rbd: drop dev reference on error in rbd_open()

If a read-only rbd device is opened for writing in rbd_open(), it
returns without dropping the just-acquired device reference.

Fix this by moving the read-only check before getting the reference.

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Yehuda Sadeh <yehuda@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>

1 files changed, 3 insertions, 4 deletions

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index 9917943a3572..54a55f03115d 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -246,13 +246,12 @@ static int rbd_open(struct block_device *bdev, fmode_t mode)
 {
         struct rbd_device *rbd_dev = bdev->bd_disk->private_data;
 
-        rbd_get_dev(rbd_dev);
-
-        set_device_ro(bdev, rbd_dev->read_only);
-
         if ((mode & FMODE_WRITE) && rbd_dev->read_only)
                 return -EROFS;
 
+        rbd_get_dev(rbd_dev);
+        set_device_ro(bdev, rbd_dev->read_only);
+
         return 0;
 }