block: Fix partition check for host-aware zoned block devices

Commit a33df75 ("block: use an xarray for disk->part_tbl") modified
the method to check partition existence in host-aware zoned block
devices from disk_has_partitions() helper function call to empty check
of xarray disk->part_tbl. However, disk->part_tbl always has single
entry for disk->part0 and never becomes empty. This resulted in the
host-aware zoned devices always judged to have partitions, and it made
the sysfs queue/zoned attribute to be "none" instead of "host-aware"
regardless of partition existence in the devices.

This also caused DEBUG_LOCKS_WARN_ON(lock->magic != lock) for
sdkp->rev_mutex in scsi layer when the kernel detects host-aware zoned
device. Since block layer handled the host-aware zoned devices as non-
zoned devices, scsi layer did not have chance to initialize the mutex
for zone revalidation. Therefore, the warning was triggered.

To fix the issues, call the helper function disk_has_partitions() in
place of disk->part_tbl empty check. Since the function was removed with
the commit a33df75, reimplement it to walk through entries in the
xarray disk->part_tbl.

Fixes: a33df75 ("block: use an xarray for disk->part_tbl")
Signed-off-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Cc: stable@vger.kernel.org # v5.14+
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20211026060115.753746-1-shinichiro.kawasaki@wdc.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: kawasaki

block/blk-settings.c

@@ -842,6 +842,24 @@ bool blk_queue_can_use_dma_map_merging(struct request_queue *q,
 }
 EXPORT_SYMBOL_GPL(blk_queue_can_use_dma_map_merging);
 
+static bool disk_has_partitions(struct gendisk *disk)
+{
+	unsigned long idx;
+	struct block_device *part;
+	bool ret = false;
+
+	rcu_read_lock();
+	xa_for_each(&disk->part_tbl, idx, part) {
+		if (bdev_is_partition(part)) {
+			ret = true;
+			break;
+		}
+	}
+	rcu_read_unlock();
+
+	return ret;
+}
+
 /**
  * blk_queue_set_zoned - configure a disk queue zoned model.
  * @disk:	the gendisk of the queue to configure
@@ -876,7 +894,7 @@ void blk_queue_set_zoned(struct gendisk *disk, enum blk_zoned_model model)
 		 * we do nothing special as far as the block layer is concerned.
 		 */
 		if (!IS_ENABLED(CONFIG_BLK_DEV_ZONED) ||
-		    !xa_empty(&disk->part_tbl))
+		    disk_has_partitions(disk))
 			model = BLK_ZONED_NONE;
 		break;
 	case BLK_ZONED_NONE: