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 4E243C0015E for ; Wed, 19 Jul 2023 17:59:26 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id B751D28007C; Wed, 19 Jul 2023 13:59:25 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id AFE2B28004C; Wed, 19 Jul 2023 13:59:25 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 99F2128007C; Wed, 19 Jul 2023 13:59:25 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 8692928004C for ; Wed, 19 Jul 2023 13:59:25 -0400 (EDT) Received: from smtpin16.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 4434514037F for ; Wed, 19 Jul 2023 17:59:25 +0000 (UTC) X-FDA: 81029123490.16.A839650 Received: from resqmta-a1p-077723.sys.comcast.net (resqmta-a1p-077723.sys.comcast.net [96.103.146.57]) by imf15.hostedemail.com (Postfix) with ESMTP id 6F092A0014 for ; Wed, 19 Jul 2023 17:59:23 +0000 (UTC) Authentication-Results: imf15.hostedemail.com; dkim=pass header.d=comcastmailservice.net header.s=20211018a header.b=RwcNQ1ox; dmarc=none; spf=pass (imf15.hostedemail.com: domain of kernel@mattwhitlock.name designates 96.103.146.57 as permitted sender) smtp.mailfrom=kernel@mattwhitlock.name ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1689789563; 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:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=/6lKYap9PZZRLrRmess6iU23U+m+a8OOtwMIqKZ8RIU=; b=NajnNbHYmT9f89FS3pGO1MctPr2sC1Kl4Sh1KYSBz620PEoRhcvvK42WKykO15MJLorZZn +wXHwtp56fOUQiWAy4qHBNvmB5QMF7cTK2IKbejjDujT7x2J5ZcrqJjncGMekGMdKvJay4 EKm65Mgvqbypu/T1qbV3YiQ0JfmhWYQ= ARC-Authentication-Results: i=1; imf15.hostedemail.com; dkim=pass header.d=comcastmailservice.net header.s=20211018a header.b=RwcNQ1ox; dmarc=none; spf=pass (imf15.hostedemail.com: domain of kernel@mattwhitlock.name designates 96.103.146.57 as permitted sender) smtp.mailfrom=kernel@mattwhitlock.name ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1689789563; a=rsa-sha256; cv=none; b=lnIjk6ob4Jnm1fFq2OR0b+CU9DGGG2xSw7yXHg7ia53yhHFDoEfBXFgRKCX0WaY2hrFssb 7jknsFAN2Se25/Tf/ApKTD/QJZvOr0P8ImMQ0Fh2sMo+caML6Ovjpiqk6CpQAEiJgUEmCc iksxMQOKE3HGZZILD6h1gUzddYeUc3k= Received: from resomta-a1p-076786.sys.comcast.net ([96.103.145.235]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 256/256 bits) (Client did not present a certificate) by resqmta-a1p-077723.sys.comcast.net with ESMTP id M67NqkkkbHilbMBSMqc5jE; Wed, 19 Jul 2023 17:59:22 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=comcastmailservice.net; s=20211018a; t=1689789562; bh=/6lKYap9PZZRLrRmess6iU23U+m+a8OOtwMIqKZ8RIU=; h=Received:Received:From:To:Subject:Date:MIME-Version:Message-ID: Content-Type:Xfinity-Spam-Result; b=RwcNQ1oxMcVUv5jZkr1Th2K6j1eUCF1lTBNR1RO8Wb586fwKt7y+AD/z1M9R1wFMF bcMm4jLGnmYBywyRQv9kdf3wzF38ApYm4c37QCMkg++tKEJio0b3IHYn5Bh3P1zVyH 8CP7O/f1uKREyR0xe+IVOkJcSFjBaq5tyDDz43bx9anhgPRSATM+eQsetq+XsbNF2g udyK2FDPE+RiiUuWwn8zrLg9GZ1leJohkg1I3d3+156iBRYMwlqjLJDNqHxzhoex7u wYMM+RJNl+n0iFVcSblChbZxxYjQ+2H9U/PDT/QESgUvYizIcoCQ01dB8wo4ELe5PL By/ATbbOiWgrg== Received: from localhost ([IPv6:2601:18c:9082:afd:219:d1ff:fe75:dc2f]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 256/256 bits) (Client did not present a certificate) by resomta-a1p-076786.sys.comcast.net with ESMTPSA id MBSEqFdsmeadOMBSEqzqUD; Wed, 19 Jul 2023 17:59:18 +0000 X-Xfinity-VMeta: sc=-100.00;st=legit From: Matt Whitlock To: Miklos Szeredi Cc: David Howells , , Matthew Wilcox , Dave Chinner , Linus Torvalds , Jens Axboe , , , , Christoph Hellwig , Subject: Re: [RFC PATCH 1/4] splice: Fix corruption of spliced data after =?iso-8859-1?Q?splice()_returns?= Date: Wed, 19 Jul 2023 13:59:13 -0400 MIME-Version: 1.0 Message-ID: In-Reply-To: References: <20230629155433.4170837-1-dhowells@redhat.com> <20230629155433.4170837-2-dhowells@redhat.com> User-Agent: Trojita/v0.7-595-g7738cd47; Qt/5.15.10; xcb; Linux; Gentoo Linux Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 6F092A0014 X-Stat-Signature: t3yy3s8eokj64kq38x6gkbkrfkc66a8s X-HE-Tag: 1689789563-705702 X-HE-Meta: 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 hY7oKTUG V1MAi5liwwbjoVvb3IQGJlhOliLOOHwNqyaBQTm4cl/uhre048EZC/AlmjHCO3qw3yqIaQdwBqjLU6Qrq6BoaWUyx4wgHsEXI/yQbYDJWpF8pFXk7+JeUvYkgsG1l2FppZHD+ltMtHyDKrRKHpu7hZbCMF2VDD35cbs92w6MQ8wdb7yL+yckdrXMtiaAEVjOrogFrnSr5ppzD3CwhEYyiRpuQaoz339KGDBbvqLy9w5n4DNeY2CGU12jLMmHOwVuUKeKk5duLkTo47XgjKIlDEYgiCcvXMOm0E1pwF8Jop0ZGOTsL0YhlxUpEM4GgkvE1NQK42vD/CO2DMN+KjzYKSy6BC6925wnCr+iwNDOUsl1qlkP/hRHVAQuUDGf1JWjxAIvWbivFGk5ElLZL1h8cXxq++kp9h6O2RCQKmG5bZS1f3I+wq9ucpdM77g== 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 Wednesday, 19 July 2023 06:17:51 EDT, Miklos Szeredi wrote: > On Thu, 29 Jun 2023 at 17:56, David Howells wrote: >>=20 >> Splicing data from, say, a file into a pipe currently leaves the source >> pages in the pipe after splice() returns - but this means that those pages= >> can be subsequently modified by shared-writable mmap(), write(), >> fallocate(), etc. before they're consumed. > > What is this trying to fix? The above behavior is well known, so > it's not likely to be a problem. Respectfully, it's not well-known, as it's not documented. If the splice(2)=20= man page had mentioned that pages can be mutated after they're already=20 ostensibly at rest in the output pipe buffer, then my nightly backups=20 wouldn't have been incurring corruption silently for many months.