[PATCH] block: fix leaking minors of hidden disks

[Christoph Hellwig <hch@lst.de>]

The major/minor of a hidden gendisk is not propagated to the block
device because it is never registered using bdev_add.  But the lack of
bd_dev also causes the dynamic major minor number not to be freed.
Assign bd_dev manually to ensure the dynamic major minor gets freed.

Based on a patch by Keith Busch.

Fixes:  8ddcd653257c ("block: introduce GENHD_FL_HIDDEN")
Reported-by: Daniel Wagner <dwagner@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: Daniel Wagner <dwagner@suse.de>
---
 block/genhd.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/block/genhd.c b/block/genhd.c
index 514395361d7c5..17b33c62423df 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -507,6 +507,13 @@ int __must_check device_add_disk(struct device *parent, struct gendisk *disk,
 		 */
 		dev_set_uevent_suppress(ddev, 0);
 		disk_uevent(disk, KOBJ_ADD);
+	} else {
+		/*
+		 * Even if the block_device for a hidden gendisk is not
+		 * registered, it needs to have a valid bd_dev so that the
+		 * freeing of the dynamic major works.
+		 */
+		disk->part0->bd_dev = MKDEV(disk->major, disk->first_minor);
 	}
 
 	disk_update_readahead(disk);
-- 
2.30.2