block: add capacity field to zone descriptors

In the zoned storage model, the sectors within a zone are typically all
writeable. With the introduction of the Zoned Namespace (ZNS) Command
Set in the NVM Express organization, the model was extended to have a
specific writeable capacity.

Extend the zone descriptor data structure with a zone capacity field to
indicate to the user how many sectors in a zone are writeable.

Introduce backward compatibility in the zone report ioctl by extending
the zone report header data structure with a flags field to indicate if
the capacity field is available.

Reviewed-by: Jens Axboe <axboe@kernel.dk>
Reviewed-by: Javier González <javier.gonz@samsung.com>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Reviewed-by: Himanshu Madhani <himanshu.madhani@oracle.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Daniel Wagner <dwagner@suse.de>
Signed-off-by: Matias Bjørling <matias.bjorling@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

block/blk-zoned.c

@@ -312,6 +312,7 @@ int blkdev_report_zones_ioctl(struct block_device *bdev, fmode_t mode,
 		return ret;
 
 	rep.nr_zones = ret;
+	rep.flags = BLK_ZONE_REP_CAPACITY;
 	if (copy_to_user(argp, &rep, sizeof(struct blk_zone_report)))
 		return -EFAULT;
 	return 0;

drivers/block/null_blk_zoned.c

@@ -47,6 +47,7 @@ int null_init_zoned_dev(struct nullb_device *dev, struct request_queue *q)
 
 		zone->start = sector;
 		zone->len = dev->zone_size_sects;
+		zone->capacity = zone->len;
 		zone->wp = zone->start + zone->len;
 		zone->type = BLK_ZONE_TYPE_CONVENTIONAL;
 		zone->cond = BLK_ZONE_COND_NOT_WP;
@@ -59,6 +60,7 @@ int null_init_zoned_dev(struct nullb_device *dev, struct request_queue *q)
 
 		zone->start = zone->wp = sector;
 		zone->len = dev->zone_size_sects;
+		zone->capacity = zone->len;
 		zone->type = BLK_ZONE_TYPE_SEQWRITE_REQ;
 		zone->cond = BLK_ZONE_COND_EMPTY;
 

drivers/scsi/sd_zbc.c

@@ -59,6 +59,7 @@ static int sd_zbc_parse_report(struct scsi_disk *sdkp, u8 *buf,
 		zone.non_seq = 1;
 
 	zone.len = logical_to_sectors(sdp, get_unaligned_be64(&buf[8]));
+	zone.capacity = zone.len;
 	zone.start = logical_to_sectors(sdp, get_unaligned_be64(&buf[16]));
 	zone.wp = logical_to_sectors(sdp, get_unaligned_be64(&buf[24]));
 	if (zone.type != ZBC_ZONE_TYPE_CONV &&

include/uapi/linux/blkzoned.h

@@ -73,6 +73,15 @@ enum blk_zone_cond {
 	BLK_ZONE_COND_OFFLINE	= 0xF,
 };
 
+/**
+ * enum blk_zone_report_flags - Feature flags of reported zone descriptors.
+ *
+ * @BLK_ZONE_REP_CAPACITY: Zone descriptor has capacity field.
+ */
+enum blk_zone_report_flags {
+	BLK_ZONE_REP_CAPACITY	= (1 << 0),
+};
+
 /**
  * struct blk_zone - Zone descriptor for BLKREPORTZONE ioctl.
  *
@@ -99,7 +108,9 @@ struct blk_zone {
 	__u8	cond;		/* Zone condition */
 	__u8	non_seq;	/* Non-sequential write resources active */
 	__u8	reset;		/* Reset write pointer recommended */
-	__u8	reserved[36];
+	__u8	resv[4];
+	__u64	capacity;	/* Zone capacity in number of sectors */
+	__u8	reserved[24];
 };
 
 /**
@@ -115,7 +126,7 @@ struct blk_zone {
 struct blk_zone_report {
 	__u64		sector;
 	__u32		nr_zones;
-	__u8		reserved[4];
+	__u32		flags;
 	struct blk_zone zones[0];
 };