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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 993E3C2D0EC for ; Wed, 8 Apr 2020 02:23:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5B063206BE for ; Wed, 8 Apr 2020 02:23:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726508AbgDHCXZ (ORCPT ); Tue, 7 Apr 2020 22:23:25 -0400 Received: from mail104.syd.optusnet.com.au ([211.29.132.246]:41575 "EHLO mail104.syd.optusnet.com.au" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726416AbgDHCXY (ORCPT ); Tue, 7 Apr 2020 22:23:24 -0400 Received: from dread.disaster.area (pa49-180-164-3.pa.nsw.optusnet.com.au [49.180.164.3]) by mail104.syd.optusnet.com.au (Postfix) with ESMTPS id 796657EC541; Wed, 8 Apr 2020 12:23:19 +1000 (AEST) Received: from dave by dread.disaster.area with local (Exim 4.92.3) (envelope-from ) id 1jM0N4-0006SI-9E; Wed, 08 Apr 2020 12:23:18 +1000 Date: Wed, 8 Apr 2020 12:23:18 +1000 From: Dave Chinner To: ira.weiny@intel.com Cc: linux-kernel@vger.kernel.org, "Darrick J. Wong" , Dan Williams , Christoph Hellwig , "Theodore Y. Ts'o" , Jan Kara , Jeff Moyer , linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH V6 7/8] fs/xfs: Change xfs_ioctl_setattr_dax_invalidate() to xfs_ioctl_dax_check() Message-ID: <20200408022318.GJ24067@dread.disaster.area> References: <20200407182958.568475-1-ira.weiny@intel.com> <20200407182958.568475-8-ira.weiny@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200407182958.568475-8-ira.weiny@intel.com> User-Agent: Mutt/1.10.1 (2018-07-13) X-Optus-CM-Score: 0 X-Optus-CM-Analysis: v=2.3 cv=LYdCFQXi c=1 sm=1 tr=0 a=K0+o7W9luyMo1Ua2eXjR1w==:117 a=K0+o7W9luyMo1Ua2eXjR1w==:17 a=jpOVt7BSZ2e4Z31A5e1TngXxSK0=:19 a=kj9zAlcOel0A:10 a=cl8xLZFz6L8A:10 a=QyXUC8HyAAAA:8 a=7-415B0cAAAA:8 a=iDAWdUprJv7Cp1nHmGUA:9 a=CjuIK1q_8ugA:10 a=biEYGPWJfzWAr4FL6Ov7:22 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 07, 2020 at 11:29:57AM -0700, ira.weiny@intel.com wrote: > From: Ira Weiny > > We only support changing FS_XFLAG_DAX on directories. Files get their > flag from the parent directory on creation only. So no data > invalidation needs to happen. Which leads me to ask: how are users and/or admins supposed to remove the flag from regular files once it is set in the filesystem? Only being able to override the flag via the "dax=never" mount option means that once the flag is set, nobody can ever remove it and they can only globally turn off dax if it gets set incorrectly. It also means a global interrupt because all apps on the filesystem need to be stopped so the filesystem can be unmounted and mounted again with dax=never. This is highly unfriendly to admins and users. IOWs, we _must_ be able to clear this inode flag on regular inodes in some way. I don't care if it doesn't change the current in-memory state, but we must be able to clear the flags so that the next time the inodes are instantiated DAX is not enabled for those files... Cheers, Dave. -- Dave Chinner david@fromorbit.com