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=-2.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, 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 74BB3C282DA for ; Wed, 17 Apr 2019 19:33:12 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 31ED920835 for ; Wed, 17 Apr 2019 19:33:12 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="G+K/q8tG" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 31ED920835 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id BD98A6B000A; Wed, 17 Apr 2019 15:33:11 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id B874E6B000D; Wed, 17 Apr 2019 15:33:11 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A50836B000E; Wed, 17 Apr 2019 15:33:11 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from mail-qk1-f200.google.com (mail-qk1-f200.google.com [209.85.222.200]) by kanga.kvack.org (Postfix) with ESMTP id 833DA6B000A for ; Wed, 17 Apr 2019 15:33:11 -0400 (EDT) Received: by mail-qk1-f200.google.com with SMTP id y64so21814319qka.3 for ; Wed, 17 Apr 2019 12:33:11 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:dkim-signature:sender:date:from:to:cc:subject :message-id:references:mime-version:content-disposition:in-reply-to :user-agent; bh=DOvyhaD8UYdSm2Vgv7oMv8UKm8AtpoXnW18vA0Gu7bI=; b=lMK+xaQc5kk2OXPeN3dY6MFUICOkfM7EExAGc6EGbYlGGaPSC5mnw50ZiVfdl1NYMq cWund+TgYncFWt1/TGc5lS15CnGddgnEmrgiPEs5ocPQyKev2IAniiCnuM3LFa/AIZGK RjI4sz77ZeQEiLeFBEBIgaR5o2UjKtaFpaps5apB0OGcKCyhq3/V1V69SSOZKAtTb+TP wwEUvL0DREhlkGgSozQijZ0DF6pwnp++sp7DwwQzVhlBlp94TWu/+nf4wGFk29L079bb UvFRd7i3LzvExzvvA4ZerpmbHWfobXRfA2sNX3Pu2Ni3AX4T7VnsN8KmtrRk7MVvAs32 cn7Q== X-Gm-Message-State: APjAAAXb3TRiRxVt5UgTSXTpPHc3Q6kJNV939RIheFeuWvcQhB/l+5AS gVSp8Q0kDo80B59yUgobej2gLrKJyN1OKSGScHJwR1cs+cUROdj/JLa3KaW9UcrHCVYWhGlGRxM xLexY4gYaleUxgxSMnEIs3ZGkUGaTMSQAbtnUGgU187a2r8D+wnemKfBaC8VX/zs= X-Received: by 2002:ac8:71c3:: with SMTP id i3mr45277629qtp.140.1555529591228; Wed, 17 Apr 2019 12:33:11 -0700 (PDT) X-Received: by 2002:ac8:71c3:: with SMTP id i3mr45277606qtp.140.1555529590692; Wed, 17 Apr 2019 12:33:10 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1555529590; cv=none; d=google.com; s=arc-20160816; b=YnQaq5dFaLJHtwkwKmX3IWTt5ABwh4MnO06/uDoB2Ddb7Z+bQ2g513D8BF0tlPmbj1 GCEbuiH/ZzLnsnfFW63vdlWH5ZcsacbnCu0NX7lqON3aLIRjaV/A8Sagm/jpu2aIT6h7 V15gGXJou8JAd0Ik9AQS4UQIiRpM7TvrPqpUB1NbAni9Hzhz67EGLev4zL2DPjRdeELK ALujzghNv4zKu/CuKfwzBko6SHE3ZHuF8R4OEmRlBXMhtEXO2a4vI+36o+T4qsAdv9Hr hWsTTMYagNg7SlC+6HoafZzS4IjxmK+TJ2IQ4JzQo2XbYVrwaP6aQEbHS7kCNMcJEy8u +vgQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=user-agent:in-reply-to:content-disposition:mime-version:references :message-id:subject:cc:to:from:date:sender:dkim-signature; bh=DOvyhaD8UYdSm2Vgv7oMv8UKm8AtpoXnW18vA0Gu7bI=; b=KGrdbEYIXwJgpbR3DKsxptRzmI47MLNw9hV/9gTM+xvhmBtaEmFWtEgh5iK1phbrSA +duZfYW/G2WUxhAJj50W7FPMYLCLW9CFbaNuvnMvM/FWQEHUUS8jGMEn79t4Ew5X8pPn TZB8LS7FLlmYmuZ0QMBYdd7zM17eP7bAKQ8da+rWUNqC39fBpvICUanccduAwlhwKRMH fI+XlMjx0J2UckpWVxtKJBJsyIfljBt+YapB2hPxC2R9KSPzUIyzOsCPeeoL/bH4IR9v Dm973mIAw6U9f5PybgJhalf0MYXx1HW8GLTwN5nF6WLR0+85gJ3TZbY21wHMEflCM7p9 PFWQ== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b="G+K/q8tG"; spf=pass (google.com: domain of htejun@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=htejun@gmail.com; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=kernel.org Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id d16sor29776615qkj.124.2019.04.17.12.33.10 for (Google Transport Security); Wed, 17 Apr 2019 12:33:10 -0700 (PDT) Received-SPF: pass (google.com: domain of htejun@gmail.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b="G+K/q8tG"; spf=pass (google.com: domain of htejun@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=htejun@gmail.com; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=kernel.org 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=DOvyhaD8UYdSm2Vgv7oMv8UKm8AtpoXnW18vA0Gu7bI=; b=G+K/q8tGKTnlv7InetTqxljKuwUd3WFeH/9PINgqo9/wtLSvb5dr8RIY6GMteOYwxg keyu/4T1TSgaUHyvaJZVjytRQPhL1Dry26oFQpSJTJYmdEVdSMZH9CBg2EjoNX0rlUJq P+MipN8w8DZ6VkHJccSQlegj2WxTZD4zYGmj3rvlT/RgpP/wODPNqWMKODrucK94QARS APBP/MvDke+RXWKsSrgJOPpBGkS4R3CUqMyYjuVP6iBNk+ZpF1FsIzrxAkejisfu2h3d 13D+YkmTv1zidtlGT931ukuwoDbmZ++ypEl1e7oLBXErb1C7B8MDMmb87wiSimgKanP0 VuYg== X-Google-Smtp-Source: APXvYqwwsHOijzy5+qi54DMe1CUqg+364Ctp56sTADYW6ZdkvMX3KxBajWgTrNG6hjWJFl3Tu/7Fug== X-Received: by 2002:a37:5547:: with SMTP id j68mr6182374qkb.199.1555529590306; Wed, 17 Apr 2019 12:33:10 -0700 (PDT) Received: from localhost ([2620:10d:c091:200::3:556d]) by smtp.gmail.com with ESMTPSA id h22sm44750929qth.68.2019.04.17.12.33.08 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 17 Apr 2019 12:33:09 -0700 (PDT) Date: Wed, 17 Apr 2019 12:33:07 -0700 From: Tejun Heo To: Jiufei Xue Cc: cgroups@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, joseph.qi@linux.alibaba.com Subject: Re: [PATCH v2] fs/fs-writeback: wait isw_nr_in_flight to be zero when umount Message-ID: <20190417193307.GF374014@devbig004.ftw2.facebook.com> References: <20190416120902.18616-1-jiufei.xue@linux.alibaba.com> <20190416150415.GB374014@devbig004.ftw2.facebook.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Hello, On Wed, Apr 17, 2019 at 09:04:48AM +0800, Jiufei Xue wrote: > Yes, it can be fixed if we replace synchronize_rcu() with rcu_barrier(). > However, I'm worried that rcu_barrier() is too heavyweight and we have > encountered some hung tasks that rcu_barrier() waiting for callbacks that > other drivers queued but not handled correctly. rcu_barrier() wait for the pending callbacks to finish and none of the callbacks can block, so I don't think it'd be much worse than synchronize_rcu(). Also, it'd probably make sense to inc isw_nr_in_flight after call_rcu() in inode_switch_wbs(). Given that all inodes must be gone by umount, the actual race window isn't there but that ordering still makes a lot more sense. Thanks. -- tejun