sd_zbc: clear zone resources for non-zoned case

For host-aware ZBC disk, setting the device zoned model to BLK_ZONED_HA
using blk_queue_set_zoned() in sd_read_block_characteristics() may
result in the block device effective zoned model to be "none"
(BLK_ZONED_NONE) if partitions are present on the device. In this case,
sd_zbc_read_zones() should not setup the zone related queue limits for
the disk so that the device limits and configuration is consistent with
a regular disk and resources not uselessly allocated (e.g. the zone
write pointer tracking array for zone append emulation).

Furthermore, if the disk zoned model changes at run time due to the
creation of a partition by the user, the zone related resources can be
released.

Fix both problems by introducing the function sd_zbc_clear_zone_info()
to reset the scsi disk zone information and free resources and by
returning early in sd_zbc_read_zones() for a block device that has a
zoned model equal to BLK_ZONED_NONE.

Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@edc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/scsi/sd_zbc.c

@@ -665,12 +665,28 @@ static int sd_zbc_init_disk(struct scsi_disk *sdkp)
 	return 0;
 }
 
-void sd_zbc_release_disk(struct scsi_disk *sdkp)
+static void sd_zbc_clear_zone_info(struct scsi_disk *sdkp)
 {
+	/* Serialize against revalidate zones */
+	mutex_lock(&sdkp->rev_mutex);
+
 	kvfree(sdkp->zones_wp_offset);
 	sdkp->zones_wp_offset = NULL;
 	kfree(sdkp->zone_wp_update_buf);
 	sdkp->zone_wp_update_buf = NULL;
+
+	sdkp->nr_zones = 0;
+	sdkp->rev_nr_zones = 0;
+	sdkp->zone_blocks = 0;
+	sdkp->rev_zone_blocks = 0;
+
+	mutex_unlock(&sdkp->rev_mutex);
+}
+
+void sd_zbc_release_disk(struct scsi_disk *sdkp)
+{
+	if (sd_is_zoned(sdkp))
+		sd_zbc_clear_zone_info(sdkp);
 }
 
 static void sd_zbc_revalidate_zones_cb(struct gendisk *disk)
@@ -769,6 +785,21 @@ int sd_zbc_read_zones(struct scsi_disk *sdkp, unsigned char *buf)
 		 */
 		return 0;
 
+	/* READ16/WRITE16 is mandatory for ZBC disks */
+	sdkp->device->use_16_for_rw = 1;
+	sdkp->device->use_10_for_rw = 0;
+
+	if (!blk_queue_is_zoned(q)) {
+		/*
+		 * This can happen for a host aware disk with partitions.
+		 * The block device zone information was already cleared
+		 * by blk_queue_set_zoned(). Only clear the scsi disk zone
+		 * information and exit early.
+		 */
+		sd_zbc_clear_zone_info(sdkp);
+		return 0;
+	}
+
 	/* Check zoned block device characteristics (unconstrained reads) */
 	ret = sd_zbc_check_zoned_characteristics(sdkp, buf);
 	if (ret)
@@ -797,10 +828,6 @@ int sd_zbc_read_zones(struct scsi_disk *sdkp, unsigned char *buf)
 	if (blk_queue_zoned_model(q) == BLK_ZONED_HM)
 		blk_queue_zone_write_granularity(q, sdkp->physical_block_size);
 
-	/* READ16/WRITE16 is mandatory for ZBC disks */
-	sdkp->device->use_16_for_rw = 1;
-	sdkp->device->use_10_for_rw = 0;
-
 	sdkp->rev_nr_zones = nr_zones;
 	sdkp->rev_zone_blocks = zone_blocks;