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 C49D5C3A59E for ; Wed, 21 Aug 2019 16:04:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 96BD92339F for ; Wed, 21 Aug 2019 16:04:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1566403475; bh=KF4ylo3kCKBHAk1AFfcHDCAAl5qTya2CfQYF7CXKCus=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=Kwz76dKKgX2TcYQN/MLg7xIPhZRdShrs97wxsNLGzvEh03sXNizgOOc98fpdeLlTi KH04Evgv4YneEkRasZdXqA7njTO5plAszg/lvbNP93drKc/vlO0n6WyREy59rCeOJG kcTE9/a1YWo5pzicBwklNa/Fq9NOd+OZG+7+QkSU= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728797AbfHUQEe (ORCPT ); Wed, 21 Aug 2019 12:04:34 -0400 Received: from mail-qt1-f196.google.com ([209.85.160.196]:43769 "EHLO mail-qt1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727480AbfHUQEe (ORCPT ); Wed, 21 Aug 2019 12:04:34 -0400 Received: by mail-qt1-f196.google.com with SMTP id b11so3630990qtp.10; Wed, 21 Aug 2019 09:04:33 -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=pSYvDILhSH8fJWFn1Ay93bkSas+NlIGIDDL+tHz2nnY=; b=FcPaI0pBK/tsTJ85fkJV0GzNaa0VI6xq2/3C77dJ9Ksg2LPi+NeYin58kEZaHWQ4+c yNts5ywVYjfMNCER2xvTfME0oKqC0YC2I4+K1tsuNpQiaJjKZTyj3LDo3/o+40aLy1b3 xFROy6h268Qz/2709NunEce2lWelxf9pFlX7BM8kPI3y5yOWd5UyF8HaxBcv8mpUorwb 8wJ1/du7AiJGYKqbpfRUjO9rT+TCM/8hnViWhPuAotTO6NOkCjN1Clp8ecE6hIl6tYqF MHer6bExHhfCK5pjD900mPPO3BKg9ILIPrD3FA13M/iRdL1oZqc+Ge1OIPSGrhdITT6H MvGA== 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=pSYvDILhSH8fJWFn1Ay93bkSas+NlIGIDDL+tHz2nnY=; b=MPxfueIILTWXOUzpA+Z0oV1cWWEcBMtN+G/Vs2jwKy89V0dG1gg+05X5HgrU6UkPw9 w+na9w4JaEBfEp9rZ3fJZ7YJbSblKg59j+WC1nEetRvV5j73u2HbFsRH4b+y7/RsY3EI Tkts2Mn8dP5s3Wujb2S5TGbbR59x820Wtuw6d3E/UtAuIHrVIfZjvoDpzbfzxECN6bpi HbckURyFhBT5525tD8fT7cBHsvQ8kc7tB0XKmeT7vY63ek0qAma35Tt+XqzAHwsgl/vp EagHObKFIBFAf4UopwBtkoFRTmf+eeepFAciZ+VP5rwHFu0nxkR2eW68/qotVogXWO2d EzVQ== X-Gm-Message-State: APjAAAWJEw5RBtXNw0i1drRcZTSGtdL1HPiF09aFzepx5WV6Oytkv4dw 5sUhikAyYYl9L4gzjo7D93WIQfdE X-Google-Smtp-Source: APXvYqxpFrzdsIp5vYz/r7TIVsm3AF8l2qHkWaxK1IbWJsfJxsILknQZQre8GqBdTdcjbqhL1sL5hQ== X-Received: by 2002:a0c:edcb:: with SMTP id i11mr18388359qvr.206.1566403473118; Wed, 21 Aug 2019 09:04:33 -0700 (PDT) Received: from localhost ([2620:10d:c091:500::1:1f05]) by smtp.gmail.com with ESMTPSA id v126sm10464175qkh.3.2019.08.21.09.04.32 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 21 Aug 2019 09:04:32 -0700 (PDT) Date: Wed, 21 Aug 2019 09:04:30 -0700 From: Tejun Heo To: Jan Kara Cc: axboe@kernel.dk, hannes@cmpxchg.org, mhocko@kernel.org, vdavydov.dev@gmail.com, cgroups@vger.kernel.org, linux-mm@kvack.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com, guro@fb.com, akpm@linux-foundation.org Subject: Re: [PATCH 5/5] writeback, memcg: Implement foreign dirty flushing Message-ID: <20190821160430.GL2263813@devbig004.ftw2.facebook.com> References: <20190815195619.GA2263813@devbig004.ftw2.facebook.com> <20190815195930.GF2263813@devbig004.ftw2.facebook.com> <20190816160256.GI3041@quack2.suse.cz> <20190821160037.GK2263813@devbig004.ftw2.facebook.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190821160037.GK2263813@devbig004.ftw2.facebook.com> 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 On Wed, Aug 21, 2019 at 09:00:37AM -0700, Tejun Heo wrote: > > 2) When you invalidate frn entry here by writing 0 to 'at', it's likely to get > > reused soon. Possibly while the writeback is still running. And then you > > won't start any writeback for the new entry because of the > > atomic_read(&frn->done.cnt) == 1 check. This seems like it could happen > > pretty frequently? > > Hmm... yeah, the clearing might not make sense. I'll remove that. Oh, the reuse logic checks whether done.cnt == 1 and only reuse if no writeback is still in flight, so this one should be fine. Thanks. -- tejun