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=-17.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 3D5EAC433ED for ; Tue, 20 Apr 2021 13:20:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 08688613CD for ; Tue, 20 Apr 2021 13:20:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230408AbhDTNUq (ORCPT ); Tue, 20 Apr 2021 09:20:46 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:23601 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232084AbhDTNUo (ORCPT ); Tue, 20 Apr 2021 09:20:44 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1618924813; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=QYX7/AuHi6hgPHf6tRYqK2+HrNaM+fnSnNKD7KzrRzs=; b=OZ0onuVeHycPzs9LHxf4KV7aE8n1VgCkf/KZSsh82ahhr37LLZdd/qEIpm7dUNWbRD0pN5 F9WM8P5vFCYsObHhmCuA50CEvX7hfuWCovfW5pwUZFR9qyvBlF2xTPA96DJnCNQvdgY+Iu C0ztYqLdWESINjyxYgN2f7zhYEk2zIs= Received: from mail-wm1-f69.google.com (mail-wm1-f69.google.com [209.85.128.69]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-100-ENHxC0EdPV6BcExByX4yKw-1; Tue, 20 Apr 2021 09:20:00 -0400 X-MC-Unique: ENHxC0EdPV6BcExByX4yKw-1 Received: by mail-wm1-f69.google.com with SMTP id k26-20020a7bc41a0000b0290125f388fcfbso5684368wmi.9 for ; Tue, 20 Apr 2021 06:20:00 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:organization :message-id:date:user-agent:mime-version:in-reply-to :content-language:content-transfer-encoding; bh=QYX7/AuHi6hgPHf6tRYqK2+HrNaM+fnSnNKD7KzrRzs=; b=uaEbp67ax5+h/PbnqN7onf0qJLfXTbGwL5Ew7pE2nEPrCcy49g2ArYT8sF/BgaHrqX PCfx8r+bIvKXrpSRz7Ng7XrZY+04vG8+Pce3OOldGWeZfI6HTYwNu45auPH6nCSeL6FD 4sDLew0HNYmxa6vzLz4h2D4ogMGCum6dWKUOKpY6Ua1FMZV0RDbJVFXAujeP9H0MBuTf zvNTfTmPBYBYs9Gi7QH0lrvJvgly8i048culTiUvQauWj4COBrleXNt4Nn7wUkUFjFo9 2vP5geTkT6y7DqWr50+VrjM7zAckZVLK78eXdoKZr8JTgYBkbXYWv8yIiT1f9zPHf53m oQ6Q== X-Gm-Message-State: AOAM531YY1GzF4chFs38gsVXZCmG+i7VCAA1VT2qR+STyXjnL1JV4+6T GxQku0is5Mcy1kLw/hf7TiCbQBfO/GTlaMB00cazjkLgWVUW33P+G6rdtzkK6eKn6X8XBXYGJfg KcyWZelRoWOHvupLdx/4lq8ue8g== X-Received: by 2002:a05:6000:128f:: with SMTP id f15mr20916808wrx.19.1618924799176; Tue, 20 Apr 2021 06:19:59 -0700 (PDT) X-Google-Smtp-Source: ABdhPJyfOGjRv02X/zmH7pcY7EIgqs8w+z5KR0gU0RfoaYN+dlGesRC5fI0lFDDiwZRbvB39JmbKYA== X-Received: by 2002:a05:6000:128f:: with SMTP id f15mr20916761wrx.19.1618924798995; Tue, 20 Apr 2021 06:19:58 -0700 (PDT) Received: from [192.168.3.132] (p4ff2390a.dip0.t-ipconnect.de. [79.242.57.10]) by smtp.gmail.com with ESMTPSA id f6sm3291518wmf.28.2021.04.20.06.19.56 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 20 Apr 2021 06:19:58 -0700 (PDT) Subject: Re: [PATCH v2 1/2] secretmem/gup: don't check if page is secretmem without reference To: Mike Rapoport , Andrew Morton Cc: Alexander Viro , Andy Lutomirski , Arnd Bergmann , Borislav Petkov , Catalin Marinas , Christopher Lameter , Dan Williams , Dave Hansen , Elena Reshetova , "H. Peter Anvin" , Ingo Molnar , James Bottomley , "Kirill A. Shutemov" , Matthew Wilcox , Matthew Garrett , Mark Rutland , Michal Hocko , Mike Rapoport , Michael Kerrisk , Palmer Dabbelt , Paul Walmsley , Peter Zijlstra , "Rafael J. Wysocki" , Rick Edgecombe , Roman Gushchin , Shakeel Butt , Shuah Khan , Thomas Gleixner , Tycho Andersen , Will Deacon , Yury Norov , linux-api@vger.kernel.org, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-nvdimm@lists.01.org, linux-riscv@lists.infradead.org, x86@kernel.org References: <20210420131611.8259-1-rppt@kernel.org> <20210420131611.8259-2-rppt@kernel.org> From: David Hildenbrand Organization: Red Hat Message-ID: <95b7fa81-f72e-c63f-0456-4c25dee8a5eb@redhat.com> Date: Tue, 20 Apr 2021 15:19:56 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <20210420131611.8259-2-rppt@kernel.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On 20.04.21 15:16, Mike Rapoport wrote: > From: Mike Rapoport > > The check in gup_pte_range() whether a page belongs to a secretmem mapping > is performed before grabbing the page reference. > > To avoid potential race move the check after try_grab_compound_head(). > > Signed-off-by: Mike Rapoport > --- > mm/gup.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/mm/gup.c b/mm/gup.c > index c3a17b189064..4b58c016e949 100644 > --- a/mm/gup.c > +++ b/mm/gup.c > @@ -2080,13 +2080,13 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end, > VM_BUG_ON(!pfn_valid(pte_pfn(pte))); > page = pte_page(pte); > > - if (page_is_secretmem(page)) > - goto pte_unmap; > - > head = try_grab_compound_head(page, 1, flags); > if (!head) > goto pte_unmap; > > + if (page_is_secretmem(page)) > + goto pte_unmap; > + Looking at the hunk below, I wonder if you're missing a put_compound_head(). (also, I'd do if unlikely(page_is_secretmem()) but that's a different discussion) > if (unlikely(pte_val(pte) != pte_val(*ptep))) { > put_compound_head(head, 1, flags); > goto pte_unmap; > -- Thanks, David / dhildenb