linux-kernel - [RFC 16/19] netmem: use _Generic to cover const casting for page_to

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Message-Id: <20250509115126.63190-17-byungchul@sk.com>
Date: Fri,  9 May 2025 20:51:23 +0900
From: Byungchul Park <byungchul@...com>
To: willy@...radead.org,
	netdev@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	kernel_team@...ynix.com,
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	vishal.moola@...il.com
Subject: [RFC 16/19] netmem: use _Generic to cover const casting for page_to_netmem()

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@...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 c87a604e980b9..ce3765e675d19 100644
--- a/include/net/netmem.h
+++ b/include/net/netmem.h
@@ -133,10 +133,9 @@ static inline netmem_ref net_iov_to_netmem(struct netmem_desc *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