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=-20.4 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT,USER_IN_DEF_DKIM_WL autolearn=unavailable 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 6292CC433DF for ; Tue, 18 Aug 2020 18:47:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3D47B206B5 for ; Tue, 18 Aug 2020 18:47:22 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="bQ/GzzWC" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726716AbgHRSrV (ORCPT ); Tue, 18 Aug 2020 14:47:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36438 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726552AbgHRSrP (ORCPT ); Tue, 18 Aug 2020 14:47:15 -0400 Received: from mail-qt1-x84a.google.com (mail-qt1-x84a.google.com [IPv6:2607:f8b0:4864:20::84a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4A7DFC061389 for ; Tue, 18 Aug 2020 11:47:15 -0700 (PDT) Received: by mail-qt1-x84a.google.com with SMTP id q7so15055470qtd.1 for ; Tue, 18 Aug 2020 11:47:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=gehHRqDo170D8ggpcqt5L8gyM4hpiP3lcUb1NEGWSW0=; b=bQ/GzzWCVMuhyt2laZU2VxcoEcEJ0awKHw177BB3iK9JBuhbMoqOMb55rEFzzispi4 ywbPZWNcaLgifIEPXSTOz563MWK+2uyPYoJ0xUHlueLw8MgtrLdr8wbNjMFUN+Or3S0P iFQIqxP58WduRybClJ8bhoc927M7lCiLlkV056WLQRc3mFjEth5caAjZwDkc0tSlDRK7 PR4W0wMOT8pAoPiyhV5ylKxZPeOSn9Qj6yms7eHC9/mfODiKNLp2EDPyQcC/1OlsvYma q9N9WYkzvVBiWbNQ07qYsS7ND29LTFcqHnC9eCJY4qJyPTjUgMP56T2G8gvL5L+zvWDx lx8g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=gehHRqDo170D8ggpcqt5L8gyM4hpiP3lcUb1NEGWSW0=; b=Xv6WCYgR3Ucae1yFQbYBY2/rOhQmourMSQAretUZXbu30VBHk598qleFjG/5d4sqCi ZaS4lBRo3eBqYNnlFtMiCzzrPnzzIMAnxgkHFqCWj8vPt5H3S+tNKhmjYr1nId5E/Yb0 csPjZZCWzmzPAoXdecJjyKODmwTII5fuTpXSqfgmtWZKkmOVtHL7ISk1SJdcOKfXtmGG 8JZFcXTkvrFMOG4Wbf+L07dELnAqg2LfnnDkDJLy2/efDYrlaBf3toKWgVMuLxJ4Ruqh d820eUZpfRnRToFlaGAJ8X5XxGnfCSd2HHTR6YMRG0MEFMww3qYhNxZR2htVvOEVTFZt ojXg== X-Gm-Message-State: AOAM532qrF0xrfsZLJ+2FeYuEusj0LNhszFfpjms9eY8zpmSEjbypaMR kxbK7ai3sDhQcr84Fv2bZgdCyYYMRYg= X-Google-Smtp-Source: ABdhPJyX7PxrdwZp8JKMZ0YQglNCQFusxUHnYaz351dVMOTyN3ebFvNOcxIaiSUrRohWV46bcjlxOvwE/VU= X-Received: by 2002:ad4:54c6:: with SMTP id j6mr20694395qvx.126.1597776433446; Tue, 18 Aug 2020 11:47:13 -0700 (PDT) Date: Tue, 18 Aug 2020 12:47:03 -0600 In-Reply-To: <20200818184704.3625199-1-yuzhao@google.com> Message-Id: <20200818184704.3625199-2-yuzhao@google.com> Mime-Version: 1.0 References: <20200818184704.3625199-1-yuzhao@google.com> X-Mailer: git-send-email 2.28.0.220.ged08abb693-goog Subject: [PATCH v2 2/3] mm: remove superfluous __ClearPageActive() From: Yu Zhao To: Andrew Morton Cc: Alexander Duyck , Huang Ying , David Hildenbrand , Michal Hocko , Yang Shi , Qian Cai , Mel Gorman , Nicholas Piggin , "=?UTF-8?q?J=C3=A9r=C3=B4me=20Glisse?=" , Hugh Dickins , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Joonsoo Kim , Yu Zhao Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org To activate a page, mark_page_accessed() always holds a reference on it. It either gets a new reference when adding a page to lru_pvecs.activate_page or reuses an existing one it previously got when it added a page to lru_pvecs.lru_add. So it doesn't call SetPageActive() on a page that doesn't have any reference left. Therefore, the race is impossible these days (I didn't brother to dig into its history). For other paths, namely reclaim and migration, a reference count is always held while calling SetPageActive() on a page. SetPageSlabPfmemalloc() also uses SetPageActive(), but it's irrelevant to LRU pages. Signed-off-by: Yu Zhao --- mm/memremap.c | 2 -- mm/swap.c | 2 -- 2 files changed, 4 deletions(-) diff --git a/mm/memremap.c b/mm/memremap.c index 03e38b7a38f1..3a06eb91cb59 100644 --- a/mm/memremap.c +++ b/mm/memremap.c @@ -451,8 +451,6 @@ void free_devmap_managed_page(struct page *page) return; } - /* Clear Active bit in case of parallel mark_page_accessed */ - __ClearPageActive(page); __ClearPageWaiters(page); mem_cgroup_uncharge(page); diff --git a/mm/swap.c b/mm/swap.c index 25c4043491b3..999a84dbe12c 100644 --- a/mm/swap.c +++ b/mm/swap.c @@ -900,8 +900,6 @@ void release_pages(struct page **pages, int nr) del_page_from_lru_list(page, lruvec, page_off_lru(page)); } - /* Clear Active bit in case of parallel mark_page_accessed */ - __ClearPageActive(page); __ClearPageWaiters(page); list_add(&page->lru, &pages_to_free); -- 2.28.0.220.ged08abb693-goog