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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 CC2D0C54FD0 for ; Thu, 23 Apr 2020 14:13:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A9E672098B for ; Thu, 23 Apr 2020 14:13:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728367AbgDWONz (ORCPT ); Thu, 23 Apr 2020 10:13:55 -0400 Received: from lhrrgout.huawei.com ([185.176.76.210]:2088 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726450AbgDWONz (ORCPT ); Thu, 23 Apr 2020 10:13:55 -0400 Received: from lhreml724-chm.china.huawei.com (unknown [172.18.7.106]) by Forcepoint Email with ESMTP id A235B288AFABC7CBEA83; Thu, 23 Apr 2020 15:13:53 +0100 (IST) Received: from [127.0.0.1] (10.47.5.255) by lhreml724-chm.china.huawei.com (10.201.108.75) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.1913.5; Thu, 23 Apr 2020 15:13:51 +0100 Subject: Re: [PATCH RFC v2 02/24] scsi: allocate separate queue for reserved commands To: Christoph Hellwig , Hannes Reinecke CC: , , , , , , , , , , , Hannes Reinecke References: <1583857550-12049-1-git-send-email-john.garry@huawei.com> <1583857550-12049-3-git-send-email-john.garry@huawei.com> <20200310183243.GA14549@infradead.org> <79cf4341-f2a2-dcc9-be0d-2efc6e83028a@huawei.com> <20200311062228.GA13522@infradead.org> <9c6ced82-b3f1-9724-b85e-d58827f1a4a4@huawei.com> <39bc2d82-2676-e329-5d32-8acb99b0a204@suse.de> <20200407163033.GA26568@infradead.org> From: John Garry Message-ID: Date: Thu, 23 Apr 2020 15:13:15 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.1.2 MIME-Version: 1.0 In-Reply-To: <20200407163033.GA26568@infradead.org> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.47.5.255] X-ClientProxiedBy: lhreml722-chm.china.huawei.com (10.201.108.73) To lhreml724-chm.china.huawei.com (10.201.108.75) X-CFilter-Loop: Reflected Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 07/04/2020 17:30, Christoph Hellwig wrote: > On Tue, Apr 07, 2020 at 04:00:10PM +0200, Hannes Reinecke wrote: >> My concern is this: >> >> struct scsi_device *scsi_get_host_dev(struct Scsi_Host *shost) >> { >> [ .. ] >> starget = scsi_alloc_target(&shost->shost_gendev, 0, shost->this_id); >> [ .. ] >> >> and we have typically: >> >> drivers/scsi/hisi_sas/hisi_sas_v3_hw.c: .this_id = -1, >> >> It's _very_ uncommon to have a negative number as the SCSI target device; in >> fact, it _is_ an unsigned int already. >> >> But alright, I'll give it a go; let's see what I'll end up with. > > But this shouldn't be exposed anywhere. And I prefer that over having > magic requests/scsi_cmnd that do not have a valid ->device pointer. > . > (just looking at this again) Hi Christoph, So how would this look added in scsi_lib.c: struct scsi_cmnd *scsi_get_reserved_cmd(struct Scsi_Host *shost) { struct scsi_cmnd *scmd; struct request *rq; struct scsi_device *sdev = scsi_get_host_dev(shost); if (!sdev) return NULL; rq = blk_mq_alloc_request(sdev->request_queue, REQ_OP_DRV_OUT | REQ_NOWAIT, BLK_MQ_REQ_RESERVED); if (IS_ERR(rq)) // fix tidy-up return NULL; WARN_ON(rq->tag == -1); scmd = blk_mq_rq_to_pdu(rq); scmd->request = rq; scmd->device = sdev; return scmd; } EXPORT_SYMBOL_GPL(scsi_get_reserved_cmd); void scsi_put_reserved_cmd(struct scsi_cmnd *scmd) { struct request *rq = blk_mq_rq_from_pdu(scmd); if (blk_mq_rq_is_reserved(rq)) { struct scsi_device *sdev = scmd->device; blk_mq_free_request(rq); scsi_free_host_dev(sdev); } } EXPORT_SYMBOL_GPL(scsi_put_reserved_cmd); Not sure if we want a static scsi_device per host, or alloc and free dynamically. (@Hannes, I also have some proper patches for libsas if you want to add it) Cheers, John