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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_MUTT 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 99A5EC2BCA1 for ; Fri, 7 Jun 2019 14:51:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 71F642083D for ; Fri, 7 Jun 2019 14:51:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729642AbfFGOvB (ORCPT ); Fri, 7 Jun 2019 10:51:01 -0400 Received: from mga18.intel.com ([134.134.136.126]:24997 "EHLO mga18.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728446AbfFGOvB (ORCPT ); Fri, 7 Jun 2019 10:51:01 -0400 X-Amp-Result: UNSCANNABLE X-Amp-File-Uploaded: False Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by orsmga106.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 07 Jun 2019 07:51:00 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.63,563,1557212400"; d="scan'208";a="182683628" Received: from iweiny-desk2.sc.intel.com ([10.3.52.157]) by fmsmga002.fm.intel.com with ESMTP; 07 Jun 2019 07:51:00 -0700 Date: Fri, 7 Jun 2019 07:52:13 -0700 From: Ira Weiny To: Jason Gunthorpe Cc: Jan Kara , Dan Williams , Theodore Ts'o , Jeff Layton , Dave Chinner , Matthew Wilcox , linux-xfs@vger.kernel.org, Andrew Morton , John Hubbard , =?iso-8859-1?B?Suly9G1l?= Glisse , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nvdimm@lists.01.org, linux-ext4@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH RFC 00/10] RDMA/FS DAX truncate proposal Message-ID: <20190607145213.GB14559@iweiny-DESK2.sc.intel.com> References: <20190606014544.8339-1-ira.weiny@intel.com> <20190606104203.GF7433@quack2.suse.cz> <20190606195114.GA30714@ziepe.ca> <20190606222228.GB11698@iweiny-DESK2.sc.intel.com> <20190607103636.GA12765@quack2.suse.cz> <20190607121729.GA14802@ziepe.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190607121729.GA14802@ziepe.ca> 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 Fri, Jun 07, 2019 at 09:17:29AM -0300, Jason Gunthorpe wrote: > On Fri, Jun 07, 2019 at 12:36:36PM +0200, Jan Kara wrote: > > > Because the pins would be invisible to sysadmin from that point on. > > It is not invisible, it just shows up in a rdma specific kernel > interface. You have to use rdma netlink to see the kernel object > holding this pin. > > If this visibility is the main sticking point I suggest just enhancing > the existing MR reporting to include the file info for current GUP > pins and teaching lsof to collect information from there as well so it > is easy to use. > > If the ownership of the lease transfers to the MR, and we report that > ownership to userspace in a way lsof can find, then I think all the > concerns that have been raised are met, right? I was contemplating some new lsof feature yesterday. But what I don't think we want is sysadmins to have multiple tools for multiple subsystems. Or even have to teach lsof something new for every potential new subsystem user of GUP pins. I was thinking more along the lines of reporting files which have GUP pins on them directly somewhere (dare I say procfs?) and teaching lsof to report that information. That would cover any subsystem which does a longterm pin. > > > ugly to live so we have to come up with something better. The best I can > > currently come up with is to have a method associated with the lease that > > would invalidate the RDMA context that holds the pins in the same way that > > a file close would do it. > > This is back to requiring all RDMA HW to have some new behavior they > currently don't have.. > > The main objection to the current ODP & DAX solution is that very > little HW can actually implement it, having the alternative still > require HW support doesn't seem like progress. > > I think we will eventually start seein some HW be able to do this > invalidation, but it won't be universal, and I'd rather leave it > optional, for recovery from truely catastrophic errors (ie my DAX is > on fire, I need to unplug it). Agreed. I think software wise there is not much some of the devices can do with such an "invalidate". Ira