[PATCH] O_DIRECT open() fix

Trivial bugfix: opening a file that doesn't have ->direct_IO() with
O_DIRECT passed in flags fails (as it should) but doesn't call
->release() even though ->open() had been successful.

IOW, we have a leak there - e.g.  open() of a tty with O_DIRECT will
leak a reference to tty and tty_driver.  Besides, quite a few drivers
are _not_ happy with struct file being freed without ->release() after
->open() has returned 0.

fs/open.c

@@ -671,8 +671,8 @@ struct file *dentry_open(struct dentry *dentry, struct vfsmount *mnt, int flags)
 	if (f->f_flags & O_DIRECT) {
 		if (!inode->i_mapping || !inode->i_mapping->a_ops ||
 			!inode->i_mapping->a_ops->direct_IO) {
-				error = -EINVAL;
-				goto cleanup_all;
+				fput(f);
+				f = ERR_PTR(-EINVAL);
 		}
 	}