linux-kernel - Re: [PATCH v11 8/9] nvmet-passthru: Add enable/disable helpers

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Date:   Thu, 27 Feb 2020 10:37:21 -0700
From:   Logan Gunthorpe <logang@...tatee.com>
To:     Sagi Grimberg <sagi@...mberg.me>, linux-kernel@...r.kernel.org,
        linux-nvme@...ts.infradead.org
Cc:     Christoph Hellwig <hch@....de>, Keith Busch <kbusch@...nel.org>,
        Jens Axboe <axboe@...com>,
        Chaitanya Kulkarni <Chaitanya.Kulkarni@....com>,
        Max Gurtovoy <maxg@...lanox.com>,
        Stephen Bates <sbates@...thlin.com>
Subject: Re: [PATCH v11 8/9] nvmet-passthru: Add enable/disable helpers



On 2020-02-26 4:33 p.m., Sagi Grimberg wrote:
> 
>> +    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.

>> +    }
>> +
>> +    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.

>> +
>> +void nvmet_passthru_ctrl_disable(struct nvmet_subsys *subsys)
>> +{
>> +    mutex_lock(&subsys->lock);
>> +    __nvmet_passthru_ctrl_disable(subsys);
>> +    mutex_unlock(&subsys->lock);
>> +}
>> +
>> +void nvmet_passthru_subsys_free(struct nvmet_subsys *subsys)
>> +{
>> +    mutex_lock(&subsys->lock);
>> +    __nvmet_passthru_ctrl_disable(subsys);
>> +    kfree(subsys->passthru_ctrl_path);
>> +    mutex_unlock(&subsys->lock);
> 
> Nit, any reason why the free is in the mutex?

Nope. Will fix.