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=-2.5 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 91D53C282C4 for ; Sat, 9 Feb 2019 13:52:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5C05921919 for ; Sat, 9 Feb 2019 13:52:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="ho854t0V" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726791AbfBINwf (ORCPT ); Sat, 9 Feb 2019 08:52:35 -0500 Received: from mail-wm1-f66.google.com ([209.85.128.66]:54628 "EHLO mail-wm1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726724AbfBINwf (ORCPT ); Sat, 9 Feb 2019 08:52:35 -0500 Received: by mail-wm1-f66.google.com with SMTP id a62so8493432wmh.4; Sat, 09 Feb 2019 05:52:34 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=a1FxRbJ08wKgp4Co0znQWeKyAEWRpt3r5CDQgl/lzA4=; b=ho854t0VeE6vkAj0xsMCBVg+GmgJHVfw5OjfuHOJNNggl2sV7EERA8YSfPVlbMvOI/ 8VfPfvbCOdKdg1UTWHM/i0jDat3tgSYv0ewqUWVbUABw4sOc26cXz78V1kDZdl0FeXcU fUUbDB73SdMwb9ZQit//tkf/yJmMy+BsmPYc5egWKEuM9+cJW5rYCz/vmSeWAyyx8Fsk hc27LyFIpXFFNT7f/0lYIbAdpujM488pot5HUf31+3kyX5gkm3JvloV91OtiSEWmXl4a S+ls75NLMEcJxwYPKh92JNiCRLHdMp4QjFpU7eGPGle1WxcJM7BvMOUeEOWjSkya9ZGO 1TGw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=a1FxRbJ08wKgp4Co0znQWeKyAEWRpt3r5CDQgl/lzA4=; b=t6BRZl1Q/YW3JS1badTRVLnueZPBU0w8U/1r7k/QExXkPggRGaler3vw/OcxU02XuK /eXpT3dq050t1wKPtUrSDDk1NUMtZ80dK+S4lBgkEuCX6/cc3eAP6wr6quD8BpOHISBU hvPo1l4l7uI27O6pUUmJqG+pM47nad8eUAi5o4h+kxATnXtJ2b8ytuC4U1m/b4w9zV2l w470QHq/hI2kk3OqQQ+K8yEBIXWTpiXoxk9EhNU3CFJ8TK/vAkxnt7SQVsTSbC9hjeiE fuiM8aR4eU8vcvSOUV8kuki3bPxrdz3GKY4SfKGgnLtXJpYcd+2xhKFqDRf+zaWcXmJ4 1fvA== X-Gm-Message-State: AHQUAua/5MdPPT2hLzzGPh/K+clJMOHdXIUFKbz+aAnhDhbZm5JO410w UiwTEjiSrZOynkGp6SNe5A== X-Google-Smtp-Source: AHgI3IYCGgyeMoumNCNf/hlgXlYmgnGoCIA2EAC1vCyg+s6hZ7Scw34UnmRgzD6RTx7omoGjVtJXAw== X-Received: by 2002:adf:9004:: with SMTP id h4mr13476386wrh.121.1549720353621; Sat, 09 Feb 2019 05:52:33 -0800 (PST) Received: from localhost ([95.238.120.247]) by smtp.gmail.com with ESMTPSA id r12sm6648362wrt.76.2019.02.09.05.52.32 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Sat, 09 Feb 2019 05:52:32 -0800 (PST) Date: Sat, 9 Feb 2019 14:52:31 +0100 From: Andrea Righi To: Josef Bacik Cc: Paolo Valente , Tejun Heo , Li Zefan , Johannes Weiner , Jens Axboe , Vivek Goyal , Dennis Zhou , cgroups@vger.kernel.org, linux-block@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH] blkcg: prevent priority inversion problem during sync() Message-ID: <20190209135231.GA1910@xps-13> References: <20190209120633.GA2506@xps-13> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190209120633.GA2506@xps-13> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Sat, Feb 09, 2019 at 01:06:33PM +0100, Andrea Righi wrote: ... > +/** > + * blkcg_wb_waiters_on_bdi - check for writeback waiters on a block device > + * @bdi: block device to check > + * > + * Return true if any other blkcg is waiting for writeback on the target block > + * device, false otherwise. > + */ > +bool blkcg_wb_waiters_on_bdi(struct backing_dev_info *bdi) > +{ > + struct blkcg *blkcg, *curr_blkcg; > + bool ret = false; > + > + if (unlikely(!bdi)) > + return false; > + > + rcu_read_lock(); > + curr_blkcg = css_to_blkcg(task_css(current, io_cgrp_id)); Sorry, the logic is messed up here. We shouldn't get curr_blkcg from the current task, because during writeback throttling the context is obviously not the current task. I'll post a new patch soon. > + list_for_each_entry_rcu(blkcg, &bdi->cgwb_waiters, cgwb_wait_node) > + if (blkcg != curr_blkcg) { > + ret = true; > + break; > + } > + rcu_read_unlock(); > + > + return ret; > +} -Andrea