dm: cleanup close_table_device

Take the list unlink and free into close_table_device so that no half
torn down table_devices exist.  Also remove the check for a NULL bdev
as that can't happen - open_table_device never adds a table_device to
the list that does not have a valid block_device.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Mike Snitzer <snitzer@kernel.org>
Link: https://lore.kernel.org/r/20221115141054.1051801-5-yukuai1@huaweicloud.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

drivers/md/dm.c

@@ -774,14 +774,11 @@ static struct table_device *open_table_device(struct mapped_device *md,
  */
 static void close_table_device(struct table_device *td, struct mapped_device *md)
 {
-	if (!td->dm_dev.bdev)
-		return;
-
 	bd_unlink_disk_holder(td->dm_dev.bdev, dm_disk(md));
 	blkdev_put(td->dm_dev.bdev, td->dm_dev.mode | FMODE_EXCL);
 	put_dax(td->dm_dev.dax_dev);
-	td->dm_dev.bdev = NULL;
-	td->dm_dev.dax_dev = NULL;
+	list_del(&td->list);
+	kfree(td);
 }
 
 static struct table_device *find_table_device(struct list_head *l, dev_t dev,
@@ -823,11 +820,8 @@ void dm_put_table_device(struct mapped_device *md, struct dm_dev *d)
 	struct table_device *td = container_of(d, struct table_device, dm_dev);
 
 	mutex_lock(&md->table_devices_lock);
-	if (refcount_dec_and_test(&td->count)) {
+	if (refcount_dec_and_test(&td->count))
 		close_table_device(td, md);
-		list_del(&td->list);
-		kfree(td);
-	}
 	mutex_unlock(&md->table_devices_lock);
 }