From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C3348C433F5 for ; Sun, 8 May 2022 13:09:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233062AbiEHNNV (ORCPT ); Sun, 8 May 2022 09:13:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50930 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233114AbiEHNNP (ORCPT ); Sun, 8 May 2022 09:13:15 -0400 Received: from out30-132.freemail.mail.aliyun.com (out30-132.freemail.mail.aliyun.com [115.124.30.132]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 10CA338F; Sun, 8 May 2022 06:09:22 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R121e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04394;MF=baolin.wang@linux.alibaba.com;NM=1;PH=DS;RN=31;SR=0;TI=SMTPD_---0VCaceu-_1652015354; Received: from 30.15.195.77(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0VCaceu-_1652015354) by smtp.aliyun-inc.com(127.0.0.1); Sun, 08 May 2022 21:09:16 +0800 Message-ID: Date: Sun, 8 May 2022 21:09:55 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.8.1 Subject: Re: [PATCH v2 1/3] mm: change huge_ptep_clear_flush() to return the original pte To: Muchun Song Cc: akpm@linux-foundation.org, mike.kravetz@oracle.com, catalin.marinas@arm.com, will@kernel.org, tsbogend@alpha.franken.de, James.Bottomley@HansenPartnership.com, deller@gmx.de, mpe@ellerman.id.au, benh@kernel.crashing.org, paulus@samba.org, hca@linux.ibm.com, gor@linux.ibm.com, agordeev@linux.ibm.com, borntraeger@linux.ibm.com, svens@linux.ibm.com, ysato@users.sourceforge.jp, dalias@libc.org, davem@davemloft.net, arnd@arndb.de, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-ia64@vger.kernel.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org References: <012a484019e7ad77c39deab0af52a6755d8438c8.1652002221.git.baolin.wang@linux.alibaba.com> From: Baolin Wang In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 5/8/2022 7:09 PM, Muchun Song wrote: > On Sun, May 08, 2022 at 05:36:39PM +0800, Baolin Wang wrote: >> It is incorrect to use ptep_clear_flush() to nuke a hugetlb page >> table when unmapping or migrating a hugetlb page, and will change >> to use huge_ptep_clear_flush() instead in the following patches. >> >> So this is a preparation patch, which changes the huge_ptep_clear_flush() >> to return the original pte to help to nuke a hugetlb page table. >> >> Signed-off-by: Baolin Wang >> Acked-by: Mike Kravetz > > Reviewed-by: Muchun Song Thanks for reviewing. > > But one nit below: > > [...] >> diff --git a/mm/hugetlb.c b/mm/hugetlb.c >> index 8605d7e..61a21af 100644 >> --- a/mm/hugetlb.c >> +++ b/mm/hugetlb.c >> @@ -5342,7 +5342,7 @@ static vm_fault_t hugetlb_wp(struct mm_struct *mm, struct vm_area_struct *vma, >> ClearHPageRestoreReserve(new_page); >> >> /* Break COW or unshare */ >> - huge_ptep_clear_flush(vma, haddr, ptep); >> + (void)huge_ptep_clear_flush(vma, haddr, ptep); > > Why add a "(void)" here? Is there any warning if no "(void)"? > IIUC, I think we can remove this, right? I did not meet any warning without the casting, but this is per Mike's comment[1] to make the code consistent with other functions casting to void type explicitly in hugetlb.c file. [1] https://lore.kernel.org/all/495c4ebe-a5b4-afb6-4cb0-956c1b18d0cc@oracle.com/