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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,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 9C98BC2BA15 for ; Thu, 2 Apr 2020 20:55:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7CBA02078B for ; Thu, 2 Apr 2020 20:55:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389950AbgDBUzV (ORCPT ); Thu, 2 Apr 2020 16:55:21 -0400 Received: from mga11.intel.com ([192.55.52.93]:46980 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727412AbgDBUzV (ORCPT ); Thu, 2 Apr 2020 16:55:21 -0400 IronPort-SDR: HvX8PTnsRwsdV7NgJbUfU0c8d8qEGuDIWYKkfp6qg1t4NgkZEVSEZhF+lJsaHGmNws25xH9pv2 zG5CuBBU+CEQ== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga006.jf.intel.com ([10.7.209.51]) by fmsmga102.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Apr 2020 13:55:20 -0700 IronPort-SDR: n7VuT2YXbKLcmeUbGxcVNFXBqmmw/fPac17FJw0a0KoOKT0y+uax/DxdhYqSxrNozLBsG2D32X Ll5cGSDLDUmA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.72,336,1580803200"; d="scan'208";a="253141592" Received: from iweiny-desk2.sc.intel.com ([10.3.52.147]) by orsmga006.jf.intel.com with ESMTP; 02 Apr 2020 13:55:19 -0700 Date: Thu, 2 Apr 2020 13:55:19 -0700 From: Ira Weiny To: Christoph Hellwig Cc: Jan Kara , "Darrick J. Wong" , Dave Chinner , "Theodore Y. Ts'o" , Dan Williams , Linux Kernel Mailing List , Alexander Viro , linux-ext4 , linux-xfs , linux-fsdevel , Andrew Morton , Linus Torvalds Subject: Re: [PATCH V5 00/12] Enable per-file/per-directory DAX operations V5 Message-ID: <20200402205518.GF3952565@iweiny-DESK2.sc.intel.com> References: <20200305155144.GA5598@lst.de> <20200309170437.GA271052@iweiny-DESK2.sc.intel.com> <20200311033614.GQ1752567@magnolia> <20200311062952.GA11519@lst.de> <20200316095224.GF12783@quack2.suse.cz> <20200316095509.GA13788@lst.de> <20200401040021.GC56958@magnolia> <20200401102511.GC19466@quack2.suse.cz> <20200402085327.GA19109@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200402085327.GA19109@lst.de> User-Agent: Mutt/1.11.1 (2018-12-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Apr 02, 2020 at 10:53:27AM +0200, Christoph Hellwig wrote: > On Wed, Apr 01, 2020 at 12:25:11PM +0200, Jan Kara wrote: > > > - Applications must call statx to discover the current S_DAX state. > > > > > > - There exists an advisory file inode flag FS_XFLAG_DAX that can be > > > changed on files that have no blocks allocated to them. Changing > > > this flag does not necessarily change the S_DAX state immediately > > > but programs can query the S_DAX state via statx. > > > > I generally like the proposal but I think the fact that toggling > > FS_XFLAG_DAX will not have immediate effect on S_DAX will cause quite some > > confusion and ultimately bug reports. I'm thinking whether we could somehow > > improve this... For example an ioctl that would try to make set inode flags > > effective by evicting the inode (and returning EBUSY if the eviction is > > impossible for some reason)? > > I'd just return an error for that case, don't play silly games like > evicting the inode. I think I agree with Christoph here. But I want to clarify. I was heading in a direction of failing the ioctl completely. But we could have the flag change with an appropriate error which could let the user know the change has been delayed. But I don't immediately see what error code is appropriate for such an indication. Candidates I can envision: EAGAIN ERESTART EUSERS EINPROGRESS None are perfect but I'm leaning toward EINPROGRESS. Ira