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Subject: Re: [PATCH v15 7/9] nvmet-passthru: Add passthru code to process
 commands
To:     Keith Busch <kbusch@kernel.org>,
        Logan Gunthorpe <logang@deltatee.com>
Cc:     Chaitanya Kulkarni <Chaitanya.Kulkarni@wdc.com>,
        linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org,
        Stephen Bates <sbates@raithlin.com>, Jens Axboe <axboe@fb.com>,
        Max Gurtovoy <maxg@mellanox.com>,
        Christoph Hellwig <hch@lst.de>
References: <20200716203319.16022-1-logang@deltatee.com>
 <20200716203319.16022-8-logang@deltatee.com> <20200720141606.GF4627@lst.de>
 <e939dd43-9e7f-8ef0-162b-2a27f53e6e1a@grimberg.me>
 <5cc390cf-9b0b-b48b-7447-37934be51ee0@deltatee.com>
 <2dc39232-4042-1f93-3dcc-3266e70cf6f0@grimberg.me>
 <b8fc47a2-0b53-3316-775f-0e9a8eddfdc2@deltatee.com>
 <20200720231701.GA682160@dhcp-10-100-145-180.wdl.wdc.com>
From:   Sagi Grimberg <sagi@grimberg.me>
Message-ID: <d7596065-f33b-5533-7254-153b82e6b88b@grimberg.me>
Date:   Mon, 20 Jul 2020 16:28:26 -0700
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On 7/20/20 4:17 PM, Keith Busch wrote:
> On Mon, Jul 20, 2020 at 05:01:19PM -0600, Logan Gunthorpe wrote:
>> On 2020-07-20 4:35 p.m., Sagi Grimberg wrote:
>>
>>> passthru commands are in essence REQ_OP_DRV_IN/REQ_OP_DRV_OUT, which
>>> means that the driver shouldn't need the ns at all. So if you have a
>>> dedicated request queue (mapped to the I/O tagset), you don't need the
>>> ns->queue and we can lose the ns lookup altogether.
> 
> We still need a request_queue to dispatch the command. I guess you could
> make a generic one for the controller that isn't tied to a namespace,
> but we lose the fair shared tag allocation.

What do you mean fair shared tag allocation?