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_MUTT autolearn=unavailable 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 56637C31E49 for ; Thu, 13 Jun 2019 23:58:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2DE39207E0 for ; Thu, 13 Jun 2019 23:58:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726900AbfFMX6u (ORCPT ); Thu, 13 Jun 2019 19:58:50 -0400 Received: from mga06.intel.com ([134.134.136.31]:12081 "EHLO mga06.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725836AbfFMX6u (ORCPT ); Thu, 13 Jun 2019 19:58:50 -0400 X-Amp-Result: UNSCANNABLE X-Amp-File-Uploaded: False Received: from fmsmga007.fm.intel.com ([10.253.24.52]) by orsmga104.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 13 Jun 2019 16:58:49 -0700 X-ExtLoop1: 1 Received: from iweiny-desk2.sc.intel.com ([10.3.52.157]) by fmsmga007.fm.intel.com with ESMTP; 13 Jun 2019 16:58:49 -0700 Date: Thu, 13 Jun 2019 17:00:11 -0700 From: Ira Weiny To: Jason Gunthorpe Cc: Matthew Wilcox , Dave Chinner , Jan Kara , Dan Williams , Theodore Ts'o , Jeff Layton , 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, linux-rdma@vger.kernel.org Subject: Re: [PATCH RFC 00/10] RDMA/FS DAX truncate proposal Message-ID: <20190614000010.GA783@iweiny-DESK2.sc.intel.com> References: <20190606104203.GF7433@quack2.suse.cz> <20190606220329.GA11698@iweiny-DESK2.sc.intel.com> <20190607110426.GB12765@quack2.suse.cz> <20190607182534.GC14559@iweiny-DESK2.sc.intel.com> <20190608001036.GF14308@dread.disaster.area> <20190612123751.GD32656@bombadil.infradead.org> <20190613002555.GH14363@dread.disaster.area> <20190613152755.GI32656@bombadil.infradead.org> <20190613211321.GC32404@iweiny-DESK2.sc.intel.com> <20190613234530.GK22901@ziepe.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190613234530.GK22901@ziepe.ca> User-Agent: Mutt/1.11.1 (2018-12-01) Sender: linux-ext4-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org On Thu, Jun 13, 2019 at 08:45:30PM -0300, Jason Gunthorpe wrote: > On Thu, Jun 13, 2019 at 02:13:21PM -0700, Ira Weiny wrote: > > On Thu, Jun 13, 2019 at 08:27:55AM -0700, Matthew Wilcox wrote: > > > On Thu, Jun 13, 2019 at 10:25:55AM +1000, Dave Chinner wrote: > > > > e.g. Process A has an exclusive layout lease on file F. It does an > > > > IO to file F. The filesystem IO path checks that Process A owns the > > > > lease on the file and so skips straight through layout breaking > > > > because it owns the lease and is allowed to modify the layout. It > > > > then takes the inode metadata locks to allocate new space and write > > > > new data. > > > > > > > > Process B now tries to write to file F. The FS checks whether > > > > Process B owns a layout lease on file F. It doesn't, so then it > > > > tries to break the layout lease so the IO can proceed. The layout > > > > breaking code sees that process A has an exclusive layout lease > > > > granted, and so returns -ETXTBSY to process B - it is not allowed to > > > > break the lease and so the IO fails with -ETXTBSY. > > > > > > This description doesn't match the behaviour that RDMA wants either. > > > Even if Process A has a lease on the file, an IO from Process A which > > > results in blocks being freed from the file is going to result in the > > > RDMA device being able to write to blocks which are now freed (and > > > potentially reallocated to another file). > > > > I don't understand why this would not work for RDMA? As long as the layout > > does not change the page pins can remain in place. > > Because process A had a layout lease (and presumably a MR) and the > layout was still modified in way that invalidates the RDMA MR. Oh sorry I miss read the above... (got Process A and B mixed up...) Right, but Process A still can't free those blocks because the gup pin exists on them... So yea it can't _just_ be a layout lease which controls this on the "file fd". Ira