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Subject: Re: [PATCH v11 8/9] nvmet-passthru: Add enable/disable helpers
To:     Logan Gunthorpe <logang@deltatee.com>,
        linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org
Cc:     Christoph Hellwig <hch@lst.de>, 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: <20200220203652.26734-1-logang@deltatee.com>
 <20200220203652.26734-9-logang@deltatee.com>
 <96234649-fbc1-fb56-54d8-2f73dc455ffd@grimberg.me>
 <9c6355d8-cf4e-9932-1cef-0a7140f0fa7e@deltatee.com>
From:   Sagi Grimberg <sagi@grimberg.me>
Message-ID: <283c563a-06a9-9c12-bd4e-d15e790fad57@grimberg.me>
Date:   Thu, 27 Feb 2020 15:13:07 -0800
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>>> +    if (subsys->ver < NVME_VS(1, 2, 1)) {
>>> +        pr_warn("nvme controller version is too old: %d.%d.%d,
>>> advertising 1.2.1\n",
>>> +            (int)NVME_MAJOR(subsys->ver),
>>> +            (int)NVME_MINOR(subsys->ver),
>>> +            (int)NVME_TERTIARY(subsys->ver));
>>> +        subsys->ver = NVME_VS(1, 2, 1);
>>
>> Umm.. is this OK? do we implement the mandatory 1.2.1 features on behalf
>> of the passthru device?
> 
> This was the approach that Christoph suggested. It seemed sensible to
> me. However, it would also *probably* be ok to just reject these
> devices. Unless you feel strongly about this, I'll probably leave it the
> way it is.

Sounds ok to me.

>>> +    }
>>> +
>>> +    mutex_unlock(&subsys->lock);
>>> +    return 0;
>>> +
>>> +out_put_ctrl:
>>> +    nvme_put_ctrl(ctrl);
>>> +out_unlock:
>>> +    mutex_unlock(&subsys->lock);
>>> +    return ret;
>>> +}
>>> +
>>> +static void __nvmet_passthru_ctrl_disable(struct nvmet_subsys *subsys)
>>> +{
>>> +    if (subsys->passthru_ctrl) {
>>> +        xa_erase(&passthru_subsystems, subsys->passthru_ctrl->cntlid);
>>> +        nvme_put_ctrl(subsys->passthru_ctrl);
>>> +    }
>>> +    subsys->passthru_ctrl = NULL;
>>> +    subsys->ver = NVMET_DEFAULT_VS;
>>> +}
>>
>> Isn't it strange that a subsystem changes its version in its lifetime?
> 
> It does seem strange. However, it's not at all unprecedented. See
> nvmet_subsys_attr_version_store() which gives the user direct control of
> the version through configfs.

You're right.