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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id AC26EC77B7E for ; Fri, 28 Apr 2023 17:42:47 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 1F8846B007D; Fri, 28 Apr 2023 13:42:47 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 1B45F6B007E; Fri, 28 Apr 2023 13:42:47 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 048796B0080; Fri, 28 Apr 2023 13:42:46 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id E28C16B007D for ; Fri, 28 Apr 2023 13:42:46 -0400 (EDT) Received: from smtpin09.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 7715FC02DC for ; Fri, 28 Apr 2023 17:42:46 +0000 (UTC) X-FDA: 80731519932.09.790BFED Received: from mail-wr1-f52.google.com (mail-wr1-f52.google.com [209.85.221.52]) by imf21.hostedemail.com (Postfix) with ESMTP id 9DCAF1C0022 for ; Fri, 28 Apr 2023 17:42:44 +0000 (UTC) Authentication-Results: imf21.hostedemail.com; dkim=pass header.d=gmail.com header.s=20221208 header.b=CMnGzA5I; spf=pass (imf21.hostedemail.com: domain of lstoakes@gmail.com designates 209.85.221.52 as permitted sender) smtp.mailfrom=lstoakes@gmail.com; dmarc=pass (policy=none) header.from=gmail.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1682703764; h=from:from:sender: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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=a7uMAN4inFdAmgs2662MiDQxbIMz/NYQ0viDeHuh/7A=; b=KByau8lbZpHf0JBEUlbdwiKFj1rUqE30iHqjtJmZplejal/C5XLYBlPMQpb12d4l/j8uf/ BZx/RqP4uj1Bw/r890imr7c+0N8aBgPK5l8Q3lImiqNpCaHRvlgds2UJZJKFzT72KogKU4 ih1QTX5XOv28bwP9hWZUrnhPSsnQU74= ARC-Authentication-Results: i=1; imf21.hostedemail.com; dkim=pass header.d=gmail.com header.s=20221208 header.b=CMnGzA5I; spf=pass (imf21.hostedemail.com: domain of lstoakes@gmail.com designates 209.85.221.52 as permitted sender) smtp.mailfrom=lstoakes@gmail.com; dmarc=pass (policy=none) header.from=gmail.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1682703764; a=rsa-sha256; cv=none; b=hlMY9Wu4mYYqdcy7xXTyPEi9+zAQrXVBlj7eIgLSia4c48LBr8TYgqD0EuAiwp2sOdHbo+ XyeDNeF+bQ2jMT1I0wNWFci3jnrGu6KCe/Xay1/Tap1fZ9m+RBWDV1/OMWgzyORjP9knQu lSvNbCJIlbo8APu1mWkymuj4BYvcnNo= Received: by mail-wr1-f52.google.com with SMTP id ffacd0b85a97d-2f7c281a015so7970f8f.1 for ; Fri, 28 Apr 2023 10:42:44 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20221208; t=1682703763; x=1685295763; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=a7uMAN4inFdAmgs2662MiDQxbIMz/NYQ0viDeHuh/7A=; b=CMnGzA5IvVawATNWyQUiLXjSQMbc3k7Ou4ptro6AT4w0gpDvp1RmBl95mjRKX0I7HZ GQuHVAYZIS8xU01Dbwql57be47Lm+Y4Jlup4Ve2oF+73ZXWawVQ7NH20BEgB470z/qdp 0BxzsNAI8mCD6pIs3KzIhhcJOwpd2YHCRZZL7NeGa0Z2edavcVma1h88s8pXS1pEiSks aJm6gFRmEf4Lh7wgXg9YS8d5CdMoYQ5oEZHk5e2WCinTzMDA2Qr/ofzC/Hmq0xA193tt KgSxzTmCLCR3TBV1T/DUBTAl19W7yTfK6oRmsuSBMF2xeWc6wjtdXm47alSRv+X1sVsr EKhw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1682703763; x=1685295763; 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 :message-id:reply-to; bh=a7uMAN4inFdAmgs2662MiDQxbIMz/NYQ0viDeHuh/7A=; b=I3o5EWnaIgKCrqTreee40pn/9OB4UpRUAy/b1ymGspC+U5L25WoTiLgRTYBhHttWCr IbDBH/FoUO6O2lZnv0NQ83PnSPYBIfRWd7bTrImojhIBlEF7N++/twVjsp0u/oBBJRHl Qhd0MsawV/W4Ct7+6tD2cez3oB7vR489t1rtJ7KZNaQw75gF+lHg9lyQOLjoni1mjkVG AQXznFC8s/LdVeKsTbKdwitxRg2qw+s+wviAA0OpJhcI1sLDY8S6TGUVh8h/3N45CjW0 ZqOEYYQBItId45ODf1xgcSqmhX4BTcGUV1u9WQkYRBq/LB9qqKRmc/JhFS8stISDkhPb 7Eyw== X-Gm-Message-State: AC+VfDxjUGCKkxSV0KGs1ktIrxziO+neyL0/TOvhcbYmFXCyBZtVU+e8 QWSGrZXO6TqyWn9+fuyLjBE= X-Google-Smtp-Source: ACHHUZ489c8i55WQeazaUSoDba4YXhLZWyaFW7PUQj7k71PVXJgOr7z/SgZw+VBCsKqNxaLBezbriw== X-Received: by 2002:a5d:4651:0:b0:2f9:9763:1357 with SMTP id j17-20020a5d4651000000b002f997631357mr4210267wrs.8.1682703763194; Fri, 28 Apr 2023 10:42:43 -0700 (PDT) Received: from localhost (host86-156-84-164.range86-156.btcentralplus.com. [86.156.84.164]) by smtp.gmail.com with ESMTPSA id v15-20020a05600c444f00b003f09cda253esm28758504wmn.34.2023.04.28.10.42.42 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 28 Apr 2023 10:42:42 -0700 (PDT) Date: Fri, 28 Apr 2023 18:42:41 +0100 From: Lorenzo Stoakes To: Jason Gunthorpe Cc: David Hildenbrand , "Kirill A . Shutemov" , Peter Xu , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , Jens Axboe , Matthew Wilcox , Dennis Dalessandro , Leon Romanovsky , Christian Benvenuti , Nelson Escobar , Bernard Metzler , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Mark Rutland , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Ian Rogers , Adrian Hunter , Bjorn Topel , Magnus Karlsson , Maciej Fijalkowski , Jonathan Lemon , "David S . Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Christian Brauner , Richard Cochran , Alexei Starovoitov , Daniel Borkmann , Jesper Dangaard Brouer , John Fastabend , linux-fsdevel@vger.kernel.org, linux-perf-users@vger.kernel.org, netdev@vger.kernel.org, bpf@vger.kernel.org, Oleg Nesterov , John Hubbard , Jan Kara , Pavel Begunkov , Mika Penttila , David Howells , Christoph Hellwig Subject: Re: [PATCH v5] mm/gup: disallow GUP writing to file-backed mappings by default Message-ID: <34bc4f3c-8dfe-46ec-9f9b-358cdf4c37e3@lucifer.local> References: <62ec50da-5f73-559c-c4b3-bde4eb215e08@redhat.com> <6ddc7ac4-4091-632a-7b2c-df2005438ec4@redhat.com> <20230428160925.5medjfxkyvmzfyhq@box.shutemov.name> <39cc0f26-8fc2-79dd-2e84-62238d27fd98@redhat.com> <20230428162207.o3ejmcz7rzezpt6n@box.shutemov.name> <173337c0-14f4-3246-15ff-7fbf03861c94@redhat.com> <20230428165623.pqchgi5gtfhxd5b5@box.shutemov.name> <1039c830-acec-d99b-b315-c2a6e26c34ca@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 9DCAF1C0022 X-Stat-Signature: 5u3k9s4f7x6xgy3z9shbqxbb3wyoyu51 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1682703764-921948 X-HE-Meta: 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 G+FY4Mpp 1rJuaA8NDszwimNiJSUGYAS+5w318YiaSzsGsYOVVnpMigUTT8i2+TASDrsFAovent7gYB65Jy248e0B85UOYB8DiVqmmWmPGt9MxvHXuDrdd0xckuItgUVpmg+QHIPA0lZG2TQKKq4E3wqCQa84LAXHvpA+08QFEse30lZsy0Zo74iciOZlp0g2Kg1dBA0Kg0KoMB9xJcpKw0iQ4SP5OsKTDgnYOTQjjAc5fClwskRYbeqfm1o8aj5hNn+7Obr4Ltn+H0C/fVPBn8B0jLLbZPjTK9e0ygpXsX/5dGbntaYbeVT0eVnHbKN8p9088i7pDQMsR1LeJ06Rod36CDD678kbFUcySYC4wHWhnx36hoXyY/TmoO9jD5t3hMPRr2oW7Gdf8QtI5h2JG/ZjwKuco10ne7PyQIvG/U5JSbYGbhxpKn2J3iPLIs9LasKRi86tzjm+aK5Ikp+LLWWFuFv3iSo3ptg== 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: On Fri, Apr 28, 2023 at 02:31:38PM -0300, Jason Gunthorpe wrote: > On Fri, Apr 28, 2023 at 07:02:22PM +0200, David Hildenbrand wrote: > > > > No. VMA cannot get away before PTEs are unmapped and TLB is flushed. And > > > TLB flushing is serialized against GUP_fast(). > > > > The whole CONFIG_MMU_GATHER_RCU_TABLE_FREE handling makes the situation more > > complicated. > > Yeah, you have to think of gup_fast as RCU with a hacky pre-RCU implementation > on most architectures. > > We could make page->mapping safe under RCU, for instance. > > Jason Does it really require a change though? I might be missing some details, but afaict with interrupts disabled we should be ok to deref page->mapping to check PageAnon and a_ops before handing back a page right?