Re: [PATCH] null_blk: add zoned config support information

[Laurence Oberman <loberman@redhat.com>]

On Fri, 2019-01-04 at 10:42 -0500, John Pittman wrote:
> If the kernel is built without CONFIG_BLK_DEV_ZONED, a modprobe
> of the null_blk driver with zoned=1 fails with 'Invalid argument'.
> This can be confusing to users, prompting a search as to why the
> parameter is invalid. To assist in that search, add a bit more
> information to the failure, additionally adding to the documentation
> that CONFIG_BLK_DEV_ZONED is needed for zoned=1.
> 
> Signed-off-by: John Pittman <jpittman@redhat.com>
> ---
>  Documentation/block/null_blk.txt | 3 ++-
>  drivers/block/null_blk.h         | 1 +
>  2 files changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/block/null_blk.txt
> b/Documentation/block/null_blk.txt
> index ea2dafe49ae8..4cad1024fff7 100644
> --- a/Documentation/block/null_blk.txt
> +++ b/Documentation/block/null_blk.txt
> @@ -88,7 +88,8 @@ shared_tags=[0/1]: Default: 0
>  
>  zoned=[0/1]: Default: 0
>    0: Block device is exposed as a random-access block device.
> -  1: Block device is exposed as a host-managed zoned block device.
> +  1: Block device is exposed as a host-managed zoned block device.
> Requires
> +     CONFIG_BLK_DEV_ZONED.
>  
>  zone_size=[MB]: Default: 256
>    Per zone size when exposed as a zoned block device. Must be a
> power of two.
> diff --git a/drivers/block/null_blk.h b/drivers/block/null_blk.h
> index b3df2793e7cd..cab4808f14bd 100644
> --- a/drivers/block/null_blk.h
> +++ b/drivers/block/null_blk.h
> @@ -97,6 +97,7 @@ void null_zone_reset(struct nullb_cmd *cmd,
> sector_t sector);
>  #else
>  static inline int null_zone_init(struct nullb_device *dev)
>  {
> +	pr_info("CONFIG_BLK_DEV_ZONED not enabled\n");
>  	return -EINVAL;
>  }
>  static inline void null_zone_exit(struct nullb_device *dev) {}

Looks good to me, useful change in my opinion.

Reviewed-by: Laurence Oberman <loberman@redhat.com>