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=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no 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 9203BC34044 for ; Tue, 18 Feb 2020 16:02:51 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 3CB2B22527 for ; Tue, 18 Feb 2020 16:02:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="sJmwamej" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3CB2B22527 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id A512B6B0003; Tue, 18 Feb 2020 11:02:50 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id A014B6B0008; Tue, 18 Feb 2020 11:02:50 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 916706B000A; Tue, 18 Feb 2020 11:02:50 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0046.hostedemail.com [216.40.44.46]) by kanga.kvack.org (Postfix) with ESMTP id 771C56B0003 for ; Tue, 18 Feb 2020 11:02:50 -0500 (EST) Received: from smtpin18.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 10536181AC9C6 for ; Tue, 18 Feb 2020 16:02:50 +0000 (UTC) X-FDA: 76503716100.18.horse77_6fe95f7ba8b3a X-HE-Tag: horse77_6fe95f7ba8b3a X-Filterd-Recvd-Size: 3010 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf30.hostedemail.com (Postfix) with ESMTP for ; Tue, 18 Feb 2020 16:02:48 +0000 (UTC) Received: from willie-the-truck (236.31.169.217.in-addr.arpa [217.169.31.236]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id D9BE3208C4; Tue, 18 Feb 2020 16:02:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1582041768; bh=o4w+569dv1GCGrISoBWEYP5IMjCUbMFmPglubauRSUw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=sJmwamejBIh3JXI/OSELinawXIDJYC1HxfJRZVLI5ILdnQ7aawHvEqfEt0T0dI05k topeyzIoba5rPa/6up/cflILnFesz1plk8Qf7fAGQJDWV8/GXTtQW3Wu9+ag8OoamK ShWIVWTZHDliROe7qPK2rjufBVu0wLY1kdMxeWbs= Date: Tue, 18 Feb 2020 16:02:42 +0000 From: Will Deacon To: Sean Christopherson Cc: David Hildenbrand , Christian Borntraeger , Janosch Frank , Andrew Morton , KVM , Cornelia Huck , Thomas Huth , Ulrich Weigand , Claudio Imbrenda , linux-s390 , Michael Mueller , Vasily Gorbik , Andrea Arcangeli , linux-mm@kvack.org Subject: Re: [PATCH v2 01/42] mm:gup/writeback: add callbacks for inaccessible pages Message-ID: <20200218160242.GB1133@willie-the-truck> References: <20200214222658.12946-1-borntraeger@de.ibm.com> <20200214222658.12946-2-borntraeger@de.ibm.com> <107a8a72-b745-26f2-5805-c4d99ce77b35@redhat.com> <20200218154610.GB27565@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200218154610.GB27565@linux.intel.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000008, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Feb 18, 2020 at 07:46:10AM -0800, Sean Christopherson wrote: > On Tue, Feb 18, 2020 at 09:27:20AM +0100, David Hildenbrand wrote: > > On 17.02.20 12:10, Christian Borntraeger wrote: > > > So yes, if everything is setup properly this should not fail in real life > > > and only we have a kernel (or firmware) bug. > > > > > > > Then, without feedback from other possible users, this should be a void > > function. So either introduce error handling or convert it to a void for > > now (and add e.g., BUG_ON and a comment inside the s390x implementation). > > My preference would also be for a void function (versus ignoring an int > return). The gup code could certainly handle the error value, although the writeback is a lot less clear (so a BUG_ON() would seem to be sufficient for now). Will