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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_2 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 14AEDC2BB55 for ; Thu, 16 Apr 2020 14:59:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EA2AB206D9 for ; Thu, 16 Apr 2020 14:59:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2407129AbgDPO7W (ORCPT ); Thu, 16 Apr 2020 10:59:22 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:63996 "EHLO mx0b-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2409558AbgDPO7O (ORCPT ); Thu, 16 Apr 2020 10:59:14 -0400 Received: from pps.filterd (m0127361.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.42/8.16.0.42) with SMTP id 03GEX74o061412 for ; Thu, 16 Apr 2020 10:59:12 -0400 Received: from e06smtp04.uk.ibm.com (e06smtp04.uk.ibm.com [195.75.94.100]) by mx0a-001b2d01.pphosted.com with ESMTP id 30erh9a0b4-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Thu, 16 Apr 2020 10:59:11 -0400 Received: from localhost by e06smtp04.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! 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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Thu, 16 Apr 2020 15:58:27 +0100 Received: from d06av21.portsmouth.uk.ibm.com (d06av21.portsmouth.uk.ibm.com [9.149.105.232]) by b06avi18878370.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 03GEx34v46596366 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 16 Apr 2020 14:59:03 GMT Received: from d06av21.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 559385205A; Thu, 16 Apr 2020 14:59:03 +0000 (GMT) Received: from p-imbrenda (unknown [9.145.0.99]) by d06av21.portsmouth.uk.ibm.com (Postfix) with ESMTP id 88FAA5204E; Thu, 16 Apr 2020 14:59:02 +0000 (GMT) Date: Thu, 16 Apr 2020 16:59:00 +0200 From: Claudio Imbrenda To: Dave Hansen Cc: Peter Zijlstra , Andy Lutomirski , linux-next@vger.kernel.org, akpm@linux-foundation.org, jack@suse.cz, kirill@shutemov.name, "Edgecombe, Rick P" , Sean Christopherson , borntraeger@de.ibm.com, david@redhat.com, aarcange@redhat.com, linux-mm@kvack.org, frankja@linux.ibm.com, sfr@canb.auug.org.au, jhubbard@nvidia.com, linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org, Will Deacon , "Williams, Dan J" Subject: Re: [PATCH v4 2/2] mm/gup/writeback: add callbacks for inaccessible pages In-Reply-To: References: <20200306132537.783769-1-imbrenda@linux.ibm.com> <20200306132537.783769-3-imbrenda@linux.ibm.com> <3ae46945-0c7b-03cd-700a-a6fe8003c6ab@intel.com> <20200415221754.GM2483@worktop.programming.kicks-ass.net> <20200416141547.29be5ea0@p-imbrenda> Organization: IBM X-Mailer: Claws Mail 3.17.5 (GTK+ 2.24.32; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 x-cbid: 20041614-0016-0000-0000-00000305A88E X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 20041614-0017-0000-0000-00003369AD2E Message-Id: <20200416165900.68bd4dba@p-imbrenda> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138,18.0.676 definitions=2020-04-16_05:2020-04-14,2020-04-16 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxlogscore=658 impostorscore=0 lowpriorityscore=0 phishscore=0 clxscore=1015 mlxscore=0 priorityscore=1501 adultscore=0 suspectscore=0 bulkscore=0 spamscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2004160105 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 16 Apr 2020 07:20:48 -0700 Dave Hansen wrote: > On 4/16/20 5:15 AM, Claudio Imbrenda wrote: > >> I assumed that this was all anonymous-only so it's always dirty > >> before writeback starts. > > it could also be mmapped > > Let's say you have a mmap()'d ramfs file. Another process calls which > doesn't have it mapped calls sys_write() and writes to the file. > > This means that host host has to write to the physical page and must > do arch_make_page_accessible() in the sys_write() path somewhere. > > There is a get_user_pages() in that path, but it's on the _source_ > buffer, not the ramfs page because the ramfs page is not mapped. > There's also no __test_set_page_writeback() because you can't write > back ramfs. > > Where is the arch_make_page_accessible() in this case on the ramfs > page? it's in the fault handler for the exception the CPU will get when attempting to write the data to the protected page