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_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,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 845F8C433DF for ; Mon, 6 Jul 2020 13:34:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 52A2B2070C for ; Mon, 6 Jul 2020 13:34:49 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=web.de header.i=@web.de header.b="dykUl5Z/" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729151AbgGFNer (ORCPT ); Mon, 6 Jul 2020 09:34:47 -0400 Received: from mout.web.de ([212.227.17.11]:47009 "EHLO mout.web.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729382AbgGFNen (ORCPT ); Mon, 6 Jul 2020 09:34:43 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=web.de; s=dbaedf251592; t=1594042443; bh=zyikPEHRSl6AfWnrIJsptm0zk3698RDADIrgUvP6JL4=; h=X-UI-Sender-Class:Subject:To:Cc:References:From:Date:In-Reply-To; b=dykUl5Z/jkWGSiBqMz4YjIFMzhj+0rJ2OaWEPiEAI/j5AfTD1SwZFV1ngl4I5f6DO fijeLzd/p3DfhXKJkRQvhkv+isL05Ej0ziAXBthUrNufqYBB/WWo6wwmf1fWJTqATk cYlILoX2ryhGkRtx0jITSpMnqpQpvbZEDDZTmaq0= X-UI-Sender-Class: c548c8c5-30a9-4db5-a2e7-cb6cb037b8f9 Received: from [192.168.1.2] ([2.244.113.119]) by smtp.web.de (mrweb103 [213.165.67.124]) with ESMTPSA (Nemesis) id 0MDxCN-1k85vJ4AkJ-00HOMY; Mon, 06 Jul 2020 15:34:03 +0200 Subject: Re: [RFC PATCH] vfio: type1: fix kthread use case To: Hillf Danton , Alex Williamson , iommu@lists.linux-foundation.org Cc: kernel-janitors@vger.kernel.org, linux-kernel@vger.kernel.org, Christoph Hellwig , =?UTF-8?B?SsO2cmcgUsO2ZGVs?= , Kevin Tian , Yan Zhao References: <20200706104915.11460-1-hdanton@sina.com> <20200706124241.4392-1-hdanton@sina.com> From: Markus Elfring Autocrypt: addr=Markus.Elfring@web.de; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 MIME-Version: 1.0 In-Reply-To: <20200706124241.4392-1-hdanton@sina.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-GB Content-Transfer-Encoding: quoted-printable X-Provags-ID: V03:K1:hQRlprojWG/gbX7gfH4IvEPq/yWggqojlOSRndeRHXRFyV6gflb 3xWgaDC2zU027iUUZvbgo88UWGbzSIKD1b6S9AvXbVA8CeL2Azt1uZ6fGcKlDfKdy55quTE cR+Mt+yHCVh8apr9KJGjIMgZJ81TahgojBeJcPw65TliQU1reY7BHvAV2cKvE9ISZVV9TD3 mmKhR5yHSmjdIY3H8yxjg== X-UI-Out-Filterresults: notjunk:1;V03:K0:Bc4I7rzFw7Y=:cNVHiMPx6Tz5XJ2v2Fet5L WPSOVTbpBAx5uuo8/zhhlc01QKoJzuLXGC5tm7GTsqLsqF6Wt09RES/ga7QxdZFRnPt0aFAIz 3zLqiQAp9V7FZSYx6pDzbhdT+j9Wqjr5NY0HvJsmQxaiKNAGvcdT9pSBjmWozz3G3extGph9I BGpdf97jPf7BdR/w7t7l8KjaPMm9goumyruTzQAs+kLIUt1jhpxtLcRxOTO9oEZqC0gqDoyfb 6s/fiYsSBXIX+8EKmroKYlI+JjAMxQfm5bZ/kcNck7EJuT5TBMT9L3RbBwiaxn5yDg9uXsrRe N7/6G6A8QNsw+bbZHejh+b1aAaHA5boGwT1hEMnMj2zi0G1SS/vE55HF/UsIYdynSGdKe+ksL +Jq73DwtM/9cbsrDHu/pW9WgI23InPXZqLaSGKBGBefhLOof//8shNiSnBhvmAltY5A06u1Z0 XuyCoTNig4322Y3ZI/zqNO1tWLlCsDXNjrZSLPvzYrVNMQ5I7XH89ODiYgZBUrfEFOCHaJCS2 thHyPSx1XF6w+zqUGXAMHJY/vGOh2a89sVrlsXIcvZm0MvEa4BaJ+1A175S51nkcxSdgdpx0s IX0lY/CF/mpfQO1DifuCravqMPX6w/NV3nRPGG3dw3jUD9TDKrz2o67R7e7zZTBUOKtfnqvFy EBqjodHKBN6PiWihbfekk+kgsu9j9olhWiRTCBC9FHGO004FfnqBcw6I0uUJvZVWP06USeqY/ d2RNleTGOxan7MtsOJZSeVWA6j8UC26b4Nrwz3Pl970LLoQmhsCkvn7T2GSKw0FhchAwx3FIG S01GqDhvvW/c0Gi5GxGCifx75z0MTvpv2kJGda7EgmOnJkdC4Zc8zarKGicsgY8qZniU65+Dh aVZUimK5ogOuWpOkaKvBPXb4xJr2f6J51lGDy5PzwqEpD8TDY4nynfvc2GRDTxtwYJazuwXov H8qtq2wbzcBeA2k+mta2Wa2Pep6tuBf0SLArTxho3N/XireqaYZAEQUyTrsgj9h5zh6i4yEOg sv+n1Em1NRa/BVDBQIrEhrc2UVI/qowXwI7ocjOeEHpklgX7k3fYyZOG2CZHenUJZIgd0qJcx Jyl4p+DEu/ZA7y8NwFnSjz+ckFRw9QcyuWSSqQH2EFMhXW0hbHyu9g/GCUCzoLftX9gPHTHW4 75ItyfO5X7Egz9+QRliWT6qhP5QXWHNHtS+4AQT/fSrmBNyCBT54B5wQhqNPTZz8eTMol0cLN cGWL2wYTGPTO7DVuz8ES+C7IveaDdFdjxiYNqhw== Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >> Can it be helpful to convert initialisations for these variables >> into later assignments? > > Perhaps. Then it looks like the below. =E2=80=A6 > +++ b/drivers/vfio/vfio_iommu_type1.c > @@ -2798,9 +2798,12 @@ static int vfio_iommu_type1_dma_rw_chunk =E2=80=A6 > - bool kthread =3D current->mm =3D=3D NULL; > + bool kthread; > + bool use_mm; I would prefer the following variable declarations then. + bool kthread, use_mm; > size_t offset; > > + kthread =3D current->flags & PF_KTHREAD; > + use_mm =3D current->mm =3D=3D NULL; I propose to move such assignments directly before the corresponding check= . =E2=80=A6 > if (!mm) > return -EPERM; + kthread =3D current->flags & PF_KTHREAD; + use_mm =3D !current->mm; > - if (kthread) > + if (kthread && use_mm) > kthread_use_mm(mm); =E2=80=A6 Regards, Markus