Re: [PATCH] nvme: fix irq vs io_queue calculations

[Guenter Roeck <linux@roeck-us.net>]

On 12/9/18 10:21 AM, Jens Axboe wrote:
> Guenter reported an boot hang issue on HPPA after we default to 0 poll
> queues. We have two issues in the queue count calculations:
> 
> 1) We don't separate the poll queues from the read/write queues. This is
>     important, since the former doesn't need interrupts.
> 2) The adjust logic is broken.
> 
> Adjust the poll queue count before doing nvme_calc_io_queues(). The poll
> queue count is only limited by the IO queue count we were able to get
> from the controller, not failures in the IRQ allocation loop. This
> leaves nvme_calc_io_queues() just adjusting the read/write queue map.
> 
> Reported-by: Reported-by: Guenter Roeck <linux@roeck-us.net>
> Signed-off-by: Jens Axboe <axboe@kernel.dk>

Tested-by: Guenter Roeck <linux@roeck-us.net>

> 
> ---
> 
> diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
> index 7732c4979a4e..0fe48b128aff 100644
> --- a/drivers/nvme/host/pci.c
> +++ b/drivers/nvme/host/pci.c
> @@ -2030,60 +2030,40 @@ static int nvme_setup_host_mem(struct nvme_dev *dev)
>   	return ret;
>   }
>   
> -static void nvme_calc_io_queues(struct nvme_dev *dev, unsigned int nr_io_queues)
> +static void nvme_calc_io_queues(struct nvme_dev *dev, unsigned int irq_queues)
>   {
>   	unsigned int this_w_queues = write_queues;
> -	unsigned int this_p_queues = poll_queues;
>   
>   	/*
>   	 * Setup read/write queue split
>   	 */
> -	if (nr_io_queues == 1) {
> +	if (irq_queues == 1) {
>   		dev->io_queues[HCTX_TYPE_DEFAULT] = 1;
>   		dev->io_queues[HCTX_TYPE_READ] = 0;
> -		dev->io_queues[HCTX_TYPE_POLL] = 0;
>   		return;
>   	}
>   
> -	/*
> -	 * Configure number of poll queues, if set
> -	 */
> -	if (this_p_queues) {
> -		/*
> -		 * We need at least one queue left. With just one queue, we'll
> -		 * have a single shared read/write set.
> -		 */
> -		if (this_p_queues >= nr_io_queues) {
> -			this_w_queues = 0;
> -			this_p_queues = nr_io_queues - 1;
> -		}
> -
> -		dev->io_queues[HCTX_TYPE_POLL] = this_p_queues;
> -		nr_io_queues -= this_p_queues;
> -	} else
> -		dev->io_queues[HCTX_TYPE_POLL] = 0;
> -
>   	/*
>   	 * If 'write_queues' is set, ensure it leaves room for at least
>   	 * one read queue
>   	 */
> -	if (this_w_queues >= nr_io_queues)
> -		this_w_queues = nr_io_queues - 1;
> +	if (this_w_queues >= irq_queues)
> +		this_w_queues = irq_queues - 1;
>   
>   	/*
>   	 * If 'write_queues' is set to zero, reads and writes will share
>   	 * a queue set.
>   	 */
>   	if (!this_w_queues) {
> -		dev->io_queues[HCTX_TYPE_DEFAULT] = nr_io_queues;
> +		dev->io_queues[HCTX_TYPE_DEFAULT] = irq_queues;
>   		dev->io_queues[HCTX_TYPE_READ] = 0;
>   	} else {
>   		dev->io_queues[HCTX_TYPE_DEFAULT] = this_w_queues;
> -		dev->io_queues[HCTX_TYPE_READ] = nr_io_queues - this_w_queues;
> +		dev->io_queues[HCTX_TYPE_READ] = irq_queues - this_w_queues;
>   	}
>   }
>   
> -static int nvme_setup_irqs(struct nvme_dev *dev, int nr_io_queues)
> +static int nvme_setup_irqs(struct nvme_dev *dev, unsigned int nr_io_queues)
>   {
>   	struct pci_dev *pdev = to_pci_dev(dev->dev);
>   	int irq_sets[2];
> @@ -2093,6 +2073,20 @@ static int nvme_setup_irqs(struct nvme_dev *dev, int nr_io_queues)
>   		.sets = irq_sets,
>   	};
>   	int result = 0;
> +	unsigned int irq_queues, this_p_queues;
> +
> +	/*
> +	 * Poll queues don't need interrupts, but we need at least one IO
> +	 * queue left over for non-polled IO.
> +	 */
> +	this_p_queues = poll_queues;
> +	if (this_p_queues >= nr_io_queues) {
> +		this_p_queues = nr_io_queues - 1;
> +		irq_queues = 1;
> +	} else {
> +		irq_queues = nr_io_queues - this_p_queues;
> +	}
> +	dev->io_queues[HCTX_TYPE_POLL] = this_p_queues;
>   
>   	/*
>   	 * For irq sets, we have to ask for minvec == maxvec. This passes
> @@ -2100,7 +2094,7 @@ static int nvme_setup_irqs(struct nvme_dev *dev, int nr_io_queues)
>   	 * IRQ vector needs.
>   	 */
>   	do {
> -		nvme_calc_io_queues(dev, nr_io_queues);
> +		nvme_calc_io_queues(dev, irq_queues);
>   		irq_sets[0] = dev->io_queues[HCTX_TYPE_DEFAULT];
>   		irq_sets[1] = dev->io_queues[HCTX_TYPE_READ];
>   		if (!irq_sets[1])
> @@ -2111,11 +2105,11 @@ static int nvme_setup_irqs(struct nvme_dev *dev, int nr_io_queues)
>   		 * 1 + 1 queues, just ask for a single vector. We'll share
>   		 * that between the single IO queue and the admin queue.
>   		 */
> -		if (!(result < 0 && nr_io_queues == 1))
> -			nr_io_queues = irq_sets[0] + irq_sets[1] + 1;
> +		if (!(result < 0 || irq_queues == 1))
> +			irq_queues = irq_sets[0] + irq_sets[1] + 1;
>   
> -		result = pci_alloc_irq_vectors_affinity(pdev, nr_io_queues,
> -				nr_io_queues,
> +		result = pci_alloc_irq_vectors_affinity(pdev, irq_queues,
> +				irq_queues,
>   				PCI_IRQ_ALL_TYPES | PCI_IRQ_AFFINITY, &affd);
>   
>   		/*
> @@ -2125,12 +2119,12 @@ static int nvme_setup_irqs(struct nvme_dev *dev, int nr_io_queues)
>   		 * likely does not. Back down to ask for just one vector.
>   		 */
>   		if (result == -ENOSPC) {
> -			nr_io_queues--;
> -			if (!nr_io_queues)
> +			irq_queues--;
> +			if (!irq_queues)
>   				return result;
>   			continue;
>   		} else if (result == -EINVAL) {
> -			nr_io_queues = 1;
> +			irq_queues = 1;
>   			continue;
>   		} else if (result <= 0)
>   			return -EIO;
>