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 21454C05027 for ; Mon, 23 Jan 2023 11:51:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231694AbjAWLv6 (ORCPT ); Mon, 23 Jan 2023 06:51:58 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44174 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230150AbjAWLvz (ORCPT ); Mon, 23 Jan 2023 06:51:55 -0500 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 D021123666 for ; Mon, 23 Jan 2023 03:51:10 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1674474670; 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=0JJckYyBTZyBY7j44qzn90Ae9aMKGleBaEKh6HgH8NU=; b=KUR2a/J7jp7RE2YDqiAguIb8ehY1F0jRSoUiPlucql8zyJ+m1Cxww8bwZwhJFCeZICGbc6 Eq8Ps3BMdZL94HmuGwDWzE0Pfo4GIaWqbym1IJ9Ik84UTD9HVuAjMEX6rYXPQu7CKBxGk4 iIE4ofzO2T3NOlUM3WCK8HMGsEOu2o4= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-159-GDKYFcVMOFmDY9Dof81bTQ-1; Mon, 23 Jan 2023 06:51:06 -0500 X-MC-Unique: GDKYFcVMOFmDY9Dof81bTQ-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 4B25A281DE64; Mon, 23 Jan 2023 11:51:05 +0000 (UTC) Received: from warthog.procyon.org.uk (unknown [10.33.36.23]) by smtp.corp.redhat.com (Postfix) with ESMTP id B00121121330; Mon, 23 Jan 2023 11:51:03 +0000 (UTC) Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 From: David Howells In-Reply-To: <246ba813-698b-8696-7f4d-400034a3380b@redhat.com> References: <246ba813-698b-8696-7f4d-400034a3380b@redhat.com> <20230120175556.3556978-1-dhowells@redhat.com> <20230120175556.3556978-3-dhowells@redhat.com> To: David Hildenbrand Cc: dhowells@redhat.com, Al Viro , Christoph Hellwig , Matthew Wilcox , Jens Axboe , Jan Kara , Jeff Layton , Logan Gunthorpe , linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, Christoph Hellwig , John Hubbard , linux-mm@kvack.org Subject: Re: [PATCH v7 2/8] iov_iter: Add a function to extract a page list from an iterator MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <3814748.1674474663.1@warthog.procyon.org.uk> Content-Transfer-Encoding: quoted-printable Date: Mon, 23 Jan 2023 11:51:03 +0000 Message-ID: <3814749.1674474663@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.3 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org David Hildenbrand wrote: > How does this work align with the goal of no longer using FOLL_GET for > O_DIRECT? We should get rid of any FOLL_GET usage for accessing page con= tent. Would that run the risk of changes being made by the child being visible t= o the a DIO write if the parent changes the buffer first? PARENT CHILD =3D=3D=3D=3D=3D=3D =3D=3D=3D=3D=3D start-DIO-write fork() =3D pid fork() =3D 0 alter-buffer CoW happens page copied original page retained alter-buffer David