[v1] Split netmem from struct page

[PATCH 14/18] netmem: use _Generic to cover const casting for page_to_netmem()

Posted by Byungchul Park 6 months, 3 weeks ago

The current page_to_netmem() doesn't cover const casting resulting in
trying to cast const struct page * to const netmem_ref fails.

To cover the case, change page_to_netmem() to use macro and _Generic.

Signed-off-by: Byungchul Park <byungchul@sk.com>
---
 include/net/netmem.h | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/include/net/netmem.h b/include/net/netmem.h
index 29c005d70c4f..c2eb121181c2 100644
--- a/include/net/netmem.h
+++ b/include/net/netmem.h
@@ -172,10 +172,9 @@ static inline netmem_ref net_iov_to_netmem(struct net_iov *niov)
 	return (__force netmem_ref)((unsigned long)niov | NET_IOV);
 }
 
-static inline netmem_ref page_to_netmem(struct page *page)
-{
-	return (__force netmem_ref)page;
-}
+#define page_to_netmem(p)	(_Generic((p),			\
+	const struct page *:	(__force const netmem_ref)(p),	\
+	struct page *:		(__force netmem_ref)(p)))
 
 static inline netmem_ref alloc_netmems_node(int nid, gfp_t gfp_mask,
 		unsigned int order)
-- 
2.17.1

Re: [PATCH 14/18] netmem: use _Generic to cover const casting for page_to_netmem()

Posted by Mina Almasry 6 months, 3 weeks ago

On Thu, May 22, 2025 at 8:26 PM Byungchul Park <byungchul@sk.com> wrote:
>
> The current page_to_netmem() doesn't cover const casting resulting in
> trying to cast const struct page * to const netmem_ref fails.
>
> To cover the case, change page_to_netmem() to use macro and _Generic.
>
> Signed-off-by: Byungchul Park <byungchul@sk.com>

Reviewed-by: Mina Almasry <almasrymina@google.com>

> ---
>  include/net/netmem.h | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/include/net/netmem.h b/include/net/netmem.h
> index 29c005d70c4f..c2eb121181c2 100644
> --- a/include/net/netmem.h
> +++ b/include/net/netmem.h
> @@ -172,10 +172,9 @@ static inline netmem_ref net_iov_to_netmem(struct net_iov *niov)
>         return (__force netmem_ref)((unsigned long)niov | NET_IOV);
>  }
>
> -static inline netmem_ref page_to_netmem(struct page *page)
> -{
> -       return (__force netmem_ref)page;
> -}
> +#define page_to_netmem(p)      (_Generic((p),                  \
> +       const struct page *:    (__force const netmem_ref)(p),  \
> +       struct page *:          (__force netmem_ref)(p)))
>
>  static inline netmem_ref alloc_netmems_node(int nid, gfp_t gfp_mask,
>                 unsigned int order)
> --
> 2.17.1
>


-- 
Thanks,
Mina