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=-26.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,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 42B16C433DB for ; Sat, 13 Mar 2021 07:59:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 11CED64ECE for ; Sat, 13 Mar 2021 07:59:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233237AbhCMH6e (ORCPT ); Sat, 13 Mar 2021 02:58:34 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58944 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230349AbhCMH56 (ORCPT ); Sat, 13 Mar 2021 02:57:58 -0500 Received: from mail-yb1-xb49.google.com (mail-yb1-xb49.google.com [IPv6:2607:f8b0:4864:20::b49]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7B7EAC061574 for ; Fri, 12 Mar 2021 23:57:58 -0800 (PST) Received: by mail-yb1-xb49.google.com with SMTP id d8so32058455ybs.11 for ; Fri, 12 Mar 2021 23:57:58 -0800 (PST) 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=CiMQJrfmhcT/Xw28mTP3VlU5SRPV8bRsC232LNJk7tU=; b=U+bvs2P4aWZrWqfRwrXFunM/l5sWGKqRdiGQFJBSXwSH+vfw4kB3WjkPPQpoUgHwwx +4KITrOtke32as1JFmSOW/QJ8GYL6J2CyqtNZysfNDnr4dUu1eafFf0OU/BN2PlR6TZw u/bOTirXcAreUn8QrcDvxRKbQwugJdk2JWl2TqDc7KAmb0AodFb/pAgQnWip2QOqWta3 5ohqe66l196K6u9PNyDcJqEzz4CuJBMkGEAupVYjzX/HNuFZ1kLz2lz2FxSR38TqyX8I aWFk3lMppRkLaWpnC4nC3SQhZcJq9YOxrujTA4BSnsEwscy7qJzgt8w9xEMiwzmAoN1g Bm1Q== 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=CiMQJrfmhcT/Xw28mTP3VlU5SRPV8bRsC232LNJk7tU=; b=Qi2PdmMPthJWQMXSQ05Fb8upxFWwOHNAFsy8LixbQ0QGPKWVlwBzQDYwPCpG05WFP8 cYIfPhq3nv9++78Y1Pw7Q8oiGEv7KJ0j/sHIaRZGlWZdHWwciPpKdT9M4JVXYhn4NxhF 6YrPBHSTOTN7v9fuCOcPqKSOKTBYMF/eETj9XoeqtvetJVZ1i3Dqxu4TawWOlymnTTkh 9IQRnTz2ffdTJdBCH6iTA0UfrEDWDnESubVvzuRfmLvCt3b427gwHWXaK/i7F/60+65O 8gzoqIJ9gqwTfdGB3vB6HXtbmWosQ39Zy7gnpTpf0CB7afg1Gnx/4Y26GMLjtLkzeviQ 6K7w== X-Gm-Message-State: AOAM531kmbzmJE5p9rtDGXbRHYBSsGjPyFJxoBPqsQzAq6DHfRzY/is2 Lgnmsa+bse/YLa5M+1JDlGqGCZxMntQ= X-Google-Smtp-Source: ABdhPJxUTV3MKesWpiHjP1OfC2lc1y93+U3j9zDFMK1igY41oF3Fyu2enmEiwR5c1z6fz0Ykw1sgyEJETNk= X-Received: from yuzhao.bld.corp.google.com ([2620:15c:183:200:f931:d3e4:faa0:4f74]) (user=yuzhao job=sendgmr) by 2002:a25:dfd1:: with SMTP id w200mr24182984ybg.362.1615622277472; Fri, 12 Mar 2021 23:57:57 -0800 (PST) Date: Sat, 13 Mar 2021 00:57:34 -0700 In-Reply-To: <20210313075747.3781593-1-yuzhao@google.com> Message-Id: <20210313075747.3781593-2-yuzhao@google.com> Mime-Version: 1.0 References: <20210313075747.3781593-1-yuzhao@google.com> X-Mailer: git-send-email 2.31.0.rc2.261.g7f71774620-goog Subject: [PATCH v1 01/14] include/linux/memcontrol.h: do not warn in page_memcg_rcu() if !CONFIG_MEMCG From: Yu Zhao To: linux-mm@kvack.org Cc: Alex Shi , Andrew Morton , Dave Hansen , Hillf Danton , Johannes Weiner , Joonsoo Kim , Matthew Wilcox , Mel Gorman , Michal Hocko , Roman Gushchin , Vlastimil Babka , Wei Yang , Yang Shi , Ying Huang , linux-kernel@vger.kernel.org, page-reclaim@google.com, Yu Zhao Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Archived-At: List-Archive: List-Post: We want to make sure the rcu lock is held while using page_memcg_rcu(). But having a WARN_ON_ONCE() in page_memcg_rcu() when !CONFIG_MEMCG is superfluous because of the following legit use case: memcg = lock_page_memcg(page1) (rcu_read_lock() if CONFIG_MEMCG=y) do something to page1 if (page_memcg_rcu(page2) == memcg) do something to page2 too as it cannot be migrated away from the memcg either. unlock_page_memcg(page1) (rcu_read_unlock() if CONFIG_MEMCG=y) This patch removes the WARN_ON_ONCE() from page_memcg_rcu() for the !CONFIG_MEMCG case. Signed-off-by: Yu Zhao --- include/linux/memcontrol.h | 1 - 1 file changed, 1 deletion(-) diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index e6dc793d587d..f325aeb4b4e8 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -1079,7 +1079,6 @@ static inline struct mem_cgroup *page_memcg(struct page *page) static inline struct mem_cgroup *page_memcg_rcu(struct page *page) { - WARN_ON_ONCE(!rcu_read_lock_held()); return NULL; } -- 2.31.0.rc2.261.g7f71774620-goog