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=-0.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 9E619C2D0E9 for ; Mon, 30 Mar 2020 10:44:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 74E5320578 for ; Mon, 30 Mar 2020 10:44:42 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=cloud.ionos.com header.i=@cloud.ionos.com header.b="c16+qdET" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729242AbgC3Kol (ORCPT ); Mon, 30 Mar 2020 06:44:41 -0400 Received: from mail-io1-f65.google.com ([209.85.166.65]:38274 "EHLO mail-io1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728859AbgC3Kol (ORCPT ); Mon, 30 Mar 2020 06:44:41 -0400 Received: by mail-io1-f65.google.com with SMTP id m15so17223842iob.5 for ; Mon, 30 Mar 2020 03:44:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cloud.ionos.com; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=0IbOGrt0Fj4NYF3EWqyfkLqlBUBr/YJhc4WhdXCsREU=; b=c16+qdETJIOPqlNcm3XubxoDAMMm3mNE4voViPIVa1hokryeKVGll1fIc941+NF8GW 91j5rOlB38BJn6JI6Z8NRWJpA8Ax7q2trj/nKX0KVibkxqrKHF6eVTuc4cUybhOzeMKZ SCJAg5bat2oGIBj2b2SS/p2Lf8YXlObUqiNv1qwPT9S1D/+ypaI8WMrkVU5Vcy8l/hZU z7WnxkbOpFvk/GB2YZjHISOyq0qHbuEjs1IAxGaGIJhtVlwljXXqF1FkRTbWSzi1ig59 oyANOQHxCNiavUVgNC7oflKTwbNgvl9nBKsKqwp+mN9TeJPj6W9GV4qjsllrhvJ/fsdP Vo9Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=0IbOGrt0Fj4NYF3EWqyfkLqlBUBr/YJhc4WhdXCsREU=; b=aomE0BQB88fcTWjgu2g1DiAzIY+uqDaODpuV09L7z8uP3zT4sYsrOkjDB4p70gufk0 WYehQaiKCHv8o6hIhickSQO5mCsL1OFE4ObbmwTs9+wwkmhOeh6MDfNElPzDDqHePs0R 8q/l/9+SciqbeH9zeoTtrfntPovhjbOfDllDXVkqXpS+cuBLEwqNxqlhpoOtYutGLHjq IFd3v4o7wIIE3GhGJyTh4GzQgiGCOfudt6AydEemBolCAYfTyn1+Vgi+01PsddXOjvmX jdg7O1y6CZlpm/OIKaMgL5PP4fIJI5+c9EKQen5O2bjt6mdMC7oOT67VslF7pJFfvyyI kgVw== X-Gm-Message-State: ANhLgQ3rS1jmz4Ve0Xv//300Vfi4ToLhO7eZSacj9SZaAUX+lylnbxTv q8yw+z8Y2Ju7n1HycWNJIytj9CJ1HkpsTvySuLsrHA== X-Google-Smtp-Source: ADFU+vsCHoOKRh0SdFhPaKogBAD9pBeQ4tUJ7zncCd/3GrhvRYbEGI8zfyXXSOROPGqaGwbwAkq2zJ0hO7/RNxOyQIY= X-Received: by 2002:a6b:b70a:: with SMTP id h10mr10138917iof.54.1585565079727; Mon, 30 Mar 2020 03:44:39 -0700 (PDT) MIME-Version: 1.0 References: <20200320121657.1165-1-jinpu.wang@cloud.ionos.com> <20200320121657.1165-16-jinpu.wang@cloud.ionos.com> <15f25902-1f5a-a542-a311-c1e86330834b@acm.org> <20200328082953.GB16355@infradead.org> <20200329150524.GA13909@infradead.org> In-Reply-To: <20200329150524.GA13909@infradead.org> From: Jinpu Wang Date: Mon, 30 Mar 2020 12:44:28 +0200 Message-ID: Subject: Re: [PATCH v11 15/26] block: reexport bio_map_kern To: Christoph Hellwig , Bart Van Assche , Chaitanya.Kulkarni@wdc.com Cc: linux-block@vger.kernel.org, linux-rdma@vger.kernel.org, Jens Axboe , Sagi Grimberg , Leon Romanovsky , Doug Ledford , Jason Gunthorpe , Danil Kipnis , Roman Penyaev , Pankaj Gupta Content-Type: text/plain; charset="UTF-8" Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Sun, Mar 29, 2020 at 5:05 PM Christoph Hellwig wrote: > > On Sat, Mar 28, 2020 at 09:16:55AM -0700, Bart Van Assche wrote: > > There are more users in the Linux kernel of bio_add_pc_page() than only > > bio_map_kern(), e.g. the SCSI target pass-through code > > (drivers/target/target_core_pscsi.c). The code that uses bio_map_kern() > > is in patch 22/26: "block/rnbd: server: functionality for IO submission > > to file or block dev". Isn't that use case similar to the SCSI > > pass-through code? I think the RNBD server code also implements storage > > target functionality. > > No, it is not at all. The RNBD case submits normal read/write bios, for > which bio_map_kerl is the wrong interfac given that it > uses bio_add_pc_page. Read, write and other non-passthrough requests > must use bio_add_page instead. Thanks for comments, Christoph. If I understood you correctly, so the right way is to construct bio similar to bio_map_kern, but we have to use bio_add_page instead of bio_add_pc_page? As mentioned by Bart also Chaitanya, looks it's reasonable to add a helper for normal READ|WRITE operation to map and submit bio from the data buffer, but sure can be done later. Thanks!