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=-8.6 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 0E62FC433E1 for ; Tue, 25 Aug 2020 02:13:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D547220578 for ; Tue, 25 Aug 2020 02:13:33 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=nvidia.com header.i=@nvidia.com header.b="UmGWTkcr" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727999AbgHYCN3 (ORCPT ); Mon, 24 Aug 2020 22:13:29 -0400 Received: from hqnvemgate24.nvidia.com ([216.228.121.143]:8803 "EHLO hqnvemgate24.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725850AbgHYCN3 (ORCPT ); Mon, 24 Aug 2020 22:13:29 -0400 Received: from hqpgpgate101.nvidia.com (Not Verified[216.228.121.13]) by hqnvemgate24.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Mon, 24 Aug 2020 19:11:29 -0700 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate101.nvidia.com (PGP Universal service); Mon, 24 Aug 2020 19:13:28 -0700 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Mon, 24 Aug 2020 19:13:28 -0700 Received: from [10.2.53.36] (172.20.13.39) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Tue, 25 Aug 2020 02:13:28 +0000 Subject: Re: [PATCH 0/5] bio: Direct IO: convert to pin_user_pages_fast() To: Al Viro CC: Andrew Morton , Christoph Hellwig , Ilya Dryomov , Jens Axboe , Jeff Layton , , , , , , LKML References: <20200822042059.1805541-1-jhubbard@nvidia.com> <20200825015428.GU1236603@ZenIV.linux.org.uk> <20200825020700.GV1236603@ZenIV.linux.org.uk> From: John Hubbard Message-ID: <26bf92af-a7ab-b53f-45dd-9e3d7a1340ec@nvidia.com> Date: Mon, 24 Aug 2020 19:13:27 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: <20200825020700.GV1236603@ZenIV.linux.org.uk> X-Originating-IP: [172.20.13.39] X-ClientProxiedBy: HQMAIL107.nvidia.com (172.20.187.13) To HQMAIL107.nvidia.com (172.20.187.13) Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1598321489; bh=GIRbiEa7azLOIxon4iO5FS/T0uGJkiVpYwweEhJNBpo=; h=X-PGP-Universal:Subject:To:CC:References:From:Message-ID:Date: User-Agent:MIME-Version:In-Reply-To:X-Originating-IP: X-ClientProxiedBy:Content-Type:Content-Language: Content-Transfer-Encoding; b=UmGWTkcrZ9y1HwcrElFPjcGx3VjBPiGha3uyULxM2OY1I/bwLKzfacmPOQxQ9GyZK HaJxO8iWVCSV2SjHo2+oV6rNZVVtuNWVw3a/vVVyVbIVd8RMrpp+UP3P0Qbcvs7Hml dV1gOlzPwkqYsdvsO7kr1skfGk6S+1fTD2GPIOmac0RirS4lQih9RBp5lKrfB9SntS 5OPL4gnMZFbN6Ed6wHZJHy3HjGvuuzSoREEObkE/ig7JZyF0FotPHyFHVAx1B88Jo5 NSgr+DaOPpw0gqM8+krNIZpyhHdQJ6bP6DwweQCl+lwB3zfKhGjKRQYKeWO2jKZ41E RM8alNM34Jb2g== Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 8/24/20 7:07 PM, Al Viro wrote: > On Tue, Aug 25, 2020 at 02:54:28AM +0100, Al Viro wrote: >> On Fri, Aug 21, 2020 at 09:20:54PM -0700, John Hubbard wrote: >> >>> Direct IO behavior: >>> >>> ITER_IOVEC: >>> pin_user_pages_fast(); >>> break; >>> >>> ITER_KVEC: // already elevated page refcount, leave alone >>> ITER_BVEC: // already elevated page refcount, leave alone >>> ITER_PIPE: // just, no :) >> >> Why? What's wrong with splice to O_DIRECT file? > > Sorry - s/to/from/, obviously. > > To spell it out: consider generic_file_splice_read() behaviour when > the source had been opened with O_DIRECT; you will get a call of > ->read_iter() into ITER_PIPE destination. And it bloody well > will hit iov_iter_get_pages() on common filesystems, to pick the > pages we want to read into. > > So... what's wrong with having that "pin" primitive making sure > the pages are there and referenced by the pipe? > (our emails crossed) OK, yes, let me hook that up. I was just unaware of that flow, I'll go off and figure it out. Thanks for looking at this! thanks, -- John Hubbard NVIDIA