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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0DEFFC433F5 for ; Tue, 22 Mar 2022 15:17:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238372AbiCVPTA (ORCPT ); Tue, 22 Mar 2022 11:19:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60054 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238338AbiCVPS5 (ORCPT ); Tue, 22 Mar 2022 11:18:57 -0400 Received: from frasgout.his.huawei.com (frasgout.his.huawei.com [185.176.79.56]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4174F8878B; Tue, 22 Mar 2022 08:17:29 -0700 (PDT) Received: from fraeml709-chm.china.huawei.com (unknown [172.18.147.200]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4KNFRj3Vrfz67Ncp; Tue, 22 Mar 2022 23:15:45 +0800 (CST) Received: from lhreml724-chm.china.huawei.com (10.201.108.75) by fraeml709-chm.china.huawei.com (10.206.15.37) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Tue, 22 Mar 2022 16:17:26 +0100 Received: from [10.47.85.68] (10.47.85.68) 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 15.1.2308.21; Tue, 22 Mar 2022 15:17:25 +0000 Message-ID: <0f7b9765-8835-25b5-4cdb-bc78edddad37@huawei.com> Date: Tue, 22 Mar 2022 15:17:24 +0000 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.6.1 Subject: Re: [PATCH 01/11] blk-mq: Add blk_mq_init_queue_ops() To: Hannes Reinecke , Christoph Hellwig CC: , , , , , , , , , , , , References: <1647945585-197349-1-git-send-email-john.garry@huawei.com> <1647945585-197349-2-git-send-email-john.garry@huawei.com> <20220322111848.GA29270@lst.de> <306df4cf-0ee0-2b1e-044c-aed6c70122f9@suse.de> From: John Garry In-Reply-To: <306df4cf-0ee0-2b1e-044c-aed6c70122f9@suse.de> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.47.85.68] X-ClientProxiedBy: lhreml730-chm.china.huawei.com (10.201.108.81) To lhreml724-chm.china.huawei.com (10.201.108.75) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 22/03/2022 14:03, Hannes Reinecke wrote: >> >> As mentioned in the cover letter response, it just seems best to keep >> the normal scsi_cmnd payload but have other means to add on the >> internal command data, like using host_scribble or scsi_cmnd priv data. >> > Well; I found that most drivers I had been looking at the scsi command > payload isn't used at all; the drivers primarily cared about the > (driver-provided) payload, and were completely ignoring the scsi command > payload. > > Similar for ATA/libsas: you basically never issue real scsi commands, > but either 'raw' ATA requests or SCSI TMFs. None of which are scsi > commands, so providing them is a bit of a waste. > > (And causes irritations, too, as a scsi command requires associated > pointers like ->device etc to be set up. Which makes it tricky to use > for the initial device setup.) A problem I see is that in scsi_mq_init_request() we allocate memories like sense_buffer and prot_sdb and store the pointers in the scsi_cmnd payload. If we then reuse a scsi_cmnd payload as an "internal" command payload then this data may be lost. It might be possible to reuse the scsi cmnd payload for the "internal", but I would rather not get hung up on it now if possible. Thanks, John