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Message-Id: <20240409205300.1346681-2-zijianzhang@bytedance.com>
Date: Tue, 9 Apr 2024 20:52:58 +0000
From: zijianzhang@...edance.com
To: netdev@...r.kernel.org
Cc: edumazet@...gle.com,
willemdebruijn.kernel@...il.com,
davem@...emloft.net,
kuba@...nel.org,
cong.wang@...edance.com,
xiaochun.lu@...edance.com,
Zijian Zhang <zijianzhang@...edance.com>
Subject: [PATCH net-next 1/3] sock: add MSG_ZEROCOPY_UARG
From: Zijian Zhang <zijianzhang@...edance.com>
The MSG_ZEROCOPY flag enables copy avoidance for socket send calls.
However, zerocopy is not a free lunch. Apart from the management of user
pages, the combination of poll + recvmsg to receive notifications incurs
unignorable overhead in the applications. The overhead of such sometimes
might be more than the CPU savings from zerocopy. We try to solve this
problem with a new option for TCP and UDP, MSG_ZEROCOPY_UARG.
This new mechanism aims to reduce the overhead associated with receiving
notifications by embedding them directly into user arguments passed with
each sendmsg control message. By doing so, we can significantly reduce
the complexity and overhead for managing notifications. In an ideal
pattern, the user will keep calling sendmsg with MSG_ZEROCOPY_UARG
flag, and the notification will be delivered as soon as possible.
Signed-off-by: Zijian Zhang <zijianzhang@...edance.com>
Signed-off-by: Xiaochun Lu <xiaochun.lu@...edance.com>
---
include/linux/skbuff.h | 7 +-
include/linux/socket.h | 1 +
include/linux/tcp.h | 3 +
include/linux/udp.h | 3 +
include/net/sock.h | 17 +++
include/net/udp.h | 1 +
include/uapi/asm-generic/socket.h | 2 +
include/uapi/linux/socket.h | 17 +++
net/core/skbuff.c | 137 ++++++++++++++++++++++--
net/core/sock.c | 50 +++++++++
net/ipv4/ip_output.c | 6 +-
net/ipv4/tcp.c | 7 +-
net/ipv4/udp.c | 9 ++
net/ipv6/ip6_output.c | 5 +-
net/ipv6/udp.c | 9 ++
net/vmw_vsock/virtio_transport_common.c | 2 +-
16 files changed, 258 insertions(+), 18 deletions(-)
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 03ea36a82cdd..19b94ba01007 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1663,12 +1663,14 @@ static inline void skb_set_end_offset(struct sk_buff *skb, unsigned int offset)
#endif
struct ubuf_info *msg_zerocopy_realloc(struct sock *sk, size_t size,
- struct ubuf_info *uarg);
+ struct ubuf_info *uarg, bool user_args_notification);
void msg_zerocopy_put_abort(struct ubuf_info *uarg, bool have_uref);
void msg_zerocopy_callback(struct sk_buff *skb, struct ubuf_info *uarg,
bool success);
+void msg_zerocopy_uarg_callback(struct sk_buff *skb, struct ubuf_info *uarg,
+ bool success);
int __zerocopy_sg_from_iter(struct msghdr *msg, struct sock *sk,
struct sk_buff *skb, struct iov_iter *from,
@@ -1763,7 +1765,8 @@ static inline void net_zcopy_put(struct ubuf_info *uarg)
static inline void net_zcopy_put_abort(struct ubuf_info *uarg, bool have_uref)
{
if (uarg) {
- if (uarg->callback == msg_zerocopy_callback)
+ if (uarg->callback == msg_zerocopy_callback ||
+ uarg->callback == msg_zerocopy_uarg_callback)
msg_zerocopy_put_abort(uarg, have_uref);
else if (have_uref)
net_zcopy_put(uarg);
diff --git a/include/linux/socket.h b/include/linux/socket.h
index 139c330ccf2c..de01392344e1 100644
--- a/include/linux/socket.h
+++ b/include/linux/socket.h
@@ -326,6 +326,7 @@ struct ucred {
* plain text and require encryption
*/
+#define MSG_ZEROCOPY_UARG 0x2000000 /* MSG_ZEROCOPY with UARG notifications */
#define MSG_ZEROCOPY 0x4000000 /* Use user data in kernel path */
#define MSG_SPLICE_PAGES 0x8000000 /* Splice the pages from the iterator in sendmsg() */
#define MSG_FASTOPEN 0x20000000 /* Send data in TCP SYN */
diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index 55399ee2a57e..e973f4990646 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -501,6 +501,9 @@ struct tcp_sock {
*/
struct request_sock __rcu *fastopen_rsk;
struct saved_syn *saved_syn;
+
+/* TCP MSG_ZEROCOPY_UARG related information */
+ struct tx_msg_zcopy_queue tx_zcopy_queue;
};
enum tsq_enum {
diff --git a/include/linux/udp.h b/include/linux/udp.h
index 3748e82b627b..502b393eac67 100644
--- a/include/linux/udp.h
+++ b/include/linux/udp.h
@@ -95,6 +95,9 @@ struct udp_sock {
/* Cache friendly copy of sk->sk_peek_off >= 0 */
bool peeking_with_offset;
+
+ /* This field is used by sendmsg zcopy user arg mode notification */
+ struct tx_msg_zcopy_queue tx_zcopy_queue;
};
#define udp_test_bit(nr, sk) \
diff --git a/include/net/sock.h b/include/net/sock.h
index 2253eefe2848..f7c045e98213 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -544,6 +544,23 @@ struct sock {
netns_tracker ns_tracker;
};
+struct tx_msg_zcopy_node {
+ struct list_head node;
+ struct tx_msg_zcopy_info info;
+ struct sk_buff *skb;
+};
+
+struct tx_msg_zcopy_queue {
+ struct list_head head;
+ spinlock_t lock; /* protects head queue */
+};
+
+static inline void tx_message_zcopy_queue_init(struct tx_msg_zcopy_queue *q)
+{
+ spin_lock_init(&q->lock);
+ INIT_LIST_HEAD(&q->head);
+}
+
enum sk_pacing {
SK_PACING_NONE = 0,
SK_PACING_NEEDED = 1,
diff --git a/include/net/udp.h b/include/net/udp.h
index 488a6d2babcc..9e4d7b128de4 100644
--- a/include/net/udp.h
+++ b/include/net/udp.h
@@ -182,6 +182,7 @@ static inline void udp_lib_init_sock(struct sock *sk)
skb_queue_head_init(&up->reader_queue);
up->forward_threshold = sk->sk_rcvbuf >> 2;
set_bit(SOCK_CUSTOM_SOCKOPT, &sk->sk_socket->flags);
+ tx_message_zcopy_queue_init(&up->tx_zcopy_queue);
}
/* hash routines shared between UDPv4/6 and UDP-Litev4/6 */
diff --git a/include/uapi/asm-generic/socket.h b/include/uapi/asm-generic/socket.h
index 8ce8a39a1e5f..86aa4b5cb7f1 100644
--- a/include/uapi/asm-generic/socket.h
+++ b/include/uapi/asm-generic/socket.h
@@ -135,6 +135,8 @@
#define SO_PASSPIDFD 76
#define SO_PEERPIDFD 77
+#define SO_ZEROCOPY_NOTIFICATION 78
+
#if !defined(__KERNEL__)
#if __BITS_PER_LONG == 64 || (defined(__x86_64__) && defined(__ILP32__))
diff --git a/include/uapi/linux/socket.h b/include/uapi/linux/socket.h
index d3fcd3b5ec53..469ed8f4e6c8 100644
--- a/include/uapi/linux/socket.h
+++ b/include/uapi/linux/socket.h
@@ -35,4 +35,21 @@ struct __kernel_sockaddr_storage {
#define SOCK_TXREHASH_DISABLED 0
#define SOCK_TXREHASH_ENABLED 1
+/*
+ * Given the fact that MSG_ZEROCOPY_UARG tries to copy notifications
+ * back to user as soon as possible, 8 should be sufficient.
+ */
+#define SOCK_USR_ZC_INFO_MAX 8
+
+struct tx_msg_zcopy_info {
+ __u32 lo;
+ __u32 hi;
+ __u8 zerocopy;
+};
+
+struct tx_usr_zcopy_info {
+ int length;
+ struct tx_msg_zcopy_info info[SOCK_USR_ZC_INFO_MAX];
+};
+
#endif /* _UAPI_LINUX_SOCKET_H */
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 2a5ce6667bbb..d939b2c14d55 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -1661,6 +1661,16 @@ void mm_unaccount_pinned_pages(struct mmpin *mmp)
}
EXPORT_SYMBOL_GPL(mm_unaccount_pinned_pages);
+static void init_ubuf_info_msgzc(struct ubuf_info_msgzc *uarg, struct sock *sk, size_t size)
+{
+ uarg->id = ((u32)atomic_inc_return(&sk->sk_zckey)) - 1;
+ uarg->len = 1;
+ uarg->bytelen = size;
+ uarg->zerocopy = 1;
+ uarg->ubuf.flags = SKBFL_ZEROCOPY_FRAG | SKBFL_DONT_ORPHAN;
+ refcount_set(&uarg->ubuf.refcnt, 1);
+}
+
static struct ubuf_info *msg_zerocopy_alloc(struct sock *sk, size_t size)
{
struct ubuf_info_msgzc *uarg;
@@ -1682,12 +1692,38 @@ static struct ubuf_info *msg_zerocopy_alloc(struct sock *sk, size_t size)
}
uarg->ubuf.callback = msg_zerocopy_callback;
- uarg->id = ((u32)atomic_inc_return(&sk->sk_zckey)) - 1;
- uarg->len = 1;
- uarg->bytelen = size;
- uarg->zerocopy = 1;
- uarg->ubuf.flags = SKBFL_ZEROCOPY_FRAG | SKBFL_DONT_ORPHAN;
- refcount_set(&uarg->ubuf.refcnt, 1);
+ init_ubuf_info_msgzc(uarg, sk, size);
+ sock_hold(sk);
+
+ return &uarg->ubuf;
+}
+
+static struct ubuf_info *msg_zerocopy_uarg_alloc(struct sock *sk, size_t size)
+{
+ struct sk_buff *skb;
+ struct ubuf_info_msgzc *uarg;
+ struct tx_msg_zcopy_node *zcopy_node_p;
+
+ WARN_ON_ONCE(!in_task());
+
+ skb = sock_omalloc(sk, sizeof(*zcopy_node_p), GFP_KERNEL);
+ if (!skb)
+ return NULL;
+
+ BUILD_BUG_ON(sizeof(*uarg) > sizeof(skb->cb));
+ uarg = (void *)skb->cb;
+ uarg->mmp.user = NULL;
+ zcopy_node_p = (struct tx_msg_zcopy_node *)skb_put(skb, sizeof(*zcopy_node_p));
+
+ if (mm_account_pinned_pages(&uarg->mmp, size)) {
+ kfree_skb(skb);
+ return NULL;
+ }
+
+ INIT_LIST_HEAD(&zcopy_node_p->node);
+ zcopy_node_p->skb = skb;
+ uarg->ubuf.callback = msg_zerocopy_uarg_callback;
+ init_ubuf_info_msgzc(uarg, sk, size);
sock_hold(sk);
return &uarg->ubuf;
@@ -1699,7 +1735,7 @@ static inline struct sk_buff *skb_from_uarg(struct ubuf_info_msgzc *uarg)
}
struct ubuf_info *msg_zerocopy_realloc(struct sock *sk, size_t size,
- struct ubuf_info *uarg)
+ struct ubuf_info *uarg, bool usr_arg_notification)
{
if (uarg) {
struct ubuf_info_msgzc *uarg_zc;
@@ -1707,7 +1743,8 @@ struct ubuf_info *msg_zerocopy_realloc(struct sock *sk, size_t size,
u32 bytelen, next;
/* there might be non MSG_ZEROCOPY users */
- if (uarg->callback != msg_zerocopy_callback)
+ if (uarg->callback != msg_zerocopy_callback &&
+ uarg->callback != msg_zerocopy_uarg_callback)
return NULL;
/* realloc only when socket is locked (TCP, UDP cork),
@@ -1744,6 +1781,8 @@ struct ubuf_info *msg_zerocopy_realloc(struct sock *sk, size_t size,
}
new_alloc:
+ if (usr_arg_notification)
+ return msg_zerocopy_uarg_alloc(sk, size);
return msg_zerocopy_alloc(sk, size);
}
EXPORT_SYMBOL_GPL(msg_zerocopy_realloc);
@@ -1830,6 +1869,86 @@ void msg_zerocopy_callback(struct sk_buff *skb, struct ubuf_info *uarg,
}
EXPORT_SYMBOL_GPL(msg_zerocopy_callback);
+static bool skb_zerocopy_uarg_notify_extend(struct tx_msg_zcopy_node *node, u32 lo, u16 len)
+{
+ u32 old_lo, old_hi;
+ u64 sum_len;
+
+ old_lo = node->info.lo;
+ old_hi = node->info.hi;
+ sum_len = old_hi - old_lo + 1ULL + len;
+
+ if (sum_len >= (1ULL << 32))
+ return false;
+
+ if (lo != old_hi + 1)
+ return false;
+
+ node->info.hi += len;
+ return true;
+}
+
+static void __msg_zerocopy_uarg_callback(struct ubuf_info_msgzc *uarg)
+{
+ struct sk_buff *skb = skb_from_uarg(uarg);
+ struct sock *sk = skb->sk;
+ struct tx_msg_zcopy_node *zcopy_node_p, *tail;
+ struct tx_msg_zcopy_queue *zcopy_queue;
+ unsigned long flags;
+ u32 lo, hi;
+ u16 len;
+
+ mm_unaccount_pinned_pages(&uarg->mmp);
+
+ /* if !len, there was only 1 call, and it was aborted
+ * so do not queue a completion notification
+ */
+ if (!uarg->len || sock_flag(sk, SOCK_DEAD))
+ goto release;
+
+ /* only support TCP and UCP currently */
+ if (sk_is_tcp(sk)) {
+ zcopy_queue = &tcp_sk(sk)->tx_zcopy_queue;
+ } else if (sk_is_udp(sk)) {
+ zcopy_queue = &udp_sk(sk)->tx_zcopy_queue;
+ } else {
+ pr_warn("MSG_ZEROCOPY_UARG only support TCP && UDP sockets");
+ goto release;
+ }
+
+ len = uarg->len;
+ lo = uarg->id;
+ hi = uarg->id + len - 1;
+
+ zcopy_node_p = (struct tx_msg_zcopy_node *)skb->data;
+ zcopy_node_p->info.lo = lo;
+ zcopy_node_p->info.hi = hi;
+ zcopy_node_p->info.zerocopy = uarg->zerocopy;
+
+ spin_lock_irqsave(&zcopy_queue->lock, flags);
+ tail = list_last_entry(&zcopy_queue->head, struct tx_msg_zcopy_node, node);
+ if (!tail || !skb_zerocopy_uarg_notify_extend(tail, lo, len)) {
+ list_add_tail(&zcopy_node_p->node, &zcopy_queue->head);
+ skb = NULL;
+ }
+ spin_unlock_irqrestore(&zcopy_queue->lock, flags);
+release:
+ consume_skb(skb);
+ sock_put(sk);
+}
+
+void msg_zerocopy_uarg_callback(struct sk_buff *skb, struct ubuf_info *uarg,
+ bool success)
+{
+ struct ubuf_info_msgzc *uarg_zc = uarg_to_msgzc(uarg);
+
+ uarg_zc->zerocopy = uarg_zc->zerocopy & success;
+
+ if (refcount_dec_and_test(&uarg->refcnt))
+ __msg_zerocopy_uarg_callback(uarg_zc);
+}
+EXPORT_SYMBOL_GPL(msg_zerocopy_uarg_callback);
+
void msg_zerocopy_put_abort(struct ubuf_info *uarg, bool have_uref)
{
struct sock *sk = skb_from_uarg(uarg_to_msgzc(uarg))->sk;
@@ -1838,7 +1957,7 @@ void msg_zerocopy_put_abort(struct ubuf_info *uarg, bool have_uref)
uarg_to_msgzc(uarg)->len--;
if (have_uref)
- msg_zerocopy_callback(NULL, uarg, true);
+ uarg->callback(NULL, uarg, true);
}
EXPORT_SYMBOL_GPL(msg_zerocopy_put_abort);
diff --git a/net/core/sock.c b/net/core/sock.c
index 5ed411231fc7..a00ebd71f6ed 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -2843,6 +2843,56 @@ int __sock_cmsg_send(struct sock *sk, struct cmsghdr *cmsg,
case SCM_RIGHTS:
case SCM_CREDENTIALS:
break;
+ case SO_ZEROCOPY_NOTIFICATION:
+ if (sock_flag(sk, SOCK_ZEROCOPY)) {
+ int i = 0;
+ struct tx_usr_zcopy_info sys_zcopy_info;
+ struct tx_msg_zcopy_node *zcopy_node_p, *tmp;
+ struct tx_msg_zcopy_queue *zcopy_queue;
+ struct tx_msg_zcopy_node *zcopy_node_ps[SOCK_USR_ZC_INFO_MAX];
+ unsigned long flags;
+
+ if (cmsg->cmsg_len != CMSG_LEN(sizeof(void *)))
+ return -EINVAL;
+
+ if (sk_is_tcp(sk))
+ zcopy_queue = &tcp_sk(sk)->tx_zcopy_queue;
+ else if (sk_is_udp(sk))
+ zcopy_queue = &udp_sk(sk)->tx_zcopy_queue;
+ else
+ return -EINVAL;
+
+ spin_lock_irqsave(&zcopy_queue->lock, flags);
+ list_for_each_entry_safe(zcopy_node_p, tmp, &zcopy_queue->head, node) {
+ sys_zcopy_info.info[i].lo = zcopy_node_p->info.lo;
+ sys_zcopy_info.info[i].hi = zcopy_node_p->info.hi;
+ sys_zcopy_info.info[i].zerocopy = zcopy_node_p->info.zerocopy;
+ list_del(&zcopy_node_p->node);
+ zcopy_node_ps[i++] = zcopy_node_p;
+ if (i == SOCK_USR_ZC_INFO_MAX)
+ break;
+ }
+ spin_unlock_irqrestore(&zcopy_queue->lock, flags);
+
+ if (i > 0) {
+ sys_zcopy_info.length = i;
+ if (unlikely(copy_to_user(*(void **)CMSG_DATA(cmsg),
+ &sys_zcopy_info,
+ sizeof(sys_zcopy_info))
+ )) {
+ spin_lock_irqsave(&zcopy_queue->lock, flags);
+ while (i > 0)
+ list_add(&zcopy_node_ps[--i]->node,
+ &zcopy_queue->head);
+ spin_unlock_irqrestore(&zcopy_queue->lock, flags);
+ return -EFAULT;
+ }
+
+ while (i > 0)
+ consume_skb(zcopy_node_ps[--i]->skb);
+ }
+ }
+ break;
default:
return -EINVAL;
}
diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index 1fe794967211..5adb737c4c01 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -1005,7 +1005,7 @@ static int __ip_append_data(struct sock *sk,
(!exthdrlen || (rt->dst.dev->features & NETIF_F_HW_ESP_TX_CSUM)))
csummode = CHECKSUM_PARTIAL;
- if ((flags & MSG_ZEROCOPY) && length) {
+ if (((flags & MSG_ZEROCOPY) || (flags & MSG_ZEROCOPY_UARG)) && length) {
struct msghdr *msg = from;
if (getfrag == ip_generic_getfrag && msg->msg_ubuf) {
@@ -1022,7 +1022,9 @@ static int __ip_append_data(struct sock *sk,
uarg = msg->msg_ubuf;
}
} else if (sock_flag(sk, SOCK_ZEROCOPY)) {
- uarg = msg_zerocopy_realloc(sk, length, skb_zcopy(skb));
+ bool user_args = flags & MSG_ZEROCOPY_UARG;
+
+ uarg = msg_zerocopy_realloc(sk, length, skb_zcopy(skb), user_args);
if (!uarg)
return -ENOBUFS;
extra_uref = !skb_zcopy(skb); /* only ref on new uarg */
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index e767721b3a58..6254d0eef3af 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -462,6 +462,8 @@ void tcp_init_sock(struct sock *sk)
set_bit(SOCK_SUPPORT_ZC, &sk->sk_socket->flags);
sk_sockets_allocated_inc(sk);
+
+ tx_message_zcopy_queue_init(&tp->tx_zcopy_queue);
}
EXPORT_SYMBOL(tcp_init_sock);
@@ -1050,14 +1052,15 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size)
flags = msg->msg_flags;
- if ((flags & MSG_ZEROCOPY) && size) {
+ if (((flags & MSG_ZEROCOPY) || (flags & MSG_ZEROCOPY_UARG)) && size) {
if (msg->msg_ubuf) {
uarg = msg->msg_ubuf;
if (sk->sk_route_caps & NETIF_F_SG)
zc = MSG_ZEROCOPY;
} else if (sock_flag(sk, SOCK_ZEROCOPY)) {
+ bool zc_uarg = flags & MSG_ZEROCOPY_UARG;
skb = tcp_write_queue_tail(sk);
- uarg = msg_zerocopy_realloc(sk, size, skb_zcopy(skb));
+ uarg = msg_zerocopy_realloc(sk, size, skb_zcopy(skb), zc_uarg);
if (!uarg) {
err = -ENOBUFS;
goto out_err;
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 11460d751e73..6c62aacd74d6 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1126,6 +1126,15 @@ int udp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
if (ipc.opt)
free = 1;
connected = 0;
+
+ /* If len is zero and flag MSG_ZEROCOPY_UARG is set,
+ * it means this call just wants to get zcopy notifications
+ * instead of sending packets. It is useful when users
+ * finish sending and want to get trailing notifications.
+ */
+ if ((msg->msg_flags & MSG_ZEROCOPY_UARG) &&
+ sock_flag(sk, SOCK_ZEROCOPY) && len == 0)
+ return 0;
}
if (!ipc.opt) {
struct ip_options_rcu *inet_opt;
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index b9dd3a66e423..891526ddd74c 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -1493,7 +1493,7 @@ static int __ip6_append_data(struct sock *sk,
rt->dst.dev->features & (NETIF_F_IPV6_CSUM | NETIF_F_HW_CSUM))
csummode = CHECKSUM_PARTIAL;
- if ((flags & MSG_ZEROCOPY) && length) {
+ if (((flags & MSG_ZEROCOPY) || (flags & MSG_ZEROCOPY_UARG)) && length) {
struct msghdr *msg = from;
if (getfrag == ip_generic_getfrag && msg->msg_ubuf) {
@@ -1510,7 +1510,8 @@ static int __ip6_append_data(struct sock *sk,
uarg = msg->msg_ubuf;
}
} else if (sock_flag(sk, SOCK_ZEROCOPY)) {
- uarg = msg_zerocopy_realloc(sk, length, skb_zcopy(skb));
+ uarg = msg_zerocopy_realloc(sk, length, skb_zcopy(skb),
+ flags & MSG_ZEROCOPY_UARG);
if (!uarg)
return -ENOBUFS;
extra_uref = !skb_zcopy(skb); /* only ref on new uarg */
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 2e4dc5e6137b..98f6905c5db9 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -1490,6 +1490,15 @@ int udpv6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
if (!(opt->opt_nflen|opt->opt_flen))
opt = NULL;
connected = false;
+
+ /* If len is zero and flag MSG_ZEROCOPY_UARG is set,
+ * it means this call just wants to get zcopy notifications
+ * instead of sending packets. It is useful when users
+ * finish sending and want to get trailing notifications.
+ */
+ if ((msg->msg_flags & MSG_ZEROCOPY_UARG) &&
+ sock_flag(sk, SOCK_ZEROCOPY) && len == 0)
+ return 0;
}
if (!opt) {
opt = txopt_get(np);
diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index 16ff976a86e3..d6e6830f6ffe 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c
@@ -84,7 +84,7 @@ static int virtio_transport_init_zcopy_skb(struct vsock_sock *vsk,
uarg = msg_zerocopy_realloc(sk_vsock(vsk),
iter->count,
- NULL);
+ NULL, false);
if (!uarg)
return -1;
--
2.20.1
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