[PATCH 01/18] netmem: introduce struct netmem_desc struct_group_tagged()'ed on struct net_iov

Byungchul Park
2025-05-23T03:26:21Z

To simplify struct page, the page pool members of struct page should be
moved to other, allowing these members to be removed from struct page.

Introduce a network memory descriptor to store the members, struct
netmem_desc, reusing struct net_iov that already mirrored struct page.

While at it, relocate _pp_mapping_pad to group struct net_iov's fields.

Signed-off-by: Byungchul Park <byungchul@sk.com>
---
include/linux/mm_types.h | 2 +-
include/net/netmem.h | 43 +++++++++++++++++++++++++++++++++-------
2 files changed, 37 insertions(+), 8 deletions(-)

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 56d07edd01f9..873e820e1521 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -120,13 +120,13 @@ struct page {
unsigned long private;
};
struct { /* page_pool used by netstack */
+ unsigned long _pp_mapping_pad;
/**
* @pp_magic: magic value to avoid recycling non
* page_pool allocated pages.
*/
unsigned long pp_magic;
struct page_pool *pp;
- unsigned long _pp_mapping_pad;
unsigned long dma_addr;
atomic_long_t pp_ref_count;
};
diff --git a/include/net/netmem.h b/include/net/netmem.h
index 386164fb9c18..08e9d76cdf14 100644
--- a/include/net/netmem.h
+++ b/include/net/netmem.h
@@ -31,12 +31,41 @@ enum net_iov_type {
};

struct net_iov {
- enum net_iov_type type;
- unsigned long pp_magic;
- struct page_pool *pp;
- struct net_iov_area *owner;
- unsigned long dma_addr;
- atomic_long_t pp_ref_count;
+ /*
+ * XXX: Now that struct netmem_desc overlays on struct page,
+ * struct_group_tagged() should cover all of them. However,
+ * a separate struct netmem_desc should be declared and embedded,
+ * once struct netmem_desc is no longer overlayed but it has its
+ * own instance from slab. The final form should be:
+ *
+ * struct netmem_desc {
+ * unsigned long pp_magic;
+ * struct page_pool *pp;
+ * unsigned long dma_addr;
+ * atomic_long_t pp_ref_count;
+ * };
+ *
+ * struct net_iov {
+ * enum net_iov_type type;
+ * struct net_iov_area *owner;
+ * struct netmem_desc;
+ * };
+ */
+ struct_group_tagged(netmem_desc, desc,
+ /*
+ * only for struct net_iov
+ */
+ enum net_iov_type type;
+ struct net_iov_area *owner;
+
+ /*
+ * actually for struct netmem_desc
+ */
+ unsigned long pp_magic;
+ struct page_pool *pp;
+ unsigned long dma_addr;
+ atomic_long_t pp_ref_count;
+ );
};

struct net_iov_area {
@@ -51,9 +80,9 @@ struct net_iov_area {
/* These fields in struct page are used by the page_pool and net stack:
*
* struct {
+ * unsigned long _pp_mapping_pad;
* unsigned long pp_magic;
* struct page_pool *pp;
- * unsigned long _pp_mapping_pad;
* unsigned long dma_addr;
* atomic_long_t pp_ref_count;
* };
--
2.17.1