Re: [PATCH v3 09/11] block: Expose queue nr_zones in sysfs

[Hannes Reinecke <hare@suse.de>]

On 10/12/18 4:30 AM, Damien Le Moal wrote:
> Expose through sysfs the nr_zones field of struct request_queue.
> Exposing this value helps in debugging disk issues as well as
> facilitating scripts based use of the disk (e.g. blktests).
> 
> For zoned block devices, the nr_zones field indicates the total number
> of zones of the device calculated using the known disk capacity and
> zone size. This number of zones is always 0 for regular block devices.
> 
> Since nr_zones is defined conditionally with CONFIG_BLK_DEV_ZONED,
> introduce the blk_queue_nr_zones() function to return the correct value
> for any device, regardless if CONFIG_BLK_DEV_ZONED is set.
> 
> Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
> ---
>   block/blk-sysfs.c      | 11 +++++++++++
>   include/linux/blkdev.h | 10 ++++++++++
>   2 files changed, 21 insertions(+)
> 
> diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
> index 3772671cf2bc..92be8092ca4f 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(blk_queue_nr_zones(q), 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..879753b10263 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -804,6 +804,11 @@ static inline unsigned int blk_queue_zone_sectors(struct request_queue *q)
>   }
>   
>   #ifdef CONFIG_BLK_DEV_ZONED
> +static inline unsigned int blk_queue_nr_zones(struct request_queue *q)
> +{
> +	return blk_queue_is_zoned(q) ? q->nr_zones : 0;
> +}
> +
>   static inline unsigned int blk_queue_zone_no(struct request_queue *q,
>   					     sector_t sector)
>   {
> @@ -819,6 +824,11 @@ static inline bool blk_queue_zone_is_seq(struct request_queue *q,
>   		return false;
>   	return test_bit(blk_queue_zone_no(q, sector), q->seq_zones_bitmap);
>   }
> +#else /* CONFIG_BLK_DEV_ZONED */
> +static inline unsigned int blk_queue_nr_zones(struct request_queue *q)
> +{
> +	return 0;
> +}
>   #endif /* CONFIG_BLK_DEV_ZONED */
>   
>   static inline bool rq_is_sync(struct request *rq)
> 
Actually, we should be checking whether we can't blank out this 
attribute via the is_visible mechanism; after all, not every block 
device is zoned, and those which are not have no need of the attribute...

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		   Teamlead Storage & Networking
hare@suse.de			               +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: F. Imendörffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton
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