From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lf0-f69.google.com (mail-lf0-f69.google.com [209.85.215.69]) by kanga.kvack.org (Postfix) with ESMTP id 62D756B0005 for ; Wed, 20 Jul 2016 09:00:58 -0400 (EDT) Received: by mail-lf0-f69.google.com with SMTP id 33so32112374lfw.1 for ; Wed, 20 Jul 2016 06:00:58 -0700 (PDT) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id o5si875743wjs.198.2016.07.20.06.00.56 for (version=TLS1 cipher=AES128-SHA bits=128/128); Wed, 20 Jul 2016 06:00:56 -0700 (PDT) Date: Wed, 20 Jul 2016 15:00:56 +0200 From: Michal Hocko Subject: Re: [PATCH v2] mm/hugetlb: fix race when migrate pages Message-ID: <20160720130055.GL11249@dhcp22.suse.cz> References: <1468935958-21810-1-git-send-email-zhongjiang@huawei.com> <20160720073859.GE11249@dhcp22.suse.cz> <578F4C7C.6000706@huawei.com> <20160720121645.GJ11249@dhcp22.suse.cz> <20160720124501.GK11249@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160720124501.GK11249@dhcp22.suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: zhong jiang Cc: vbabka@suse.cz, qiuxishi@huawei.com, akpm@linux-foundation.org, linux-mm@kvack.org, Mike Kravetz , Naoya Horiguchi , Mel Gorman On Wed 20-07-16 14:45:01, Michal Hocko wrote: [...] > I was talking to Mel (CCed) and he has raised a good question. So if you > encounter a page under migration and fail to share the pmd with it how > can you have a proper content of the target page in the end? Hmm, I was staring into the code some more and it seems this would be OK because we should hit hugetlb_no_page with the newel instantiated pmd and associate it with a page from the radix tree. So unless I am missing something the corruption shouldn't be possible. I believe the post pmd_populate race is still there, though, so I believe the approach should be rethought. -- Michal Hocko SUSE Labs -- 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