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,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 64727C3A59E for ; Wed, 4 Sep 2019 22:25:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 40C80208E4 for ; Wed, 4 Sep 2019 22:25:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730454AbfIDWZw (ORCPT ); Wed, 4 Sep 2019 18:25:52 -0400 Received: from mga05.intel.com ([192.55.52.43]:12586 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725965AbfIDWZw (ORCPT ); Wed, 4 Sep 2019 18:25:52 -0400 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from orsmga003.jf.intel.com ([10.7.209.27]) by fmsmga105.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 04 Sep 2019 15:25:51 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.64,468,1559545200"; d="scan'208";a="185252801" Received: from iweiny-desk2.sc.intel.com ([10.3.52.157]) by orsmga003.jf.intel.com with ESMTP; 04 Sep 2019 15:25:50 -0700 Date: Wed, 4 Sep 2019 15:25:50 -0700 From: Ira Weiny To: Jason Gunthorpe Cc: Andrew Morton , Dan Williams , Matthew Wilcox , Jan Kara , Theodore Ts'o , John Hubbard , Michal Hocko , Dave Chinner , linux-xfs@vger.kernel.org, linux-rdma@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-nvdimm@lists.01.org, linux-ext4@vger.kernel.org, linux-mm@kvack.org Subject: Re: [RFC PATCH v2 16/19] RDMA/uverbs: Add back pointer to system file object Message-ID: <20190904222549.GC31319@iweiny-DESK2.sc.intel.com> References: <20190809225833.6657-17-ira.weiny@intel.com> <20190812130039.GD24457@ziepe.ca> <20190812172826.GA19746@iweiny-DESK2.sc.intel.com> <20190812175615.GI24457@ziepe.ca> <20190812211537.GE20634@iweiny-DESK2.sc.intel.com> <20190813114842.GB29508@ziepe.ca> <20190813174142.GB11882@iweiny-DESK2.sc.intel.com> <20190813180022.GF29508@ziepe.ca> <20190813203858.GA12695@iweiny-DESK2.sc.intel.com> <20190814122308.GB13770@ziepe.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190814122308.GB13770@ziepe.ca> User-Agent: Mutt/1.11.1 (2018-12-01) Sender: linux-rdma-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-rdma@vger.kernel.org On Wed, Aug 14, 2019 at 09:23:08AM -0300, Jason Gunthorpe wrote: > On Tue, Aug 13, 2019 at 01:38:59PM -0700, Ira Weiny wrote: > > On Tue, Aug 13, 2019 at 03:00:22PM -0300, Jason Gunthorpe wrote: > > > On Tue, Aug 13, 2019 at 10:41:42AM -0700, Ira Weiny wrote: > > > > > > > And I was pretty sure uverbs_destroy_ufile_hw() would take care of (or ensure > > > > that some other thread is) destroying all the MR's we have associated with this > > > > FD. > > > > > > fd's can't be revoked, so destroy_ufile_hw() can't touch them. It > > > deletes any underlying HW resources, but the FD persists. > > > > I misspoke. I should have said associated with this "context". And of course > > uverbs_destroy_ufile_hw() does not touch the FD. What I mean is that the > > struct file which had file_pins hanging off of it would be getting its file > > pins destroyed by uverbs_destroy_ufile_hw(). Therefore we don't need the FD > > after uverbs_destroy_ufile_hw() is done. > > > > But since it does not block it may be that the struct file is gone before the > > MR is actually destroyed. Which means I think the GUP code would blow up in > > that case... :-( > > Oh, yes, that is true, you also can't rely on the struct file living > longer than the HW objects either, that isn't how the lifetime model > works. Reviewing all these old threads... And this made me think. While the HW objects may out live the struct file. They _are_ going away in a finite amount of time right? It is not like they could be held forever right? Ira > > If GUP consumes the struct file it must allow the struct file to be > deleted before the GUP pin is released. > > > The drivers could provide some generic object (in RDMA this could be the > > uverbs_attr_bundle) which represents their "context". > > For RDMA the obvious context is the struct ib_mr * > > > But for the procfs interface, that context then needs to be associated with any > > file which points to it... For RDMA, or any other "FD based pin mechanism", it > > would be up to the driver to "install" a procfs handler into any struct file > > which _may_ point to this context. (before _or_ after memory pins). > > Is this all just for debugging? Seems like a lot of complication just > to print a string > > Generally, I think you'd be better to associate things with the > mm_struct not some struct file... The whole design is simpler as GUP > already has the mm_struct. > > Jason