[PATCH 1/5] NVMe: Fix admin queue ring wrap

[Jens Axboe]

On 12/30/2015 10:27 AM, Keith Busch wrote:
> The tag set queue depth needs to be one less than the h/w queue depth
> so we don't wrap the circular buffer. This conforms to the specification
> defined "Full Queue" condition.
>
> Signed-off-by: Keith Busch <keith.busch at intel.com>
> ---
>   drivers/nvme/host/pci.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
> index b82bbea..2e6e665 100644
> --- a/drivers/nvme/host/pci.c
> +++ b/drivers/nvme/host/pci.c
> @@ -1271,7 +1271,7 @@ static int nvme_alloc_admin_tags(struct nvme_dev *dev)
>   	if (!dev->ctrl.admin_q) {
>   		dev->admin_tagset.ops = &nvme_mq_admin_ops;
>   		dev->admin_tagset.nr_hw_queues = 1;
> -		dev->admin_tagset.queue_depth = NVME_AQ_BLKMQ_DEPTH;
> +		dev->admin_tagset.queue_depth = NVME_AQ_BLKMQ_DEPTH - 1;
>   		dev->admin_tagset.timeout = ADMIN_TIMEOUT;
>   		dev->admin_tagset.numa_node = dev_to_node(dev->dev);
>   		dev->admin_tagset.cmd_size = nvme_cmd_size(dev);

I missed this during review, which is a little sad since I ran into the 
same thing in the initial conversion of the nvme driver to blk-mq.

-- 
Jens Axboe