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mptcp: rethink 'is writable' conditional 

Currently, when checking for the 'msk is writable' condition, we
look at the individual subflows write space.
That works well while we send data via a single subflow, but will
not as soon as we will enable concurrent xmit on multiple subflows.

With this change msk becomes writable when the following conditions
hold:
- the socket has some free write space
- there is at least a subflow with write free space

Additionally we need to set the NOSPACE bit on all subflows
before blocking.

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Paolo Abeni 2020-09-14 10:01:07 +02:00 committed by David S. Miller
parent 26cdb8f72a
commit 63561a403c
2 changed files with 50 additions and 27 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

71
net/mptcp/protocol.c
View File

@ -472,7 +472,7 @@ void mptcp_data_acked(struct sock *sk)
{
mptcp_reset_timer(sk);
if ((!sk_stream_is_writeable(sk) ||
if ((!test_bit(MPTCP_SEND_SPACE, &mptcp_sk(sk)->flags) ||
(inet_sk_state_load(sk) != TCP_ESTABLISHED)) &&
schedule_work(&mptcp_sk(sk)->work))
sock_hold(sk);
@ -567,6 +567,20 @@ static void dfrag_clear(struct sock *sk, struct mptcp_data_frag *dfrag)
put_page(dfrag->page);
}
static bool mptcp_is_writeable(struct mptcp_sock *msk)
{
struct mptcp_subflow_context *subflow;
if (!sk_stream_is_writeable((struct sock *)msk))
return false;
mptcp_for_each_subflow(msk, subflow) {
if (sk_stream_is_writeable(subflow->tcp_sock))
return true;
}
return false;
}
static void mptcp_clean_una(struct sock *sk)
{
struct mptcp_sock *msk = mptcp_sk(sk);
@ -609,8 +623,15 @@ out:
sk_mem_reclaim_partial(sk);
/* Only wake up writers if a subflow is ready */
if (test_bit(MPTCP_SEND_SPACE, &msk->flags))
if (mptcp_is_writeable(msk)) {
set_bit(MPTCP_SEND_SPACE, &mptcp_sk(sk)->flags);
smp_mb__after_atomic();
/* set SEND_SPACE before sk_stream_write_space clears
* NOSPACE
*/
sk_stream_write_space(sk);
}
}
}
@ -801,21 +822,31 @@ out:
return ret;
}
static void mptcp_nospace(struct mptcp_sock *msk, struct socket *sock)
static void mptcp_nospace(struct mptcp_sock *msk)
{
struct mptcp_subflow_context *subflow;
clear_bit(MPTCP_SEND_SPACE, &msk->flags);
smp_mb__after_atomic(); /* msk->flags is changed by write_space cb */
/* enables sk->write_space() callbacks */
set_bit(SOCK_NOSPACE, &sock->flags);
mptcp_for_each_subflow(msk, subflow) {
struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
struct socket *sock = READ_ONCE(ssk->sk_socket);
/* enables ssk->write_space() callbacks */
if (sock)
set_bit(SOCK_NOSPACE, &sock->flags);
}
}
static struct sock *mptcp_subflow_get_send(struct mptcp_sock *msk)
{
struct mptcp_subflow_context *subflow;
struct sock *sk = (struct sock *)msk;
struct sock *backup = NULL;
bool free;
sock_owned_by_me((const struct sock *)msk);
sock_owned_by_me(sk);
if (!mptcp_ext_cache_refill(msk))
return NULL;
@ -823,12 +854,9 @@ static struct sock *mptcp_subflow_get_send(struct mptcp_sock *msk)
mptcp_for_each_subflow(msk, subflow) {
struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
if (!sk_stream_memory_free(ssk)) {
struct socket *sock = ssk->sk_socket;
if (sock)
mptcp_nospace(msk, sock);
free = sk_stream_is_writeable(subflow->tcp_sock);
if (!free) {
mptcp_nospace(msk);
return NULL;
}
@ -845,16 +873,10 @@ static struct sock *mptcp_subflow_get_send(struct mptcp_sock *msk)
return backup;
}
static void ssk_check_wmem(struct mptcp_sock *msk, struct sock *ssk)
static void ssk_check_wmem(struct mptcp_sock *msk)
{
struct socket *sock;
if (likely(sk_stream_is_writeable(ssk)))
return;
sock = READ_ONCE(ssk->sk_socket);
if (sock)
mptcp_nospace(msk, sock);
if (unlikely(!mptcp_is_writeable(msk)))
mptcp_nospace(msk);
}
static int mptcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
@ -907,6 +929,7 @@ restart:
mptcp_reset_timer(sk);
}
mptcp_nospace(msk);
ret = sk_stream_wait_memory(sk, &timeo);
if (ret)
goto out;
@ -945,7 +968,6 @@ restart:
if (!sk_stream_memory_free(ssk) ||
!mptcp_page_frag_refill(ssk, pfrag) ||
!mptcp_ext_cache_refill(msk)) {
set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
tcp_push(ssk, msg->msg_flags, mss_now,
tcp_sk(ssk)->nonagle, size_goal);
mptcp_set_timeout(sk, ssk);
@ -993,9 +1015,9 @@ restart:
mptcp_reset_timer(sk);
}
ssk_check_wmem(msk, ssk);
release_sock(ssk);
out:
ssk_check_wmem(msk);
release_sock(sk);
return copied ? : ret;
}
@ -2291,8 +2313,7 @@ static __poll_t mptcp_poll(struct file *file, struct socket *sock,
if (state != TCP_SYN_SENT && state != TCP_SYN_RECV) {
mask |= mptcp_check_readable(msk);
if (sk_stream_is_writeable(sk) &&
test_bit(MPTCP_SEND_SPACE, &msk->flags))
if (test_bit(MPTCP_SEND_SPACE, &msk->flags))
mask |= EPOLLOUT | EPOLLWRNORM;
}
if (sk->sk_shutdown & RCV_SHUTDOWN)

6
net/mptcp/subflow.c
View File

@ -996,8 +996,10 @@ static void subflow_write_space(struct sock *sk)
struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
struct sock *parent = subflow->conn;
sk_stream_write_space(sk);
if (sk_stream_is_writeable(sk)) {
if (!sk_stream_is_writeable(sk))
return;
if (sk_stream_is_writeable(parent)) {
set_bit(MPTCP_SEND_SPACE, &mptcp_sk(parent)->flags);
smp_mb__after_atomic();
/* set SEND_SPACE before sk_stream_write_space clears NOSPACE */