diff --git a/fs/block_dev.c b/fs/block_dev.c
index 470c10c..10d8a0a 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -931,8 +931,16 @@
 	struct gendisk *disk;
 	int ret;
 	int part;
+	int perm = 0;
 
-	ret = devcgroup_inode_permission(bdev->bd_inode, file->f_mode);
+	if (file->f_mode & FMODE_READ)
+		perm |= MAY_READ;
+	if (file->f_mode & FMODE_WRITE)
+		perm |= MAY_WRITE;
+	/*
+	 * hooks: /n/, see "layering violations".
+	 */
+	ret = devcgroup_inode_permission(bdev->bd_inode, perm);
 	if (ret != 0)
 		return ret;