Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933903AbbEMK7v (ORCPT ); Wed, 13 May 2015 06:59:51 -0400 Received: from forward-corp1f.mail.yandex.net ([95.108.130.40]:34337 "EHLO forward-corp1f.mail.yandex.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933516AbbEMK7s (ORCPT ); Wed, 13 May 2015 06:59:48 -0400 Authentication-Results: smtpcorp1m.mail.yandex.net; dkim=pass header.i=@yandex-team.ru Message-ID: <55532E9D.1040702@yandex-team.ru> Date: Wed, 13 May 2015 13:59:41 +0300 From: Konstantin Khlebnikov User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.6.0 MIME-Version: 1.0 To: "Kirill A. Shutemov" CC: linux-mm@kvack.org, Naoya Horiguchi , linux-kernel@vger.kernel.org, Andrew Morton , Mark Williamson , Pavel Emelyanov , linux-api@vger.kernel.org, Andy Lutomirski , Vlastimil Babka , Pavel Machek , Mark Seaborn , Linus Torvalds , Daniel James , Finn Grimwood Subject: Re: [PATCH v2 1/3] pagemap: add mmap-exclusive bit for marking pages mapped only here References: <20150512090156.24768.2521.stgit@buzz> <20150512094303.24768.10282.stgit@buzz> <20150512104055.GB18365@node.dhcp.inet.fi> In-Reply-To: <20150512104055.GB18365@node.dhcp.inet.fi> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1115 Lines: 26 On 12.05.2015 13:40, Kirill A. Shutemov wrote: > On Tue, May 12, 2015 at 12:43:03PM +0300, Konstantin Khlebnikov wrote: >> This patch sets bit 56 in pagemap if this page is mapped only once. >> It allows to detect exclusively used pages without exposing PFN: >> >> present file exclusive state >> 0 0 0 non-present >> 1 1 0 file page mapped somewhere else >> 1 1 1 file page mapped only here >> 1 0 0 anon non-CoWed page (shared with parent/child) >> 1 0 1 anon CoWed page (or never forked) > > Probably, worth noting that file-private pages are anon in this context. > You mean there's another kind of CoW pages? Yep, but from the kernel point of view these pages are the same. Anyway Userspace could look into /proc/*/maps and see is there any file beyond anon vma. -- Konstantin -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/