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=-9.6 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS 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 D0383C433DF for ; Wed, 19 Aug 2020 23:05:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AD34B20758 for ; Wed, 19 Aug 2020 23:05:03 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="qZSmHS4s" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727070AbgHSXFC (ORCPT ); Wed, 19 Aug 2020 19:05:02 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45662 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726342AbgHSXFB (ORCPT ); Wed, 19 Aug 2020 19:05:01 -0400 Received: from mail-ed1-x544.google.com (mail-ed1-x544.google.com [IPv6:2a00:1450:4864:20::544]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 64A8EC061757 for ; Wed, 19 Aug 2020 16:05:00 -0700 (PDT) Received: by mail-ed1-x544.google.com with SMTP id a14so159573edx.7 for ; Wed, 19 Aug 2020 16:05:00 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=bvQtPoZORjN9LSo3BZs0SVbBGr5W+CxKyp0VPJwa6A0=; b=qZSmHS4sO/ZGrvttBIvLzipAMFOquz4Zqw/AkbbrSiWDp8ebhZEbNsRun+QLs5RzW8 UuH/zowE2waML75yRWyD/AOgYN40Drg+zRIQSRShMZFpBK3H5qrK2kh0s83hutMOss4e Cbe2ToHcwoLyp3LrwRMu2LGsi13u2yFkYIVn6f97+HIxEz8PCSep0YfvOfUooGBdrvrZ ETdyv60upWe7lFEs3UkKfoWgT654paG3bZFFK0yUmDDQZiSwjatyrECNt/g4kRoHCSon mJybiLctGWBfWSuAHBMvbwGDSK2GwP+OJXr/SyBMrO3IeKBmczF5ULQmADr8T2oUr8f7 rX5Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=bvQtPoZORjN9LSo3BZs0SVbBGr5W+CxKyp0VPJwa6A0=; b=ZfA7QoESxXn0pBkPqJNruar64YGhAREsuie3VZ03pN3OfdGyJUdArczLoVDMB3g4N9 FFIJFMIh4i7hGY46CS5PJ3Q0c/QijXEQ7D/J2oth4MsF+2LNukssR3GRNxYGCbumTO6L WBL1pbTAefVXU+UM1UGVQmzF5iZnnDTfX7INULwg2K+YkoS1Bum66nm98ct847M/dZbL YTbl52EIHtQcNVEfYjH31CAarOarriGOGeXQGBizWRbONF5l+h1+6pONvW6/DlahFYU4 QhxJJjIc5lPJBg6eiyCw127CaHVZB+eOn5fSUyo3wLAi9yLwTVtnofgsssc2FA39agA3 nujQ== X-Gm-Message-State: AOAM532MpAiJ+iRuusSnBW4rD5r7Sl7K+6MLAKgR/VKCNP+46j0xVsmi 8Ozl026aTYTEkDiGFrvASTUn35+BgcroO8Il624= X-Google-Smtp-Source: ABdhPJxRbtnGrPQQXQAlbTTU4Qe7MeN3M0rqgblk7edh9EXRmGlfvOQtZOOznLOoNL/71rRzYI6Gj1NgnkVHOWPrJvY= X-Received: by 2002:a50:e844:: with SMTP id k4mr279877edn.237.1597878299120; Wed, 19 Aug 2020 16:04:59 -0700 (PDT) MIME-Version: 1.0 References: <20200818184704.3625199-1-yuzhao@google.com> <20200818184704.3625199-2-yuzhao@google.com> In-Reply-To: <20200818184704.3625199-2-yuzhao@google.com> From: Yang Shi Date: Wed, 19 Aug 2020 16:04:47 -0700 Message-ID: Subject: Re: [PATCH v2 2/3] mm: remove superfluous __ClearPageActive() To: Yu Zhao Cc: Andrew Morton , Alexander Duyck , Huang Ying , David Hildenbrand , Michal Hocko , Yang Shi , Qian Cai , Mel Gorman , Nicholas Piggin , =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= , Hugh Dickins , Linux MM , Linux Kernel Mailing List , Joonsoo Kim 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 On Tue, Aug 18, 2020 at 11:47 AM Yu Zhao wrote: > > 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. Seems fine to me. Reviewed-by: Yang Shi > > 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 > >