bcache: move the del_gendisk call out of bcache_device_free

Let the callers call del_gendisk so that we can check if add_disk
has been called properly for the cached device case instead of relying
on the block layer internal GENHD_FL_UP flag.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Coly Li <colyli@suse.de>
Link: https://lore.kernel.org/r/20210809064028.1198327-8-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

drivers/md/bcache/super.c

@@ -885,11 +885,6 @@ static void bcache_device_free(struct bcache_device *d)
 		bcache_device_detach(d);
 
 	if (disk) {
-		bool disk_added = (disk->flags & GENHD_FL_UP) != 0;
-
-		if (disk_added)
-			del_gendisk(disk);
-
 		blk_cleanup_disk(disk);
 		ida_simple_remove(&bcache_device_idx,
 				  first_minor_to_idx(disk->first_minor));
@@ -1371,8 +1366,10 @@ static void cached_dev_free(struct closure *cl)
 
 	mutex_lock(&bch_register_lock);
 
-	if (atomic_read(&dc->running))
+	if (atomic_read(&dc->running)) {
 		bd_unlink_disk_holder(dc->bdev, dc->disk.disk);
+		del_gendisk(dc->disk.disk);
+	}
 	bcache_device_free(&dc->disk);
 	list_del(&dc->list);
 
@@ -1518,6 +1515,7 @@ static void flash_dev_free(struct closure *cl)
 	mutex_lock(&bch_register_lock);
 	atomic_long_sub(bcache_dev_sectors_dirty(d),
 			&d->c->flash_dev_dirty_sectors);
+	del_gendisk(d->disk);
 	bcache_device_free(d);
 	mutex_unlock(&bch_register_lock);
 	kobject_put(&d->kobj);