Re: [PATCH 1/2] block: add zone_desc_ext_bytes to sysfs

[Damien Le Moal]

On 2020/06/29 8:01, Matias Bjorling wrote:
> The NVMe Zoned Namespace Command Set adds support for associating
> data to a zone through the Zone Descriptor Extension feature.
> 
> The Zone Descriptor Extension size is fixed to a multiple of 64
> bytes. A value of zero communicates the feature is not available.
> A value larger than zero communites the feature is available, and
> the specified Zone Descriptor Extension size in bytes.
> 
> The Zone Descriptor Extension feature is only available in the
> NVMe Zoned Namespaces Command Set. Devices that supports ZAC/ZBC
> therefore reports this value as zero, where as the NVMe device
> driver reports the Zone Descriptor Extension size from the
> specific device.
> 
> Signed-off-by: Matias Bjørling <matias.bjorling@xxxxxxx>
> ---
>  Documentation/block/queue-sysfs.rst |  6 ++++++
>  block/blk-sysfs.c                   | 15 ++++++++++++++-
>  drivers/nvme/host/zns.c             |  1 +
>  drivers/scsi/sd_zbc.c               |  1 +
>  include/linux/blkdev.h              | 22 ++++++++++++++++++++++
>  5 files changed, 44 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/block/queue-sysfs.rst b/Documentation/block/queue-sysfs.rst
> index f261a5c84170..c4fa195c87b4 100644
> --- a/Documentation/block/queue-sysfs.rst
> +++ b/Documentation/block/queue-sysfs.rst
> @@ -265,4 +265,10 @@ devices are described in the ZBC (Zoned Block Commands) and ZAC
>  do not support zone commands, they will be treated as regular block devices
>  and zoned will report "none".
>  
> +zone_desc_ext_bytes (RO)
> +-------------------------
> +This indicates the zone description extension (ZDE) size, in bytes, of a zoned
> +block device. A value of '0' means that zone description extension is not
> +supported.
> +
>  Jens Axboe <jens.axboe@xxxxxxxxxx>, February 2009
> diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
> index 624bb4d85fc7..0c99454823b7 100644
> --- a/block/blk-sysfs.c
> +++ b/block/blk-sysfs.c
> @@ -315,6 +315,12 @@ static ssize_t queue_max_active_zones_show(struct request_queue *q, char *page)
>  	return queue_var_show(queue_max_active_zones(q), page);
>  }
>  
> +static ssize_t queue_zone_desc_ext_bytes_show(struct request_queue *q,
> +		char *page)
> +{
> +	return queue_var_show(queue_zone_desc_ext_bytes(q), page);
> +}
> +
>  static ssize_t queue_nomerges_show(struct request_queue *q, char *page)
>  {
>  	return queue_var_show((blk_queue_nomerges(q) << 1) |
> @@ -687,6 +693,11 @@ static struct queue_sysfs_entry queue_max_active_zones_entry = {
>  	.show = queue_max_active_zones_show,
>  };
>  
> +static struct queue_sysfs_entry queue_zone_desc_ext_bytes_entry = {
> +	.attr = {.name = "zone_desc_ext_bytes", .mode = 0444 },
> +	.show = queue_zone_desc_ext_bytes_show,
> +};
> +
>  static struct queue_sysfs_entry queue_nomerges_entry = {
>  	.attr = {.name = "nomerges", .mode = 0644 },
>  	.show = queue_nomerges_show,
> @@ -787,6 +798,7 @@ static struct attribute *queue_attrs[] = {
>  	&queue_nr_zones_entry.attr,
>  	&queue_max_open_zones_entry.attr,
>  	&queue_max_active_zones_entry.attr,

Which tree is this patch based on ? Not I have seen any patch introducing max
active zones.

> +	&queue_zone_desc_ext_bytes_entry.attr,
>  	&queue_nomerges_entry.attr,
>  	&queue_rq_affinity_entry.attr,
>  	&queue_iostats_entry.attr,
> @@ -815,7 +827,8 @@ static umode_t queue_attr_visible(struct kobject *kobj, struct attribute *attr,
>  			return 0;
>  
>  	if ((attr == &queue_max_open_zones_entry.attr ||
> -	     attr == &queue_max_active_zones_entry.attr) &&
> +	     attr == &queue_max_active_zones_entry.attr ||
> +	     attr == &queue_zone_desc_ext_bytes_entry.attr) &&
>  	    !blk_queue_is_zoned(q))
>  		return 0;
>  
> diff --git a/drivers/nvme/host/zns.c b/drivers/nvme/host/zns.c
> index 502070763266..5792d953a8f3 100644
> --- a/drivers/nvme/host/zns.c
> +++ b/drivers/nvme/host/zns.c
> @@ -84,6 +84,7 @@ int nvme_update_zone_info(struct gendisk *disk, struct nvme_ns *ns,
>  	blk_queue_flag_set(QUEUE_FLAG_ZONE_RESETALL, q);
>  	blk_queue_max_open_zones(q, le32_to_cpu(id->mor) + 1);
>  	blk_queue_max_active_zones(q, le32_to_cpu(id->mar) + 1);
> +	blk_queue_zone_desc_ext_bytes(q, id->lbafe[lbaf].zdes << 6);
>  free_data:
>  	kfree(id);
>  	return status;
> diff --git a/drivers/scsi/sd_zbc.c b/drivers/scsi/sd_zbc.c
> index d8b2c49d645b..a4b6d6cf5457 100644
> --- a/drivers/scsi/sd_zbc.c
> +++ b/drivers/scsi/sd_zbc.c
> @@ -722,6 +722,7 @@ int sd_zbc_read_zones(struct scsi_disk *sdkp, unsigned char *buf)
>  	else
>  		blk_queue_max_open_zones(q, sdkp->zones_max_open);
>  	blk_queue_max_active_zones(q, 0);
> +	blk_queue_zone_desc_ext_bytes(q, 0);
>  	nr_zones = round_up(sdkp->capacity, zone_blocks) >> ilog2(zone_blocks);
>  
>  	/* READ16/WRITE16 is mandatory for ZBC disks */
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index 3776140f8f20..2ed55055f68d 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -522,6 +522,7 @@ struct request_queue {
>  	unsigned long		*seq_zones_wlock;
>  	unsigned int		max_open_zones;
>  	unsigned int		max_active_zones;
> +	unsigned int		zone_desc_ext_bytes;

Why is this not a queue limit ? This may need to be to be gracefully handled by
device mapper for a target device using multiple zoned drives.

>  #endif /* CONFIG_BLK_DEV_ZONED */
>  
>  	/*
> @@ -753,6 +754,18 @@ static inline unsigned int queue_max_active_zones(const struct request_queue *q)
>  {
>  	return q->max_active_zones;
>  }
> +
> +static inline void blk_queue_zone_desc_ext_bytes(struct request_queue *q,
> +		unsigned int zone_desc_ext_bytes)
> +{
> +	q->zone_desc_ext_bytes = zone_desc_ext_bytes;
> +}
> +
> +static inline unsigned int queue_zone_desc_ext_bytes(
> +		const struct request_queue *q)
> +{
> +	return q->zone_desc_ext_bytes;
> +}
>  #else /* CONFIG_BLK_DEV_ZONED */
>  static inline unsigned int blk_queue_nr_zones(struct request_queue *q)
>  {
> @@ -784,6 +797,15 @@ static inline unsigned int queue_max_active_zones(const struct request_queue *q)
>  {
>  	return 0;
>  }
> +static inline void blk_queue_zone_desc_ext_bytes(struct request_queue *q,
> +		unsigned int zone_desc_ext_bytes)
> +{
> +}
> +static inline unsigned int queue_zone_desc_ext_bytes(
> +		const struct request_queue *q)
> +{
> +	return 0;
> +}
>  #endif /* CONFIG_BLK_DEV_ZONED */
>  
>  static inline bool rq_is_sync(struct request *rq)
> 


-- 
Damien Le Moal
Western Digital Research