[PATCH net-next v2 2/4] netmem: store memory provider private pointer directly in struct net_iov
From: Mina Almasry
Date: Mon Nov 02 2026 - 18:23:36 EST
Resolving the memory provider instance from a struct net_iov currently
chases niov->owner (struct net_iov_area) and then dereferences the
provider-specific container struct (such as net_devmem_dmabuf_binding
or io_zcrx_area->ifq).
Alias void *mp_priv over the unused _pp_mapping_pad slot inside struct
net_iov (keeping sizeof(struct net_iov) == 64 bytes unchanged) and populate
it in net_iov_init() for both TX and RX net_iovs so callers can obtain the
provider instance pointer in a single load from the net_iov cacheline.
Signed-off-by: Mina Almasry <almasrymina@xxxxxxxxxx>
---
include/net/netmem.h | 15 +++++++++++++--
io_uring/zcrx.c | 2 +-
net/core/devmem.c | 3 ++-
net/core/devmem.h | 3 +--
net/core/net_test.c | 10 +++++-----
5 files changed, 22 insertions(+), 11 deletions(-)
diff --git a/include/net/netmem.h b/include/net/netmem.h
index fb693bc1702a4..c869be9c4d266 100644
--- a/include/net/netmem.h
+++ b/include/net/netmem.h
@@ -95,11 +95,20 @@ enum net_iov_type {
* supported.
*/
struct net_iov {
- struct netmem_desc desc;
+ union {
+ struct netmem_desc desc;
+ struct {
+ unsigned long _pad[3];
+ void *mp_priv;
+ };
+ };
enum net_iov_type type;
struct net_iov_area *owner;
};
+static_assert(offsetof(struct net_iov, mp_priv) ==
+ offsetof(struct netmem_desc, _pp_mapping_pad));
+
struct net_iov_area {
/* Array of net_iovs for this area. */
struct net_iov *niovs;
@@ -120,10 +129,12 @@ static inline unsigned int net_iov_idx(const struct net_iov *niov)
*/
static inline void net_iov_init(struct net_iov *niov,
struct net_iov_area *owner,
- enum net_iov_type type)
+ enum net_iov_type type,
+ void *mp_priv)
{
niov->owner = owner;
niov->type = type;
+ niov->mp_priv = mp_priv;
}
/* netmem */
diff --git a/io_uring/zcrx.c b/io_uring/zcrx.c
index 6d7abb1636e7f..6ec618d325606 100644
--- a/io_uring/zcrx.c
+++ b/io_uring/zcrx.c
@@ -562,7 +562,7 @@ static int __zcrx_create_area(struct io_zcrx_ifq *ifq,
for (i = 0; i < nr_iovs; i++) {
struct net_iov *niov = &area->nia.niovs[i];
- net_iov_init(niov, &area->nia, NET_IOV_IOURING);
+ net_iov_init(niov, &area->nia, NET_IOV_IOURING, ifq);
area->freelist[i] = i;
atomic_set(&area->user_refs[i], 0);
}
diff --git a/net/core/devmem.c b/net/core/devmem.c
index 32fafbfa1359e..fe99c005cbc5e 100644
--- a/net/core/devmem.c
+++ b/net/core/devmem.c
@@ -323,7 +323,8 @@ net_devmem_bind_dmabuf(struct net_device *dev, void *vdev,
nr_niovs = len >> niov_shift;
for (i = 0; i < nr_niovs; i++, niov_idx++) {
niov = &binding->area.niovs[niov_idx];
- net_iov_init(niov, &binding->area, NET_IOV_DMABUF);
+ net_iov_init(niov, &binding->area, NET_IOV_DMABUF,
+ binding);
if (net_mp_niov_set_dma_addr(niov, dma_addr)) {
err = -EFAULT;
NL_SET_ERR_MSG(extack,
diff --git a/net/core/devmem.h b/net/core/devmem.h
index 8fa089776610a..942b8caf36e99 100644
--- a/net/core/devmem.h
+++ b/net/core/devmem.h
@@ -102,8 +102,7 @@ int net_devmem_bind_dmabuf_to_queue(struct net_device *dev, u32 rxq_idx,
static inline struct net_devmem_dmabuf_binding *
net_devmem_iov_binding(const struct net_iov *niov)
{
- return container_of(net_iov_owner(niov),
- struct net_devmem_dmabuf_binding, area);
+ return niov->mp_priv;
}
static inline u32 net_devmem_iov_binding_id(const struct net_iov *niov)
diff --git a/net/core/net_test.c b/net/core/net_test.c
index 2b5080c226636..63124dbf3c9a8 100644
--- a/net/core/net_test.c
+++ b/net/core/net_test.c
@@ -857,7 +857,7 @@ static void netmem_ref_test_net_iov(struct kunit *test)
PERCPU_REF_INIT_ATOMIC, GFP_KERNEL);
KUNIT_ASSERT_EQ(test, err, 0);
- net_iov_init(&niov, &binding.area, NET_IOV_DMABUF);
+ net_iov_init(&niov, &binding.area, NET_IOV_DMABUF, &binding);
netmem = net_iov_to_netmem(&niov);
base_ref = atomic_long_read(&binding.ref.data->count);
@@ -1145,7 +1145,7 @@ static void netmem_ref_test_release_data(struct kunit *test)
percpu_ref_init(&binding.ref, dummy_percpu_ref_release,
PERCPU_REF_INIT_ATOMIC, GFP_KERNEL),
0);
- net_iov_init(&niov, &binding.area, NET_IOV_DMABUF);
+ net_iov_init(&niov, &binding.area, NET_IOV_DMABUF, &binding);
netmem = net_iov_to_netmem(&niov);
netmem_set_pp(netmem, pool);
netmem_or_pp_magic(netmem, PP_SIGNATURE);
@@ -1206,7 +1206,7 @@ static void netmem_ref_test_skb_segment(struct kunit *test)
percpu_ref_init(&binding.ref, dummy_percpu_ref_release,
PERCPU_REF_INIT_ATOMIC, GFP_KERNEL),
0);
- net_iov_init(&niov, &binding.area, NET_IOV_DMABUF);
+ net_iov_init(&niov, &binding.area, NET_IOV_DMABUF, &binding);
niov_nm = net_iov_to_netmem(&niov);
netmem_set_pp(niov_nm, pool);
netmem_or_pp_magic(niov_nm, PP_SIGNATURE);
@@ -1508,7 +1508,7 @@ static void netmem_ref_test_try_coalesce(struct kunit *test)
percpu_ref_init(&binding.ref, dummy_percpu_ref_release,
PERCPU_REF_INIT_ATOMIC, GFP_KERNEL),
0);
- net_iov_init(&niov, &binding.area, NET_IOV_DMABUF);
+ net_iov_init(&niov, &binding.area, NET_IOV_DMABUF, &binding);
niov_nm = net_iov_to_netmem(&niov);
netmem_set_pp(niov_nm, pool);
netmem_or_pp_magic(niov_nm, PP_SIGNATURE);
@@ -1654,7 +1654,7 @@ static void netmem_ref_test_tcp_devmem_recv(struct kunit *test)
KUNIT_ASSERT_EQ(test, ret, 0);
}
binding.area.niovs = &niov;
- net_iov_init(&niov, &binding.area, NET_IOV_DMABUF);
+ net_iov_init(&niov, &binding.area, NET_IOV_DMABUF, &binding);
niov_nm = net_iov_to_netmem(&niov);
netmem_set_pp(niov_nm, pool);
netmem_or_pp_magic(niov_nm, PP_SIGNATURE);
--
2.56.0.385.gac671c819a-goog