From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757530Ab1KUWXn (ORCPT ); Mon, 21 Nov 2011 17:23:43 -0500 Received: from mail-gy0-f174.google.com ([209.85.160.174]:61451 "EHLO mail-gy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752645Ab1KUWXj (ORCPT ); Mon, 21 Nov 2011 17:23:39 -0500 Message-ID: <4ECACF68.3020701@gmail.com> Date: Mon, 21 Nov 2011 14:23:36 -0800 From: David Daney User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.15) Gecko/20101027 Fedora/3.0.10-1.fc12 Thunderbird/3.0.10 MIME-Version: 1.0 To: David Rientjes , Andrew Morton , Linus Torvalds CC: linux-mips@linux-mips.org, ralf@linux-mips.org, linux-kernel@vger.kernel.org, David Daney , linux-arch@vger.kernel.org, Robin Holt Subject: Re: [patch] hugetlb: remove dummy definitions of HPAGE_MASK and HPAGE_SIZE References: <1321567050-13197-1-git-send-email-ddaney.cavm@gmail.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Linus, It may not have been evident when you committed this (commit a5c86e986f0b2fe779f13cf53ce6e9f467b03950), but there was considerable discussion around this patch. Andrew had taken into his tree a couple of patches to make the definitions that David Rientjes is removing safer: http://marc.info/?l=linux-kernel&m=132156712623915&w=2 http://marc.info/?l=linux-kernel&m=132156712523914&w=2 David objected, but Andrew wasn't convinced, see all the replies to this patch but especially: http://marc.info/?l=linux-kernel&m=132157428626522&w=2 On 11/17/2011 03:22 PM, David Rientjes wrote: > Dummy, non-zero definitions for HPAGE_MASK and HPAGE_SIZE were added in > 51c6f666fceb ("mm: ZAP_BLOCK causes redundant work") to avoid a divide > by zero in generic kernel code. > > That code has since been removed, but probably should never have been > added in the first place: we don't want HPAGE_SIZE to act like PAGE_SIZE > for code that is working with hugepages, for example, when the dependency > on CONFIG_HUGETLB_PAGE has not been fulfilled. > > Because hugepage size can differ from architecture to architecture, each > is required to have their own definitions for both HPAGE_MASK and > HPAGE_SIZE. This is always done in arch/*/include/asm/page.h. > > So, just remove the dummy and dangerous definitions since they are no > longer needed and reveals the correct dependencies. Tested on > architectures using the definitions with allyesconfig: x86 (even with > thp), hppa, mips, powerpc, s390, sh3, sh4, sparc, and sparc64, and > with defconfig on ia64. > This whole comment strikes me as somewhat dishonest, as at the time David Rientjes wrote it, he knew that there were dependencies on these symbols in the linux-next tree. Now we can add these: +#define HPAGE_SHIFT ({ BUG(); 0; }) +#define HPAGE_SIZE ({ BUG(); 0; }) +#define HPAGE_MASK ({ BUG(); 0; }) To the different architecture header files instead of having them in the common include/linux/hugetlb.h If this is the way Linus wants it, I can live with that. But it was a little surprising to see that this was merged when there were strong arguments against it. David Daney > Cc: Robin Holt > Cc: David Daney > Signed-off-by: David Rientjes > --- > include/linux/hugetlb.h | 5 ----- > 1 files changed, 0 insertions(+), 5 deletions(-) > > diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h > --- a/include/linux/hugetlb.h > +++ b/include/linux/hugetlb.h > @@ -110,11 +110,6 @@ static inline void copy_huge_page(struct page *dst, struct page *src) > > #define hugetlb_change_protection(vma, address, end, newprot) > > -#ifndef HPAGE_MASK > -#define HPAGE_MASK PAGE_MASK /* Keep the compiler happy */ > -#define HPAGE_SIZE PAGE_SIZE > -#endif > - > #endif /* !CONFIG_HUGETLB_PAGE */ > > #define HUGETLB_ANON_FILE "anon_hugepage" >