[PATCH v15 4/9] namei: LOOKUP_BENEATH: O_BENEATH-like scoped resolution

[Al Viro]

On Tue, Nov 05, 2019 at 08:05:48PM +1100, Aleksa Sarai wrote:

Minor nit here - I'd split "move the conditional call of set_root()
into nd_jump_root()" into a separate patch before that one.  Makes
for fewer distractions in this one.  I'd probably fold "and be
ready for errors other than -ECHILD" into the same preliminary
patch.

> +			/* Not currently safe for scoped-lookups. */
> +			if (unlikely(nd->flags & LOOKUP_IS_SCOPED))
> +				return ERR_PTR(-EXDEV);

Also a candidate for doing in nd_jump_link()...

> @@ -1373,8 +1403,11 @@ static int follow_dotdot_rcu(struct nameidata *nd)
>  	struct inode *inode = nd->inode;
>  
>  	while (1) {
> -		if (path_equal(&nd->path, &nd->root))
> +		if (path_equal(&nd->path, &nd->root)) {
> +			if (unlikely(nd->flags & LOOKUP_BENEATH))
> +				return -EXDEV;

Umm...  Are you sure it's not -ECHILD?