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Subject: Re: [PATCH v15 7/9] nvmet-passthru: Add passthru code to process
 commands
To:     Christoph Hellwig <hch@lst.de>,
        Logan Gunthorpe <logang@deltatee.com>
Cc:     linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org,
        Keith Busch <kbusch@kernel.org>, Jens Axboe <axboe@fb.com>,
        Chaitanya Kulkarni <Chaitanya.Kulkarni@wdc.com>,
        Max Gurtovoy <maxg@mellanox.com>,
        Stephen Bates <sbates@raithlin.com>
References: <20200716203319.16022-1-logang@deltatee.com>
 <20200716203319.16022-8-logang@deltatee.com> <20200720141606.GF4627@lst.de>
From:   Sagi Grimberg <sagi@grimberg.me>
Message-ID: <e939dd43-9e7f-8ef0-162b-2a27f53e6e1a@grimberg.me>
Date:   Mon, 20 Jul 2020 12:35:12 -0700
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>> Add passthru command handling capability for the NVMeOF target and
>> export passthru APIs which are used to integrate passthru
>> code with nvmet-core.
>>
>> The new file passthru.c handles passthru cmd parsing and execution.
>> In the passthru mode, we create a block layer request from the nvmet
>> request and map the data on to the block layer request.
>>
>> Admin commands and features are on a white list as there are a number
>> of each that don't make too much sense with passthrough. We use a
>> white list so that new commands can be considered before being blindly
>> passed through. In both cases, vendor specific commands are always
>> allowed.
>>
>> We also blacklist reservation IO commands as the underlying device
>> cannot differentiate between multiple hosts behind a fabric.
> 
> I'm still not so happy about having to look up the namespace and still
> wonder if we should generalize the connect_q to a passthrough_q.  But
> I guess we can do that later and then reduce some of the exports here..

That is a neat idea! should be easy to do (and we can then lose the host
xarray stuff). I don't mind having it on a later patch, but it should be
easy enough to do even before...