From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from verein.lst.de ([213.95.11.211]:56652 "EHLO newverein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725973AbeIAMk1 (ORCPT ); Sat, 1 Sep 2018 08:40:27 -0400 Date: Sat, 1 Sep 2018 10:32:17 +0200 From: Christoph Hellwig Subject: Re: [PATCH, RFC] xfs: re-enable FIBMAP on reflink; disable for swap Message-ID: <20180901083217.GD670@lst.de> References: <20180830163614.GA27069@lst.de> <65e818f2-885d-50a4-0d4a-7700c703c2af@sandeen.net> <20180830180204.GC2853@bfoster> <20180830182849.GA4359@magnolia> <10d35380-6f5f-22a5-7b6a-1cfb60c53cfd@sandeen.net> <20180831001106.GG5631@dastard> <7ae98d88-7cbf-1314-83b6-dc15da5124eb@sandeen.net> <20180831030542.GK5631@dastard> <19b4da59-3720-6647-e557-9d7353ed509b@sandeen.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <19b4da59-3720-6647-e557-9d7353ed509b@sandeen.net> Sender: linux-xfs-owner@vger.kernel.org List-ID: List-Id: xfs To: Eric Sandeen Cc: Dave Chinner , "Darrick J. Wong" , Brian Foster , Christoph Hellwig , Eric Sandeen , linux-xfs On Fri, Aug 31, 2018 at 08:08:11AM -0500, Eric Sandeen wrote: > If you can directly read the block device hosting the files, file > permissions of shared blocks are completely beside the point. The point is that you should never, ever directly read blocks from the block device, nevermind write. And we need to make sure userspace stops doing that instead of catering to it in any way. > The "typical use case" is to map a file for a bootloader to /read/ > at boot, and our arbitrary restriction has broken systems in > the real world, and burned a lot of institutional effort getting > to the bottom of the problem and working around it. And even that 'use case' is utterly broken.