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=-3.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS 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 8FF3BC43382 for ; Thu, 27 Sep 2018 15:59:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CED3F21571 for ; Thu, 27 Sep 2018 15:59:48 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=ehuk.net header.i=@ehuk.net header.b="Yplx7gBg" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CED3F21571 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ehuk.net Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728263AbeI0WSm (ORCPT ); Thu, 27 Sep 2018 18:18:42 -0400 Received: from schatzi.steelbluetech.co.uk ([92.63.139.240]:20293 "EHLO schatzi.steelbluetech.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727262AbeI0WSl (ORCPT ); Thu, 27 Sep 2018 18:18:41 -0400 X-Greylist: delayed 400 seconds by postgrey-1.27 at vger.kernel.org; Thu, 27 Sep 2018 18:18:41 EDT Received: from [10.0.5.25] (tv.ehuk.net [10.0.5.25]) by schatzi.steelbluetech.co.uk (Postfix) with ESMTP id 38930BFD9D; Thu, 27 Sep 2018 16:53:07 +0100 (BST) DKIM-Filter: OpenDKIM Filter v2.10.3 schatzi.steelbluetech.co.uk 38930BFD9D DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ehuk.net; s=default; t=1538063587; bh=WNEFfHpCfyRzcbusg4oaXRZRRFlQ4V1L/pGtXbDijko=; h=Subject:To:Cc:References:From:Reply-To:Date:In-Reply-To:From; b=Yplx7gBgq+WvL/cmCZ+hWrQoa1cPMGXTDGswt/yPq7c2qIWhZaFim/nZYYtQQUkHb UwqVKDSxcFDiVi9tUlnqEHCKN6JKcS7cqKRD9xQb0tDE/lfAYbziNBPUNxTTyaM2U/ 8genTI1YdA2YHv2WC0K+Cvxc9SS8ppLiI3nVEHiY= Subject: Re: [PATCH] bcache: add separate workqueue for journal_write to avoid deadlock To: Coly Li , guoju Cc: kent.overstreet@gmail.com, linux-bcache@vger.kernel.org, linux-kernel@vger.kernel.org References: <1538055919-5757-1-git-send-email-fangguoju@gmail.com> From: Eddie Chapman Reply-To: Eddie Chapman Message-ID: <9b1abe65-c6f5-77b4-290e-e6af21723cfc@ehuk.net> Date: Thu, 27 Sep 2018 16:53:06 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 27/09/18 16:23, Coly Li wrote: > > On 9/27/18 9:45 PM, guoju wrote: >> After write SSD completed, bcache schedule journal_write work to >> system_wq, that is a public workqueue in system, without WQ_MEM_RECLAIM >> flag. system_wq is also a bound wq, and there may be no idle kworker on >> current processor. Creating a new kworker may unfortunately need to >> reclaim memory first, by shrinking cache and slab used by vfs, which >> depends on bcache device. That's a deadlock. >> >> This patch create a new workqueue for journal_write with WQ_MEM_RECLAIM >> flag. It's rescuer thread will work to avoid the deadlock. >> >> Signed-off-by: guoju > > Nice catch, this fix is quite important. I will try to submit to Jens ASAP. > > Thanks. > > Coly Li Once this goes into 4.19, would this be a candidate for backporting to any stable kernels, or does it only fix something introduced in this cycle? thanks, Eddie