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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, 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 6283CC2D0E9 for ; Sun, 29 Mar 2020 15:05:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 24CDF2073E for ; Sun, 29 Mar 2020 15:05:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="PEz8hf0l" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728267AbgC2PF2 (ORCPT ); Sun, 29 Mar 2020 11:05:28 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:41084 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727167AbgC2PF2 (ORCPT ); Sun, 29 Mar 2020 11:05:28 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=bJFSAZG1n+xzVtSP1SVc825QUuF9GdC/2ZtU7S6cLkA=; b=PEz8hf0lPNmRCSWD16vqwenN8R dMerh5AqGy54wYPNu34Q1sZWVb3NRoRgHC8EW5iQIzT5I+nhaX/Xenj2IVTd3m6UAp7B9GNk6+LJn YgmkE3twkrMKLyoIC1HG4RdwMXgtPh86nO3s3ja3IqIAp8R5vV3pplvCR1IOsjz/VdVUklxmDMZWY uymiEw1eHSe1w86hSvrCMd3Zh3me3FRujRr1bXG2vB560+3mej+NTFwBpbOxCE0DyD0fY7BBIjaHm NczVwADlVMCO7iE+gjNEvvwPPdw1LVme8VCNGh3yU/80KHZK8u8XprJagnmyi6Q0tzmhBKgVL39/p BISc2ODQ==; Received: from hch by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1jIZV6-0004wG-IX; Sun, 29 Mar 2020 15:05:24 +0000 Date: Sun, 29 Mar 2020 08:05:24 -0700 From: Christoph Hellwig To: Bart Van Assche Cc: Christoph Hellwig , Jack Wang , linux-block@vger.kernel.org, linux-rdma@vger.kernel.org, axboe@kernel.dk, sagi@grimberg.me, leon@kernel.org, dledford@redhat.com, jgg@ziepe.ca, danil.kipnis@cloud.ionos.com, rpenyaev@suse.de, pankaj.gupta@cloud.ionos.com Subject: Re: [PATCH v11 15/26] block: reexport bio_map_kern Message-ID: <20200329150524.GA13909@infradead.org> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Sender: linux-rdma-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-rdma@vger.kernel.org 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.