To eliminate the use of the page pool fields in struct page, the page
pool code should use netmem descriptor and APIs instead.
However, some code e.g. __netmem_to_page() is still used to access the
page pool fields e.g. ->pp via struct page, which should be changed so
as to access them via netmem descriptor, struct netmem_desc instead,
since the fields no longer will be available in struct page.
Introduce utility APIs to make them easy to use struct netmem_desc as
descriptor. The APIs are:
1. __netmem_to_nmdesc(), to convert netmem_ref to struct netmem_desc,
but unsafely without checking if it's net_iov or system memory.
2. netmem_to_nmdesc(), to convert netmem_ref to struct netmem_desc,
safely with checking if it's net_iov or system memory.
3. nmdesc_to_page(), to convert struct netmem_desc to struct page,
assuming struct netmem_desc overlays on struct page.
4. page_to_nmdesc(), to convert struct page to struct netmem_desc,
assuming struct netmem_desc overlays on struct page, allowing only
head page to be converted.
5. nmdesc_adress(), to get its virtual address corresponding to the
struct netmem_desc.
Signed-off-by: Byungchul Park <byungchul@xxxxxx>
---
include/net/netmem.h | 41 +++++++++++++++++++++++++++++++++++++++++
1 file changed, 41 insertions(+)
diff --git a/include/net/netmem.h b/include/net/netmem.h
index 535cf17b9134..ad9444be229a 100644
--- a/include/net/netmem.h
+++ b/include/net/netmem.h
@@ -198,6 +198,32 @@ static inline struct page *netmem_to_page(netmem_ref netmem)
return __netmem_to_page(netmem);
}
+/**
+ * __netmem_to_nmdesc - unsafely get pointer to the &netmem_desc backing
+ * @netmem
+ * @netmem: netmem reference to convert
+ *
+ * Unsafe version of netmem_to_nmdesc(). When @netmem is always backed
+ * by system memory, performs faster and generates smaller object code
+ * (no check for the LSB, no WARN). When @netmem points to IOV, provokes
+ * undefined behaviour.
+ *
+ * Return: pointer to the &netmem_desc (garbage if @netmem is not backed
+ * by system memory).
+ */
+static inline struct netmem_desc *__netmem_to_nmdesc(netmem_ref netmem)
+{
+ return (__force struct netmem_desc *)netmem;
+}
+
+static inline struct netmem_desc *netmem_to_nmdesc(netmem_ref netmem)
+{
+ if (WARN_ON_ONCE(netmem_is_net_iov(netmem)))
+ return NULL;
+
+ return __netmem_to_nmdesc(netmem);
+}
+
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)))
+
+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));
+}
+
/**
* __netmem_address - unsafely get pointer to the memory backing @netmem
* @netmem: netmem reference to get the pointer for
--
2.17.1
