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=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no 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 66BBDC3A5A6 for ; Fri, 30 Aug 2019 15:49:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3CA4923428 for ; Fri, 30 Aug 2019 15:49:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1567180166; bh=nXSVc79MwADtvMh03MpKMbHC0zBWv30zWalqSvd2N88=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=t9rLMKozAx++AnJh28sRHWgsivtcsBwSn5V4dsl/E59+rnOeYVuDhf8deFoPi4z6r I44oYQ5TzQFUfqPhxTDC0P6QUpPjz/czfR6lLuMXCJqwGgkQg9qM0MFfLsH0pBH/ei MOvxYCoW6wbjNvrp/yBjERHbv23LiuQR9ovoGmg4= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728176AbfH3PtZ (ORCPT ); Fri, 30 Aug 2019 11:49:25 -0400 Received: from mail-qt1-f196.google.com ([209.85.160.196]:43964 "EHLO mail-qt1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727304AbfH3PtZ (ORCPT ); Fri, 30 Aug 2019 11:49:25 -0400 Received: by mail-qt1-f196.google.com with SMTP id b11so8052706qtp.10; Fri, 30 Aug 2019 08:49:24 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=EWG1xprHq5soDnqsOoV5sXd5YRcA3js3J4A3/q6CGlU=; b=Wgqj8hYGo0A/I1gghmpb6uViT1RJgL5Ci/oQGuwImhV3JUnrMed5W6Api9CJ4JKZmb jY/ufazdF5ggWnW70uWNMlWT1cKToe11F9WFbdSXajVHeyCRRXDzkotHY3xf9VDEyA7A JQD4yjvtNO20WNyKTLvfU88pTkfrk+FZ+BIdC9xtrc/qTUdY1cOmUC5IhhdbwCJTm9eD I/znZT9RBs31QbkRncZVHi5g8UE2o2JQDMWWxc1jXx3BISZ4D3lq4/F14jhTzfMfOpih 8isdIRt9jNllkKjnRdMIH7l4sV1Gojj5gdUHbt0KActpBD/L3fu/QUTTMOuteCilHqth G4sw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to:user-agent; bh=EWG1xprHq5soDnqsOoV5sXd5YRcA3js3J4A3/q6CGlU=; b=Yz+XfjDcGp+BsuDUxQQOFhUYRz+8+sfctyuk7or5hB1KR5DAwoGRWtMZa1+8naKzBa j7uA8Bdw3evI5uvyLP1YddIAtO9THfhKTARSQco8GTOB3VuP5130LjTkQOFCeYC6SmUR GJ6OCOZeazi046lq2/5n8FX8gR2UCDOfMt8VxTinAdeBki3acwFUAcGt2U0+qbC2QSgp lNXZmga8BJo8qmkR+nywe2EwRP9SwlWZFAoISKULUEgKniDuJDMtbsvkc7bGH3dEUeBA knB7+8IBtGistFEaM0EIvfQejQk8uHNYRSVRR+c9notF/B8P7HVjh+kRFSO9CIbYZMdZ kKsQ== X-Gm-Message-State: APjAAAWhTAA1O8LYLs2Xd5YPBxgkLUuHX8cZiyFSUfDAbOTZNP1mXCwZ A+LHax2PCuLIUPi621o9iOM= X-Google-Smtp-Source: APXvYqyFRZU9QBAkzb28H9Q+R/5xB+7uaYqUf2sCiz0G9RGsOQcoyI03rNeLOsDzNUFbov3MavZYTQ== X-Received: by 2002:ac8:363c:: with SMTP id m57mr9461040qtb.240.1567180163904; Fri, 30 Aug 2019 08:49:23 -0700 (PDT) Received: from localhost ([2620:10d:c091:480::d0dd]) by smtp.gmail.com with ESMTPSA id y67sm2965672qkd.40.2019.08.30.08.49.23 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 30 Aug 2019 08:49:23 -0700 (PDT) Date: Fri, 30 Aug 2019 08:49:21 -0700 From: Tejun Heo To: Jan Kara Cc: Jens Axboe , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH block/for-next] writeback: add tracepoints for cgroup foreign writebacks Message-ID: <20190830154921.GZ2263813@devbig004.ftw2.facebook.com> References: <20190829224701.GX2263813@devbig004.ftw2.facebook.com> <20190830154023.GC25069@quack2.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190830154023.GC25069@quack2.suse.cz> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, Jan. On Fri, Aug 30, 2019 at 05:40:23PM +0200, Jan Kara wrote: > > + TP_fast_assign( > > + strncpy(__entry->name, dev_name(wb->bdi->dev), 32); > > + __entry->bdi_id = wb->bdi->id; > > + __entry->ino = page->mapping->host->i_ino; > > + __entry->memcg_id = wb->memcg_css->id; > > + __entry->cgroup_ino = __trace_wb_assign_cgroup(wb); > > + __entry->page_cgroup_ino = page->mem_cgroup->css.cgroup->kn->id.ino; > > + ), > > Are the page dereferences above safe? I suppose lock_page_memcg() protects > the page->mem_cgroup->css.cgroup->kn->id dereference? But page->mapping > does not seem to be protected by page lock? Hah, I assumed it would work because there are preceding if (page_mapping()) tests in the dirty paths - e.g. __set_page_dirty_nobuffers(). Oh, regardless of that assumption, I should have used page_mapping(). Thanks. -- tejun