From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753973AbbAMWv5 (ORCPT ); Tue, 13 Jan 2015 17:51:57 -0500 Received: from a.ns.miles-group.at ([95.130.255.143]:65275 "EHLO radon.swed.at" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751314AbbAMWvz (ORCPT ); Tue, 13 Jan 2015 17:51:55 -0500 Message-ID: <54B5A188.2000001@nod.at> Date: Tue, 13 Jan 2015 23:51:52 +0100 From: Richard Weinberger User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.3.0 MIME-Version: 1.0 To: Christoph Hellwig CC: dedekind1@gmail.com, dwmw2@infradead.org, computersforpeace@gmail.com, linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org, axboe@fb.com, tom.leiming@gmail.com Subject: Re: [PATCH 2/2 v2] UBI: Block: Add blk-mq support References: <1420926734-16417-1-git-send-email-richard@nod.at> <1420926734-16417-2-git-send-email-richard@nod.at> <20150113162553.GA24351@infradead.org> In-Reply-To: <20150113162553.GA24351@infradead.org> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am 13.01.2015 um 17:25 schrieb Christoph Hellwig: >> + struct ubi_sgl usgl; > > Btw, what's in struct ubi_sgl? Can't find that in my tree. "[PATCH 1/2] UBI: Add initial support for scatter gather" adds it. /** * struct ubi_sgl - UBI scatter gather list data structure. * @list_pos: current position in @sg[] * @page_pos: current position in @sg[@list_pos] * @sg: the scatter gather list itself * * ubi_sgl is a wrapper around a scatter list which keeps track of the * current position in the list and the current list item such that * it can be used across multiple ubi_leb_read_sg() calls. */ struct ubi_sgl { int list_pos; int page_pos; struct scatterlist sg[UBI_MAX_SG_COUNT]; }; >> +static void ubiblock_do_work(struct work_struct *work) >> +{ >> + int ret; >> + struct ubiblock_pdu *pdu = container_of(work, struct ubiblock_pdu, work); >> + struct request *req = blk_mq_rq_from_pdu(pdu); >> + >> + blk_mq_start_request(req); >> + blk_rq_map_sg(req->q, req, pdu->usgl.sg); > > blk_rq_map_sg returns the number of entries actually mapped, which > might be smaller than the number passed in due to merging. Yep, but the ubi_sql has a fixed number of scatterlist entries, UBI_MAX_SG_COUNT. And I limit it also to that using: blk_queue_max_segments(dev->rq, UBI_MAX_SG_COUNT); Is there another reason why I should use the return value of blk_rq_map_sg()? Please also note that the UBI block driver is read-only. Thanks, //richard