# \[PATCH 02/24\] netmem: Add utility functions

- From: Matthew Wilcox (Oracle) \<willy@infradead.org\>
- Date: 2022-11-30 22:08:35 
- List: netdev
- Page: https://ratatoskr.run/netdev/2022/11/6520155
- Thread: https://ratatoskr.run/netdev/2022/11/6520146/t.md

```text
netmem_page() is defined this way to preserve constness.  page_netmem()
doesn't call compound_head() because netmem users always use the head
page; it does include a debugging assert to check that it's true.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 include/net/page_pool.h | 42 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/include/net/page_pool.h b/include/net/page_pool.h
index af6ff8c302a0..0ce20b95290b 100644
--- a/include/net/page_pool.h
+++ b/include/net/page_pool.h
@@ -91,6 +91,48 @@ NETMEM_MATCH(_refcount, _refcount);
 #undef NETMEM_MATCH
 static_assert(sizeof(struct netmem) <= sizeof(struct page));
 
+#define netmem_page(nmem) (_Generic((*nmem),				\
+	const struct netmem:	(const struct page *)nmem,		\
+	struct netmem:		(struct page *)nmem))
+
+static inline struct netmem *page_netmem(struct page *page)
+{
+	VM_BUG_ON_PAGE(PageTail(page), page);
+	return (struct netmem *)page;
+}
+
+static inline unsigned long netmem_pfn(const struct netmem *nmem)
+{
+	return page_to_pfn(netmem_page(nmem));
+}
+
+static inline unsigned long netmem_nid(const struct netmem *nmem)
+{
+	return page_to_nid(netmem_page(nmem));
+}
+
+static inline struct netmem *virt_to_netmem(const void *x)
+{
+	return page_netmem(virt_to_head_page(x));
+}
+
+static inline int netmem_ref_count(const struct netmem *nmem)
+{
+	return page_ref_count(netmem_page(nmem));
+}
+
+static inline void netmem_put(struct netmem *nmem)
+{
+	struct folio *folio = (struct folio *)nmem;
+
+	return folio_put(folio);
+}
+
+static inline bool netmem_is_pfmemalloc(const struct netmem *nmem)
+{
+	return nmem->pp_magic & BIT(1);
+}
+
 /*
  * Fast allocation side cache array/stack
  *
-- 
2.35.1

```