From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ot0-f200.google.com (mail-ot0-f200.google.com [74.125.82.200]) by kanga.kvack.org (Postfix) with ESMTP id 16B5C6B0009 for ; Wed, 31 Jan 2018 12:48:44 -0500 (EST) Received: by mail-ot0-f200.google.com with SMTP id l17so2906106otf.12 for ; Wed, 31 Jan 2018 09:48:44 -0800 (PST) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id b187si7963747oih.542.2018.01.31.09.48.43 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 31 Jan 2018 09:48:43 -0800 (PST) Date: Wed, 31 Jan 2018 12:48:40 -0500 From: Jerome Glisse Subject: Re: [LSF/MM TOPIC] Killing reliance on struct page->mapping Message-ID: <20180131174840.GF2912@redhat.com> References: <20180130004347.GD4526@redhat.com> <111f49c1-02d1-3355-e403-a8f91c0191e2@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <111f49c1-02d1-3355-e403-a8f91c0191e2@huawei.com> Sender: owner-linux-mm@kvack.org List-ID: To: Igor Stoppa Cc: lsf-pc@lists.linux-foundation.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-block@vger.kernel.org On Wed, Jan 31, 2018 at 07:09:48PM +0200, Igor Stoppa wrote: > On 30/01/18 02:43, Jerome Glisse wrote: > > [...] > > > Maybe we can kill page->mapping altogether as a result of this. However this is > > not my motivation at this time. > > We had a discussion some time ago > > http://www.openwall.com/lists/kernel-hardening/2017/07/07/7 > > where you advised to use it for tracking pmalloc pages vs area, which > generated this patch: > > http://www.openwall.com/lists/kernel-hardening/2018/01/24/7 > > Could you please comment what wold happen to the shortcut from struct > page to vm_struct that this patch is now introducing? Sadly struct page fields means different thing depending on the context in which the page is use. This is confusing i know. So when i say kill page->mapping i am not saying shrink the struct page and remove that field, i am saying maybe we can kill current user of page->mapping for regular process page (ie page that are in some mmap() area of a process). Other use of that field in different context like yours are not affected by this change and can ignore it alltogether. Hope this clarify it :) Cheers, Jerome -- 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