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Date:   Wed, 1 Jul 2020 13:16:52 +0200
From:   Javier =?utf-8?B?R29uesOhbGV6?= <javier@javigon.com>
To:     Niklas Cassel <niklas.cassel@wdc.com>
Cc:     Jonathan Corbet <corbet@lwn.net>, Jens Axboe <axboe@kernel.dk>,
        Keith Busch <kbusch@kernel.org>,
        Christoph Hellwig <hch@lst.de>,
        Sagi Grimberg <sagi@grimberg.me>,
        "James E.J. Bottomley" <jejb@linux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@oracle.com>,
        linux-scsi@vger.kernel.org, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org,
        linux-block@vger.kernel.org
Subject: Re: [PATCH 2/2] block: add max_active_zones to blk-sysfs
Message-ID: <20200701111330.3vpivrovh3i46maa@mpHalley.local>
References: <20200616102546.491961-1-niklas.cassel@wdc.com>
 <20200616102546.491961-3-niklas.cassel@wdc.com>
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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@wdc.com>
>---
> 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