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 2D8CEC43334 for ; Tue, 14 Jun 2022 09:30:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233875AbiFNJaV (ORCPT ); Tue, 14 Jun 2022 05:30:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44310 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230333AbiFNJaU (ORCPT ); Tue, 14 Jun 2022 05:30:20 -0400 Received: from frasgout.his.huawei.com (frasgout.his.huawei.com [185.176.79.56]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2606840E53; Tue, 14 Jun 2022 02:30:20 -0700 (PDT) Received: from fraeml736-chm.china.huawei.com (unknown [172.18.147.200]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4LMjmY2nw7z6H7Tb; Tue, 14 Jun 2022 17:28:45 +0800 (CST) Received: from lhreml724-chm.china.huawei.com (10.201.108.75) by fraeml736-chm.china.huawei.com (10.206.15.217) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Tue, 14 Jun 2022 11:30:18 +0200 Received: from [10.195.33.253] (10.195.33.253) 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 15.1.2375.24; Tue, 14 Jun 2022 10:30:17 +0100 Message-ID: <731c26d2-5124-60a6-c8de-d979ee2af467@huawei.com> Date: Tue, 14 Jun 2022 10:33:24 +0100 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 RFC v2 02/18] scsi: core: Resurrect scsi_{get,free}_host_dev() To: Christoph Hellwig CC: , , , , , , , , , , References: <1654770559-101375-1-git-send-email-john.garry@huawei.com> <1654770559-101375-3-git-send-email-john.garry@huawei.com> <20220614064403.GB31683@lst.de> From: John Garry In-Reply-To: <20220614064403.GB31683@lst.de> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.195.33.253] X-ClientProxiedBy: lhreml746-chm.china.huawei.com (10.201.108.196) To lhreml724-chm.china.huawei.com (10.201.108.75) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-ide@vger.kernel.org On 14/06/2022 07:44, Christoph Hellwig wrote: > On Thu, Jun 09, 2022 at 06:29:03PM +0800, John Garry wrote: >> This reverts commit 6bd49b1a8d43ec118c55f3aaa7577729b52bde15. > > Please add an actual text describing why you are doing this and how > insteasd of this completely pointless revert line. > > > . OK. And in hindsight it would have been a good opportunity to mention something which I am undecided on - that is which scsi_device to use for these reserved commands? In this series I use the scsi shost sdev for all reserved commands, but maybe we should use the target sdev. Pros of using scsi host sdev: - don't need to worry about request queue freezing - don't need to worry about running out of request queue budget - available when scsi host is added - libata adds target sdev after some internal commands are sent, and this would be a bit painful to change, however adding the sdev earlier would seem to be a good change to make Cons: - generally better to use same scsi device as target (or is it?). For example, it seems better to have reserved scsi_cmnd.device actually set to the target sdev. - don't need to add stuff like ata_is_scmd_ata_internal() later in this series Prob other reasons which I have forgot about. Please let me know if you have any thoughts on this. Cheers, John