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: Byungchul Park Reviewed-by: Toke Høiland-Jørgensen Reviewed-by: Pavel Begunkov Reviewed-by: Mina Almasry Reviewed-by: Vlastimil Babka Acked-by: Harry Yoo --- include/net/netmem.h | 116 +++++++++++++++++++++++++++++++++++-------- 1 file changed, 95 insertions(+), 21 deletions(-) diff --git a/include/net/netmem.h b/include/net/netmem.h index de1d95f04076..535cf17b9134 100644 --- a/include/net/netmem.h +++ b/include/net/netmem.h @@ -12,6 +12,50 @@ #include #include +/* 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); @@ -30,13 +74,48 @@ 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; - unsigned long pp_magic; - struct page_pool *pp; + 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; + unsigned long _pp_mapping_pad; + unsigned long dma_addr; + atomic_long_t pp_ref_count; + }; + }; struct net_iov_area *owner; - unsigned long dma_addr; - atomic_long_t pp_ref_count; + enum net_iov_type type; }; struct net_iov_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 -- 2.17.1