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=-20.6 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=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 7860DC433DF for ; Wed, 12 Aug 2020 04:06:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 54D9220768 for ; Wed, 12 Aug 2020 04:06:10 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="PQ79oX9p" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726591AbgHLEGJ (ORCPT ); Wed, 12 Aug 2020 00:06:09 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35458 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725944AbgHLEGI (ORCPT ); Wed, 12 Aug 2020 00:06:08 -0400 Received: from mail-yb1-xb4a.google.com (mail-yb1-xb4a.google.com [IPv6:2607:f8b0:4864:20::b4a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CBA84C06174A for ; Tue, 11 Aug 2020 21:06:07 -0700 (PDT) Received: by mail-yb1-xb4a.google.com with SMTP id l13so1448929ybf.5 for ; Tue, 11 Aug 2020 21:06:07 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=reply-to:date:message-id:mime-version:subject:from:to:cc; bh=iTZlcV/HDVMBUj3vIm/BeqimkSAgE6ss1JTWwnLuV7w=; b=PQ79oX9ptj1DcJboGkk/u9/eQM7QFOR6pkv9sTiA01Hwr5+qHsW4r3uy0R08hjkTKp /CGVUpYvsZpiJSP2BZd8pHrisgM8KQ/93wShpsQgZewNcxXZtwvTJy3EZbNkz8elsegd NrNHbhn5UVyj8Ud8kqsD+vrD4izt8H0g0wlNhXYkSPW8zXa+KuWeLMUpzZM+0UKzVpqh MLwOcLIFz/2gLQcW1Eq51kH5i8/duG99bp7CxDzAxr3VucjSC6RJ65ntwLr7r2S/87wm dLFTWtK0LNRLAYYEzUx75mVivIuScTZ7ZR55V1k1A/+PdAjWzSy97ogq+Qz9S1n1k4KA tA2g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:reply-to:date:message-id:mime-version:subject :from:to:cc; bh=iTZlcV/HDVMBUj3vIm/BeqimkSAgE6ss1JTWwnLuV7w=; b=dWHJVTGUR9iptwKCyaLlk5eCAtefdRjkCCQR/wyxB4NLuXVFtaUvYv6n6hE3mQPcpL nPWvBJsGkYW3EfO3AyRzL3vvyzFAWLc938VSstHu0y/D5pjqrtagpYhy9PtP2qVmDI9r UeP8449+HtmKYndvQOExpVxmeDhiBjnFEELNjcGsXyRuvch1/a13EbVfDxwzSN4d+rJo qpLAu275N4it1CvH/9M+F4zPR3MgavyLvSZlAkHZW+0ta5aE2fNfkEWB/K8oYCWMMM9U WBujmOtst+yqFoAVvH1N3PVizLjHYpyxpG6WO4+l4jHC3c0YDWRWyvHGkIGVQBXZvP8h xFRQ== X-Gm-Message-State: AOAM5302lZctDa40UXKgvHLoHJsMs1OEWShyVHMSy1C7O0q2TCh9V9jH 00S/JoHtHD4R9qE56nZ0OEyLlHNaUhU= X-Google-Smtp-Source: ABdhPJzfk920y7QXdilL0gnKVShIBZWvJH75i46mC6Pu2Hx2kdFQ86wy4FJrpeAKB11/nSfL2M/Q++UqnJY= X-Received: by 2002:a25:bdc4:: with SMTP id g4mr52297610ybk.187.1597205166994; Tue, 11 Aug 2020 21:06:06 -0700 (PDT) Reply-To: <20200812040454.2708263-1-yuzhao@google.com> Date: Tue, 11 Aug 2020 22:05:50 -0600 Message-Id: <20200812040550.2708444-1-yuzhao@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.28.0.236.gb10cc79966-goog Subject: [PATCH 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, 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 can't call SetPageActive() on a page that doesn't have any reference left. Therefore, the race is impossible, not 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 de257c0a89b1..1f223a02549d 100644 --- a/mm/swap.c +++ b/mm/swap.c @@ -898,8 +898,6 @@ 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); -- 2.28.0.236.gb10cc79966-goog