1 files changed, 174 insertions, 0 deletions
diff --git a/include/net/netmem.h b/include/net/netmem.h
new file mode 100644
index 000000000000..8a6e20be4b9d
--- /dev/null
+++ b/include/net/netmem.h
@@ -0,0 +1,174 @@
+/* SPDX-License-Identifier: GPL-2.0
+ *
+ *	Network memory
+ *
+ *	Author:	Mina Almasry <almasrymina@google.com>
+ */
+
+#ifndef _NET_NETMEM_H
+#define _NET_NETMEM_H
+
+#include <linux/mm.h>
+#include <net/net_debug.h>
+
+/* net_iov */
+
+DECLARE_STATIC_KEY_FALSE(page_pool_mem_providers);
+
+/*  We overload the LSB of the struct page pointer to indicate whether it's
+ *  a page or net_iov.
+ */
+#define NET_IOV 0x01UL
+
+struct net_iov {
+	unsigned long __unused_padding;
+	unsigned long pp_magic;
+	struct page_pool *pp;
+	struct dmabuf_genpool_chunk_owner *owner;
+	unsigned long dma_addr;
+	atomic_long_t pp_ref_count;
+};
+
+/* These fields in struct page are used by the page_pool and net stack:
+ *
+ *        struct {
+ *                unsigned long pp_magic;
+ *                struct page_pool *pp;
+ *                unsigned long _pp_mapping_pad;
+ *                unsigned long dma_addr;
+ *                atomic_long_t pp_ref_count;
+ *        };
+ *
+ * We mirror the page_pool fields here so the page_pool can access these fields
+ * without worrying whether the underlying fields belong to a page or net_iov.
+ *
+ * The non-net stack fields of struct page are private to the mm stack and must
+ * never be mirrored to net_iov.
+ */
+#define NET_IOV_ASSERT_OFFSET(pg, iov)             \
+	static_assert(offsetof(struct page, pg) == \
+		      offsetof(struct net_iov, iov))
+NET_IOV_ASSERT_OFFSET(pp_magic, pp_magic);
+NET_IOV_ASSERT_OFFSET(pp, pp);
+NET_IOV_ASSERT_OFFSET(dma_addr, dma_addr);
+NET_IOV_ASSERT_OFFSET(pp_ref_count, pp_ref_count);
+#undef NET_IOV_ASSERT_OFFSET
+
+/* netmem */
+
+/**
+ * typedef netmem_ref - a nonexistent type marking a reference to generic
+ * network memory.
+ *
+ * A netmem_ref currently is always a reference to a struct page. This
+ * abstraction is introduced so support for new memory types can be added.
+ *
+ * Use the supplied helpers to obtain the underlying memory pointer and fields.
+ */
+typedef unsigned long __bitwise netmem_ref;
+
+static inline bool netmem_is_net_iov(const netmem_ref netmem)
+{
+	return (__force unsigned long)netmem & NET_IOV;
+}
+
+/* This conversion fails (returns NULL) if the netmem_ref is not struct page
+ * backed.
+ */
+static inline struct page *netmem_to_page(netmem_ref netmem)
+{
+	if (WARN_ON_ONCE(netmem_is_net_iov(netmem)))
+		return NULL;
+
+	return (__force struct page *)netmem;
+}
+
+static inline struct net_iov *netmem_to_net_iov(netmem_ref netmem)
+{
+	if (netmem_is_net_iov(netmem))
+		return (struct net_iov *)((__force unsigned long)netmem &
+					  ~NET_IOV);
+
+	DEBUG_NET_WARN_ON_ONCE(true);
+	return NULL;
+}
+
+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;
+}
+
+static inline int netmem_ref_count(netmem_ref netmem)
+{
+	/* The non-pp refcount of net_iov is always 1. On net_iov, we only
+	 * support pp refcounting which uses the pp_ref_count field.
+	 */
+	if (netmem_is_net_iov(netmem))
+		return 1;
+
+	return page_ref_count(netmem_to_page(netmem));
+}
+
+static inline unsigned long netmem_pfn_trace(netmem_ref netmem)
+{
+	if (netmem_is_net_iov(netmem))
+		return 0;
+
+	return page_to_pfn(netmem_to_page(netmem));
+}
+
+static inline struct net_iov *__netmem_clear_lsb(netmem_ref netmem)
+{
+	return (struct net_iov *)((__force unsigned long)netmem & ~NET_IOV);
+}
+
+static inline struct page_pool *netmem_get_pp(netmem_ref netmem)
+{
+	return __netmem_clear_lsb(netmem)->pp;
+}
+
+static inline atomic_long_t *netmem_get_pp_ref_count_ref(netmem_ref netmem)
+{
+	return &__netmem_clear_lsb(netmem)->pp_ref_count;
+}
+
+static inline bool netmem_is_pref_nid(netmem_ref netmem, int pref_nid)
+{
+	/* NUMA node preference only makes sense if we're allocating
+	 * system memory. Memory providers (which give us net_iovs)
+	 * choose for us.
+	 */
+	if (netmem_is_net_iov(netmem))
+		return true;
+
+	return page_to_nid(netmem_to_page(netmem)) == pref_nid;
+}
+
+static inline netmem_ref netmem_compound_head(netmem_ref netmem)
+{
+	/* niov are never compounded */
+	if (netmem_is_net_iov(netmem))
+		return netmem;
+
+	return page_to_netmem(compound_head(netmem_to_page(netmem)));
+}
+
+static inline void *netmem_address(netmem_ref netmem)
+{
+	if (netmem_is_net_iov(netmem))
+		return NULL;
+
+	return page_address(netmem_to_page(netmem));
+}
+
+static inline unsigned long netmem_get_dma_addr(netmem_ref netmem)
+{
+	return __netmem_clear_lsb(netmem)->dma_addr;
+}
+
+#endif /* _NET_NETMEM_H */