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 B91ACC54FD0 for ; Thu, 23 Apr 2020 14:49:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9D3B62087E for ; Thu, 23 Apr 2020 14:49:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728731AbgDWOtH (ORCPT ); Thu, 23 Apr 2020 10:49:07 -0400 Received: from mx2.suse.de ([195.135.220.15]:58852 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728397AbgDWOtG (ORCPT ); Thu, 23 Apr 2020 10:49:06 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 3A8A9ABB2; Thu, 23 Apr 2020 14:49:03 +0000 (UTC) Subject: Re: [PATCH RFC v2 02/24] scsi: allocate separate queue for reserved commands To: John Garry , Christoph Hellwig Cc: axboe@kernel.dk, jejb@linux.ibm.com, martin.petersen@oracle.com, ming.lei@redhat.com, bvanassche@acm.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org, virtualization@lists.linux-foundation.org, esc.storagedev@microsemi.com, chenxiang66@hisilicon.com, 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: Hannes Reinecke Message-ID: Date: Thu, 23 Apr 2020 16:49:00 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 4/23/20 4:13 PM, John Garry wrote: > 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) > Hold your horses. I'm currently preparing a patchset implementing things by improving the current scsi_get_host_dev() etc. RFC should be ready by the end of the week. Cheers, Hannes -- Dr. Hannes Reinecke Teamlead Storage & Networking hare@suse.de +49 911 74053 688 SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer