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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 A5941C43441 for ; Fri, 9 Nov 2018 20:36:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 73FA420827 for ; Fri, 9 Nov 2018 20:36:37 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 73FA420827 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728461AbeKJGSs (ORCPT ); Sat, 10 Nov 2018 01:18:48 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:48196 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726110AbeKJGSs (ORCPT ); Sat, 10 Nov 2018 01:18:48 -0500 Received: from akpm3.svl.corp.google.com (unknown [104.133.8.65]) by mail.linuxfoundation.org (Postfix) with ESMTPSA id 01AFCC46; Fri, 9 Nov 2018 20:36:34 +0000 (UTC) Date: Fri, 9 Nov 2018 12:36:34 -0800 From: Andrew Morton To: "Joel Fernandes (Google)" Cc: linux-kernel@vger.kernel.org, jreck@google.com, john.stultz@linaro.org, tkjos@google.com, gregkh@linuxfoundation.org, hch@infradead.org, Al Viro , dancol@google.com, "J. Bruce Fields" , Jeff Layton , Khalid Aziz , Lei Yang , linux-fsdevel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, =?ISO-8859-1?Q?Marc-Andr=E9?= Lureau , Mike Kravetz , minchan@kernel.org, Shuah Khan , valdis.kletnieks@vt.edu Subject: Re: [PATCH v3 resend 1/2] mm: Add an F_SEAL_FUTURE_WRITE seal to memfd Message-Id: <20181109123634.6fe7467bb9237851250c9c56@linux-foundation.org> In-Reply-To: <20181108041537.39694-1-joel@joelfernandes.org> References: <20181108041537.39694-1-joel@joelfernandes.org> X-Mailer: Sylpheed 3.6.0 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 7 Nov 2018 20:15:36 -0800 "Joel Fernandes (Google)" wrote: > Android uses ashmem for sharing memory regions. We are looking forward > to migrating all usecases of ashmem to memfd so that we can possibly > remove the ashmem driver in the future from staging while also > benefiting from using memfd and contributing to it. Note staging drivers > are also not ABI and generally can be removed at anytime. > > One of the main usecases Android has is the ability to create a region > and mmap it as writeable, then add protection against making any > "future" writes while keeping the existing already mmap'ed > writeable-region active. This allows us to implement a usecase where > receivers of the shared memory buffer can get a read-only view, while > the sender continues to write to the buffer. > See CursorWindow documentation in Android for more details: > https://developer.android.com/reference/android/database/CursorWindow It appears that the memfd_create and fcntl manpages will require updating. Please attend to this at the appropriate time? Actually, it would help the review process if those updates were available now.