nvme: add function to get ZNS max active zones

Add a function to get the number of max active zones for a zoned
namespace.

The value inside the identify namespace struct is a 0's based value,
where 0xffffffff means unlimited.
If unlimited, the addition will overflow and return 0,
which is the intended value to represent unlimited for this API.

Signed-off-by: Niklas Cassel <niklas.cassel@wdc.com>
Change-Id: Ia09e3db157ca0afadbd3ca4032eedd7bcd88248c
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/6443
Community-CI: Broadcom CI
Community-CI: Mellanox Build Bot
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>
Reviewed-by: sunshihao <sunshihao@huawei.com>
Reviewed-by: Shuhei Matsumoto <shuhei.matsumoto.xt@hitachi.com>

include/spdk/nvme_zns.h

@@ -113,6 +113,23 @@ uint64_t spdk_nvme_zns_ns_get_num_zones(struct spdk_nvme_ns *ns);
  */
 uint32_t spdk_nvme_zns_ns_get_max_open_zones(struct spdk_nvme_ns *ns);
 
+/**
+ * Get the maximum number of active zones for the given namespace.
+ *
+ * An active zone is a zone in any of the zone states:
+ * EXPLICIT OPEN, IMPLICIT OPEN or CLOSED.
+ *
+ * If this value is 0, there is no limit.
+ *
+ * This function is thread safe and can be called at any point while the controller
+ * is attached to the SPDK NVMe driver.
+ *
+ * \param ns Namespace to query.
+ *
+ * \return the maximum number of active zones.
+ */
+uint32_t spdk_nvme_zns_ns_get_max_active_zones(struct spdk_nvme_ns *ns);
+
 /**
  * Get the Zoned Namespace Command Set Specific Identify Controller data
  * as defined by the NVMe Zoned Namespace Command Set Specification.

lib/nvme/nvme_zns.c

@@ -68,6 +68,14 @@ spdk_nvme_zns_ns_get_max_open_zones(struct spdk_nvme_ns *ns)
 	return nsdata_zns->mor + 1;
 }
 
+uint32_t
+spdk_nvme_zns_ns_get_max_active_zones(struct spdk_nvme_ns *ns)
+{
+	const struct spdk_nvme_zns_ns_data *nsdata_zns = spdk_nvme_zns_ns_get_data(ns);
+
+	return nsdata_zns->mar + 1;
+}
+
 const struct spdk_nvme_zns_ctrlr_data *
 spdk_nvme_zns_ctrlr_get_data(struct spdk_nvme_ctrlr *ctrlr)
 {

lib/nvme/spdk_nvme.map

@@ -174,6 +174,7 @@
 	spdk_nvme_zns_ns_get_zone_size;
 	spdk_nvme_zns_ns_get_num_zones;
 	spdk_nvme_zns_ns_get_max_open_zones;
+	spdk_nvme_zns_ns_get_max_active_zones;
 	spdk_nvme_zns_ctrlr_get_data;
 	spdk_nvme_zns_ctrlr_get_max_zone_append_size;
 	spdk_nvme_zns_zone_append;