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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id DD30CC433F5 for ; Tue, 4 Oct 2022 00:28:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229739AbiJDA2Q (ORCPT ); Mon, 3 Oct 2022 20:28:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59610 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229481AbiJDA2M (ORCPT ); Mon, 3 Oct 2022 20:28:12 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 12A0815700 for ; Mon, 3 Oct 2022 17:28:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1664843290; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=pj+13W7HFM06WePLHe+jsxNPLN/rwSpvvUEX7p+XOZo=; b=aejP18nD6WsJOX5VuG0YPhRp0FmSf7SdRCJDNlsvZb08rwg26ld+7KuvcqsIgGRYewxqx7 cdgYbEGIRp1pw1xa9O56u04/zoTs+zYeOUVobT5JEMVHc9YoBw5DX7k97hbd4LQ7aHkW5E ksD5QO82CD6LOe8QGvFk/w14ga8KnuU= Received: from mail-qk1-f199.google.com (mail-qk1-f199.google.com [209.85.222.199]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_128_GCM_SHA256) id us-mta-611-Z2yicR0hPsWNP67nnKj0dQ-1; Mon, 03 Oct 2022 20:28:06 -0400 X-MC-Unique: Z2yicR0hPsWNP67nnKj0dQ-1 Received: by mail-qk1-f199.google.com with SMTP id i7-20020a05620a404700b006ced0d02b68so10415173qko.10 for ; Mon, 03 Oct 2022 17:28:06 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date; bh=pj+13W7HFM06WePLHe+jsxNPLN/rwSpvvUEX7p+XOZo=; b=R+1UMDurwa55Vs54TX3ucmPpAtFRA6sOXcmY5rIg2GtLlAEkJTg6KlteA4SMseTBQD 76l0O1cwJ8nYX10x8y+vr1hWl1txMWaQYRflVNbosvB410CnqED7okwy3Ig6DCwnU99l Ir4Y0jL95ugvLcAzg/AV0ufmpyf+V8/vTyMy2icy8wt95YaL6Of80G60kMt3eAqbq7ow pzIRg4I7Zrf9d6KfBQtyDbuHWbJSSrZslJ7qH5Uplm3KlcNpHhBUA2HVqKdXgR1crFw9 bH1C6tnjMT2/3hHmVrpiJm5xHkICawlq7MLxwBPDQb34Ubv8Df30wU6CWd8fKpd/Wgqz 9JFw== X-Gm-Message-State: ACrzQf14YXMt6aPVV37hO7b/kRDKXDkOiBszl3SbY0D/hA1whDXu1Xhi Fy6eUWzXIU2HVUx+yQYTUpkgpvzorcMA1C5S1faBBZIthnoZjf+7YUM9k/qgo8CltoYFUWHn/fT mFBeGwvgt49cUP7shsdAPB7to X-Received: by 2002:ac8:5b95:0:b0:35c:e579:1feb with SMTP id a21-20020ac85b95000000b0035ce5791febmr17993204qta.481.1664843286440; Mon, 03 Oct 2022 17:28:06 -0700 (PDT) X-Google-Smtp-Source: AMsMyM5IEwX3LFHu386ZT/atsDghlRieK/y5Wumcw8asQhPJ2iC/POzF1khL8FoV+rLT3iH/Y5mXaA== X-Received: by 2002:ac8:5b95:0:b0:35c:e579:1feb with SMTP id a21-20020ac85b95000000b0035ce5791febmr17993193qta.481.1664843286247; Mon, 03 Oct 2022 17:28:06 -0700 (PDT) Received: from x1n (bras-base-aurron9127w-grc-46-70-31-27-79.dsl.bell.ca. [70.31.27.79]) by smtp.gmail.com with ESMTPSA id r10-20020ac85e8a000000b00342f8d4d0basm10584846qtx.43.2022.10.03.17.28.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 03 Oct 2022 17:28:05 -0700 (PDT) Date: Mon, 3 Oct 2022 20:28:03 -0400 From: Peter Xu To: Mike Kravetz Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrea Arcangeli , Mike Rapoport , David Hildenbrand , Andrew Morton , Axel Rasmussen , Nadav Amit Subject: Re: [PATCH 1/3] mm/hugetlb: Fix race condition of uffd missing/minor handling Message-ID: References: <20221003155630.469263-1-peterx@redhat.com> <20221003155630.469263-2-peterx@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Oct 03, 2022 at 02:45:47PM -0700, Mike Kravetz wrote: > This also explains why the new locking exposes the race. > hugetlb_change_protection needs to take the i_mmap_sema in write mode because > it could unshare pmds. Previously, hugetlb page faults took i_mmap_sema in > read mode so this race could not happen. Makes sense, thanks for explaining. -- Peter Xu