[PATCH] nvme-pci: add module parameter for io queue depth

[Keith Busch]

On Fri, Jul 07, 2017 at 05:05:47PM +0800, weiping zhang wrote:
> Adjust io queue depth more easily.
> 
> Signed-off-by: weiping zhang <zhangweiping at didichuxing.com>
> ---
>  drivers/nvme/host/pci.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
> index 951042a..f1ac0f8 100644
> --- a/drivers/nvme/host/pci.c
> +++ b/drivers/nvme/host/pci.c
> @@ -48,7 +48,6 @@
>  
>  #include "nvme.h"
>  
> -#define NVME_Q_DEPTH		1024
>  #define NVME_AQ_DEPTH		256
>  #define SQ_SIZE(depth)		(depth * sizeof(struct nvme_command))
>  #define CQ_SIZE(depth)		(depth * sizeof(struct nvme_completion))
> @@ -66,6 +65,10 @@ static bool use_cmb_sqes = true;
>  module_param(use_cmb_sqes, bool, 0644);
>  MODULE_PARM_DESC(use_cmb_sqes, "use controller's memory buffer for I/O SQes");
>  
> +static int io_queue_depth = 1024;
> +module_param(io_queue_depth, int, 0644);
> +MODULE_PARM_DESC(io_queue_depth, "set io queue depth");
> +
>  static struct workqueue_struct *nvme_workq;
>  
>  struct nvme_dev;
> @@ -1730,7 +1733,7 @@ static int nvme_pci_enable(struct nvme_dev *dev)
>  
>  	cap = lo_hi_readq(dev->bar + NVME_REG_CAP);
>  
> -	dev->q_depth = min_t(int, NVME_CAP_MQES(cap) + 1, NVME_Q_DEPTH);
> +	dev->q_depth = min_t(int, NVME_CAP_MQES(cap) + 1, io_queue_depth);

We need to be a little more careful about this field if users can write
whatever they want. It's gotta be >= 2 or else trouble will occur.