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From: Max Gurtovoy <maxg@mellanox.com>
To: Logan Gunthorpe <logang@deltatee.com>,
	<linux-kernel@vger.kernel.org>, <linux-nvme@lists.infradead.org>,
	<linux-block@vger.kernel.org>, <linux-fsdevel@vger.kernel.org>
Cc: Christoph Hellwig <hch@lst.de>, Sagi Grimberg <sagi@grimberg.me>,
	"Keith Busch" <kbusch@kernel.org>, Jens Axboe <axboe@fb.com>,
	Chaitanya Kulkarni <Chaitanya.Kulkarni@wdc.com>,
	Stephen Bates <sbates@raithlin.com>
Subject: Re: [PATCH v7 08/14] nvmet-core: allow one host per passthru-ctrl
Date: Sun, 18 Aug 2019 13:33:47 +0300
Message-ID: <5717f515-e051-c420-07b7-299bcfcd1f32@mellanox.com> (raw)
In-Reply-To: <a6b9db95-a7f0-d1f6-1fa2-8dc13a6aa29e@deltatee.com>


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 ?


  reply index

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-01 23:44 [PATCH v7 00/14] nvmet: add target passthru commands support Logan Gunthorpe
2019-08-01 23:45 ` [PATCH v7 01/14] nvme-core: introduce nvme_ctrl_get_by_path() Logan Gunthorpe
2019-08-14 14:20   ` Max Gurtovoy
2019-08-15 11:46   ` Max Gurtovoy
2019-08-15 15:59     ` Logan Gunthorpe
2019-08-01 23:45 ` [PATCH v7 02/14] nvme-core: export existing ctrl and ns interfaces Logan Gunthorpe
2019-08-01 23:45 ` [PATCH v7 03/14] nvmet: add return value to nvmet_add_async_event() Logan Gunthorpe
2019-08-14 14:26   ` Max Gurtovoy
2019-08-14 16:59     ` Logan Gunthorpe
2019-08-01 23:45 ` [PATCH v7 04/14] nvmet: make nvmet_copy_ns_identifier() non-static Logan Gunthorpe
2019-08-14 14:29   ` Max Gurtovoy
2019-08-15  7:15     ` Chaitanya Kulkarni
2019-08-01 23:45 ` [PATCH v7 05/14] nvmet-passthru: update KConfig with config passthru option Logan Gunthorpe
2019-08-14 14:31   ` Max Gurtovoy
2019-08-01 23:45 ` [PATCH v7 06/14] nvmet-passthru: add passthru code to process commands Logan Gunthorpe
2019-08-01 23:45 ` [PATCH v7 07/14] nvmet-passthru: add enable/disable helpers Logan Gunthorpe
2019-08-15 12:20   ` Max Gurtovoy
2019-08-15 16:02     ` Logan Gunthorpe
2019-08-01 23:45 ` [PATCH v7 08/14] nvmet-core: allow one host per passthru-ctrl Logan Gunthorpe
2019-08-15 12:36   ` Max Gurtovoy
2019-08-15 16:06     ` Logan Gunthorpe
2019-08-18 10:33       ` Max Gurtovoy [this message]
2019-08-22  0:09         ` Sagi Grimberg
2019-08-22  8:50           ` Max Gurtovoy
2019-08-22 17:41             ` Sagi Grimberg
2019-08-22 19:17               ` Sagi Grimberg
2019-08-22 19:41                 ` Logan Gunthorpe
2019-08-01 23:45 ` [PATCH v7 09/14] nvmet-core: don't check the data len for pt-ctrl Logan Gunthorpe
2019-08-01 23:45 ` [PATCH v7 10/14] nvmet-tcp: don't check data_len in nvmet_tcp_map_data() Logan Gunthorpe
2019-08-01 23:45 ` [PATCH v7 11/14] nvmet-configfs: introduce passthru configfs interface Logan Gunthorpe
2019-08-15 12:46   ` Max Gurtovoy
2019-08-01 23:45 ` [PATCH v7 12/14] block: don't check blk_rq_is_passthrough() in blk_do_io_stat() Logan Gunthorpe
2019-08-01 23:45 ` [PATCH v7 13/14] block: call blk_account_io_start() in blk_execute_rq_nowait() Logan Gunthorpe
2019-08-01 23:45 ` [PATCH v7 14/14] nvmet-passthru: support block accounting Logan Gunthorpe

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