null_blk: Add conventional zone configuration for zoned support

Allow the creation of conventional zones by adding the zone_nr_conv
configuration attribute. This new attribute is used only for zoned devices
and indicates the number of conventional zones to create. The default value
is 0. Since host-managed zoned block devices must always have at least one
sequential zone, if the value of zone_nr_conv is larger than or equal to
the total number of zones of the device nr_zones, zone_nr_conv is
automatically changed to nr_zones - 1.
Reviewed-by: Matias Bjorling <matias.bjorling@wdc.com>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Masato Suzuki <masato.suzuki@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/null_blk.h

@@ -49,6 +49,7 @@ struct nullb_device {
 	unsigned long completion_nsec; /* time in ns to complete a request */
 	unsigned long cache_size; /* disk cache size in MB */
 	unsigned long zone_size; /* zone size in MB if device is zoned */
+	unsigned int zone_nr_conv; /* number of conventional zones */
 	unsigned int submit_queues; /* number of submission queues */
 	unsigned int home_node; /* home node for the device */
 	unsigned int queue_mode; /* block interface */

drivers/block/null_blk_main.c

@@ -188,6 +188,10 @@ static unsigned long g_zone_size = 256;
 module_param_named(zone_size, g_zone_size, ulong, S_IRUGO);
 MODULE_PARM_DESC(zone_size, "Zone size in MB when block device is zoned. Must be power-of-two: Default: 256");
 
+static unsigned int g_zone_nr_conv;
+module_param_named(zone_nr_conv, g_zone_nr_conv, uint, 0444);
+MODULE_PARM_DESC(zone_nr_conv, "Number of conventional zones when block device is zoned. Default: 0");
+
 static struct nullb_device *null_alloc_dev(void);
 static void null_free_dev(struct nullb_device *dev);
 static void null_del_dev(struct nullb *nullb);
@@ -293,6 +297,7 @@ NULLB_DEVICE_ATTR(mbps, uint);
 NULLB_DEVICE_ATTR(cache_size, ulong);
 NULLB_DEVICE_ATTR(zoned, bool);
 NULLB_DEVICE_ATTR(zone_size, ulong);
+NULLB_DEVICE_ATTR(zone_nr_conv, uint);
 
 static ssize_t nullb_device_power_show(struct config_item *item, char *page)
 {
@@ -407,6 +412,7 @@ static struct configfs_attribute *nullb_device_attrs[] = {
 	&nullb_device_attr_badblocks,
 	&nullb_device_attr_zoned,
 	&nullb_device_attr_zone_size,
+	&nullb_device_attr_zone_nr_conv,
 	NULL,
 };
 
@@ -520,6 +526,7 @@ static struct nullb_device *null_alloc_dev(void)
 	dev->use_per_node_hctx = g_use_per_node_hctx;
 	dev->zoned = g_zoned;
 	dev->zone_size = g_zone_size;
+	dev->zone_nr_conv = g_zone_nr_conv;
 	return dev;
 }
 

drivers/block/null_blk_zoned.c

@@ -29,7 +29,25 @@ int null_zone_init(struct nullb_device *dev)
 	if (!dev->zones)
 		return -ENOMEM;
 
-	for (i = 0; i < dev->nr_zones; i++) {
+	if (dev->zone_nr_conv >= dev->nr_zones) {
+		dev->zone_nr_conv = dev->nr_zones - 1;
+		pr_info("null_blk: changed the number of conventional zones to %u",
+			dev->zone_nr_conv);
+	}
+
+	for (i = 0; i <  dev->zone_nr_conv; i++) {
+		struct blk_zone *zone = &dev->zones[i];
+
+		zone->start = sector;
+		zone->len = dev->zone_size_sects;
+		zone->wp = zone->start + zone->len;
+		zone->type = BLK_ZONE_TYPE_CONVENTIONAL;
+		zone->cond = BLK_ZONE_COND_NOT_WP;
+
+		sector += dev->zone_size_sects;
+	}
+
+	for (i = dev->zone_nr_conv; i < dev->nr_zones; i++) {
 		struct blk_zone *zone = &dev->zones[i];
 
 		zone->start = zone->wp = sector;
@@ -98,6 +116,8 @@ void null_zone_write(struct nullb_cmd *cmd, sector_t sector,
 		if (zone->wp == zone->start + zone->len)
 			zone->cond = BLK_ZONE_COND_FULL;
 		break;
+	case BLK_ZONE_COND_NOT_WP:
+		break;
 	default:
 		/* Invalid zone condition */
 		cmd->error = BLK_STS_IOERR;
@@ -111,6 +131,11 @@ void null_zone_reset(struct nullb_cmd *cmd, sector_t sector)
 	unsigned int zno = null_zone_no(dev, sector);
 	struct blk_zone *zone = &dev->zones[zno];
 
+	if (zone->type == BLK_ZONE_TYPE_CONVENTIONAL) {
+		cmd->error = BLK_STS_IOERR;
+		return;
+	}
+
 	zone->cond = BLK_ZONE_COND_EMPTY;
 	zone->wp = zone->start;
 }