From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io0-f198.google.com (mail-io0-f198.google.com [209.85.223.198]) by kanga.kvack.org (Postfix) with ESMTP id 49FF26B0253 for ; Thu, 21 Jul 2016 10:27:37 -0400 (EDT) Received: by mail-io0-f198.google.com with SMTP id m101so162987084ioi.0 for ; Thu, 21 Jul 2016 07:27:37 -0700 (PDT) Received: from szxga02-in.huawei.com (szxga02-in.huawei.com. [119.145.14.65]) by mx.google.com with ESMTP id a198si3994074oii.256.2016.07.21.07.27.32 for ; Thu, 21 Jul 2016 07:27:36 -0700 (PDT) Message-ID: <5790D8A3.3090808@huawei.com> Date: Thu, 21 Jul 2016 22:13:55 +0800 From: zhong jiang MIME-Version: 1.0 Subject: Re: + mm-hugetlb-fix-race-when-migrate-pages.patch added to -mm tree References: <20160721074340.GA26398@dhcp22.suse.cz> <5790A9D1.6060304@huawei.com> <20160721112754.GH26379@dhcp22.suse.cz> <5790BCB1.4020800@huawei.com> <20160721123001.GI26379@dhcp22.suse.cz> <5790C3DB.8000505@huawei.com> <20160721125555.GJ26379@dhcp22.suse.cz> <5790CD52.6050200@huawei.com> <20160721134044.GL26379@dhcp22.suse.cz> <5790D4FF.8070907@huawei.com> <20160721140124.GN26379@dhcp22.suse.cz> In-Reply-To: <20160721140124.GN26379@dhcp22.suse.cz> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Naoya Horiguchi , akpm@linux-foundation.org, qiuxishi@huawei.com, vbabka@suse.cz, mm-commits@vger.kernel.org, Mike Kravetz , Mel Gorman , linux-mm@kvack.org On 2016/7/21 22:01, Michal Hocko wrote: > On Thu 21-07-16 21:58:23, zhong jiang wrote: >> On 2016/7/21 21:40, Michal Hocko wrote: >>> On Thu 21-07-16 21:25:38, zhong jiang wrote: >>>> On 2016/7/21 20:55, Michal Hocko wrote: >>> [...] >>>>> OK, now I understand what you mean. So you mean that a different process >>>>> initiates the migration while this path copies to pte. That is certainly >>>>> possible but I still fail to see what is the problem about that. >>>>> huge_pte_alloc will return the identical pte whether it is regular or >>>>> migration one. So what exactly is the problem? >>>>> >>>> copy_hugetlb_page_range obtain the shared dst_pte, it may be not equal >>>> to the src_pte. The dst_pte can come from other process sharing the >>>> mapping. >>> So you mean that the parent doesn't have the shared pte while the child >>> would get one? >>> >> no, parent must have the shared pte because the the child copy the >> parent. but parent is not the only source pte we can get. when we >> scan the maping->i_mmap, firstly ,it can obtain a shared pte from >> other process. but I am not sure. > But then all the shared ptes should be identical, no? Or am I missing > something? all the shared ptes should be identical, but there is a possibility that new process want to share the pte from other process , other than the parent, For the first time the process is about to share pte with it. is it possiblity? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org