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=-8.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 2370DC07E99 for ; Mon, 5 Jul 2021 13:02:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 089DA61447 for ; Mon, 5 Jul 2021 13:02:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231309AbhGENEv (ORCPT ); Mon, 5 Jul 2021 09:04:51 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:56697 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231274AbhGENEu (ORCPT ); Mon, 5 Jul 2021 09:04:50 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1625490133; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=EQiaDZSDRoWhnvLd0y+F7CVOe8BAX1HmtgpDqCLODno=; b=UCobMq1xVyocOei0GJppSkR7p6enEZj+efKzAXpkr3P6A3YCw+qO7ZLKWBg+SshPLTcJn1 uLzVXALMg3C8SLTVPg/yOd5A1gV3X07/QagXc0bhwCf7Nic2Py/Yoy4yvO5K4qJ7XLwGt3 CH472QUC+/59qszjiahfKKCFfJc2LF8= Received: from mail-wm1-f72.google.com (mail-wm1-f72.google.com [209.85.128.72]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-469-jfXcOXBIOIO1RKY_oGrO2A-1; Mon, 05 Jul 2021 09:02:12 -0400 X-MC-Unique: jfXcOXBIOIO1RKY_oGrO2A-1 Received: by mail-wm1-f72.google.com with SMTP id y14-20020a1c7d0e0000b02901edd7784928so9869308wmc.2 for ; Mon, 05 Jul 2021 06:02:12 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=EQiaDZSDRoWhnvLd0y+F7CVOe8BAX1HmtgpDqCLODno=; b=bye3oR7c19w8UgmCe7GJdisxsttgBwrpHbY3Ip2CCkjVk9RmYAesxolCQG5FV/dbpG Ij8RZkmJZWTA2w4nb+sZ0COWPirgjBlV4svhgGJgYASmnEVHnVW3Eykiy1+M8jrXTM4c I9DznSEqoYm/tH4EkzC44smHwmZdLbcS6+8vOk6RaUj1aX4y4ZVY7cg2/TYUHdfiTyhw B507F+EnsRfglThsI5IMelSCAXY6OH/ZJrz20/UatWT3z57qafjXn6nsZ+346p1HbEHg zSNXOoEuYWJeEuhPbi+bKtIJqC9ppQ/uCzFdBrKYntqGDXgUSKxjBxfaQtb6WKwqolwb Qwxg== X-Gm-Message-State: AOAM5336O3z8OrCtZdKPj6ufOvQlSB6d+xSVFrVHMUBX19GnnuS2ZQXy KT8qA/FMBRc6WVRVz7PmbI1k6T5g+vcGpqY8A+1ouR6rCnO92/u2oY7kNiV+lfQM8qyGxi6F+Rz 9smoQY623owQj4UqgTuw1DGc= X-Received: by 2002:a7b:ca43:: with SMTP id m3mr14772432wml.74.1625490131334; Mon, 05 Jul 2021 06:02:11 -0700 (PDT) X-Google-Smtp-Source: ABdhPJzS6R45eQdBafjJCfhd1vm8LmWsahyCdE9gLBl2N2UbSQMBfrvMPQtX8pBLO/KLwWonQWqk0g== X-Received: by 2002:a7b:ca43:: with SMTP id m3mr14772386wml.74.1625490130998; Mon, 05 Jul 2021 06:02:10 -0700 (PDT) Received: from ?IPv6:2001:b07:6468:f312:c8dd:75d4:99ab:290a? ([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.gmail.com with ESMTPSA id 16sm12186756wmk.18.2021.07.05.06.02.09 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 05 Jul 2021 06:02:09 -0700 (PDT) Subject: Re: [dm-devel] [PATCH v5 3/3] dm mpath: add CONFIG_DM_MULTIPATH_SG_IO - failover for SG_IO To: Martin Wilck , Christoph Hellwig Cc: Mike Snitzer , linux-scsi@vger.kernel.org, Daniel Wagner , emilne@redhat.com, linux-block@vger.kernel.org, dm-devel@redhat.com, "Martin K. Petersen" , nkoenig@redhat.com, Bart Van Assche , Alasdair G Kergon References: <20210628151558.2289-1-mwilck@suse.com> <20210628151558.2289-4-mwilck@suse.com> <20210701075629.GA25768@lst.de> <20210701113442.GA10793@lst.de> <003727e7a195cb0f525cc2d7abda3a19ff16eb98.camel@suse.com> From: Paolo Bonzini Message-ID: Date: Mon, 5 Jul 2021 15:02:08 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <003727e7a195cb0f525cc2d7abda3a19ff16eb98.camel@suse.com> Content-Type: text/plain; charset=iso-8859-15; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 02/07/21 16:21, Martin Wilck wrote: >> SG_IO gives you raw access to the SCSI logic unit, and you get to >> keep the pieces if anything goes wrong. > > That's a very fragile user space API, on the fringe of being useless > IMO. Indeed. If SG_IO is for raw access to an ITL nexus, it shouldn't be supported at all by mpath devices. If on the other hand SG_IO is for raw access to a LUN, there is no reason for it to not support failover. Paolo