linux-kernel - Re: [PATCH] NVMe: do not touch sq door bell if nvmeq has been suspended

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Message-ID: <56AF8DB5.70206@fb.com>
Date:	Mon, 1 Feb 2016 09:54:13 -0700
From:	Jens Axboe <axboe@...com>
To:	Wenbo Wang <mail_weber_wang@....com>, <keith.busch@...el.com>
CC:	<linux-kernel@...r.kernel.org>,
	Wenbo Wang <wenbo.wang@...blaze.com>,
	<linux-nvme@...ts.infradead.org>
Subject: Re: [PATCH] NVMe: do not touch sq door bell if nvmeq has been
 suspended

On 02/01/2016 08:42 AM, Wenbo Wang wrote:
> If __nvme_submit_cmd races with nvme_dev_disable, nvmeq
> could have been suspended and dev->bar could have been
> unmapped. Do not touch sq door bell in this case.
>
> Signed-off-by: Wenbo Wang <wenbo.wang@...blaze.com>
> Reviewed-by: Wenwei Tao <wenwei.tao@...blaze.com>
> CC: linux-nvme@...ts.infradead.org
> ---
>   drivers/nvme/host/pci.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
> index 8b1a725..2288712 100644
> --- a/drivers/nvme/host/pci.c
> +++ b/drivers/nvme/host/pci.c
> @@ -325,7 +325,8 @@ static void __nvme_submit_cmd(struct nvme_queue *nvmeq,
>
>   	if (++tail == nvmeq->q_depth)
>   		tail = 0;
> -	writel(tail, nvmeq->q_db);
> +	if (likely(nvmeq->cq_vector >= 0))
> +		writel(tail, nvmeq->q_db);
>   	nvmeq->sq_tail = tail;

What Keith said (this should not happen), and additionally, this won't 
work for a polled CQ without a vector.

-- 
Jens Axboe