scsi: sd: sd_zbc: Hide gap zones

ZBC-2 allows host-managed disks to report gap zones. This allow zoned disks
to report an offset between data zone starts that is a power of two even if
the number of logical blocks with data per zone is not a power of two.

Another new feature in ZBC-2 is support for constant zone starting LBA
offsets. For zoned disks that report a constant zone starting LBA offset,
hide the gap zones from the block layer. Report the offset between data
zone starts as zone size and report the number of logical blocks with data
per zone as the zone capacity.

Link: https://lore.kernel.org/r/20220421183023.3462291-7-bvanassche@acm.org
Acked-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
[ bvanassche: Reworked this patch ]
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/sd.h

@@ -99,6 +99,11 @@ struct scsi_disk {
 	u32		zones_optimal_open;
 	u32		zones_optimal_nonseq;
 	u32		zones_max_open;
+	/*
+	 * Either zero or a power of two. If not zero it means that the offset
+	 * between zone starting LBAs is constant.
+	 */
+	u32		zone_starting_lba_gran;
 	u32		*zones_wp_offset;
 	spinlock_t	zones_wp_offset_lock;
 	u32		*rev_wp_offset;

drivers/scsi/sd_zbc.c

@@ -50,6 +50,12 @@ static unsigned int sd_zbc_get_zone_wp_offset(struct blk_zone *zone)
 	}
 }
 
+/* Whether or not a SCSI zone descriptor describes a gap zone. */
+static bool sd_zbc_is_gap_zone(const u8 buf[64])
+{
+	return (buf[0] & 0xf) == ZBC_ZONE_TYPE_GAP;
+}
+
 /**
  * sd_zbc_parse_report - Parse a SCSI zone descriptor
  * @sdkp: SCSI disk pointer.
@@ -69,8 +75,12 @@ static int sd_zbc_parse_report(struct scsi_disk *sdkp, const u8 buf[64],
 {
 	struct scsi_device *sdp = sdkp->device;
 	struct blk_zone zone = { 0 };
+	sector_t start_lba, gran;
 	int ret;
 
+	if (WARN_ON_ONCE(sd_zbc_is_gap_zone(buf)))
+		return -EINVAL;
+
 	zone.type = buf[0] & 0x0f;
 	zone.cond = (buf[1] >> 4) & 0xf;
 	if (buf[1] & 0x01)
@@ -78,9 +88,27 @@ static int sd_zbc_parse_report(struct scsi_disk *sdkp, const u8 buf[64],
 	if (buf[1] & 0x02)
 		zone.non_seq = 1;
 
-	zone.len = logical_to_sectors(sdp, get_unaligned_be64(&buf[8]));
+	start_lba = get_unaligned_be64(&buf[16]);
-	zone.capacity = zone.len;
+	zone.start = logical_to_sectors(sdp, start_lba);
-	zone.start = logical_to_sectors(sdp, get_unaligned_be64(&buf[16]));
+	zone.capacity = logical_to_sectors(sdp, get_unaligned_be64(&buf[8]));
+	zone.len = zone.capacity;
+	if (sdkp->zone_starting_lba_gran) {
+		gran = logical_to_sectors(sdp, sdkp->zone_starting_lba_gran);
+		if (zone.len > gran) {
+			sd_printk(KERN_ERR, sdkp,
+				  "Invalid zone at LBA %llu with capacity %llu and length %llu; granularity = %llu\n",
+				  start_lba,
+				  sectors_to_logical(sdp, zone.capacity),
+				  sectors_to_logical(sdp, zone.len),
+				  sectors_to_logical(sdp, gran));
+			return -EINVAL;
+		}
+		/*
+		 * Use the starting LBA granularity instead of the zone length
+		 * obtained from the REPORT ZONES command.
+		 */
+		zone.len = gran;
+	}
 	if (zone.cond == ZBC_ZONE_COND_FULL)
 		zone.wp = zone.start + zone.len;
 	else
@@ -227,6 +255,7 @@ int sd_zbc_report_zones(struct gendisk *disk, sector_t sector,
 	sector_t lba = sectors_to_logical(sdkp->device, sector);
 	unsigned int nr, i;
 	unsigned char *buf;
+	u64 zone_length, start_lba;
 	size_t offset, buflen = 0;
 	int zone_idx = 0;
 	int ret;
@@ -255,14 +284,36 @@ int sd_zbc_report_zones(struct gendisk *disk, sector_t sector,
 
 		for (i = 0; i < nr && zone_idx < nr_zones; i++) {
 			offset += 64;
+			start_lba = get_unaligned_be64(&buf[offset + 16]);
+			zone_length = get_unaligned_be64(&buf[offset + 8]);
+			if ((zone_idx == 0 &&
+			    (lba < start_lba ||
+			     lba >= start_lba + zone_length)) ||
+			    (zone_idx > 0 && start_lba != lba) ||
+			    start_lba + zone_length < start_lba) {
+				sd_printk(KERN_ERR, sdkp,
+					  "Zone %d at LBA %llu is invalid: %llu + %llu\n",
+					  zone_idx, lba, start_lba, zone_length);
+				ret = -EINVAL;
+				goto out;
+			}
+			lba = start_lba + zone_length;
+			if (sd_zbc_is_gap_zone(&buf[offset])) {
+				if (sdkp->zone_starting_lba_gran)
+					continue;
+				sd_printk(KERN_ERR, sdkp,
+					  "Gap zone without constant LBA offsets\n");
+				ret = -EINVAL;
+				goto out;
+			}
+
 			ret = sd_zbc_parse_report(sdkp, buf + offset, zone_idx,
 						  cb, data);
 			if (ret)
 				goto out;
+
 			zone_idx++;
 		}
-
-		lba += sdkp->zone_info.zone_blocks * i;
 	}
 
 	ret = zone_idx;
@@ -579,6 +630,7 @@ unsigned int sd_zbc_complete(struct scsi_cmnd *cmd, unsigned int good_bytes,
 static int sd_zbc_check_zoned_characteristics(struct scsi_disk *sdkp,
 					      unsigned char *buf)
 {
+	u64 zone_starting_lba_gran;
 
 	if (scsi_get_vpd_page(sdkp->device, 0xb6, buf, 64)) {
 		sd_printk(KERN_NOTICE, sdkp,
@@ -600,6 +652,29 @@ static int sd_zbc_check_zoned_characteristics(struct scsi_disk *sdkp,
 	sdkp->zones_optimal_open = 0;
 	sdkp->zones_optimal_nonseq = 0;
 	sdkp->zones_max_open = get_unaligned_be32(&buf[16]);
+	/* Check zone alignment method */
+	switch (buf[23] & 0xf) {
+	case 0:
+	case ZBC_CONSTANT_ZONE_LENGTH:
+		/* Use zone length */
+		break;
+	case ZBC_CONSTANT_ZONE_START_OFFSET:
+		zone_starting_lba_gran = get_unaligned_be64(&buf[24]);
+		if (zone_starting_lba_gran == 0 ||
+		    !is_power_of_2(zone_starting_lba_gran) ||
+		    logical_to_sectors(sdkp->device, zone_starting_lba_gran) >
+		    UINT_MAX) {
+			sd_printk(KERN_ERR, sdkp,
+				  "Invalid zone starting LBA granularity %llu\n",
+				  zone_starting_lba_gran);
+			return -ENODEV;
+		}
+		sdkp->zone_starting_lba_gran = zone_starting_lba_gran;
+		break;
+	default:
+		sd_printk(KERN_ERR, sdkp, "Invalid zone alignment method\n");
+		return -ENODEV;
+	}
 
 	/*
 	 * Check for unconstrained reads: host-managed devices with
@@ -654,14 +729,18 @@ static int sd_zbc_check_capacity(struct scsi_disk *sdkp, unsigned char *buf,
 		}
 	}
 
-	/* Get the size of the first reported zone */
+	if (sdkp->zone_starting_lba_gran == 0) {
-	rec = buf + 64;
+		/* Get the size of the first reported zone */
-	zone_blocks = get_unaligned_be64(&rec[8]);
+		rec = buf + 64;
-	if (logical_to_sectors(sdkp->device, zone_blocks) > UINT_MAX) {
+		zone_blocks = get_unaligned_be64(&rec[8]);
-		if (sdkp->first_scan)
+		if (logical_to_sectors(sdkp->device, zone_blocks) > UINT_MAX) {
-			sd_printk(KERN_NOTICE, sdkp,
+			if (sdkp->first_scan)
-				  "Zone size too large\n");
+				sd_printk(KERN_NOTICE, sdkp,
-		return -EFBIG;
+					  "Zone size too large\n");
+			return -EFBIG;
+		}
+	} else {
+		zone_blocks = sdkp->zone_starting_lba_gran;
 	}
 
 	if (!is_power_of_2(zone_blocks)) {

include/scsi/scsi_proto.h

@@ -307,7 +307,9 @@ enum zbc_zone_type {
 	ZBC_ZONE_TYPE_CONV		= 0x1,
 	ZBC_ZONE_TYPE_SEQWRITE_REQ	= 0x2,
 	ZBC_ZONE_TYPE_SEQWRITE_PREF	= 0x3,
-	/* 0x4 to 0xf are reserved */
+	ZBC_ZONE_TYPE_SEQ_OR_BEFORE_REQ	= 0x4,
+	ZBC_ZONE_TYPE_GAP		= 0x5,
+	/* 0x6 to 0xf are reserved */
 };
 
 /* Zone conditions of REPORT ZONES zone descriptors */
@@ -323,6 +325,11 @@ enum zbc_zone_cond {
 	ZBC_ZONE_COND_OFFLINE		= 0xf,
 };
 
+enum zbc_zone_alignment_method {
+	ZBC_CONSTANT_ZONE_LENGTH	= 0x1,
+	ZBC_CONSTANT_ZONE_START_OFFSET	= 0x8,
+};
+
 /* Version descriptor values for INQUIRY */
 enum scsi_version_descriptor {
 	SCSI_VERSION_DESCRIPTOR_FCP4	= 0x0a40,