[PATCH RFC 3/5] NVMe: Asynchronous device scan support

[Matthew Wilcox]

On Mon, Dec 30, 2013 at 03:57:18PM +0530, Santosh Y wrote:
> This patch provides asynchronous device enumeration
> capability. The 'probe' need not wait until the namespace scanning is
> complete.

I'm very interested in having something like this, except I don't think
it's complete.  You don't seem to handle the cases where the device
is shut down in the middle of an async scan.  Also, the only piece you
seem to make async is the calls to add_disk(), which are surely not the
timeconsuming parts of the scan.  I would think the time consuming parts
are sending the IDENTIFY commands, which you don't make async.

> Signed-off-by: Ravi Kumar <ravi.android at gmail.com>
> Signed-off-by: Santosh Y <santoshsy at gmail.com>
> 
> diff --git a/drivers/block/nvme-core.c b/drivers/block/nvme-core.c
> index 8a02135..cd37335 100644
> --- a/drivers/block/nvme-core.c
> +++ b/drivers/block/nvme-core.c
> @@ -17,6 +17,9 @@
>   */
>  
>  #include <linux/nvme.h>
> +#ifdef CONFIG_BLK_DEV_NVME_HP
> +#include <linux/async.h>
> +#endif
>  #include <linux/bio.h>
>  #include <linux/bitops.h>
>  #include <linux/blkdev.h>
> @@ -2115,8 +2118,10 @@ static int nvme_dev_add(struct nvme_dev *dev)
>  		if (ns)
>  			list_add_tail(&ns->list, &dev->namespaces);
>  	}
> +#ifndef CONFIG_BLK_DEV_NVME_HP
>  	list_for_each_entry(ns, &dev->namespaces, list)
>  		add_disk(ns->disk);
> +#endif
>  	res = 0;
>  
>   out:
> @@ -2546,6 +2551,19 @@ static void nvme_reset_failed_dev(struct work_struct *ws)
>  	nvme_dev_reset(dev);
>  }
>  
> +#ifdef CONFIG_BLK_DEV_NVME_HP
> +static void nvme_async_add(void *data, async_cookie_t cookie)
> +{
> +	struct nvme_dev *dev = (struct nvme_dev *)data;
> +	struct nvme_ns *ns;
> +
> +	list_for_each_entry(ns, &dev->namespaces, list)
> +		add_disk(ns->disk);
> +	if (!test_bit(NVME_HOT_REM, &dev->hp_flag))
> +		dev->initialized = 1;
> +}
> +#endif
> +
>  static int nvme_probe(struct pci_dev *pdev, const struct pci_device_id *id)
>  {
>  	int result = -ENOMEM;
> @@ -2595,14 +2613,16 @@ static int nvme_probe(struct pci_dev *pdev, const struct pci_device_id *id)
>  	if (result)
>  		goto remove;
>  
> -	dev->initialized = 1;
> -	kref_init(&dev->kref);
> -
>  #ifdef CONFIG_BLK_DEV_NVME_HP
> +	async_schedule(nvme_async_add, dev);
>  	if (!pdev->is_added)
>  		dev_info(&pdev->dev,
>  			"Device 0x%x is on-line\n", pdev->device);
> +#else
> +	dev->initialized = 1;
>  #endif
> +	kref_init(&dev->kref);
> +
>  	return 0;
>  
>   remove:
> -- 
> 1.8.3.2