block: fix leaking minors of hidden disks

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>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Link: https://lore.kernel.org/r/20221010131857.748129-1-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/genhd.c b/block/genhd.c
index d6a2180..dc9b61d 100644 (file)
--- 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);