xen/blkfront: don't put bdev right after getting it

We should hang onto bdev until we're done with it.
Signed-off-by: Andrew Jones <drjones@redhat.com>
[v1: Fixed up git commit description]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

drivers/block/xen-blkfront.c

@@ -1409,7 +1409,6 @@ static int blkif_release(struct gendisk *disk, fmode_t mode)
 	mutex_lock(&blkfront_mutex);
 
 	bdev = bdget_disk(disk, 0);
-	bdput(bdev);
 
 	if (bdev->bd_openers)
 		goto out;
@@ -1440,6 +1439,7 @@ static int blkif_release(struct gendisk *disk, fmode_t mode)
 	}
 
 out:
+	bdput(bdev);
 	mutex_unlock(&blkfront_mutex);
 	return 0;
 }