mptcp: add subflow write space signalling and mptcp_poll

Add new SEND_SPACE flag to indicate that a subflow has enough space to
accept more data for transmission.

It gets cleared at the end of mptcp_sendmsg() in case ssk has run
below the free watermark.

It is (re-set) from the wspace callback.

This allows us to use msk->flags to determine the poll mask.

Co-developed-by: Peter Krystad <peter.krystad@linux.intel.com>
Signed-off-by: Peter Krystad <peter.krystad@linux.intel.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Christoph Paasch <cpaasch@apple.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 71250149180b28f3690ba1fa41455cb8334c35f8..408efbe3475346a50ca88f2a2422325365a5423c 100644 (file)
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -176,6 +176,23 @@ static int mptcp_sendmsg_frag(struct sock *sk, struct sock *ssk,
        return ret;
 }
 
+static void ssk_check_wmem(struct mptcp_sock *msk, struct sock *ssk)
+{
+       struct socket *sock;
+
+       if (likely(sk_stream_is_writeable(ssk)))
+               return;
+
+       sock = READ_ONCE(ssk->sk_socket);
+
+       if (sock) {
+               clear_bit(MPTCP_SEND_SPACE, &msk->flags);
+               smp_mb__after_atomic();
+               /* set NOSPACE only after clearing SEND_SPACE flag */
+               set_bit(SOCK_NOSPACE, &sock->flags);
+       }
+}
+
 static int mptcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 {
        struct mptcp_sock *msk = mptcp_sk(sk);
@@ -219,6 +236,7 @@ static int mptcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
        if (copied > 0)
                ret = copied;
 
+       ssk_check_wmem(msk, ssk);
        release_sock(ssk);
        release_sock(sk);
        return ret;
@@ -315,6 +333,7 @@ static int mptcp_init_sock(struct sock *sk)
        struct mptcp_sock *msk = mptcp_sk(sk);
 
        INIT_LIST_HEAD(&msk->conn_list);
+       __set_bit(MPTCP_SEND_SPACE, &msk->flags);
 
        return 0;
 }
@@ -576,6 +595,13 @@ static void mptcp_sock_graft(struct sock *sk, struct socket *parent)
        write_unlock_bh(&sk->sk_callback_lock);
 }
 
+static bool mptcp_memory_free(const struct sock *sk, int wake)
+{
+       struct mptcp_sock *msk = mptcp_sk(sk);
+
+       return wake ? test_bit(MPTCP_SEND_SPACE, &msk->flags) : true;
+}
+
 static struct proto mptcp_prot = {
        .name           = "MPTCP",
        .owner          = THIS_MODULE,
@@ -591,6 +617,7 @@ static struct proto mptcp_prot = {
        .hash           = inet_hash,
        .unhash         = inet_unhash,
        .get_port       = mptcp_get_port,
+       .stream_memory_free     = mptcp_memory_free,
        .obj_size       = sizeof(struct mptcp_sock),
        .no_autobind    = true,
 };
@@ -767,8 +794,34 @@ unlock_fail:
 static __poll_t mptcp_poll(struct file *file, struct socket *sock,
                           struct poll_table_struct *wait)
 {
+       const struct mptcp_sock *msk;
+       struct sock *sk = sock->sk;
+       struct socket *ssock;
        __poll_t mask = 0;
 
+       msk = mptcp_sk(sk);
+       lock_sock(sk);
+       ssock = __mptcp_nmpc_socket(msk);
+       if (ssock) {
+               mask = ssock->ops->poll(file, ssock, wait);
+               release_sock(sk);
+               return mask;
+       }
+
+       release_sock(sk);
+       sock_poll_wait(file, sock, wait);
+       lock_sock(sk);
+
+       if (test_bit(MPTCP_DATA_READY, &msk->flags))
+               mask = EPOLLIN | EPOLLRDNORM;
+       if (sk_stream_is_writeable(sk) &&
+           test_bit(MPTCP_SEND_SPACE, &msk->flags))
+               mask |= EPOLLOUT | EPOLLWRNORM;
+       if (sk->sk_shutdown & RCV_SHUTDOWN)
+               mask |= EPOLLIN | EPOLLRDNORM | EPOLLRDHUP;
+
+       release_sock(sk);
+
        return mask;
 }
 

diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index c6d8217e24d404c8f0426a74703802b3982300aa..59a83eb64d375504f7a0d94f6320e42cd951f5cf 100644 (file)
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -56,6 +56,7 @@
 
 /* MPTCP socket flags */
 #define MPTCP_DATA_READY       BIT(0)
+#define MPTCP_SEND_SPACE       BIT(1)
 
 /* MPTCP connection sock */
 struct mptcp_sock {

diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index 528351e26371f55dc4c1211e2c0037767bab09f9..9fb3eb87a20faec46181e93ae3176d6a1a58eb34 100644 (file)
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -529,6 +529,9 @@ static void subflow_write_space(struct sock *sk)
 
        sk_stream_write_space(sk);
        if (parent && sk_stream_is_writeable(sk)) {
+               set_bit(MPTCP_SEND_SPACE, &mptcp_sk(parent)->flags);
+               smp_mb__after_atomic();
+               /* set SEND_SPACE before sk_stream_write_space clears NOSPACE */
                sk_stream_write_space(parent);
        }
 }