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=-0.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no 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 87EA9C33C9E for ; Thu, 30 Jan 2020 12:19:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 58A47206D3 for ; Thu, 30 Jan 2020 12:19:59 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="D0WwOnHP" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727208AbgA3MT6 (ORCPT ); Thu, 30 Jan 2020 07:19:58 -0500 Received: from us-smtp-2.mimecast.com ([207.211.31.81]:39974 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726873AbgA3MT6 (ORCPT ); Thu, 30 Jan 2020 07:19:58 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1580386797; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=6Xqdu8J6TOj9He6qQ+BqrK7qHeGQ1dIibFBQ/FqCh1s=; b=D0WwOnHP24mRjhrfcRwZYM+JuqHTBH2t/xypTKgVP3o030xg1EGGmN39SeW9n8VZs41+O9 +SVxUvhqbEPPAheL58Xwx2LORq17Cyd8oPxZaP6bHgISL7lVXbk71LCIIsvsRl2nsgCOoP LPC675ERSwQ3tmADIwyScp/fvCorzIw= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-23-n6jIJxsQONivvhbjyMM1Ng-1; Thu, 30 Jan 2020 07:19:51 -0500 X-MC-Unique: n6jIJxsQONivvhbjyMM1Ng-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 94C6D8010EE; Thu, 30 Jan 2020 12:19:49 +0000 (UTC) Received: from oldenburg2.str.redhat.com (ovpn-116-29.ams2.redhat.com [10.36.116.29]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 967175DA75; Thu, 30 Jan 2020 12:19:41 +0000 (UTC) From: Florian Weimer To: Brian Geffon Cc: Andrew Morton , "Michael S . Tsirkin" , Arnd Bergmann , LKML , linux-mm , linux-api@vger.kernel.org, Andy Lutomirski , Andrea Arcangeli , Sonny Rao , Minchan Kim , Joel Fernandes , Yu Zhao , Jesse Barnes Subject: Re: [PATCH v2] mm: Add MREMAP_DONTUNMAP to mremap(). References: <20200123014627.71720-1-bgeffon@google.com> <20200124190625.257659-1-bgeffon@google.com> <87imkxxl5d.fsf@oldenburg2.str.redhat.com> Date: Thu, 30 Jan 2020 13:19:39 +0100 In-Reply-To: (Brian Geffon's message of "Mon, 27 Jan 2020 14:33:44 -0800") Message-ID: <87eevh3zms.fsf@oldenburg2.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Brian Geffon: > Hi Florian, > copy_vma will make a copy of the existing VMA leaving the old VMA > unchanged, so the source keeps its existing protections, this is what > makes it very useful along with userfaultfd. I see. On the other hand, it's impossible to get the PROT_NONE behavior by a subsequent mprotect call because the mremap has to fail in some cases in vm.overcommit_memory=2 mode. But maybe that other behavior can be provided with a different flag if it turns out to be useful in the future. Thanks, Florian