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netmem: introduce struct netmem_desc mirroring struct page

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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 <byungchul@sk.com>
Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com>
Reviewed-by: Pavel Begunkov <asml.silence@gmail.com>
Reviewed-by: Mina Almasry <almasrymina@google.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Harry Yoo <harry.yoo@oracle.com>
Link: https://patch.msgid.link/20250721021835.63939-2-byungchul@sk.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Byungchul Park
2025-07-21 11:18:24 +09:00
committed by Jakub Kicinski
parent 918c675b20
commit f3d85c9ee5
1 changed files with 95 additions and 21 deletions
Download Patch File Download Diff File Expand all files Collapse all files

116
include/net/netmem.h
View File

@@ -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);
@@ -30,13 +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