Re: [PATCH 1/2] block: add max_open_zones to blk-sysfs

["Javier González" <javier@javigon.com>]

On 16.06.2020 12:25, Niklas Cassel wrote:
>Add a new max_open_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 open 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_open_zones struct member to the request_queue, rather
>than as a queue limit, since this property cannot be split across stacking
>drivers.
>
>Signed-off-by: Niklas Cassel <niklas.cassel@wdc.com>
>---
> Documentation/block/queue-sysfs.rst |  7 +++++++
> block/blk-sysfs.c                   | 15 +++++++++++++++
> drivers/nvme/host/zns.c             |  1 +
> drivers/scsi/sd_zbc.c               |  4 ++++
> include/linux/blkdev.h              | 20 ++++++++++++++++++++
> 5 files changed, 47 insertions(+)
>
>diff --git a/Documentation/block/queue-sysfs.rst b/Documentation/block/queue-sysfs.rst
>index 6a8513af9201..f01cf8530ae4 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_open_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 or IMPLICIT OPEN, is limited by this value.
>+If this value is 0, there is no limit.
>+
> max_sectors_kb (RW)
> -------------------
> This is the maximum number of kilobytes that the block layer will allow
>diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
>index 02643e149d5e..fa42961e9678 100644
>--- a/block/blk-sysfs.c
>+++ b/block/blk-sysfs.c
>@@ -305,6 +305,11 @@ 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_max_open_zones_show(struct request_queue *q, char *page)
>+{
>+	return queue_var_show(queue_max_open_zones(q), page);
>+}
>+
> static ssize_t queue_nomerges_show(struct request_queue *q, char *page)
> {
> 	return queue_var_show((blk_queue_nomerges(q) << 1) |
>@@ -667,6 +672,11 @@ static struct queue_sysfs_entry queue_nr_zones_entry = {
> 	.show = queue_nr_zones_show,
> };
>
>+static struct queue_sysfs_entry queue_max_open_zones_entry = {
>+	.attr = {.name = "max_open_zones", .mode = 0444 },
>+	.show = queue_max_open_zones_show,
>+};
>+
> static struct queue_sysfs_entry queue_nomerges_entry = {
> 	.attr = {.name = "nomerges", .mode = 0644 },
> 	.show = queue_nomerges_show,
>@@ -765,6 +775,7 @@ static struct attribute *queue_attrs[] = {
> 	&queue_nonrot_entry.attr,
> 	&queue_zoned_entry.attr,
> 	&queue_nr_zones_entry.attr,
>+	&queue_max_open_zones_entry.attr,
> 	&queue_nomerges_entry.attr,
> 	&queue_rq_affinity_entry.attr,
> 	&queue_iostats_entry.attr,
>@@ -792,6 +803,10 @@ 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 &&
>+	    !blk_queue_is_zoned(q))
>+		return 0;
>+
> 	return attr->mode;
> }
>
>diff --git a/drivers/nvme/host/zns.c b/drivers/nvme/host/zns.c
>index c08f6281b614..af156529f3b6 100644
>--- a/drivers/nvme/host/zns.c
>+++ b/drivers/nvme/host/zns.c
>@@ -82,6 +82,7 @@ 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);
> free_data:
> 	kfree(id);
> 	return status;
>diff --git a/drivers/scsi/sd_zbc.c b/drivers/scsi/sd_zbc.c
>index 183a20720da9..aa3564139b40 100644
>--- a/drivers/scsi/sd_zbc.c
>+++ b/drivers/scsi/sd_zbc.c
>@@ -717,6 +717,10 @@ int sd_zbc_read_zones(struct scsi_disk *sdkp, unsigned char *buf)
> 	/* The drive satisfies the kernel restrictions: set it up */
> 	blk_queue_flag_set(QUEUE_FLAG_ZONE_RESETALL, q);
> 	blk_queue_required_elevator_features(q, ELEVATOR_F_ZBD_SEQ_WRITE);
>+	if (sdkp->zones_max_open == U32_MAX)
>+		blk_queue_max_open_zones(q, 0);
>+	else
>+		blk_queue_max_open_zones(q, sdkp->zones_max_open);
> 	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 8fd900998b4e..2f332f00501d 100644
>--- a/include/linux/blkdev.h
>+++ b/include/linux/blkdev.h
>@@ -520,6 +520,7 @@ struct request_queue {
> 	unsigned int		nr_zones;
> 	unsigned long		*conv_zones_bitmap;
> 	unsigned long		*seq_zones_wlock;
>+	unsigned int		max_open_zones;
> #endif /* CONFIG_BLK_DEV_ZONED */
>
> 	/*
>@@ -729,6 +730,17 @@ static inline bool blk_queue_zone_is_seq(struct request_queue *q,
> 		return true;
> 	return !test_bit(blk_queue_zone_no(q, sector), q->conv_zones_bitmap);
> }
>+
>+static inline void blk_queue_max_open_zones(struct request_queue *q,
>+		unsigned int max_open_zones)
>+{
>+	q->max_open_zones = max_open_zones;
>+}
>+
>+static inline unsigned int queue_max_open_zones(const struct request_queue *q)
>+{
>+	return q->max_open_zones;
>+}
> #else /* CONFIG_BLK_DEV_ZONED */
> static inline unsigned int blk_queue_nr_zones(struct request_queue *q)
> {
>@@ -744,6 +756,14 @@ static inline unsigned int blk_queue_zone_no(struct request_queue *q,
> {
> 	return 0;
> }
>+static inline void blk_queue_max_open_zones(struct request_queue *q,
>+		unsigned int max_open_zones)
>+{
>+}
>+static inline unsigned int queue_max_open_zones(const struct request_queue *q)
>+{
>+	return 0;
>+}
> #endif /* CONFIG_BLK_DEV_ZONED */
>
> static inline bool rq_is_sync(struct request *rq)
>-- 
>2.26.2
>
>
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Looks good to me.

Reviewed-by: Javier González <javier@javigon.com>

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