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=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 7B15CC433E0 for ; Thu, 4 Mar 2021 12:32:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 53BD664F1E for ; Thu, 4 Mar 2021 12:32:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240705AbhCDMbq (ORCPT ); Thu, 4 Mar 2021 07:31:46 -0500 Received: from szxga04-in.huawei.com ([45.249.212.190]:12692 "EHLO szxga04-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240726AbhCDMbc (ORCPT ); Thu, 4 Mar 2021 07:31:32 -0500 Received: from DGGEMS413-HUB.china.huawei.com (unknown [172.30.72.59]) by szxga04-in.huawei.com (SkyGuard) with ESMTP id 4Drqsh5BZLzlShH; Thu, 4 Mar 2021 20:28:40 +0800 (CST) Received: from huawei.com (10.175.104.175) by DGGEMS413-HUB.china.huawei.com (10.3.19.213) with Microsoft SMTP Server id 14.3.498.0; Thu, 4 Mar 2021 20:30:40 +0800 From: Miaohe Lin To: CC: , , , , , , Subject: [PATCH 2/5] khugepaged: reuse the smp_wmb() inside __SetPageUptodate() Date: Thu, 4 Mar 2021 07:30:10 -0500 Message-ID: <20210304123013.23560-3-linmiaohe@huawei.com> X-Mailer: git-send-email 2.19.1 In-Reply-To: <20210304123013.23560-1-linmiaohe@huawei.com> References: <20210304123013.23560-1-linmiaohe@huawei.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7BIT Content-Type: text/plain; charset=US-ASCII X-Originating-IP: [10.175.104.175] X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Signed-off-by: Miaohe Lin --- mm/khugepaged.c | 13 ++++++------- 1 file changed, 6 insertions(+), 7 deletions(-) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index d43812c5ce16..287e7ecf978c 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1183,19 +1183,18 @@ static void collapse_huge_page(struct mm_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); -- 2.19.1