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 B98A5C43462 for ; Tue, 13 Apr 2021 06:56:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9970A613D1 for ; Tue, 13 Apr 2021 06:56:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S245186AbhDMG5J (ORCPT ); Tue, 13 Apr 2021 02:57:09 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44138 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242333AbhDMG5C (ORCPT ); Tue, 13 Apr 2021 02:57:02 -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 28542C061574 for ; Mon, 12 Apr 2021 23:56:43 -0700 (PDT) Received: by mail-yb1-xb4a.google.com with SMTP id i2so15393704ybl.21 for ; Mon, 12 Apr 2021 23:56:43 -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=uoN+cWnulcs+MZz6Yfoth7IiX8iwaSm44WY0GAxt+Q4=; b=Ky/g/4nTpvE6H1kNq4Im8vCSVqJJWgdY64updRqr3NGODL/gY7XSLNlMuXa/Yqagpg 8h8aUIGoWcm6zgtJI5Fw5fMN+PJDxOQb+W3x0OLBhrQ+nOe/aDQ/DaNsTpFLgKXpBR7/ Nvvw4ruE5Db9uCII9HC5YVMWkv6n0oPwKqmHcIgXqyJRfj6NX9MMyHBXVjqP883hb1k1 Uts/76AmsciIF0vpEK2WDi/7DTKQWJN38NKXgOIJgZwI3uctZHJ221m0qvGUkZ8xVQ8M LJm2bY+K9olC9c50QyUPY+bxF/x11l+o56tHmajIr/WsoQoJ64e/eJ6Tpi1C0nsUQsqW HHBQ== 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=uoN+cWnulcs+MZz6Yfoth7IiX8iwaSm44WY0GAxt+Q4=; b=q4VjA6z3lTu7Y75EQkCaOUnGPrZr+a8VxIneVHg9KIy8GcVnTbV6azYx3iJlfN/mqY nM4GFUu6opNihX2CTE1sYviNzX90nlsf6Ip3WykacM0NVKoiD/02EGRPQvc0l3EE/8K0 43Y8NKqjqKspr7Tjz074a8EJrkBUqhaBpFzDGZwvcg5JCb19/+tTrjWSio3YSp1gtbA+ 8OB8fTMMZlhaH5pTQWlQnQM3YN8CNJBooHERVgByq78Q7xObvheM9tjTza0hz5coErNv aLMQMSIT87k3f7EWq0H6qOBAaxbbR8uChrhfVLanXWxhaw/G+ZI5csPO154ctl5A0+5/ Yc5g== X-Gm-Message-State: AOAM5311I++jOq9dpMAS7ctzsZDbqRUOtVWfMxjhdktZjjKeusU8mSAv AjoVQqVxKqAzXcw+CT2fcJSxxzNjPAU= X-Google-Smtp-Source: ABdhPJyfoyUlusz71TmeoRvttPw/GuUM1FYO9KnbxFJsUN5OFDqRz4J7wq87XkLveCWglWGJeEC6Et9cWvE= X-Received: from yuzhao.bld.corp.google.com ([2620:15c:183:200:d02d:cccc:9ebe:9fe9]) (user=yuzhao job=sendgmr) by 2002:a25:bb41:: with SMTP id b1mr41562657ybk.249.1618297002301; Mon, 12 Apr 2021 23:56:42 -0700 (PDT) Date: Tue, 13 Apr 2021 00:56:18 -0600 In-Reply-To: <20210413065633.2782273-1-yuzhao@google.com> Message-Id: <20210413065633.2782273-2-yuzhao@google.com> Mime-Version: 1.0 References: <20210413065633.2782273-1-yuzhao@google.com> X-Mailer: git-send-email 2.31.1.295.g9ea45b61b8-goog Subject: [PATCH v2 01/16] 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 , Andi Kleen , Andrew Morton , Benjamin Manes , Dave Chinner , Dave Hansen , Hillf Danton , Jens Axboe , Johannes Weiner , Jonathan Corbet , Joonsoo Kim , Matthew Wilcox , Mel Gorman , Miaohe Lin , Michael Larabel , Michal Hocko , Michel Lespinasse , Rik van Riel , Roman Gushchin , Rong Chen , SeongJae Park , Tim Chen , Vlastimil Babka , Yang Shi , Ying Huang , Zi Yan , linux-kernel@vger.kernel.org, lkp@lists.01.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: page_memcg_rcu() warns on !rcu_read_lock_held() regardless of CONFIG_MEMCG. The following code is legit, but it triggers the warning when !CONFIG_MEMCG, since lock_page_memcg() and unlock_page_memcg() are empty for this config. 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) Locking/unlocking rcu consistently for both configs is rigorous but it also forces unnecessary locking upon users who have no interest in CONFIG_MEMCG. This patch removes the assertion for !CONFIG_MEMCG, because page_memcg_rcu() has a few callers and there are no concerns regarding their correctness at the moment. 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 0c04d39a7967..f13dc02cf277 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -1077,7 +1077,6 @@ 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; } -- 2.31.1.295.g9ea45b61b8-goog