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 X-Spam-Level: X-Spam-Status: No, score=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E9679C433B4 for ; Wed, 5 May 2021 01:33:43 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 949E7613EB for ; Wed, 5 May 2021 01:33:43 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 949E7613EB Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id A84AC8D0019; Tue, 4 May 2021 21:33:42 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id A37A18D0003; Tue, 4 May 2021 21:33:42 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 78AEC8D0019; Tue, 4 May 2021 21:33:42 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0138.hostedemail.com [216.40.44.138]) by kanga.kvack.org (Postfix) with ESMTP id 572938D0003 for ; Tue, 4 May 2021 21:33:42 -0400 (EDT) Received: from smtpin13.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 0A8C1A748 for ; Wed, 5 May 2021 01:33:42 +0000 (UTC) X-FDA: 78105455484.13.38CEFEF Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf08.hostedemail.com (Postfix) with ESMTP id 2F16C80192D4 for ; Wed, 5 May 2021 01:33:17 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id B6D55613E6; Wed, 5 May 2021 01:33:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1620178421; bh=qhUMRVT/49jl9eWLaOUD10MbkJOnzko9+kILXv0BAdU=; h=Date:From:To:Subject:In-Reply-To:From; b=1wO45tL60CRDQqpYjHiqmQaLonvXT6l+FAhuh6MDsi3cKms3peO72PAECrrDN2UCb d5ALF43RNlGqnrBR6sZz5c/TayT1VEndwRMZ7Zz5IFACuE3ecczXbE7akJCVRMtl2c 6YhjfZDiaekAu6n9SZevhG6oDWB4htYWZSZy/7Ko= Date: Tue, 04 May 2021 18:33:40 -0700 From: Andrew Morton To: akpm@linux-foundation.org, dan.carpenter@oracle.com, ebru.akagunduz@gmail.com, kirill.shutemov@linux.intel.com, linmiaohe@huawei.com, linux-mm@kvack.org, mike.kravetz@oracle.com, mm-commits@vger.kernel.org, riel@redhat.com, torvalds@linux-foundation.org Subject: [patch 018/143] khugepaged: reuse the smp_wmb() inside __SetPageUptodate() Message-ID: <20210505013340.loNVXx15X%akpm@linux-foundation.org> In-Reply-To: <20210504183219.a3cc46aee4013d77402276c5@linux-foundation.org> User-Agent: s-nail v14.8.16 X-Rspamd-Queue-Id: 2F16C80192D4 Authentication-Results: imf08.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=1wO45tL6; dmarc=none; spf=pass (imf08.hostedemail.com: domain of akpm@linux-foundation.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org X-Rspamd-Server: rspam04 X-Stat-Signature: gadiinayosionf8q5p7fts673ap9s4h4 Received-SPF: none (linux-foundation.org>: No applicable sender policy available) receiver=imf08; identity=mailfrom; envelope-from=""; helo=mail.kernel.org; client-ip=198.145.29.99 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1620178397-236561 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: From: Miaohe Lin Subject: khugepaged: reuse the smp_wmb() inside __SetPageUptodate() smp_wmb() is needed to avoid the copy_huge_page writes to become visible after the set_pmd_at() write here. But we can reuse the smp_wmb() inside __SetPageUptodate() to remove this redundant one. Link: https://lkml.kernel.org/r/20210306032947.35921-3-linmiaohe@huawei.com Signed-off-by: Miaohe Lin Acked-by: Kirill A. Shutemov Cc: Dan Carpenter Cc: Ebru Akagunduz Cc: Mike Kravetz Cc: Rik van Riel Signed-off-by: Andrew Morton --- mm/khugepaged.c | 13 ++++++------- 1 file changed, 6 insertions(+), 7 deletions(-) --- a/mm/khugepaged.c~khugepaged-reuse-the-smp_wmb-inside-__setpageuptodate +++ a/mm/khugepaged.c @@ -1183,19 +1183,18 @@ static void collapse_huge_page(struct mm __collapse_huge_page_copy(pte, new_page, vma, address, pte_ptl, &compound_pagelist); pte_unmap(pte); + /* + * spin_lock() below is not the equivalent of smp_wmb(), but + * the smp_wmb() inside __SetPageUptodate() can be reused to + * avoid the copy_huge_page writes to become visible after + * the set_pmd_at() write. + */ __SetPageUptodate(new_page); pgtable = pmd_pgtable(_pmd); _pmd = mk_huge_pmd(new_page, vma->vm_page_prot); _pmd = maybe_pmd_mkwrite(pmd_mkdirty(_pmd), vma); - /* - * spin_lock() below is not the equivalent of smp_wmb(), so - * this is needed to avoid the copy_huge_page writes to become - * visible after the set_pmd_at() write. - */ - smp_wmb(); - spin_lock(pmd_ptl); BUG_ON(!pmd_none(*pmd)); page_add_new_anon_rmap(new_page, vma, address, true); _