ovl: do not set overlay.opaque on non-dir create

The optimization for opaque dir create was wrongly being applied
also to non-dir create.

Fixes: 97c684cc ("ovl: create directories inside merged parent opaque")
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Cc: <stable@vger.kernel.org> # v4.10

fs/overlayfs/dir.c

@@ -210,7 +210,7 @@ static int ovl_create_upper(struct dentry *dentry, struct inode *inode,
 	if (err)
 		goto out_dput;
 
-	if (ovl_type_merge(dentry->d_parent)) {
+	if (ovl_type_merge(dentry->d_parent) && d_is_dir(newdentry)) {
 		/* Setting opaque here is just an optimization, allow to fail */
 		ovl_set_opaque(dentry, newdentry);
 	}