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=-3.8 required=3.0 tests=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 BF065C43382 for ; Thu, 27 Sep 2018 20:19:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3D9C3216C4 for ; Thu, 27 Sep 2018 20:19:00 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3D9C3216C4 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=profihost.ag 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 S1728529AbeI1Ci6 (ORCPT ); Thu, 27 Sep 2018 22:38:58 -0400 Received: from cloud1-vm154.de-nserver.de ([178.250.10.56]:21045 "EHLO cloud1-vm154.de-nserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727265AbeI1Ci6 (ORCPT ); Thu, 27 Sep 2018 22:38:58 -0400 Received: (qmail 23768 invoked from network); 27 Sep 2018 22:18:56 +0200 X-Fcrdns: No Received: from phoffice.de-nserver.de (HELO [10.242.2.3]) (185.39.223.5) (smtp-auth username hostmaster@profihost.com, mechanism plain) by cloud1-vm154.de-nserver.de (qpsmtpd/0.92) with (ECDHE-RSA-AES256-GCM-SHA384 encrypted) ESMTPSA; Thu, 27 Sep 2018 22:18:56 +0200 From: Stefan Priebe - Profihost AG Subject: [PATCH] bcache: add separate workqueue for journal_write to avoid deadlock To: Eddie Chapman Cc: Coly Li , guoju , kent.overstreet@gmail.com, linux-bcache@vger.kernel.org, linux-kernel@vger.kernel.org References: <1538055919-5757-1-git-send-email-fangguoju@gmail.com> <9b1abe65-c6f5-77b4-290e-e6af21723cfc@ehuk.net> Message-ID: Date: Thu, 27 Sep 2018 22:18:55 +0200 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: <9b1abe65-c6f5-77b4-290e-e6af21723cfc@ehuk.net> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: de-DE X-User-Auth: Auth by hostmaster@profihost.com through 185.39.223.5 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Coly, is this the deadlock I reported some weeks ago? Greets, Stefan Excuse my typo sent from my mobile phone. Am 27.09.2018 um 17:53 schrieb Eddie Chapman >: > 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