memstick/mspro_block: fix handling of read-only devices

Use set_disk_ro to propagate the read-only state to the block layer
instead of checking for it in ->open and leaking a reference in case
of a read-only device.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20220215094514.3828912-4-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

drivers/memstick/core/mspro_block.c

@@ -186,13 +186,8 @@ static int mspro_block_bd_open(struct block_device *bdev, fmode_t mode)
 
 	mutex_lock(&mspro_block_disk_lock);
 
-	if (msb && msb->card) {
+	if (msb && msb->card)
 		msb->usage_count++;
-		if ((mode & FMODE_WRITE) && msb->read_only)
-			rc = -EROFS;
-		else
-			rc = 0;
-	}
 
 	mutex_unlock(&mspro_block_disk_lock);
 
@@ -1239,6 +1234,9 @@ static int mspro_block_init_disk(struct memstick_dev *card)
 	set_capacity(msb->disk, capacity);
 	dev_dbg(&card->dev, "capacity set %ld\n", capacity);
 
+	if (msb->read_only)
+		set_disk_ro(msb->disk, true);
+
 	rc = device_add_disk(&card->dev, msb->disk, NULL);
 	if (rc)
 		goto out_cleanup_disk;