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Sun, 18 Aug 2019 13:33:54 +0300 Received: from [10.223.0.54] (10.223.0.54) by MTLCAS01.mtl.com (10.0.8.71) with Microsoft SMTP Server (TLS) id 14.3.301.0; Sun, 18 Aug 2019 13:33:48 +0300 Subject: Re: [PATCH v7 08/14] nvmet-core: allow one host per passthru-ctrl To: Logan Gunthorpe , , , , CC: Christoph Hellwig , Sagi Grimberg , "Keith Busch" , Jens Axboe , Chaitanya Kulkarni , Stephen Bates References: <20190801234514.7941-1-logang@deltatee.com> <20190801234514.7941-9-logang@deltatee.com> <05a74e81-1dbd-725f-1369-5ca5c5918db1@mellanox.com> From: Max Gurtovoy Message-ID: <5717f515-e051-c420-07b7-299bcfcd1f32@mellanox.com> Date: Sun, 18 Aug 2019 13:33:47 +0300 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US X-Originating-IP: [10.223.0.54] X-EOPAttributedMessage: 0 X-MS-Office365-Filtering-HT: Tenant X-Forefront-Antispam-Report: CIP:193.47.165.251;IPV:NLI;CTRY:IL;EFV:NLI;SFV:NSPM;SFS:(10009020)(4636009)(136003)(376002)(346002)(396003)(39860400002)(2980300002)(189003)(199004)(2486003)(81156014)(23676004)(446003)(305945005)(7736002)(70586007)(8676002)(76176011)(106002)(53546011)(31696002)(8936002)(3846002)(26005)(16526019)(16576012)(478600001)(6306002)(65956001)(316002)(47776003)(70206006)(81166006)(336012)(110136005)(7416002)(476003)(126002)(58126008)(5660300002)(486006)(65826007)(966005)(186003)(14444005)(356004)(65806001)(11346002)(54906003)(230700001)(6246003)(2616005)(36756003)(64126003)(86362001)(2906002)(229853002)(31686004)(53936002)(50466002)(6116002)(2201001)(4326008)(3940600001)(2101003);DIR:OUT;SFP:1101;SCL:1;SRVR:VI1PR05MB3488;H:mtlcas13.mtl.com;FPR:;SPF:Pass;LANG:en;PTR:InfoDomainNonexistent;MX:1;A:1; X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: ce5ac34a-9bc2-41b6-ef74-08d723c7926c X-Microsoft-Antispam: BCL:0;PCL:0;RULEID:(2390118)(7020095)(4652040)(8989299)(4534185)(4627221)(201703031133081)(201702281549075)(8990200)(5600148)(711020)(4605104)(4709080)(1401327)(2017052603328)(7193020);SRVR:VI1PR05MB3488; X-MS-TrafficTypeDiagnostic: VI1PR05MB3488: X-MS-Exchange-PUrlCount: 1 X-Microsoft-Antispam-PRVS: X-MS-Oob-TLC-OOBClassifiers: OLM:5236; X-Forefront-PRVS: 01334458E5 X-MS-Exchange-SenderADCheck: 1 X-Microsoft-Antispam-Message-Info: c7QHZKZWgSFn7vpzdotCA7uqvz8akaZSvIG4ycVKxYc5iQzt7uCpiC4uvdAniT6tzk7IQYitaxCqMitKh2FzyCIErvc1eVPlwGI+SRhkm6DTSGuFlSGWkxNLx8Hwh0tDV0M+U1dScDdRK9EK2HDGBEIWJv63pZvTx8zsef1leKnl2+9QuW6Fp26NdsgNvaHNThR/GZYpNDsmd0eMD33wxsNNgbDKqdxpV9BZ/NHfXIY7izOs5KczxeDwlazFdD++3RGR1kadLgl/2JIiy1X9qiGShYPkSPhMfBcOstXrx5eTSOJ+4BXeVdw20PesTYcpS4OknNAYRglp79SPWSsbkTxz+xBtTVDBaAjJPiveAF7ZpV2wA3EG0Xsi8ip3daTxQDp7xXkxSzRdrq7vlo+Wj+phaxZ80i9dJt8dIr7FmjI= X-OriginatorOrg: Mellanox.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 18 Aug 2019 10:33:55.5709 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: ce5ac34a-9bc2-41b6-ef74-08d723c7926c X-MS-Exchange-CrossTenant-Id: a652971c-7d2e-4d9b-a6a4-d149256f461b X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=a652971c-7d2e-4d9b-a6a4-d149256f461b;Ip=[193.47.165.251];Helo=[mtlcas13.mtl.com] X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: VI1PR05MB3488 Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 8/15/2019 7:06 PM, Logan Gunthorpe wrote: > > On 2019-08-15 6:36 a.m., Max Gurtovoy wrote: >> On 8/2/2019 2:45 AM, Logan Gunthorpe wrote: >>> This patch rejects any new connection to the passthru-ctrl if this >>> controller is already connected to a different host. At the time of >>> allocating the controller we check if the subsys associated with >>> the passthru ctrl is already connected to a host and reject it >>> if the hostnqn differs. >> This is a big limitation. >> >> Are we plan to enable many front-end ctrl's to connect to the single >> back-end ctrl in the future ? > Honestly, I don't know that it's really necessary, but the limitation > was requested by Sagi the first time this patch-set was submitted[1] > citing unspecified user troubles. If there's consensus to remove the > restriction I certainly can. > > Logan > > [1] http://lists.infradead.org/pipermail/linux-nvme/2018-April/016588.html I don't understand why we don't limit a regular ctrl to single access and we do it for the PT ctrl. I guess the block layer helps to sync between multiple access in parallel but we can do it as well. Also, let's say you limit the access to this subsystem to 1 user, the bdev is still accessibly for local user and also you can create a different subsystem that will use this device (PT and non-PT ctrl). Sagi, can you explain the trouble you meant and how this limitation solve it ?