Re: [PATCH v2 09/11] block: Expose queue nr_zones in sysfs

["Ewan D. Milne" <emilne@redhat.com>]

So in v2 you moved the #ifdef CONFIG_BLK_DEV_ZONED
so that nr_zones is always present?  It was previously
changed to keep the request_queue size smaller.

Would make more sense to make the nr_zones sysfs
code here conditional on CONFIG_BLK_DEV_ZONED?

-Ewan


On Thu, 2018-10-11 at 16:09 +0900, Damien Le Moal wrote:
> Expose through sysfs the nr_zones field of a zoned block device request
> queue. This represents the total number of zones of the device
> calculated using the known disk capacity and zone size.
> 
> Exposing this value helps in debugging disk issues as well as
> facilitating scripts based use of the disk (e.g. blktests).
> 
> Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
> ---
>  block/blk-sysfs.c      | 11 +++++++++++
>  include/linux/blkdev.h |  2 +-
>  2 files changed, 12 insertions(+), 1 deletion(-)
> 
> diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
> index 3772671cf2bc..f7060a938bf9 100644
> --- a/block/blk-sysfs.c
> +++ b/block/blk-sysfs.c
> @@ -300,6 +300,11 @@ static ssize_t queue_zoned_show(struct request_queue *q, char *page)
>  	}
>  }
>  
> +static ssize_t queue_nr_zones_show(struct request_queue *q, char *page)
> +{
> +	return queue_var_show(q->nr_zones, page);
> +}
> +
>  static ssize_t queue_nomerges_show(struct request_queue *q, char *page)
>  {
>  	return queue_var_show((blk_queue_nomerges(q) << 1) |
> @@ -637,6 +642,11 @@ static struct queue_sysfs_entry queue_zoned_entry = {
>  	.show = queue_zoned_show,
>  };
>  
> +static struct queue_sysfs_entry queue_nr_zones_entry = {
> +	.attr = {.name = "nr_zones", .mode = 0444 },
> +	.show = queue_nr_zones_show,
> +};
> +
>  static struct queue_sysfs_entry queue_nomerges_entry = {
>  	.attr = {.name = "nomerges", .mode = 0644 },
>  	.show = queue_nomerges_show,
> @@ -727,6 +737,7 @@ static struct attribute *default_attrs[] = {
>  	&queue_write_zeroes_max_entry.attr,
>  	&queue_nonrot_entry.attr,
>  	&queue_zoned_entry.attr,
> +	&queue_nr_zones_entry.attr,
>  	&queue_nomerges_entry.attr,
>  	&queue_rq_affinity_entry.attr,
>  	&queue_iostats_entry.attr,
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index c24969b1741b..23ab53d2d4ca 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -593,7 +593,6 @@ struct request_queue {
>  
>  	struct queue_limits	limits;
>  
> -#ifdef CONFIG_BLK_DEV_ZONED
>  	/*
>  	 * Zoned block device information for request dispatch control.
>  	 * nr_zones is the total number of zones of the device. This is always
> @@ -612,6 +611,7 @@ struct request_queue {
>  	 * blk_mq_unfreeze_queue().
>  	 */
>  	unsigned int		nr_zones;
> +#ifdef CONFIG_BLK_DEV_ZONED
>  	unsigned long		*seq_zones_bitmap;
>  	unsigned long		*seq_zones_wlock;
>  #endif /* CONFIG_BLK_DEV_ZONED */