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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham 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 1257FC83000 for ; Thu, 30 Apr 2020 14:16:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id ED11B206D9 for ; Thu, 30 Apr 2020 14:16:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726631AbgD3OQc (ORCPT ); Thu, 30 Apr 2020 10:16:32 -0400 Received: from lhrrgout.huawei.com ([185.176.76.210]:2135 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726743AbgD3OQc (ORCPT ); Thu, 30 Apr 2020 10:16:32 -0400 Received: from lhreml724-chm.china.huawei.com (unknown [172.18.7.107]) by Forcepoint Email with ESMTP id B75065EE7C5E96BC1BFE; Thu, 30 Apr 2020 15:16:28 +0100 (IST) Received: from [127.0.0.1] (10.47.0.178) 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, 30 Apr 2020 15:16:27 +0100 Subject: Re: [PATCH RFC v3 01/41] scsi: add 'nr_reserved_cmds' field to the SCSI host template To: Hannes Reinecke , "Martin K. Petersen" CC: Christoph Hellwig , James Bottomley , Ming Lei , Bart van Assche , , Hannes Reinecke References: <20200430131904.5847-1-hare@suse.de> <20200430131904.5847-2-hare@suse.de> From: John Garry Message-ID: <9655eb3f-b2e3-7c9e-f2ee-1587c13df875@huawei.com> Date: Thu, 30 Apr 2020 15:15:45 +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: <20200430131904.5847-2-hare@suse.de> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.47.0.178] X-ClientProxiedBy: lhreml731-chm.china.huawei.com (10.201.108.82) To lhreml724-chm.china.huawei.com (10.201.108.75) X-CFilter-Loop: Reflected Sender: linux-scsi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org On 30/04/2020 14:18, Hannes Reinecke wrote: > From: Hannes Reinecke > > Quite a lot of drivers are using management commands internally, which > typically use the same hardware tag pool (ie they are being allocated > from the same hardware resources) as the 'normal' I/O commands. > These commands are set aside before allocating the block-mq tag bitmap, > so they'll never show up as busy in the tag map. > The block-layer, OTOH, already has 'reserved_tags' to handle precisely > this situation. > So this patch adds a new field 'nr_reserved_cmds' to the SCSI host > template to instruct the block layer to set aside a tag space for these > management commands by using reserved_tags. > > Signed-off-by: Hannes Reinecke It may be worth adding this field to scsi_host_template. And we should also prob mention this in Documentation/scsi/scsi_mid_low_api.txt Apart from that, thanks: Reviewed-by: John Garry > --- > drivers/scsi/scsi_lib.c | 1 + > include/scsi/scsi_host.h | 6 ++++++ > 2 files changed, 7 insertions(+) > > diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c > index 47835c4b4ee0..5358f553f526 100644 > --- a/drivers/scsi/scsi_lib.c > +++ b/drivers/scsi/scsi_lib.c > @@ -1885,6 +1885,7 @@ int scsi_mq_setup_tags(struct Scsi_Host *shost) > shost->tag_set.ops = &scsi_mq_ops_no_commit; > shost->tag_set.nr_hw_queues = shost->nr_hw_queues ? : 1; > shost->tag_set.queue_depth = shost->can_queue; > + shost->tag_set.reserved_tags = shost->nr_reserved_cmds; > shost->tag_set.cmd_size = cmd_size; > shost->tag_set.numa_node = NUMA_NO_NODE; > shost->tag_set.flags = BLK_MQ_F_SHOULD_MERGE; > diff --git a/include/scsi/scsi_host.h b/include/scsi/scsi_host.h > index 822e8cda8d9b..37bb7d74e4c4 100644 > --- a/include/scsi/scsi_host.h > +++ b/include/scsi/scsi_host.h > @@ -599,6 +599,12 @@ struct Scsi_Host { > * is nr_hw_queues * can_queue. > */ > unsigned nr_hw_queues; > + > + /* > + * Number of commands to reserve, if any. > + */ > + unsigned nr_reserved_cmds; > + > unsigned active_mode:2; > unsigned unchecked_isa_dma:1; > >