loop: use set_disk_ro

Use set_disk_ro instead of set_device_ro to match all other block
drivers and to ensure all partitions mirror the read-only flag.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/loop.c

@@ -1138,7 +1138,7 @@ static int loop_configure(struct loop_device *lo, fmode_t mode,
 	if (error)
 		goto out_unlock;
 
-	set_device_ro(bdev, (lo->lo_flags & LO_FLAGS_READ_ONLY) != 0);
+	set_disk_ro(lo->lo_disk, (lo->lo_flags & LO_FLAGS_READ_ONLY) != 0);
 
 	lo->use_dio = lo->lo_flags & LO_FLAGS_DIRECT_IO;
 	lo->lo_device = bdev;