14:46:46 -0500 Subject: Re: [PATCH 05/21] powerpc: Avoid comparison of unsigned long >= 0 in pfn_valid To: Michael Ellerman , Mathieu Malaterre Cc: linux-kernel@vger.kernel.org, Paul Mackerras , Jiri Slaby , linuxppc-dev@lists.ozlabs.org References: <20180225172236.29650-1-malat@debian.org> <20180225172236.29650-6-malat@debian.org> <87lgf8gley.fsf@concordia.ellerman.id.au> From: christophe leroy Message-ID: <8be155ab-ec2c-2b1e-89a2-02f8e9f0d0ba@c-s.fr> Date: Sun, 4 Mar 2018 20:46:44 +0100 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <87lgf8gley.fsf@concordia.ellerman.id.au> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: fr Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Le 04/03/2018 à 11:55, Michael Ellerman a écrit : > 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. > The following seems to give a good result: diff --git a/arch/powerpc/include/asm/page.h b/arch/powerpc/include/asm/page.h index 8da5d4c1cab2..6f74938483b7 100644 --- a/arch/powerpc/include/asm/page.h +++ b/arch/powerpc/include/asm/page.h @@ -126,7 +126,15 @@ 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) +#ifndef __ASSEMBLY__ +extern unsigned long max_mapnr; +static inline bool pfn_valid(unsigned long pfn) +{ + unsigned long min_pfn = ARCH_PFN_OFFSET; + + return pfn >= min_pfn && pfn < max_mapnr; +} +#endif #endif #define virt_to_pfn(kaddr) (__pa(kaddr) >> PAGE_SHIFT) Christophe --- L'absence de virus dans ce courrier électronique a été vérifiée par le logiciel antivirus Avast. https://www.avast.com/antivirus