Re: [PATCH net-next v9 2/8] netmem: introduce utility APIs to use struct netmem_desc

[Pavel Begunkov <asml.silence@gmail.com>]

On 7/10/25 09:28, Byungchul Park wrote:
...> +
>   static inline struct net_iov *netmem_to_net_iov(netmem_ref netmem)
>   {
>   	if (netmem_is_net_iov(netmem))
> @@ -314,6 +340,21 @@ static inline netmem_ref netmem_compound_head(netmem_ref netmem)
>   	return page_to_netmem(compound_head(netmem_to_page(netmem)));
>   }
>   
> +#define nmdesc_to_page(nmdesc)		(_Generic((nmdesc),		\
> +	const struct netmem_desc * :	(const struct page *)(nmdesc),	\
> +	struct netmem_desc * :		(struct page *)(nmdesc)))

Considering that nmdesc is going to be separated from pages and
accessed through indirection, and back reference to the page is
not needed (at least for net/), this helper shouldn't even exist.
And in fact, you don't really use it ...

> +static inline struct netmem_desc *page_to_nmdesc(struct page *page)
> +{
> +	VM_BUG_ON_PAGE(PageTail(page), page);
> +	return (struct netmem_desc *)page;
> +}
> +
> +static inline void *nmdesc_address(struct netmem_desc *nmdesc)
> +{
> +	return page_address(nmdesc_to_page(nmdesc));
> +}

... That's the only caller, and nmdesc_address() is not used, so
just nuke both of them. This helper doesn't even make sense.

Please avoid introducing functions that you don't use as a general
rule.

> +
>   /**
>    * __netmem_address - unsafely get pointer to the memory backing @netmem
>    * @netmem: netmem reference to get the pointer for

-- 
Pavel Begunkov