Re: [PATCH 2/2] block: add max_active_zones to blk-sysfs

[Javier González <javier@xxxxxxxxxxx>]

On 16.06.2020 12:25, Niklas Cassel wrote:
> Add a new max_active zones definition in the sysfs documentation.
> This definition will be common for all devices utilizing the zoned block
> device support in the kernel.
>
> Export max_active_zones according to this new definition for NVMe Zoned
> Namespace devices, ZAC ATA devices (which are treated as SCSI devices by
> the kernel), and ZBC SCSI devices.
>
> Add the new max_active_zones struct member to the request_queue, rather
> than as a queue limit, since this property cannot be split across stacking
> drivers.
>
> For SCSI devices, even though max active zones is not part of the ZBC/ZAC
> spec, export max_active_zones as 0, signifying "no limit".
>
> Signed-off-by: Niklas Cassel <niklas.cassel@xxxxxxx>
> ---
> Documentation/block/queue-sysfs.rst |  7 +++++++
> block/blk-sysfs.c                   | 14 +++++++++++++-
> drivers/nvme/host/zns.c             |  1 +
> drivers/scsi/sd_zbc.c               |  1 +
> include/linux/blkdev.h              | 20 ++++++++++++++++++++
> 5 files changed, 42 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/block/queue-sysfs.rst b/Documentation/block/queue-sysfs.rst
> index f01cf8530ae4..f261a5c84170 100644
> --- a/Documentation/block/queue-sysfs.rst
> +++ b/Documentation/block/queue-sysfs.rst
> @@ -117,6 +117,13 @@ Maximum number of elements in a DMA scatter/gather list with integrity
> data that will be submitted by the block layer core to the associated
> block driver.
>
> +max_active_zones (RO)
> +---------------------
> +For zoned block devices (zoned attribute indicating "host-managed" or
> +"host-aware"), the sum of zones belonging to any of the zone states:
> +EXPLICIT OPEN, IMPLICIT OPEN or CLOSED, is limited by this value.
> +If this value is 0, there is no limit.
> +
> max_open_zones (RO)
> -------------------
> For zoned block devices (zoned attribute indicating "host-managed" or
> diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
> index fa42961e9678..624bb4d85fc7 100644
> --- a/block/blk-sysfs.c
> +++ b/block/blk-sysfs.c
> @@ -310,6 +310,11 @@ static ssize_t queue_max_open_zones_show(struct request_queue *q, char *page)
> 	return queue_var_show(queue_max_open_zones(q), page);
> }
>
> +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_nomerges_show(struct request_queue *q, char *page)
> {
> 	return queue_var_show((blk_queue_nomerges(q) << 1) |
> @@ -677,6 +682,11 @@ static struct queue_sysfs_entry queue_max_open_zones_entry = {
> 	.show = queue_max_open_zones_show,
> };
>
> +static struct queue_sysfs_entry queue_max_active_zones_entry = {
> +	.attr = {.name = "max_active_zones", .mode = 0444 },
> +	.show = queue_max_active_zones_show,
> +};
> +
> static struct queue_sysfs_entry queue_nomerges_entry = {
> 	.attr = {.name = "nomerges", .mode = 0644 },
> 	.show = queue_nomerges_show,
> @@ -776,6 +786,7 @@ static struct attribute *queue_attrs[] = {
> 	&queue_zoned_entry.attr,
> 	&queue_nr_zones_entry.attr,
> 	&queue_max_open_zones_entry.attr,
> +	&queue_max_active_zones_entry.attr,
> 	&queue_nomerges_entry.attr,
> 	&queue_rq_affinity_entry.attr,
> 	&queue_iostats_entry.attr,
> @@ -803,7 +814,8 @@ static umode_t queue_attr_visible(struct kobject *kobj, struct attribute *attr,
> 		(!q->mq_ops || !q->mq_ops->timeout))
> 			return 0;
>
> -	if (attr == &queue_max_open_zones_entry.attr &&
> +	if ((attr == &queue_max_open_zones_entry.attr ||
> +	     attr == &queue_max_active_zones_entry.attr) &&
> 	    !blk_queue_is_zoned(q))
> 		return 0;
>
> diff --git a/drivers/nvme/host/zns.c b/drivers/nvme/host/zns.c
> index af156529f3b6..502070763266 100644
> --- a/drivers/nvme/host/zns.c
> +++ b/drivers/nvme/host/zns.c
> @@ -83,6 +83,7 @@ int nvme_update_zone_info(struct gendisk *disk, struct nvme_ns *ns,
> 	q->limits.zoned = BLK_ZONED_HM;
> 	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);
> free_data:
> 	kfree(id);
> 	return status;
> diff --git a/drivers/scsi/sd_zbc.c b/drivers/scsi/sd_zbc.c
> index aa3564139b40..d8b2c49d645b 100644
> --- a/drivers/scsi/sd_zbc.c
> +++ b/drivers/scsi/sd_zbc.c
> @@ -721,6 +721,7 @@ int sd_zbc_read_zones(struct scsi_disk *sdkp, unsigned char *buf)
> 		blk_queue_max_open_zones(q, 0);
> 	else
> 		blk_queue_max_open_zones(q, sdkp->zones_max_open);
> +	blk_queue_max_active_zones(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 2f332f00501d..3776140f8f20 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -521,6 +521,7 @@ struct request_queue {
> 	unsigned long		*conv_zones_bitmap;
> 	unsigned long		*seq_zones_wlock;
> 	unsigned int		max_open_zones;
> +	unsigned int		max_active_zones;
> #endif /* CONFIG_BLK_DEV_ZONED */

Looking a second time at these patches, wouldn't it make sense to move
this to queue_limits?

Javier