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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 822A6C433F5 for ; Tue, 1 Mar 2022 06:41:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232688AbiCAGmC (ORCPT ); Tue, 1 Mar 2022 01:42:02 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49862 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232323AbiCAGmB (ORCPT ); Tue, 1 Mar 2022 01:42:01 -0500 Received: from outgoing.mit.edu (outgoing-auth-1.mit.edu [18.9.28.11]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3A0F0583B1; Mon, 28 Feb 2022 22:41:21 -0800 (PST) Received: from cwcc.thunk.org (pool-108-7-220-252.bstnma.fios.verizon.net [108.7.220.252]) (authenticated bits=0) (User authenticated as tytso@ATHENA.MIT.EDU) by outgoing.mit.edu (8.14.7/8.12.4) with ESMTP id 2216f2HF022120 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 1 Mar 2022 01:41:03 -0500 Received: by cwcc.thunk.org (Postfix, from userid 15806) id 646DC15C0038; Tue, 1 Mar 2022 01:41:02 -0500 (EST) Date: Tue, 1 Mar 2022 01:41:02 -0500 From: "Theodore Ts'o" To: John Hubbard Cc: lsf-pc@lists.linux-foundation.org, Dave Chinner , Jan Kara , Christoph Hellwig , Jason Gary Gunthorpe , Chaitanya Kulkarni , Matthew Wilcox , Linux-MM , linux-fsdevel , "linux-block@vger.kernel.org" Subject: Re: [LSF/MM/BPF TOPIC] FOLL_PIN + file systems Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Fri, Jan 28, 2022 at 05:47:47PM -0800, John Hubbard wrote: > By the time we meet for LSF/MM/BPF in May, the Direct IO layer will > likely be converted to use FOLL_PIN page pinning (that is, changed from > using get_user_pages_fast(), to pin_user_pages_fast()). > > Direct IO conversion to FOLL_PIN was the last missing piece, and so the > time is right to discuss how to use the output of all of this work > (which is: the ability to call page_maybe_dma_pinned()), in order to fix > one of the original problems that prompted FOLL_PIN's creation. > > That problem is: file systems do not currently tolerate having their > pages pinned and DMA'd to/from. See [1] for an extensive background of > some 11 LWN articles since 2018. > .... > > I'll volunteer to present a few slides to provide the background and get > the discussion started. It's critical to have filesystem people in > attendance for this, such as Jan Kara, Dave Chinner, Christoph Hellwig, > and many more that I won't try to list explicitly here. RDMA > representation (Jason Gunthorpe, Leon Romanovsky, Chaitanya Kulkarni, > and others) will help keep the file system folks from creating rules > that break them "too much". And of course -mm folks. There are many > people who have contributed to this project, so again, apologies for not > listing everyone explicitly. I'd definitely be interested in participating in this discussion, following up on some e-mail threads that we've had on this subject. Unfortunately a number of file system folks are listed above may not be able to attend, so I really hope we can figure out some way to allow remote participation for those people who aren't able to travel due to various reasons, including corporate policies surrounding COVID. - Ted