block: grab a device refcount in disk_uevent

Sending uevents requires the struct device to be alive.  To
ensure that grab the device refcount instead of just an inode
reference.

Fixes: bc359d03 ("block: add a disk_uevent helper")
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20210701081638.246552-2-hch@lst.deSigned-off-by: NJens Axboe <axboe@kernel.dk>

block/genhd.c

@@ -365,12 +365,12 @@ void disk_uevent(struct gendisk *disk, enum kobject_action action)
 	xa_for_each(&disk->part_tbl, idx, part) {
 		if (bdev_is_partition(part) && !bdev_nr_sectors(part))
 			continue;
-		if (!bdgrab(part))
+		if (!kobject_get_unless_zero(&part->bd_device.kobj))
 			continue;
 
 		rcu_read_unlock();
 		kobject_uevent(bdev_kobj(part), action);
-		bdput(part);
+		put_device(&part->bd_device);
 		rcu_read_lock();
 	}
 	rcu_read_unlock();