Add zoned storage support to ublk: report_zones and operations:
 - REQ_OP_ZONE_OPEN
 - REQ_OP_ZONE_CLOSE
 - REQ_OP_ZONE_FINISH
 - REQ_OP_ZONE_RESET

This allows implementation of zoned storage devices in user space. An
example user space implementation based on ubdsrv is available [1].

[1] https://github.com/metaspace/ubdsrv/commit/14a2b708f74f70cfecb076d92e680dc718cc1f6d

Signed-off-by: Andreas Hindborg <redacted>
---
Changes since v1:
 - Fixed conditional compilation bug
 - Refactored to collect conditional code additions together
 - Fixed style errors
 - Zero stack allocated value used for zone report

Reported-by: Niklas Cassel <redacted>
Reported-by: kernel test robot <redacted>
Link: https://lore.kernel.org/oe-kbuild-all/202302250222.XOrw9j6z-lkp@intel.com/ (local)
v1: https://lore.kernel.org/linux-block/20230224125950.214779-1-nmi@metaspace.dk/ (local)

 drivers/block/ublk_drv.c      | 150 ++++++++++++++++++++++++++++++++--
 include/uapi/linux/ublk_cmd.h |  18 ++++
 2 files changed, 162 insertions(+), 6 deletions(-)

diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
index 6368b56eacf1..37e516903867 100644
--- a/drivers/block/ublk_drv.c
+++ b/drivers/block/ublk_drv.c

@@ -20,6 +20,7 @@
 #include <linux/major.h>
 #include <linux/wait.h>
 #include <linux/blkdev.h>
+#include <linux/blkzoned.h>
 #include <linux/init.h>
 #include <linux/swap.h>
 #include <linux/slab.h>

@@ -51,10 +52,12 @@
 		| UBLK_F_URING_CMD_COMP_IN_TASK \
 		| UBLK_F_NEED_GET_DATA \
 		| UBLK_F_USER_RECOVERY \
-		| UBLK_F_USER_RECOVERY_REISSUE)
+		| UBLK_F_USER_RECOVERY_REISSUE \
+		| UBLK_F_ZONED)
 
 /* All UBLK_PARAM_TYPE_* should be included here */
-#define UBLK_PARAM_TYPE_ALL (UBLK_PARAM_TYPE_BASIC | UBLK_PARAM_TYPE_DISCARD)
+#define UBLK_PARAM_TYPE_ALL (UBLK_PARAM_TYPE_BASIC | UBLK_PARAM_TYPE_DISCARD \
+			     | UBLK_PARAM_TYPE_ZONED)
 
 struct ublk_rq_data {
 	struct llist_node node;

@@ -187,6 +190,98 @@ static DEFINE_MUTEX(ublk_ctl_mutex);
 
 static struct miscdevice ublk_misc;
 
+#ifdef CONFIG_BLK_DEV_ZONED
+static void ublk_set_nr_zones(struct ublk_device *ub)
+{
+	const struct ublk_param_basic *p = &ub->params.basic;
+
+	if (ub->dev_info.flags & UBLK_F_ZONED && p->chunk_sectors)
+		ub->ub_disk->nr_zones = p->dev_sectors / p->chunk_sectors;
+}
+
+static void ublk_dev_param_zoned_apply(struct ublk_device *ub)
+{
+	const struct ublk_param_zoned *p = &ub->params.zoned;
+
+	if (ub->dev_info.flags & UBLK_F_ZONED) {
+		disk_set_max_active_zones(ub->ub_disk, p->max_active_zones);
+		disk_set_max_open_zones(ub->ub_disk, p->max_open_zones);
+	}
+}
+
+static int ublk_revalidate_disk_zones(struct gendisk *disk)
+{
+	return blk_revalidate_disk_zones(disk, NULL);
+}
+
+static int ublk_report_zones(struct gendisk *disk, sector_t sector,
+			     unsigned int nr_zones, report_zones_cb cb,
+			     void *data)
+{
+	struct ublk_device *ub;
+	unsigned int zone_size;
+	unsigned int first_zone;
+	int ret = 0;
+
+	ub = disk->private_data;
+
+	if (!(ub->dev_info.flags & UBLK_F_ZONED))
+		return -EINVAL;
+
+	zone_size = disk->queue->limits.chunk_sectors;
+	first_zone = sector >> ilog2(zone_size);
+	nr_zones = min(ub->ub_disk->nr_zones - first_zone, nr_zones);
+
+	for (unsigned int i = 0; i < nr_zones; i++) {
+		struct request *req;
+		blk_status_t status;
+		struct blk_zone info = {0};
+
+		req = blk_mq_alloc_request(disk->queue, REQ_OP_DRV_IN, 0);
+
+		if (IS_ERR(req)) {
+			ret = PTR_ERR(req);
+			goto out;
+		}
+
+		req->__sector = sector;
+
+		ret = blk_rq_map_kern(disk->queue, req, &info, sizeof(info),
+				      GFP_KERNEL);
+
+		if (ret)
+			goto out;
+
+		status = blk_execute_rq(req, 0);
+		ret = blk_status_to_errno(status);
+		if (ret)
+			goto out;
+
+		blk_mq_free_request(req);
+
+		ret = cb(&info, i, data);
+		if (ret)
+			goto out;
+
+		/* A zero length zone means don't ask for more zones */
+		if (!info.len) {
+			nr_zones = i;
+			break;
+		}
+
+		sector += zone_size;
+	}
+	ret = nr_zones;
+
+ out:
+	return ret;
+}
+#else
+void ublk_set_nr_zones(struct ublk_device *ub);
+void ublk_dev_param_zoned_apply(struct ublk_device *ub);
+int ublk_revalidate_disk_zones(struct gendisk *disk);