md: compare bd_disk instead of bd_contains

To check for partitions of the same disk bd_contains works as well, but
bd_disk is way more obvious.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Song Liu <song@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/md/md.c

@@ -2322,8 +2322,7 @@ static int match_mddev_units(struct mddev *mddev1, struct mddev *mddev2)
 			    test_bit(Journal, &rdev2->flags) ||
 			    rdev2->raid_disk == -1)
 				continue;
-			if (rdev->bdev->bd_contains ==
-			    rdev2->bdev->bd_contains) {
+			if (rdev->bdev->bd_disk == rdev2->bdev->bd_disk) {
 				rcu_read_unlock();
 				return 1;
 			}
@@ -5944,8 +5943,8 @@ int md_run(struct mddev *mddev)
 		rdev_for_each(rdev, mddev)
 			rdev_for_each(rdev2, mddev) {
 				if (rdev < rdev2 &&
-				    rdev->bdev->bd_contains ==
-				    rdev2->bdev->bd_contains) {
+				    rdev->bdev->bd_disk ==
+				    rdev2->bdev->bd_disk) {
 					pr_warn("%s: WARNING: %s appears to be on the same physical disk as %s.\n",
 						mdname(mddev),
 						bdevname(rdev->bdev,b),