[RESEND PATCH 2/2] NVMe: Add nvme subsystem reset IOCTL

[J Freyensee]

On Mon, 2015-08-10 at 15:20 -0600, Keith Busch wrote:
> From: Jon Derrick <jonathan.derrick at intel.com>
> 
> Controllers can perform optional subsystem resets as introduced in 
> NVMe
> 1.1. This patch adds an IOCTL to trigger the subsystem reset by 
> writing
> "NVMe" to the NSSR register.

I just took a Linux Foundation training class and one of the points the
Foundation made was the Linux community wanting to move off of IOCTLs
to other userspace-to-kernelspace mechanisms (like sysfs for example). 

I was wondering if it's a good thing to be continuing to add IOCTLs if
it is true that the Linux community would like to move off the reliance
of IOCTLs?

> 
> Signed-off-by: Jon Derrick <jonathan.derrick at intel.com>
> Acked-by: Keith Busch <keith.busch at intel.com>
> ---
>  drivers/block/nvme-core.c |   11 +++++++++++
>  include/linux/nvme.h      |    2 +-
>  include/uapi/linux/nvme.h |    1 +
>  3 files changed, 13 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/block/nvme-core.c b/drivers/block/nvme-core.c
> index 4e19c8a..613c1bc 100644
> --- a/drivers/block/nvme-core.c
> +++ b/drivers/block/nvme-core.c
> @@ -1862,6 +1862,15 @@ static int nvme_user_cmd(struct nvme_dev *dev, 
> struct nvme_ns *ns,
>  	return status;
>  }
>  
> +static int nvme_subsys_reset(struct nvme_dev *dev)
> +{
> +	if (!dev->subsystem)
> +		return -ENOTTY;
> +
> +	writel(0x4E564D65, &dev->bar->nssr); /* "NVMe" */
> +	return 0;
> +}
> +
>  static int nvme_ioctl(struct block_device *bdev, fmode_t mode, 
> unsigned int cmd,
>  							unsigned 
> long arg)
>  {
> @@ -2829,6 +2838,8 @@ static long nvme_dev_ioctl(struct file *f, 
> unsigned int cmd, unsigned long arg)
>  	case NVME_IOCTL_RESET:
>  		dev_warn(dev->dev, "resetting controller\n");
>  		return nvme_reset(dev);
> +	case NVME_IOCTL_SUBSYS_RESET:
> +		return nvme_subsys_reset(dev);
>  	default:
>  		return -ENOTTY;
>  	}
> diff --git a/include/linux/nvme.h b/include/linux/nvme.h
> index a566b41..4d08354 100644
> --- a/include/linux/nvme.h
> +++ b/include/linux/nvme.h
> @@ -28,7 +28,7 @@ struct nvme_bar {
>  	__u32			cc;	/* Controller Configuration 
> */
>  	__u32			rsvd1;	/* Reserved */
>  	__u32			csts;	/* Controller Status */
> -	__u32			rsvd2;	/* Reserved */
> +	__u32			nssr;	/* Subsystem Reset */
>  	__u32			aqa;	/* Admin Queue Attributes */
>  	__u64			asq;	/* Admin SQ Base Address */
>  	__u64			acq;	/* Admin CQ Base Address */
> diff --git a/include/uapi/linux/nvme.h b/include/uapi/linux/nvme.h
> index 732b32e..8864194 100644
> --- a/include/uapi/linux/nvme.h
> +++ b/include/uapi/linux/nvme.h
> @@ -584,5 +584,6 @@ struct nvme_passthru_cmd {
>  #define NVME_IOCTL_SUBMIT_IO	_IOW('N', 0x42, struct nvme_user_io)
>  #define NVME_IOCTL_IO_CMD	_IOWR('N', 0x43, struct 
> nvme_passthru_cmd)
>  #define NVME_IOCTL_RESET	_IO('N', 0x44)
> +#define NVME_IOCTL_SUBSYS_RESET	_IO('N', 0x45)
>  
>  #endif /* _UAPI_LINUX_NVME_H */