From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi0-f72.google.com (mail-oi0-f72.google.com [209.85.218.72]) by kanga.kvack.org (Postfix) with ESMTP id 44CDC6B025F for ; Tue, 15 Aug 2017 12:28:44 -0400 (EDT) Received: by mail-oi0-f72.google.com with SMTP id k82so1513522oih.1 for ; Tue, 15 Aug 2017 09:28:44 -0700 (PDT) Received: from mail.kernel.org (mail.kernel.org. [198.145.29.99]) by mx.google.com with ESMTPS id k18si7012616oiy.403.2017.08.15.09.28.43 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 15 Aug 2017 09:28:43 -0700 (PDT) Received: from mail-it0-f42.google.com (mail-it0-f42.google.com [209.85.214.42]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id AACA122B55 for ; Tue, 15 Aug 2017 16:28:42 +0000 (UTC) Received: by mail-it0-f42.google.com with SMTP id m34so6520795iti.1 for ; Tue, 15 Aug 2017 09:28:42 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <150277753660.23945.11500026891611444016.stgit@dwillia2-desk3.amr.corp.intel.com> References: <150277752553.23945.13932394738552748440.stgit@dwillia2-desk3.amr.corp.intel.com> <150277753660.23945.11500026891611444016.stgit@dwillia2-desk3.amr.corp.intel.com> From: Andy Lutomirski Date: Tue, 15 Aug 2017 09:28:21 -0700 Message-ID: Subject: Re: [PATCH v4 2/3] mm: introduce MAP_VALIDATE a mechanism for adding new mmap flags Content-Type: text/plain; charset="UTF-8" Sender: owner-linux-mm@kvack.org List-ID: To: Dan Williams Cc: "Darrick J. Wong" , Jan Kara , Arnd Bergmann , linux-nvdimm , Linux API , "linux-kernel@vger.kernel.org" , linux-xfs@vger.kernel.org, "linux-mm@kvack.org" , Andrew Lutomirski , Linux FS Devel , Andrew Morton , Christoph Hellwig On Mon, Aug 14, 2017 at 11:12 PM, Dan Williams wrote: > The mmap syscall suffers from the ABI anti-pattern of not validating > unknown flags. However, proposals like MAP_SYNC and MAP_DIRECT need a > mechanism to define new behavior that is known to fail on older kernels > without the feature. Use the fact that specifying MAP_SHARED and > MAP_PRIVATE at the same time is invalid as a cute hack to allow a new > set of validated flags to be introduced. While this is cute, is it actually better than a new syscall? -- 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