block: simplify partition_overlaps

Just use xa_for_each to iterate over the partitions as there is no need
to grab a reference to each partition.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210406062303.811835-8-hch@lst.deSigned-off-by: NJens Axboe <axboe@kernel.dk>

block/partitions/core.c

@@ -420,21 +420,21 @@ static struct block_device *add_partition(struct gendisk *disk, int partno,
 static bool partition_overlaps(struct gendisk *disk, sector_t start,
 		sector_t length, int skip_partno)
 {
-	struct disk_part_iter piter;
 	struct block_device *part;
 	bool overlap = false;
+	unsigned long idx;
 
-	disk_part_iter_init(&piter, disk, DISK_PITER_INCL_EMPTY);
-	while ((part = disk_part_iter_next(&piter))) {
-		if (part->bd_partno == skip_partno ||
-		    start >= part->bd_start_sect + bdev_nr_sectors(part) ||
-		    start + length <= part->bd_start_sect)
-			continue;
-		overlap = true;
-		break;
+	rcu_read_lock();
+	xa_for_each_start(&disk->part_tbl, idx, part, 1) {
+		if (part->bd_partno != skip_partno &&
+		    start < part->bd_start_sect + bdev_nr_sectors(part) &&
+		    start + length > part->bd_start_sect) {
+			overlap = true;
+			break;
+		}
 	}
+	rcu_read_unlock();
 
-	disk_part_iter_exit(&piter);
 	return overlap;
 }