Commit f3d85c9e authored by Byungchul Park's avatar Byungchul Park Committed by Jakub Kicinski
Browse files

netmem: introduce struct netmem_desc mirroring struct page 



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, and make it union'ed with the existing fields in struct
net_iov, allowing to organize the fields of struct net_iov.

Signed-off-by: default avatarByungchul Park <byungchul@sk.com>
Reviewed-by: default avatarToke Høiland-Jørgensen <toke@redhat.com>
Reviewed-by: default avatarPavel Begunkov <asml.silence@gmail.com>
Reviewed-by: default avatarMina Almasry <almasrymina@google.com>
Reviewed-by: default avatarVlastimil Babka <vbabka@suse.cz>
Acked-by: default avatarHarry Yoo <harry.yoo@oracle.com>
Link: https://patch.msgid.link/20250721021835.63939-2-byungchul@sk.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 918c675b

include/net/netmem.h

+95 −21
Original line number Diff line number Diff line
@@ -12,6 +12,50 @@ 
#include <linux/mm.h>

#include <net/net_debug.h>



/* 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 netmem_desc.

 *

 * CAUTION: Do not update the fields in netmem_desc without also

 * updating the anonymous aliasing union in struct net_iov.

 */

struct netmem_desc {

	unsigned long _flags;

	unsigned long pp_magic;

	struct page_pool *pp;

	unsigned long _pp_mapping_pad;

	unsigned long dma_addr;

	atomic_long_t pp_ref_count;

};



#define NETMEM_DESC_ASSERT_OFFSET(pg, desc)        \

	static_assert(offsetof(struct page, pg) == \

		      offsetof(struct netmem_desc, desc))

NETMEM_DESC_ASSERT_OFFSET(flags, _flags);

NETMEM_DESC_ASSERT_OFFSET(pp_magic, pp_magic);

NETMEM_DESC_ASSERT_OFFSET(pp, pp);

NETMEM_DESC_ASSERT_OFFSET(_pp_mapping_pad, _pp_mapping_pad);

NETMEM_DESC_ASSERT_OFFSET(dma_addr, dma_addr);

NETMEM_DESC_ASSERT_OFFSET(pp_ref_count, pp_ref_count);

#undef NETMEM_DESC_ASSERT_OFFSET



/*

 * Since struct netmem_desc uses the space in struct page, the size

 * should be checked, until struct netmem_desc has its own instance from

 * slab, to avoid conflicting with other members within struct page.

 */

static_assert(sizeof(struct netmem_desc) <= offsetof(struct page, _refcount));



/* net_iov */



DECLARE_STATIC_KEY_FALSE(page_pool_mem_providers);
@@ -30,14 +74,49 @@ enum net_iov_type { 
	NET_IOV_MAX = ULONG_MAX

};



/* A memory descriptor representing abstract networking I/O vectors,

 * generally for non-pages memory that doesn't have its corresponding

 * struct page and needs to be explicitly allocated through slab.

 *

 * net_iovs are allocated and used by networking code, and the size of

 * the chunk is PAGE_SIZE.

 *

 * This memory can be any form of non-struct paged memory.  Examples

 * include imported dmabuf memory and imported io_uring memory.  See

 * net_iov_type for all the supported types.

 *

 * @pp_magic:	pp field, similar to the one in struct page/struct

 *		netmem_desc.

 * @pp:		the pp this net_iov belongs to, if any.

 * @dma_addr:	the dma addrs of the net_iov. Needed for the network

 *		card to send/receive this net_iov.

 * @pp_ref_count: the pp ref count of this net_iov, exactly the same

 *		usage as struct page/struct netmem_desc.

 * @owner:	the net_iov_area this net_iov belongs to, if any.

 * @type:	the type of the memory.  Different types of net_iovs are

 *		supported.

 */

struct net_iov {

	enum net_iov_type type;

	union {

		struct netmem_desc desc;



		/* XXX: The following part should be removed once all

		 * the references to them are converted so as to be

		 * accessed via netmem_desc e.g. niov->desc.pp instead

		 * of niov->pp.

		 */

		struct {

			unsigned long _flags;

			unsigned long pp_magic;

			struct page_pool *pp;

	struct net_iov_area *owner;

			unsigned long _pp_mapping_pad;

			unsigned long dma_addr;

			atomic_long_t pp_ref_count;

		};

	};

	struct net_iov_area *owner;

	enum net_iov_type type;

};



struct net_iov_area {

	/* Array of net_iovs for this area. */
@@ -48,27 +127,22 @@ struct net_iov_area { 
	unsigned long base_virtual;

};



/* These fields in struct page are used by the page_pool and net stack:

/* net_iov is union'ed with struct netmem_desc mirroring struct page, so

 * the page_pool can access these fields without worrying whether the

 * underlying fields are accessed via netmem_desc or directly via

 * net_iov, until all the references to them are converted so as to be

 * accessed via netmem_desc e.g. niov->desc.pp instead of niov->pp.

 *

 *        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.

 * 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) == \

#define NET_IOV_ASSERT_OFFSET(desc, iov)                    \

	static_assert(offsetof(struct netmem_desc, desc) == \

		      offsetof(struct net_iov, iov))

NET_IOV_ASSERT_OFFSET(_flags, _flags);

NET_IOV_ASSERT_OFFSET(pp_magic, pp_magic);

NET_IOV_ASSERT_OFFSET(pp, pp);

NET_IOV_ASSERT_OFFSET(_pp_mapping_pad, _pp_mapping_pad);

NET_IOV_ASSERT_OFFSET(dma_addr, dma_addr);

NET_IOV_ASSERT_OFFSET(pp_ref_count, pp_ref_count);

#undef NET_IOV_ASSERT_OFFSET