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=-1.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, T_DKIMWL_WL_HIGH autolearn=ham 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 816B3C4321D for ; Thu, 23 Aug 2018 17:02:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 385702077B for ; Thu, 23 Aug 2018 17:02:25 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=oracle.com header.i=@oracle.com header.b="SayXUW/u" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 385702077B Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=oracle.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726647AbeHWUdA (ORCPT ); Thu, 23 Aug 2018 16:33:00 -0400 Received: from aserp2120.oracle.com ([141.146.126.78]:46714 "EHLO aserp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726064AbeHWUdA (ORCPT ); Thu, 23 Aug 2018 16:33:00 -0400 Received: from pps.filterd (aserp2120.oracle.com [127.0.0.1]) by aserp2120.oracle.com (8.16.0.22/8.16.0.22) with SMTP id w7NGwod8169079; Thu, 23 Aug 2018 17:02:05 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=subject : to : cc : references : from : message-id : date : mime-version : in-reply-to : content-type : content-transfer-encoding; s=corp-2018-07-02; bh=+vfOacba25ewEB/Hv6P+3QqgxyH0xomkmTfF8xQf3Qo=; b=SayXUW/uYxwF3lIiQkSYK8dJtjN9G2drVFgJ2d/XCQFBXs7Ji4jPqPAszBZ+iLBQeNNP WobMsTpdHu4k7mpP8/JbgG++MTaGJN910Qa8HTsgYNoD432wz5Zp84epfqbXmriDnLK/ /WJw/mLFZ6b4Wlh2/JuFzsrxXpt3ElDVjc7N2+BQpmMHcRfcpg77PT0FCcOtYlWJXtHd xigGiet5craYekRrSC9IqTd6ZH7ZsgksaNIkbZuZvMlP+5QkYE4gJFWlPMTZry4hjN5a obg0TnMpTBaSuQisEjZWWDtSWzF3UQGpJ30CAP4rw5twC/tT6mIFcAnOgfAjE9VirsW9 zg== Received: from userv0022.oracle.com (userv0022.oracle.com [156.151.31.74]) by aserp2120.oracle.com with ESMTP id 2kxbdqapt5-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 23 Aug 2018 17:02:04 +0000 Received: from userv0122.oracle.com (userv0122.oracle.com [156.151.31.75]) by userv0022.oracle.com (8.14.4/8.14.4) with ESMTP id w7NH1wPA016060 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 23 Aug 2018 17:01:59 GMT Received: from abhmp0003.oracle.com (abhmp0003.oracle.com [141.146.116.9]) by userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id w7NH1vJJ016809; Thu, 23 Aug 2018 17:01:57 GMT Received: from [192.168.1.164] (/50.38.38.67) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Thu, 23 Aug 2018 10:01:57 -0700 Subject: Re: [PATCH v3 1/2] mm: migration: fix migration of huge PMD shared pages To: Michal Hocko Cc: kbuild test robot , kbuild-all@01.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, "Kirill A . Shutemov" , =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= , Vlastimil Babka , Naoya Horiguchi , Davidlohr Bueso , Andrew Morton , stable@vger.kernel.org References: <20180821205902.21223-2-mike.kravetz@oracle.com> <201808220831.eM0je51n%fengguang.wu@intel.com> <975b740d-26a6-eb3f-c8ca-1a9995d0d343@oracle.com> <20180823124855.GI29735@dhcp22.suse.cz> From: Mike Kravetz Message-ID: <12ea5339-f2b1-62b4-6d37-57d737fac34a@oracle.com> Date: Thu, 23 Aug 2018 10:01:55 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20180823124855.GI29735@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=8994 signatures=668707 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1807170000 definitions=main-1808230176 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/23/2018 05:48 AM, Michal Hocko wrote: > On Tue 21-08-18 18:10:42, Mike Kravetz wrote: > [...] > > OK, after burning myself when trying to be clever here it seems like > your proposed solution is indeed simpler. > >> +bool huge_pmd_sharing_possible(struct vm_area_struct *vma, >> + unsigned long *start, unsigned long *end) >> +{ >> + unsigned long check_addr = *start; >> + bool ret = false; >> + >> + if (!(vma->vm_flags & VM_MAYSHARE)) >> + return ret; >> + >> + for (check_addr = *start; check_addr < *end; check_addr += PUD_SIZE) { >> + unsigned long a_start = check_addr & PUD_MASK; >> + unsigned long a_end = a_start + PUD_SIZE; > > I guess this should be rather in HPAGE_SIZE * PTRS_PER_PTE units as > huge_pmd_unshare does. Sure, I can do that. However, I consider the statement making that calculation in huge_pmd_unshare to be VERY ugly and confusing code. *addr = ALIGN(*addr, HPAGE_SIZE * PTRS_PER_PTE) - HPAGE_SIZE; Note that it is adjusting the value of passed argument 'unsigned long *addr'. This argument/value is part of a loop condition in all current callers of huge_pmd_unshare. For instance: for (; address < end; address += huge_page_size(h)) { So, that calculation in huge_pmd_unshare gets the calling loop back to the starting address of the unmapped range. It even takes the loop increment 'huge_page_size(h)' into account. That is why that ' - HPAGE_SIZE' is at the end of the calculation. ugly and confusing! And on my list of things to clean up. -- Mike Kravetz