From patchwork Sat Mar 6 03:29:45 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Miaohe Lin X-Patchwork-Id: 12119745 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 53733C433E0 for ; Sat, 6 Mar 2021 03:30:32 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id E04AD64FF2 for ; Sat, 6 Mar 2021 03:30:31 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E04AD64FF2 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=huawei.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 11E566B0078; Fri, 5 Mar 2021 22:30:30 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id F23006B0073; Fri, 5 Mar 2021 22:30:29 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C89EA6B0075; Fri, 5 Mar 2021 22:30:29 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0179.hostedemail.com [216.40.44.179]) by kanga.kvack.org (Postfix) with ESMTP id A53FE6B0072 for ; Fri, 5 Mar 2021 22:30:29 -0500 (EST) Received: from smtpin09.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 634418249980 for ; Sat, 6 Mar 2021 03:30:29 +0000 (UTC) X-FDA: 77888021778.09.F1D3AC2 Received: from szxga06-in.huawei.com (szxga06-in.huawei.com [45.249.212.32]) by imf10.hostedemail.com (Postfix) with ESMTP id A019D407F8DB for ; Sat, 6 Mar 2021 03:30:26 +0000 (UTC) Received: from DGGEMS413-HUB.china.huawei.com (unknown [172.30.72.59]) by szxga06-in.huawei.com (SkyGuard) with ESMTP id 4Dsqp457HZzjVCQ; Sat, 6 Mar 2021 11:29:00 +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; Sat, 6 Mar 2021 11:30:14 +0800 From: Miaohe Lin To: , CC: , , , , , Subject: [PATCH v2 2/4] khugepaged: reuse the smp_wmb() inside __SetPageUptodate() Date: Fri, 5 Mar 2021 22:29:45 -0500 Message-ID: <20210306032947.35921-3-linmiaohe@huawei.com> X-Mailer: git-send-email 2.19.1 In-Reply-To: <20210306032947.35921-1-linmiaohe@huawei.com> References: <20210306032947.35921-1-linmiaohe@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.175.104.175] X-CFilter-Loop: Reflected X-Stat-Signature: juh4bf7fmskdwbg5q4hbhhmpxj8ku9wo X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: A019D407F8DB Received-SPF: none (huawei.com>: No applicable sender policy available) receiver=imf10; identity=mailfrom; envelope-from=""; helo=szxga06-in.huawei.com; client-ip=45.249.212.32 X-HE-DKIM-Result: none/none X-HE-Tag: 1615001426-316509 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: 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 Acked-by: Kirill A. Shutemov --- 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);